Article Quantification of Irgafos P-168 and Degradative Profile in Samples of a Polypropylene/Polyethylene Composite Using Microwave, Ultrasound and Soxhlet Extraction Techniques Joaquín Hernández-Fernández 1,2,3,* , Jaime Pérez-Mendoza 4 and Rodrigo Ortega-Toro 5,* 1 Chemistry Program, Department of Natural and Exact Sciences, San Pablo Campus, University of Cartagena, Cartagena 130015, Colombia 2 Chemical Engineering Program, School of Engineering, Universidad Tecnológica de Bolivar, Parque Industrialy Tecnológico Carlos Vélez Pombo Km 1 Vía Turbaco, Cartagena 130001, Colombia 3 Department of Natural and Exact Science, Universidad de la Costa, Barranquilla 080002, Colombia 4 Complex Fluid Engineering and Food Rheology Research Group (IFCRA), Food Engineering Department, Universidad de Cartagena, Cartagena de Indias 130015, Colombia; jperezm@unicartagena.edu.co 5 Food Packaging and Shelf-Life Research Group (FP&SL), Food Engineering Department, Universidad de Cartagena, Cartagena de Indias 130015, Colombia * Correspondence: jhernandezf@unicartagena.edu.co (J.H.-F.); rortegap1@unicartagena.edu.co (R.O.-T.) Abstract: In polypropylene/polyethylene composite (C-PP/PE) production, stabilizing additives such as Irgafos P-168 are essential as antioxidant agents. In this study, an investigation was carried out that covers different solid–liquid extraction methods (Soxhlet, ultrasound, and microwaves); various variables were evaluated, such as temperature, extraction time, the choice of solvents, and the type of C-PP/PE used, and the gas chromatography coupled to mass spectrometry (GC-MS) technique was used to quantify the presence of Irgafos P-168 in the C-PP/PE samples. The results revealed that microwave extraction was the most effective in recovering Irgafos P-168. A recovery of 96.7% was achieved when using dichloromethane as a solvent, and 92.83% was achieved when using limonene as a solvent. The ultrasound technique recovered 91.74% using dichloromethane and 89.71% using Citation: Hernández-Fernández, J.; limonene. The Soxhlet extraction method showed the lowest recovery percentages of 57.39% using Pérez-Mendoza, J.; Ortega-Toro, R. dichloromethane as a solvent and 55.76% with limonene, especially when the C-PP/PE was in the Quantification of Irgafos P-168 and Degradative Profile in Samples of a form of pellets. The degradation products that obtained the highest degradation percentages were Polypropylene/Polyethylene Bis (di-test-butyl phenyl) phosphate and Mono (di-test-butyl phenyl) phosphate using the microwave Composite Using Microwave, method with dichloromethane as a solvent and PP in film. Finally, the possible mechanisms for Ultrasound and Soxhlet Extraction forming the degradation compounds of Irgafos P-168 were postulated. Techniques. J. Compos. Sci. 2024, 8, 156. https://doi.org/10.3390/jcs8040156 Keywords: polypropylene/polyethylene composite (C-PP/PE); Irgafos P-168; extraction methods Academic Editor: Francesco Tornabene Received: 20 February 2024 1. Introduction Revised: 4 April 2024 In producing polypropylene/polyethylene composite (C-PP/PE) films, additives im- Accepted: 9 April 2024 prove and modify the material’s properties. These additives play a fundamental role in Published: 21 April 2024 optimizing physical, chemical, and mechanical characteristics, allowing them to be adapted to the specific needs of various industrial applications, among which food packaging and packaging stand out [1–14]. Stabilizing additives, such as antioxidants and UV stabilizers, Copyright: © 2024 by the authors. protect C-PP/PE from oxidation and degradation caused by environmental factors [14]. Licensee MDPI, Basel, Switzerland. Fluidity and slip modifier additives improve film processing, reducing friction and facilitat- This article is an open access article ing slip in the production stages [14,15]. Plasticizers increase the flexibility and elasticity of distributed under the terms and the films, while reinforcing additives improve the mechanical resistance and rigidity of the conditions of the Creative Commons material. Additionally, color additives and pigments provide a wide range of aesthetic op- Attribution (CC BY) license (https:// tions. These additives are essential to obtain high-quality, high-performance polypropylene creativecommons.org/licenses/by/ and C-PP/PE films adapted to the needs of different industrial sectors [16–26]. 4.0/). J. Compos. Sci. 2024, 8, 156. https://doi.org/10.3390/jcs8040156 https://www.mdpi.com/journal/jcs J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 2 of 22 high-performance polypropylene and C-PP/PE films adapted to the needs of different in- dustrial sectors [16–26]. One of the antioxidant additives in most significant demand in the production of C- J. Compos. Sci. 2024, 8, 156 PP/PE films is (tris (2,4-di-tert-butylphenyl) phosphite) known as Irgafo2so fP2-1168; it is a tri- functional ester of phosphoric acid, which contains three phenyl groups substituted with butyl Ognreooufptsh einan tsipoxeicdiafinct apdodsitiitvioesnisn [m2o7s]t. sTighniisfi csatnrtudcetmuraanld cinonthfiegpurroadtuioctnio n(Foifgure 1) gives IrCg-aPfPo/sP PE-1fi6lm8 sainst(itorixsi(d2a,4n-dt ip-treortp-beurttyielpsh, eanlylol)wpihnogsp iht ittoe) akcnto awsn aa sfrIergea rfaosdPic-a16l 8s;ciatvisenger and de- laayt roixfuidncattioionnal pesrtoecreosfspehso tshpahto criacna clieda,dw thoic thhceo ndteaginrsatdharetieopnh eonf yCl -gProPu/pPsEs.u Ibnsctioturtpeodrating Irgafos P-w1i6th8 binut tyhl eg rmouoplsteinn sppoeclyifimc peor sdituiornins [g2 7th].eT ehxistrsturusicotunr aalncdon tfihgeurrmatoiomn o(Flidgiunreg 1p)rgoivceessses improves thIergramfoaslP s-1ta68bialnittiyo,x pidraonttepcrtoipnegrties, allowing it to aoxidation processes that can lea dit tforothme doexgirdadaatito cnt aasnadfr deeergardaicdal scavenger and delayion of C-PP/PE. Iantcioornp o[r1a4t]in. gTIhregsaefo csharacteristics arPe- 1e6s8sienntthiealm tool taenchpioelvyme eorpdtuimrinagl tahpepexetarruasinocnea annddth oerbmtaoimno sldtainbglep rpohceyssseicsaiml pprroovpeesrties, guaran- tetehienrmg aml sotarbei leitxy,cperloletencti ndguirtafrboimlitoyx iadnatdio nuasnedfudle lgirfaed oatfi otnhe[1 4p]r. oTdheuscetcsh a[2ra8c]t.e ristics are essential to achieve optimal appearance and obtain stable physical properties, guaranteeing more excellent durability and useful life of the products [28]. Figure 1. Molecular structure of the antioxidant additive Irgafos P-168. Figure 1. Molecular structure of the antioxidant additive Irgafos P-168. Previously, various extraction techniques have been used for Irgafos P-168 and other antioPxriedvaniotuadsldyit,i vveasriinouCs-P ePx/tPrEacatniodnP Pteficlhmnsi[q2u9,e3s0 ]h. Tavhees ebeteecnh nuiqsuedes fioncrl uIrdgeaSfooxsh Ple-t168 and other anextitoraxcitdioann, tu altdradsoituivndes-a sinsi sCte-dPePx/tPraEc taionnd( UPAPE fi),lmansd [m29o,r3e0a]d. vTahnecesde tteecchhnniqiqueusessu icnhclude Soxhlet exatsrmacictiroown,a uvelt-assisted extraction (MAE) and supercritical fluid extraction (SFE) [Soxhlet extractiroansios ua ncldas-saicssmisettheodd ewxhtrearectthioensa (mUpAleEis),p alancedd minoarcee lal-dshvaapnedceedxt 3 rtae 1–3 cctih 4]. onniques such as mciacrrtoriwdgaev, ea-nadssaishteeadti negxatrnadctciooonli n(gMcyAclEe) isacnadrr iesdupoeurt.crTithiecaslo lflveunitde veaxptorraactteisoann d(SFE) [31–34]. Socoxnhdlent sexs,terfaficctiieonntly ise xatr acclatisnsgicth me aentthiooxdid awnthaedrdei ttihves sfraompthle sisam pplalec,ebdut itnh eam cetlhlo-sdhaped extrac- tiohans ccaerrttariindlgime,i taantiodn as, hsuecahtiansglo anngdex ctroaoctliionngt icmyecsler ainsg cinagrrfireodm o6uht.t oT4h8eh saonldvehnigth eevr aporates and covnolduemnesseosf, soelffivecniternetqluyi reedxt[r3a5]c.tIinngco ntthraes ta, tnhteioUxAidEaunset s audltdraistoivniecsw farvoes to improvethe extraction efficiency of antioxidant additives. This technique generates micmro ctahveit astiaomn ple, but the maentdhotudr bhualesn cceeritnaitnhe lismolviteantti,oancsce, lseuracthin agse lxotrnagct ieoxntraancdtiooffne rtiinmgepsr ormanisgininggre fsruoltms i 6n h to 48 h and hisghhoretre rvtiomluesm[3e6s]. oLfik seowlivse,nMt AreEq, wuhiriechds t[a3n5d]s. oInut caos na tfraastsat,n dtheeffi UcieAntEt euchsneisq ueltsrinacseonic waves to imitparlloovwes tdhiree cetxetxrtaracctitoionn einffigcraiennuclayte odfo arnpteilolextiidzeadnmt aadtrdicietsivuesisn.g Trhedisu tceecdhvnoilqumuee sgoefnerates micro casvolivtaentitoann danwdit htouurtbtuhelenneceed ifnor tehxeh asuosltviveenptr, eatrcecaetmleernattionfgth eexstarmapctleios,nh aasnpdr oovffenertoing promising be effective in obtaining extraction results in significantly shorter times. In contrast, SFE reussuesltas flinui dshinoratseurp teirmcrietsic a[3l s6t]a.t eL, iwkheiwchiseexh, iMbitAs iEn,t ewrmheidciha tsetparnodpesr toieustb aestw ae efansat laiqnudid efficient tech- niaqnudea sgians.ceH oitw aelvleorw, itso dffierrescbte tetxertrpaecrftoiormn ainc egirnasneulelcatitveidty oarn dpexltlreatcitzioend emffiaciternicye;si tus sing reduced voaplupmliceasti onf csaonlvbenmt oarnedco wmiptlhicoautetd tahned neexepden fsoivre edxuheatuostthive en eperdeftorreasptmecieanlitz eodf athnde samples, has preoxpveenns itvoe beqeu eipffmeecntitv[e33 i–n3 5o].btaining extraction results in significantly shorter times. In con- trianst, IStFisEe susesnetsi aal tfloureimd eimn bae rstuhpatesroclrvietnictsapl lsatyaatec,r uwcihailcrhol eeixnheixbtirtasc tiinngtetrhme additivesall these solid–liquid extraction techniques. Although organic compoundsesduicahtea sproperties be- twdeicehnlo rao mliqetuhiadn ea, ncydc laoh gexaasn. eH, aonwd echvleorr,o fiot romffaerresr ebceottgneirz epdefrofroarcmhiaevnicneg hinig sherleeccotvievriyty and extrac- tiopenr ceeffintcaigeens,ctyh;e itrsh aigphptloicxaictiitoynr ecparnes benet smaosrieg nciofimcanptlircisaktefdor atnhed peexrpsoennnseilvien vdoulvee dto the need for spinecthiaelirizheadn dalnindg eaxndpethnesievnev ieroqnumipenmt einngt e[n3e3r–a3l 5[3]3. –35]. Specifically, dichloromethane, alsoIkt niso wesnseasntmiaelt htyol erneemcehmlorbiedre ,thisastu sbojelcvtetnotus spelraeys tari cctriouncsiadlu reotloe iitns ehxartmrafcutlinpgo- the additives tential. Therefore, it is essential to select solvents that carefully ensure the extraction inp raolcle tshs’esseeff escotilviden–elsisq,uoiffde resxatfertaycftoior nhu tmecahnnwieqlul-beesi.n Ag,latnhdoumginhim oirzgeathneiicr ecnovmiropnomuennd- s such as di- chtalol irmompaecth[2a8n–e3,2 ]c.yLcilmohoneexnaenem, aenrgde scahsloanroufpo-ramnd a-croem riencgoogpntiizonedsi nfocer iatcshtoiexviciintygi shigh recovery pecorcnesindtearagbelsy, ltohweeirr thaignhth taotxoifctirtayd irteiopnraelsseolnvtesn tas s[2ig8–n3i2fi].cant risk for the personnel involved in their handling and the environment in general [33–35]. Specifically, dichloromethane, also known as methylene chloride, is subject to use restrictions due to its harmful potential. Therefore, it is essential to select solvents that carefully ensure the extraction process’s effectiveness, offer safety for human well-being, and minimize their environmental impact J. Compos. Sci. 2024, 8, 156 3 of 21 Limonene C10H16 is a monocyclic hydrocarbon belonging to the class of terpenes. It has a highly aromatic structure, is hydrophilic, can dissolve a range of organic products, and is present in the peel of citrus fruits, especially lemons. There are two optical isomers of Limonene, d-Limonene and l-Limonene, and a racemic mixture that combines both isomers [28–32]. Its pleasant lemon aroma makes it an additive widely used in the food industry to add flavor and fragrance to various products. However, its applications go further, and it is also found in household, cosmetic, and pharmaceutical products, where it has been considered safe. In addition, studies have revealed that Limonene has anti- cancer properties [28–35]. In recent years, Limonene has also begun to be used as a green solvent since it is environmentally friendly and derived from natural sources. Limonene is biodegradable and non-toxic, which makes it an alternative to traditional solvents such as dichloromethane. It is safer and more ecological, minimizes the negative impact on ecosystems, and promotes more sustainable practices in the industry [28–33]. Unfortunately, the use of green solvents is still limited in the polymer industry for the extraction of additives such as Irgafos P-168, so in this research, extraction techniques assisted by microwaves, ultrasound, and Soxhlet will be used, using a method-sensitive microextraction coupled to gas chromatography, for the simultaneous determination of the concentration of Irgafos P-168 and degradation products in C-PP/PE samples. Three pretreatments of PP (ground, pellets, and films) will be carried out using a traditional solvent (dichloromethane) and a green solvent (Limonene). Multivariate analysis will evaluate performance, and the degradation products of Irgafos P-168 will be quantified to establish their relationship with the results of each extraction. The results of this research are essential to the scientific community, industry, and regulatory bodies involved in the extraction and characterization of Irgafos P-168 in polymeric matrices. 2. Materials and Methods 2.1. Reagents The Irgafos P-168 was acquired from Shanghai Tixiai Co., Ltd. (Shanghai, China). Butylated hydroxytoluene (BHT) was also used as an internal standard provided by Campro Science GmbH (Berlin, Germany). Limonene (HPLC grade) was obtained from Scharlab (Barcelona, Spain). Hydrogen and nitrogen with 99.9999% purity were purchased from Linde (Cartagena, Colombia), and dichloromethane with 99.99% purity was used from Sigma Aldrich (Bangalore, India). 2.2. GC-MS Analysis A specific method was designed using gas chromatography coupled with mass spec- trometry (GC-MS) to evaluate the recoveries of the master mixture. The extracts obtained by solid–liquid extraction were analyzed by GC-MS, following the degradation products of each compound analyzed, together with an internal standard (BHT). These analyses were carried out using an Agilent 7890 gas chromatograph provided by Agilent JW Scientific (Diegem, Belgium). The chromatography was coupled to an Agilent 7000 GC-MS triple quadrupole (QqQ) mass spectrometer, equipped with an electron impact ionization (EI) source, and operated in selective ion monitoring (SIM) mode. The quadrupole and the ion source temperatures were maintained at 150 ◦C and 230 ◦C, respectively. The multiplier voltage was set to 2200 V. To improve the acquisition speed, three acquisition segments were programmed with different retention times (20, 15, and 20 ms, respectively). One microliter of extract was injected into a PTV injector in pulsed, splitless mode, with an injection temperature of 280 ◦C. The column used in the gas chromatograph was a DB-5 ms of 30 m length, 0.25 mm internal diameter, and 0.25 µm film. The oven temperature was started at 60 ◦C for 3 min and then increased to 300 ◦C at a rate of 10 ◦C per minute, maintaining this temperature for 15 min. The total analysis execution time was 42 min. Helium was used as carrier gas at a constant flow of 1.0 mL per minute. J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 4 of 22 for 15 min. The total analysis execution time was 42 min. Helium was used as carrier gas J. Compos. Sci. 2024, 8, 156 at a constant flow of 1.0 mL per minute. 4 of 21 2.2.1. Prepare Irgafos 168 Calibration Standards and C-PP/PE Samples with Irgafos P-168 2.2.1. Prepare Irgafos 168 Calibration Standards and C-PP/PE Samples with Irgafos P-168 Preparation of the Curve for Calibration of the Chromatograph Preparation of the Curve for Calibration of the Chromatograph Figure 2 shows how a stock solution of Irgafos P-168 at 10,000 ppm was prepared (by adaddindg F in 1 ig g0, u0re 2 sh100,000 m0 g o m o w gf sIrhgoawof Irgfoas a Pst-o1c6k8 sino l1utfos P-168 in L io onf oLfimIrgafos P-1681 L of Limonoenneen) ea)nad aat 1ndna i 0n,0te0r0npapl smtawas prepn internal sntadnadradr dso ared (by sluoltuiotnio n of obfubtyultaytleadt ehdydhryodxryotxoylutoelnuee (nBeH(TB)H aTt )a actonacceonntrcaetniotrna otifo 1n0,o0f001 0p,0p0m0. pTphmes.e sTohleusteiosnosl guetino-ns eragteende rfoatuerd sfaomupr lseasm wpiltehs kwniothwknn coowncnecnotrnacteionntrsa otifo 5n0s0o, f1500000,, 11050000,, 1a5n0d0 ,2a0n00d p2p00m0. ppm. FigFuigreu r2e. P2.rePpreapraatriaotnio onf oIrfgIargfoasf oPs-1P6-186 s8tasntadnadrdar sdamsapmlepsl.e s. Preparation of the C-PP/PE Sample with Different Concentrations of Irgafos P-168 Preparation of the C-PP/PE Sample with Different Concentrations of Irgafos P-168 The C-PP/PE samples with Irgafos P-168 were prepared following the procedure desTchrieb Ced-PiPn/PFEig suarmep3l,ews whiicthh Ihrgadafoths eP-f1o6ll8o wweinreg psrteapgaesre: d( 1f)ol0lo.0w, i0n.5g, t1h,e 1p.5ro, caenddur2e.0 dge-of scrIribgeadfo isn PF-i1g6u8rew 3e, rwe hwicehig hhaedd tihne qfoulalonwtitiinegs sintadgievsi:d (u1a) l0ly.0. , (02.5) ,T 1o, 1e.a5c, hanodf 2th.0e gq oufa nIrtgitaifeosso f P-I1r6g8a fwoserPe- 1w6e8i,g1hkegd oinf vqiurgainntiCti-ePsP i/nPdEivridesuianllwy.a s(2a)d Tdoe dea. c(3h) oMf itxhteu rqeusawnteirteieps roefm Irixgeadfows iPth- a 16s8t,a 1n kdga rodf Pvrirogdienx Cm-PixPe/rP,EH reenssinch wela1s 1a5dJdSSe,da. t(38)0 M0 ripxtmurfeosr w7emrein p.r(e4m) Nixeexdt ,weiatchh as satmanpdlearwda s Prmodixexed mwixitehr, aHWeneslecxh-e2l0 101254JS.1S,e axtt r8u0d0e rrpemqu fioprp 7e dmwinit. h(4fi) vNeetxetm, epaecrha tsuarme zpolen ewsaisn mitsixpedat h. wiTthh ea tWemelpexer-2a0tu0r 2e4s.1u seexdtruwdeerre e1q9u0i,p1p9e5d, 2 w00it,h2 fi10v,e2 t1e0m, panerdat2u2r0e ◦zCo.nTesh iisn pitrso pceasths.g Tuhaer atenmte-ed peurantiuforrems udsiesdtr wibeurteio 1n90o,f 1t9h5e, m20i0x,t u21re0., (251)0F, iannadll y2,2f0r o°Cm. eTahcihs ptyrpoeceosfs mguealtr,a2n0tegeodf umnaifsosrwma s disfetrdibinuttoioanC oAf tRhVeE mRix3t8u9r5eh. o(5t)p Friensas.llIyn, ftrhoismC eAaRchV EtyRpme oafc hmineelt,, t2h0e gs aomf mplaesssw weares cfeodm ipnrteos sae d CAuRntVilEfiRl m38s9350 0homt mprienssd. iaInm tehtiesr CwAitRhVaEthRi cmknacehssinoef, ≈th1e0 0saµmmpwlese rwe eorbet acionmedp.rTeshseedre suunlttiiln g J. Compos. Sci. 2024, 8, x FOR PEER fiRlEmfiVlsmIE 3Ws0i0 n mthme einx pdeiarimeetnetr wweitrhe aid tehnictkifineedssa osfC ≈-1P0P0/ µPmE (w0eprpe mobotafiInregda.f oTshPe- r1e6s8u)l,tCin-gP Pfi/lmPEs 25 of 22 in (5th0e0 epxppmeroimf Ierngat fwoserPe- 1i6d8e)n, tCifi-PedP /aPsE C3-P(1P0/0P0E p(p0 mppomf I rogfa IfrogsaPfo-1s6 P8)-,1C68-P), PC/-PPEP/4P(E1 520 0(5p0p0 m ppomf I rogf aIfrogsaPfo-1s 6P8-)1, 6a8n)d, CC--PPPP//PPEE 35 ((12000000 ppppm ooff IIrrggaaffooss PP--116688))., C-PP/PE 4 (1500 ppm of Irgafos P-168), and C-PP/PE 5 (2000 ppm of Irgafos P-168). FFiigguurree 33.. PPrreeppaarraatitoionno foCf -CP-PP/PP/EPEsa smamplepslews iwthidthif fdeirffenetrecnont cceonntcraetniotrnastioofnIrsg oaff oIsrgPa-f1o6s8 .P-168. Extraction of Irgafos P-168 in C-PP/PE Samples Figure 4 presents the methodology used in this research to extract Irgafos P-168 from C-PP/PE samples in ground form, pellets, and films, to which Irgafos P-168 had been added. Solid–liquid extractions were carried out using two different solvents, dichloro- methane and Limonene. These extractions were performed using three methods: Soxhlet, ultrasound (conventional laboratory sonic bath), and microwave oven (high-power pro- grammable laboratory microwave oven), and a mass-coupled gas chromatograph was used to quantify the concentration of Irgafos P-168 and the degradation products present in the C-PP/PE film samples. In preliminary tests, it was identified that 90, 50, and 117 °C were the optimal temperatures for working with Soxhlet, ultrasound, and microwave, re- spectively. Therefore, this variable was left fixed in our experimental design, and thus, we could evaluate how other variables affect the extraction efficiency. Figure 4. Extraction of Irgafos P-168 by Soxhlet, ultrasound, and microwave and quantification by GC-MS. J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 5 of 22 J. Compos. Sci. 2024, 8, 156 5 of 21 Figure 3. Preparation of C-PP/PE samples with different concentrations of Irgafos P-168. EExtxrtarcatciotino nofo IfrgIragfoasfo Ps-1P6-81 6in8 iCn-PCP-/PPPE/ SPaEmSpalmesp les FiFgiugruer 4e p4rpesrensetsn thset hmeemtheotdholdooglyo ugsyeud siend thinis trheissearercshea troc ehxtoraecxt tIragcatfoIrsg Pa-f1o6s8P fr-1o6m8 from CC-P-P/PP/EP Esasmamplpesle isni nggroruounndd foformrm, ,ppeelleletsts, ,aanndd fifillmss,, to whiich IIrrggaaffooss PP-1-16688h haaddb ebenena dded. adSdoleid.– Slioqluidi–dlieqxutirda cetxiotrnasctwioenrse wcearer iceadrroieudt uosuitn ugstiwngo tdwioff edrieffnetresnotl vseonlvtes,ndtsi,c dhilcohrloomroe-thane maentdhaLniem aonnde Lneim. Tohnesne .e Txthreascet ieoxntsrawcteiorensp ewreforerm perdfoursminegd tuhsrienegm therteheo mdse:tShoxdhs:l eSto, xuhltlreat,s ound u(lctroansovuendti o(cnoanlvlaenbtoiorantaolr lyabsoornaitcorbya tsho)n,ica nbdathm),i carnodw maviceroowveanve( hoivgehn- p(hoiwghe-rpopwroegr rparmo-mable grlaabmomraatbolrey lmabicorroawtoaryv emoivceronw),aavned oavmena)s, sa-ncodu ap lmedasgsa-scocuhprolemd agtoags rcahprhomwaatsougrsaepdht owqaus antify utshede ctoo nqcueannttrifayti tohne ocof nIrcgeanftorastPio-n1 6o8f Iarngdaftohs ePd-1e6g8r aandda ttihoen dpergordaduacttisopnr persoednut cints tphreesCe-nPt P/PE infi tlhme Csa-PmPp/PleEs .filImn sparmelpimlesi.n Ianr yprteelismtsi,niatryw taesstisd, ietn wtiafise iddetnhtaifit e9d0 ,th5a0t, 9a0n, 5d0,1 a1n7d◦ 1C17w °Cer e the woepreti tmhea lotpetmimpaelr taetmurpeesrfaoturrweso frokri nwgowrkiitnhgS woxithhl eSto,xuhllterta, suolutrnadso,uanndd, manidcr mowicarovwe,arvees,p reec-tively. spTehcetirveefolyr.e T, htheriesfovraer,i tahbilse vwaraiasbllee fwt afisx leedft ifinxeodu irne oxupre erximpeernimtaelndtaels digensi,gann, adndth tuhsu,sw, weec ould coeuvladlu eavtaeluhaotwe hootwhe ortvhaerr ivaabrlieasbalefsfe acfftethcte thexe terxatcrtaioctnioenf fiecffiiecniecnyc. y. FiFgiugruer 4e. 4E.xtEraxctrtiaocnt ioofn IrogfaIfrogsa Pfo-1s68P -b1y6 8SobxyhlSeot,x uhllterat,souultnrda,s oanudn dm, iacrnodwmaviec raonwd aqvueanatnifidcqatuioann tbifiy cation GbCy-MGSC. -MS. For microwave extraction, 5 g of C-PP/PE resin was extracted using a solution of dichloromethane and Limonene. It was determined that heating the solution in the mi- crowave oven at 25–50% power for 45 min, stirring every 5 min, was sufficient to extract the antioxidant. Four different extractions were performed with the resin, pellets, and ground C-PP/PE, and the average results of the ultrasound, Soxhlet, and microwave extractions are presented in Table 1 and Figure 5. Concentrations are expressed in parts per million (ppm). Percentages indicate recovery relative to an initial concentration of 500 ppm. Table 1. Experimental design of the extraction of Irgafos P-168 with different extraction techniques, different solvents, and different types of C-PP/PE. Irgafos 168 Recovery Rate (%) Technique Time (min) Temperature Solvent Form of C-PP/PE 2 C-PP/PE 3 C-PP/PE 4 C-PP/PE 5C-PP/PE 500 1000 1500 2000 Soxhlet 1440 90 Dichloromethane Pellets 69.98 71.76 73.56 73.83 Soxhlet 1440 90 Dichloromethane Film 72.44 76.38 76.04 77.42 Soxhlet 1440 90 Dichloromethane Ground 77.4 79.92 77.35 79.88 J. Compos. Sci. 2024, 8, 156 6 of 21 Table 1. Cont. Irgafos 168 Recovery Rate (%) Technique Time (min) Temperature Solvent Form of C-PP/PE 2 C-PP/PE 3 C-PP/PE 4 C-PP/PE 5C-PP/PE 500 1000 1500 2000 Soxhlet 720 90 Dichloromethane Pellets 47.52 61.14 61.15 59.75 Soxhlet 720 90 Dichloromethane Film 54.68 64.42 64.67 62.81 Soxhlet 720 90 Dichloromethane Ground 59.96 69.36 67.53 67.46 Soxhlet 1440 90 Limonene Pellets 68.04 69.9 72.47 72.21 Soxhlet 1440 90 Limonene Film 69.68 74.5 74.71 76.87 Soxhlet 1440 90 Limonene Ground 74.44 77.92 75.13 79.14 Soxhlet 720 90 Limonene Pellets 45.36 59.52 59.4 58.76 Soxhlet 720 90 Limonene Film 51.84 61.96 63.41 61.15 Soxhlet 720 90 Limonene Ground 56.56 67.76 65.59 66.09 Ultrasound 90 50 Dichloromethane Pellets 73.84 76.2 79.25 77.83 Ultrasound 90 50 Dichloromethane Film 75.84 79.62 84.72 82.36 Ultrasound 90 50 Dichloromethane Ground 92.04 88.9 93.24 92.76 Ultrasound 60 50 Dichloromethane Pellets 65.48 66.3 67.77 66.09 Ultrasound 60 50 Dichloromethane Film 67.92 71.8 73.8 70.41 Ultrasound 60 50 Dichloromethane Ground 78.84 75.46 78.89 78.96 Ultrasound 90 50 Limonene Pellets 70 74.94 77.11 76.24 Ultrasound 90 50 Limonene Film 72.84 78.24 82.65 80.23 Ultrasound 90 50 Limonene Ground 89.56 87 92.05 90.23 Ultrasound 60 50 Limonene Pellets 62.6 64.3 66.25 64.31 Ultrasound 60 50 Limonene Film 65.56 69.86 71.88 69.87 Ultrasound 60 50 Limonene Ground 75.88 73.08 76.73 76.25 Microwave 45 117 Dichloromethane Pellets 77.4 78.32 82.73 79.74 Microwave 45 117 Dichloromethane Film 83.6 83.66 88.8 83.91 Microwave 45 117 Dichloromethane Ground 96.2 94.34 97.01 96.71 Microwave 25 117 Dichloromethane Pellets 70.32 69.7 72.07 68.25 Microwave 25 117 Dichloromethane Film 73.88 74.04 77.35 73.19 Microwave 25 117 Dichloromethane Ground 84.72 78.54 80.64 81.86 Microwave 45 117 Limonene Pellets 74.4 76.48 81.36 78.58 Microwave 45 117 Limonene Film 80.32 81.84 87.09 82.48 Microwave 45 117 Limonene Ground 91.88 89.78 94.72 94.94 Microwave 25 117 Limonene Pellets 65.12 66.98 70.57 65.52 Microwave 25 117 Limonene Film 68.4 71.48 75.32 71.23 Microwave 25 117 Limonene Ground 78.44 75.44 78.91 80.09 For the ultrasonic bath, 3 g of C-PP/PE placed in a 20 mL vial were used. Next, 10.0 mL of an internal standard solution was added using a 5.0 mL micropipette, as shown in Figure 4. Each test was replicated five times, and sonication was carried out for three hours in an ultrasonic bath, keeping the temperature under control, below 50 ◦C. After completion of sonication, the vials were removed from the bath and allowed to stand for 10 min before filtration of the extracted Irgafos P-168 sample solutions using disposable PTFE syringe filters. The extraction was carried out in three ways: ground C-PP/PE, pellets, and films. In the case of ground C-PP/PE, the extraction lasted for 90 min, while, for C-PP/PE pellets and films, it was carried out for 60 min in the ultrasonic bath. During extraction, the solution was shaken for at least 30 s every 10 min. Notably, the microwave oven was revealed as a fast and effective method to extract Irgafos P-168 from the crushed resin, while the ultrasonic bath provided an economical and relatively fast alternative for extracting the additives. In contrast, the Soxhlet extraction method with these C-PP/PE resins required at least 7 h to extract most of the additives. In this study, Soxhlet extraction was extended for 1440 and 720 min, suggesting that it would possibly require more than 24 h to recover the additive completely. J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 7 of 22 Ultrasound 60 50 Limonene Film 65.56 69.86 71.88 69.87 Ultrasound 60 50 Limonene Ground 75.88 73.08 76.73 76.25 Microwave 45 117 Dichloromethane Pellets 77.4 78.32 82.73 79.74 Microwave 45 117 Dichloromethane Film 83.6 83.66 88.8 83.91 Microwave 45 117 Dichloromethane Ground 96.2 94.34 97.01 96.71 Microwave 25 117 Dichloromethane Pellets 70.32 69.7 72.07 68.25 Microwave 25 117 Dichloromethane Film 73.88 74.04 77.35 73.19 Microwave 25 117 Dichloromethane Ground 84.72 78.54 80.64 81.86 Microwave 45 117 Limonene Pellets 74.4 76.48 81.36 78.58 Microwave 45 117 Limonene Film 80.32 81.84 87.09 82.48 Microwave 45 117 Limonene Ground 91.88 89.78 94.72 94.94 Microwave 25 117 Limonene Pellets 65.12 66.98 70.57 65.52 Microwave 25 117 Limonene Film 68.4 71.48 75.32 71.23 MiJc.rCoowmpaosv. eS ci. 2024, 82, 155 6 117 Limonene Ground 78.44 75.44 78.91 870o.0f 921 Recovery rate of Irgafos 168 (%) in films samples Recovery rate of Irgafos 168 (%) in ground samples C-PP/PE2 C-PP/PE3 C-PP/PE4 C-PP/PP5 DCM LIM C-PP/PE2 C-PP/PE3 C-PP/PE4 C-PP/PP5 90 DCM LIM100 Technique 85 MAE 95 Technique SOX MAESOX ULT 90 ULT 80 85 75 80 70 75 C-PP/PE2 C-PP/PE3 C-PP/PE4 C-PP/PP5 C-PP/PE2 C-PP/PE3 C-PP/PE4 C-PP/PP5 Recovery rate of Irgafos 168 (%) in pellets samples C-PP/PE2 C-PP/PE3 C-PP/PE4 C-PP/PP5 DCM LIM 100 95 Technique MAE SOX 90 ULT 85 80 75 70 C-PP/PE2 C-PP/PE3 C-PP/PE4 C-PP/PP5 FigFuigrue r5e. 5G. rGarpahpihci crerepprreesseennttaattiioonn ooff tthhee eexxtrtraacctitoionno foIfr gIragfoasfoPs- 1P6-816w8i twh idthif fderieffnetrteencth nteiqchunesi,qduieffse, rdenifft er- ents oslovlevnetnst,sa,n adndi fdfeiffreenrtentytp teyspoefs Co-fP CP-/PPPE/.PE. 2.3. Multivariate Graphical Analysis 2.3. Multivariate Graphical Analysis This study conducted a graphical analysis to examine the recovery of the antioxidant IrgTafhoiss Pst-1u6d8yi ncotnheduCc-PtePd/ aP Egrsaapmhpicleasl. aMnainlyitsaibs stota etixsatimcailnseo ftthwea rreec,owviedreyl yofr etchoeg annizteiodxfiodrant Irgitasfoasb iPli-t1y6t8o inp etrhfeo rCm-PaPd/vPaEn cseadmsptlaetsis. tMicainl iatnaabl ysstaetsi,swticaasl ussoefdtwtaorcea, rwryidoeulyt trheicsoagnnailzyesdis .for itsS ainbcileittyh etos tpuedryfoinrmvo lavdevsamncueltdip slteavtiasrtiiacabll easn, asulycshesa,s wthaes duifsfeedre tnot ecxatrrrayc toiount ttehcihs nainqauleyssis. Sin(Scoex thhlet ,sutultdrays oinunvdo,lvaensd muiclrtoipwlaev vea),rtihaeblseosl,v esnutcshu asesd th(dei cdhilfforeormenett heaxnteraacntdioLni mteocnhennieq)u, es and the types of C-PP/PE (ground, pellets, and films), a multivariate graphical analysis was performed. This made it possible to identify the existing relationships between the various extraction techniques, the solvents, and the C-PP/PE forms to extract Irgafos P-168. 3. Results and Discussion 3.1. Quantification and Recovery of the Additive Irgafos P-168 by GC For the analysis of Irgafos P-168 in the C-PP/PE samples, an internal standard method was implemented to check the validity of the GC-MS method. It should be noted that both the standard solutions and the samples were analyzed in duplicate to guarantee the precision of the results. The calibration curve demonstrated excellent linearity within the established range, with a coefficient of determination greater than 0.999. In the experimentation of this study, four different concentrations of Irgafos P-168 solutions were prepared using an internal standard (500, 1000, 1500, 2000 ppm). Following the procedure described in Section 2, GC-MS analyses were performed on Irgafos P-168 Recovery rate (%) Recovery rate (% ) Recovery rate (% ) J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 8 of 22 (Soxhlet, ultrasound, and microwave), the solvents used (dichloromethane and Limo- nene), and the types of C-PP/PE (ground, pellets, and films), a multivariate graphical anal- ysis was performed. This made it possible to identify the existing relationships between the various extraction techniques, the solvents, and the C-PP/PE forms to extract Irgafos P-168. 3. Results and Discussion 3.1. Quantification and Recovery of the Additive Irgafos P-168 by GC For the analysis of Irgafos P-168 in the C-PP/PE samples, an internal standard method was implemented to check the validity of the GC-MS method. It should be noted that both the standard solutions and the samples were analyzed in duplicate to guarantee the pre- cision of the results. The calibration curve demonstrated excellent linearity within the es- tablished range, with a coefficient of determination greater than 0.999. In the experimentation of this study, four different concentrations of Irgafos P-168 solutions were prepared using an internal standard (500, 1000, 1500, 2000 ppm). Following the procedure described in Section 2, GC-MS analyses were performed on Irgafos P-168 extracts obtained from C-PP/PE samples in various forms, such as ground C-PP/PE, C- PP/PE pellets, and C-PP/PE film. J. Compos. Sci. 2024, 8, 156 8 of 21 Multiple extraction techniques were used to evaluate the recovery of Irgafos P-168, including Soxhlet, ultrasound, and microwave, along with two different solvents, di- extracts obtained from C-PP/PE samples in various forms, such as ground C-PP/PE, chloromethane, aCn-PdP/ LPEimpeollentse, naned.C I-nPP a/dPEdfiiltmio. n, different forms of C-PP/PE were worked with, that is, ground, pelMleutlsti,p laenexdtr afictliomn ,t eachnndiq utehs ew eerexutrseadcttoioenva ltuiamte ethse wreceorveer yvoafrIiregdafo. sTPo- analyze the 168, including Soxhlet, ultrasound, and microwave, along with two different solvents, results effectiveldyi,c halo rvomareithaabniel,iatnyd Lgimraopnehne w. Inaasd dciotionns, tdrifufecretnetdfo rtmhsaotf Ca-lPlPo/wPEewde rtehweo rikdedentification of differences in thwei tmh, tehaatniss, garonudnd ,vpaelrleitas,taiondnfisl mi,na nadnthteioexxtriadctaionntt imreecs owvereervyar ieadt. To analyzethe results effectively, a variability graph was constructed that allowed thetihdeen tcifiocam- bined levels (Figure 6). tion of differences in the means and variations in antioxidant recovery at the combined levels (Figure 6). Figure 6. Average Friegucroev6e. ryA voerfa gIregreacfoovesr yP-o1f 6Ir8ga ffoosr Pm-16i8crfoorwmaicvroew, aSvoe,xShoxlehlte,t ,aanndd uultlrtarsaousnoduwnidth with dichloro- methane (DCM) andidch lLoriommeothnaenen(eD C(MLI)Mand).L imonene (LIM). Figure 6 shows the relationship between the recovery percentage of Irgafos P-168 and Figure 6 shotwhe sp rtehvieou rselylamteinotinonsehdivpa riables. The results highlight that the microwatechnique achieves the highestbreectowveeryepner tcheneta greescwohvenerapyp plieedrfcore4n5tmaig vee extractionn an odfg rIorugnadfos P-168 and the previously mCe-PnPt/iPoEnweads uvseadr. iFaubrtlheersm. oTreh, neo rseigsnuifilctasn thdiifgfehrelnicgehs wt etrhe oabts etrhveed mbetiwcereonwtraa-ve extraction ditional and green solvents since the recovery percentages remained close. Specifically, technique achievdeicsh ltohroem hetihganheersecto rveercedo9v6e.0r7y% ,pwehrilceeLnimtoangeneeso wbtahineedn9 a2.p83p%l.ied for 45 min and ground C-PP/PE was used. FThuerutlthraesroumndotreech,n niqoue soibgtaniniefidcoaptnimt adl rieffsueltrsewnitcheasn ewxtrearcteio on btimsee rovf 9e0dm ibn,etween tradi- using ground C-PP/PE with the traditional solvent dichloromethane (91.74%) and Limonene tional and green( 8s9o.7l1v%e).nTthse dsiiffnerceenc ethbetw reeencothveseersyol vpenetrscreemnatinasgmeinsi mrealm, reagainrdeledss ocfltohseex.t rSapc-ecifically, di- chloromethane rteiocnotvecehnrieqdue 9u6se.d0.7%, while Limonene obtained 92.83%. Lastly, the extraction performed by Soxhlet obtained lower recovery results than The ultrasouthnedm itcerocwhanveiqanudeu lotrbastoauinndetdec honpiqtuiems. aThl erheisghuelsttsp ewrceitnhta gaens a echxietvreadcwtiiothnth tiisme of 90 min, using ground C-tPecPhn/iPquEe owcciutrhre dthate1 4t4r0amdinit,i7o8.n64a%l ussoinlgvdeinchtl odroimcehthloanreoams aesothlvaennt ean (d9g1ro.7un4d%) and Limo- C-PP/PE, and 76.66% with Limonene in ground C-PP/PE. nene (89.71%). The dWitffh evreerynthcieng bmeetnwtioneeedna btohve,sitec asnobelvsteatnedtsth arteumsinagignrosu nmd Cin-PiPm/PaEli,n srteagdardless of the extraction technioqfufoerm us sofeCd-P. P/PE in films and pellets can improve the recovery results of Irgafos P-168due to the larger contact surface, more excellent permeability, smaller size of particles, and greater homogeneity of the material. Furthermore, the results indicate that better recoveries were obtained using microwave extraction than ultrasound and Soxhlet techniques. This can be explained by the microwave extraction technique, which selectively heats the solvent and the sample. This allows for faster and more efficient heat transfer, speeding up the extraction process. By contrast, ultrasound and Soxhlet techniques may require more time to reach the appropriate temperature and achieve complete extraction, as demonstrated in the experimental design, since Soxhlet extraction requires 1440 min to achieve good recoveries. They are significantly below the recovery percentages obtained by microwave, which only J. Compos. Sci. 2024, 8, 156 9 of 21 took 45 min. Another relevant aspect that supports the effectiveness of the microwave extraction technique is its ability to generate more intense agitation and turbulence in the sample. This improved agitation facilitates the interaction between the solvent and the analyte, thus simplifying the extraction of Irgafos P-168 and improving recovery efficiency. As is known, the microwave extraction technique achieved comparable or better results in a shorter extraction time compared to ultrasound and Soxhlet techniques. A shorter extraction time can minimize analyte degradation or loss and improve recovery, as seen in Section 2. In addition, it allows greater control of extraction conditions, such as temperature and pressure. This allows conditions to be optimized to maximize the recovery of Irgafos P-168 and minimize any possible interference or degradation of the analyte. The dichloromethane solvent showed higher recovery percentages; however, the dif- ference was insignificant enough to rule out Limonene as a green solvent option completely. In these cases, it is essential to consider Limonene’s additional benefits, such as lower environmental impact and toxicity. The choice of solvent depends on other factors, such as current environmental regulations, specific application requirements, and personal or company preferences. Choosing a solvent such as Limonene is an ideal option for those who value sustainability and seek to minimize environmental impact. In previous studies, Camacho et al. [36] have already used microwave extraction to evaluate the quality of resins such as polypropylene and low-density polyethylene (LDPE) in recycled resins and successfully extracted phenolic antioxidants such as Irgafos P-168 and Irganox 1010 using a mixture of 50/50 cyclohexane and isopropanol solvents, obtaining high recovery percentages of 97% for Irgafos P-168 and 93% for Irganox 1010. In addition, it is essential to mention that short extraction times of 30, 45, and 60 min were used with extraction temperatures of 70, 100, and 120 ◦C in the development of the method. The previously mentioned study and the present research work have achieved high re- covery percentages by applying various techniques and solvents. Within the framework of this research, some recovery percentages have been obtained that exceed the 90% threshold in the case of the conditions evaluated by microwaves and ultrasound, using both solvents, different extraction times, and different forms of the polymer. It is essential to highlight that the experimental conditions have differed between these studies, including aspects such as the type of polymer used, the particle size, the solvent combinations, and the time intervals used in the extraction process. These variations influence the results, making it difficult to compare the investigations directly. 3.2. Identification of Irgafos P-168 by Gas Chromatography Coupled to Mass Spectrometry (GC-MS) Analysis The primary purpose of extracting Irgafos P-168 was to obtain the maximum possible amount of the original substance while minimizing the presence of relevant contaminants. However, it is crucial to consider that during this process, there is a possibility of Irgafos P- 168 experiencing degradation, which could result in a decrease in recovery percentages. To address this concern, subsequent analyses of the Irgafos P-168 recovered in the extractions were conducted using gas chromatography coupled with mass spectrometry (GC-MS) to examine the potential formation of degradation products. The degradation products generated may pose challenges both in their recovery and detection during the analytical process. The application of the GC-MS technique allowed for the precise identification of these degraded products, thereby providing crucial information to assess whether Irgafos P- 168 had undergone significant degradation. When interpreting the obtained data, previous knowledge that the analyzed compounds were specific degradation products of Irgafos P- 168 was taken into account (Figure 7). These research findings are of paramount importance in understanding the potential effects of degradation on the quality and integrity of the compound. Furthermore, they significantly contribute to advancing knowledge in this field by providing a deeper understanding of degradation processes and their implications in the practical application of Irgafos P-168. J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 10 of 22 However, it is crucial to consider that during this process, there is a possibility of Irgafos P-168 experiencing degradation, which could result in a decrease in recovery percentages. To address this concern, subsequent analyses of the Irgafos P-168 recovered in the extrac- tions were conducted using gas chromatography coupled with mass spectrometry (GC- MS) to examine the potential formation of degradation products. The degradation prod- ucts generated may pose challenges both in their recovery and detection during the ana- lytical process. The application of the GC-MS technique allowed for the precise identifica- tion of these degraded products, thereby providing crucial information to assess whether Irgafos P-168 had undergone significant degradation. When interpreting the obtained data, previous knowledge that the analyzed compounds were specific degradation prod- ucts of Irgafos P-168 was taken into account (Figure 7). These research findings are of par- amount importance in understanding the potential effects of degradation on the quality and integrity of the compound. Furthermore, they significantly contribute to advancing J. Cokmnpoos.wScil. e20d24g, 8e, 1 5i6n this field by providing a deeper understanding of degradation processes 10 of 21 and their implications in the practical application of Irgafos P-168. Figure 7. IdentificationF ioguf rIerg7.afIdoesn Ptifi-c1a6ti8o nbyof gIragsa fcoshPro-1m68abtyoggarsacphhroym caotougrpalp(GC-MS) analysis. e hdy ctoou mpleadssto smpaescstsrpoemctreotmryet r(yGC- MS) analysis. Antioxidants play a crucial role in preserving copolymers like C-PP/PE, posing a Antioxidants plsaigyn iafi ccarnut cchiaalll ernogleea tinth pe irnedsuesrtrviailnlgev celowphoelnytmheeyrusn ldiekrego Cth-ePrPmo-oxidative degra-dation. This phenomenon not only compromises the durability and ph/PysEic,a pl iontseignrigty ao fsig- nificant challenge ath tehpeo lyinmderubsuttrailasol hloelvdes ls igwnihficeann ttimhepylic autinondsegrivgeon itshfienraml aop-policxaitdioantiinvdei redcet fgoroadda- tion. This phenomencoonnta nctopta coknaglyin gc.oImn tphirsocmonitsexets, Itrhgaef odsuP-r1a6b8 iilsistuys caenptdib plehtoyosxicidaalt iivnetdeeggrraitdyat ioofn the during solid–liquid extraction processes, especially in the presence of specific solvents such polymer but also hoalsdLsim soingenneifiancdanditc hilmoropmliecthaatnioe.nTsh igs ivvuelnner aitbsil ifitynaarils eas pfropmlicthaetciohenm iicna ldpriorpeecrtt iefsood contact packaging. Ionf Irtghaifso scPo-1n6t8eaxntd, Iitrsgiantfeorasc tPio-n16w8it histh seusesmceenpttioibneled stool voenxtisd. aDtuirvineg dexetgrarcatidonast,ion during solid–liquid IregxaftorsaPc-t1i6o8nm apyrboeceexspsoesesd, teosenvironmental conditions conducive to oxidation, includ-ing the presence of oxygen and vpaericaitiaolnlsyi ninte mthpeer apturrees. eSnolcveen otsfl iksepLeicmifionce nseoalvndents such as Limonene anddich dloircohmleothraonme ceatnheaxnacee.r bTahteitsh ivsuprloncesrsabbyidliitsyso alvrinisgeasn dfrtoramns ptohreti ncghIergmafoicsaPl- 1p68r,op- erties of Irgafos P-1t6h8e reabnydin ictrsea isnintgeirtsaecxtpioosnu rwe tiothox itdhaetisvee cmonednittioionsn. eTdhe sooxildvaetinontso.r Ddeugrraindagti oenxotfrac- tions, Irgafos P-168 mIrgaafyo sbPe-1 e68xdpuorisnegdth teose eenxtvraicrtoionnsmcaennhtaavle significant implications for its efficacy andquality. The resulting degradation products mcoaynbdeitcihoanllesn cgionngdtoudceitveect taon dorxeicdovaetri,on, including the presenpoctee notifa lolyxiymgpeacnti nagnthde vpuarriityatainodnesff eicnti vtenmesps oefrIargtauforse.P -S1o68lvineintstfisn lailkaep pLliicmation.ene and dichloromethane caThne reexfoarec,eirt bisaimtep etrhaitisv eptrooccoenssisd ebryth edsiussscoeplvtibiniligty aonf Idrg atrfoasnPs-1p6o8rtotionxgid aItrigonafos or degradation when conducting solid–liquid extractions involving this compound along P-168, thereby increwasitihnsgo livtesn tesxspucohsausrLeim toon oenxeidanadtidviech clooronmdeitthiaonnes. .I tTishnee coexssiadryattoioinm polerm deengt arpa-da- tion of Irgafos P-168p drouprriiantegm tehaesusree setxotrmaicntimioiznese cxapons uhrae vtoec soingdnitiiofincsatnhatt ipmropmloicteadtieognrasd aftoiorn itasn deffi- cacy and quality. Thenes urreesthueltcionmgp odunedg’sraindteagtriitoy,nb opthroindinudcutsstr imal aanyd rbeese acrhchaallpepnlicgaitniogns .tFou rdthermore,it is important to note that the oxidative degradation of Irgafos P-168 can resulettienctth eand formation of compounds with different properties, such as the generation of more polar compounds. These modified compounds may have a lower affinity for the solvents used J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 11 of 22 recover, potentially impacting the purity and effectiveness of Irgafos P-168 in its final ap- plication. Therefore, it is imperative to consider the susceptibility of Irgafos P-168 to oxidation or degradation when conducting solid–liquid extractions involving this compound along with solvents such as Limonene and dichloromethane. It is necessary to implement ap- propriate measures to minimize exposure to conditions that promote degradation and en- sure the compound’s integrity, both in industrial and research applications. Furthermore, it is important to note that the oxidative degradation of Irgafos P-168 can result in the formation of compounds with different properties, such as the generation of more polar compounds. These modified compounds may have a lower affinity for the solvents used in extraction, which could hinder their separation from the C-PP/PE polymer and, conse- quently, reduce the extraction yield. Considering various factors that can influence the oxidative degradation of Irgafos P-168, such as temperature, the presence of catalysts, the duration of the extraction process, and the storage conditions of the C-PP/PE copolymer, J. Compos.iSsci .e20s2s4e, 8n, 1t5i6al. Increased oxidative degradation of Irgafos P-168 may indicate a le11sosf 2e1fficient extraction process and, therefore, lower yield. Therefore, measures should be taken to minimize the oxiindeaxttirvacet idone,gwrhaidchactoioulnd ohifn Idregr athfeoirs sPep-1ar6a8ti odnufrroimngth tehCe- PePx/tPrEacptoiloymn eprraondce, csosn a- nd the storage of the cospeqouleynmtlye, rre,d iunc eotrhde eexrt rtaoc toion yield. Considering various factooxidative degradation of IrgafopstPim-16i8z, esu echxtarsatecmtipoenra tpuerer,ftoherm rs prea thnasenc t ce c.a ne oT ihnfluf caeta e lrye nsceutlhests, thtes of this study suggest thdautr amtioenaosfuthreinexgt rtahcteio ndpergorceses ,oanf dotxhiedstaotriavge cdonedgirtiaondsaotfiothne Co-fP PIr/gPEafcopso Ply-m1e6r8, in the copolymer indiriescestslyen tpiarl.oIvncidreeasse daonx iadsatsievessdmegerandta toiofn tohf eIr geaxfotsrPa-c1t6i8omna ypienrdfiocartme aalnescsee ffiocfi etnhte com- extraction process and, therefore, lower yield. Therefore, measures should be taken to pound in said pomliynimeizre. the oxidative degradation of Irgafos P-168 during the extraction process and An illustrattihoens toisra pgerofvtihdeecodp oinly mFeigr, uinroer d8e rtoto colpatirmifiyze tehxter adcteiognrpaedrfaotrimoann cpe.rTohceersesseuslt,s sohf owing how the breakintgh ios fs ttuhdey (sPugOge)s bt tohnatdm aenasdu rtihng the degree of oxidative degradation of Irgafos P-168in the copolymer indirectly providee tsearnt-abssuestsyml emnteotfhthyel edxtirpachtieonnyple rgforromuapncse coofmtheplicates the complete reccoovmeproyu nodf iInrsgaaidfoposl yPm-1er6. 8. This difficulty arises because a part of the molecule is lost due to fragmeAnntialltuisotrna,ti olenaisdpirnogvi dtoed tihneF ifgourrem8atoticolanri foyft hme doelgercaudaletiso nwpriothce spserso, psheorwtiinegs differ- ent from the orighoiwnathl eabnretaiokixngidoaf nthte. (APOd)dbointid and thethe complete recovery of Irgafos P-o1n68a. lTlhyi, tert- s dTiaffib bu clue ty lt l m y2a p et risr h ee y ss lednipthse nay ldgerotuapilsecomplicatebecause a part of thde mporleocfiull s ee of the degradation of Iirsgloasftodsu ePt-o1f6r8ag. mTehnitast iponr,olfiealdei nignctoluthdeefso rtmhaeti ornecoof mveorleycu pleesrwciethntparogpee rotife sedaicf-h com- pound obtainedf ertehnrtofruomghth ethoeri gfinraalgamntieonxitdaatnito. nA dodfit iotnhaell yc, rTuabcleia2l pbreosenndtssa pderteasileednpt roinfil etohfe com- the degradation of Irgafos P-168. This profile includes the recovery percentage of each pound’s structurcoem. Tpohuinsd doebttaiinleed t hinrofuogrhmthaetfiroangm pernotavtiiodneosf tah emcrourciea lcboomndps rperehseentsinivtehe vcioemw- of the resulting degradpoautniodn’s stprurcotudrue.cTthsi sadnetdai letdhienifro rmreastiponecptriovveid erseacmoovreercyom rparetheesn, sicvoe nviterwibouf tthieng to a deeper understarnesduiltningg doefg trhadea teioffnepcroducts and their respective recovery rates, contributing to a deeperunderstanding of the efftesct sooff ddeeggrraadadtiaotnioonnt hoeno rtihgien aolrciogmipnoauln cdo. mpound. Figure 8. RecovereFdig uIrreg8a. fRoesco Pve-r1e6d8Ir fgraafogsmP-1e6n8tfaratgiomnen mtateiocnhmaencihsamnis.m . J. Compos. Sci. 2024, 8, 156 12 of 21 Table 2. Degradation profile of Irgafos P-168 in different solvents. % Area under the Degradation by-Product Curve P-168 Bis(di- Mono(di- 2.4-Di- tertbuty tertbutyl Tecnhique Time Temperature Solvent Form of tertbut 2-Tert- 4-Tert- Phosphate(min) C-PP/PE ylphenol butylphenol butylphenol of P-168 lphenyl) phenyl) P-168 Phos- Phos- phate phate Soxhlet 1440 90 Dichloromethane Pellets 0.6 0.5 0.1 0.4 0.7 0.9 72.28 Soxhlet 1440 90 Dichloromethane Film 0.9 0.8 0.9 0.9 1.2 1.3 75.57 Soxhlet 1440 90 Dichloromethane Ground 0.6 0.6 0.15 0.51 0.7 0.9 78.64 Soxhlet 720 90 Dichloromethane Pellets 0.25 0.15 0.06 0.1 0.31 0.42 57.39 Soxhlet 720 90 Dichloromethane Film 0.41 0.38 0.52 0.67 0.82 0.69 61.64 Soxhlet 720 90 Dichloromethane Ground 0.28 0.17 0.1 0.11 0.33 0.46 66.08 Soxhlet 1440 90 Limonene Pellets 0.42 0.38 0.84 0.31 0.62 0.82 70.65 Soxhlet 1440 90 Limonene Film 0.82 0.76 0.84 0.79 0.95 1.12 73.94 Soxhlet 1440 90 Limonene Ground 0.52 0.53 0.09 0.37 0.58 0.86 76.66 Soxhlet 720 90 Limonene Pellets 0.18 0.07 0.01 0.08 0.19 0.31 55.76 Soxhlet 720 90 Limonene Film 0.32 0.29 0.41 0.53 0.71 0.46 59.59 Soxhlet 720 90 Limonene Ground 0.15 0.12 0.06 0.08 0.24 0.34 64.00 Ultrasound 90 50 Dichloromethane Pellets 0.72 0.68 0.15 0.47 0.82 0.97 76.78 Ultrasound 90 50 Dichloromethane Film 0.96 0.87 0.98 0.96 1.34 1.52 80.64 Ultrasound 90 50 Dichloromethane Ground 0.68 0.71 0.24 0.64 0.82 1.12 91.74 Ultrasound 60 50 Dichloromethane Pellets 0.29 0.19 0.12 0.18 0.41 0.46 66.41 Ultrasound 60 50 Dichloromethane Film 0.52 0.42 0.67 0.72 0.86 0.72 70.98 Ultrasound 60 50 Dichloromethane Ground 0.37 0.27 0.18 0.16 0.42 0.52 78.04 Ultrasound 90 50 Limonene Pellets 0.52 0.47 0.96 0.41 0.76 0.92 74.57 Ultrasound 90 50 Limonene Film 0.92 0.78 0.86 0.85 0.99 1.24 78.49 Ultrasound 90 50 Limonene Ground 0.57 0.55 0.12 0.41 0.64 0.96 89.71 Ultrasound 60 50 Limonene Pellets 0.23 0.12 0.08 0.14 0.23 0.41 64.37 Ultrasound 60 50 Limonene Film 0.42 0.34 0.53 0.64 0.83 0.52 69.29 Ultrasound 60 50 Limonene Ground 0.19 0.18 0.11 0.12 0.34 0.38 75.49 Microwave 45 117 Dichloromethane Pellets 0.82 0.75 0.19 0.62 0.99 1.24 79.55 Microwave 45 117 Dichloromethane Film 1.34 0.99 1.34 1.25 1.76 1.75 84.99 Microwave 45 117 Dichloromethane Ground 0.82 0.96 0.37 0.75 0.96 1.34 96.07 Microwave 25 117 Dichloromethane Pellets 0.38 0.41 0.33 0.42 0.66 0.67 70.08 Microwave 25 117 Dichloromethane Film 0.71 0.57 0.81 0.96 1.12 0.96 74.61 Microwave 25 117 Dichloromethane Ground 0.51 0.34 0.41 0.38 0.52 0.74 81.44 Microwave 45 117 Limonene Pellets 0.57 0.51 1.08 0.48 0.82 0.99 77.71 Microwave 45 117 Limonene Film 0.96 0.86 0.97 0.96 1.12 1.34 82.93 Microwave 45 117 Limonene Ground 0.66 0.67 0.24 0.51 0.66 0.98 92.83 Microwave 25 117 Limonene Pellets 0.29 0.18 0.11 0.16 0.29 0.47 67.05 Microwave 25 117 Limonene Film 0.45 0.31 0.55 0.69 0.89 0.61 71.61 Microwave 25 117 Limonene Ground 0.23 0.22 0.16 0.19 0.38 0.41 78.22 3.3. Determination of the Thermo-Oxidative Degradation Products of Irgafos P-168 Based on the results obtained previously, we present the possible mechanisms of the degradation of Irgafos P-168 in Figures 9–14, which exhibit the formation processes of each of the products resulting from the thermo-oxidative degradation. All these mechanisms share the characteristic of developing in conditions that involve the presence of hydrogen and oxygen radicals in abundance, which occur in the tertiary carbons present in the polypropylene structure [34–36]. 3.3.1. Mechanism of the Phosphate Product of Irgafos P-168 In Figure 8, the mechanism carried out in the first two stages involves the typical steps of all the other degradation products since they show how the hydrogen radicals that cause the degradation of Irgafos P-168 are formed. The first thing that occurs is a homolytic cleavage in the tertiary carbon of C-PP/PE caused by temperature and the presence of the peroxide bond (OO), so said carbon undergoes oxidation, and at the same time, the hydrogen radical (H·) returns to stabilize by uniting this time with oxygen. Subsequently, a homolytic cleavage occurs again between the peroxo bond (OO), which on this occasion generates a hydroxyl radical (OH·) that attacks the phosphorus of Irgafos P-168, generating a double bond with it once again. It generates homolytic cleavage by hydrogen, stabilizing the polymer chain’s carbon. J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 13 of 22 3.3. Determination of the Thermo-Oxidative Degradation Products of Irgafos P-168 Based on the results obtained previously, we present the possible mechanisms of the degradation of Irgafos P-168 in Figures 9–14, which exhibit the formation processes of each of the products resulting from the thermo-oxidative degradation. All these mecha- nisms share the characteristic of developing in conditions that involve the presence of hy- drogen and oxygen radicals in abundance, which occur in the tertiary carbons present in the polypropylene structure [34–36]. 3.3.1. Mechanism of the Phosphate Product of Irgafos P-168 In Figure 8, the mechanism carried out in the first two stages involves the typical steps of all the other degradation products since they show how the hydrogen radicals that cause the degradation of Irgafos P-168 are formed. The first thing that occurs is a homolytic cleavage in the tertiary carbon of C-PP/PE caused by temperature and the pres- ence of the peroxide bond (OO), so said carbon undergoes oxidation, and at the same time, the hydrogen radical (H·) returns to stabilize by uniting this time with oxygen. Subse- quently, a homolytic cleavage occurs again between the peroxo bond (OO), which on this occasion generates a hydroxyl radical (OH·) that attacks the phosphorus of Irgafos P-168, J. Compos. Sci. 20g24e, n8,e15r6ating a double bond with it once again. It generates homolytic cleavage by h1y3dofr2o1 gen, stabilizing the polymer chain’s carbon. Figure 9. Formation mechanism of Irgafos P-168 Phosphate. Figure 9. Formation mechanism of Irgafos P-168 Phosphate. 3.3.2. Mechanism of Formation of 2,4-Di-tert-butylphenol Figure 10 represents the process by which the degradation product previously ob- tained, Irgafos P-168 Phosphate, undergoes a homolytic breakdown due to abundanthydrogen radicals (H·) and the influence of temperature. This cleavage occurs between the PO bond, forming an alkoxyl radical (RO·). Simultaneously, this alkoxyl radical (RO·) is stabilized by bonding with a hydrogen radical (H·), forming a new alcohol bond (ROH) that generates the product of interest. Furthermore, due to the complexity of this type of molecule, other possible degradation products result. J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 14 of 22 J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 14 of 22 3.3.2. Mechanism of Formation of 2,4-Di-tert-butylphenol Figure 10 represents the process by which the degradation product previously ob- ta3i.n3.e2d. ,M Iregcahfaons iPsm-1 6o8f PFhoormspahtiaotne, oufn 2d,4e-rDgoi-etse rat -hboumtyolplyhteicn oblr eakdown due to abundant hy- drogen radicals (H·) and the influence of temperature. This cleavage occurs between the PO boFnidgu, froer 1m0i nregp arnes aelnktos xtyhle r padroiccaels s(R bOy· )w. Shiimchu tlthaen edoeugsralyd,a tthioisn a plkroodxyulc tr apdriecvailo (uRsOly·) oibs - sttaabinileidze, dIr gbayf obso nPd-1i6n8g Pwhiothsp ah ahtyed, ruongdeenr graodesic aa lh (oHm·)o, lfyotrimc binrega ak dnoewwn a dlcuoeh tool abbounndd (aRnOt Hhy) - thdarto ggeenn erraadteicsa tlhs e( Hpr·)o adnudct t ohfe iinntflerueesnt.c eF uorft hteemrmpoerraet, udruee. Ttoh itsh cel ecaovmapglee xoictcyu orsf tbheitsw tyeepne tohfe mPoOle bcuonled, ,o ftohremr pinogs saibnl ea ldkeogxryald raatdioicna lp (rRodOu·)c. tSs irmesuultlta.n eously, this alkoxyl radical (RO·) is stabilized by bonding with a hydrogen radical (H·), forming a new alcohol bond (ROH) that generates the product of interest. Furthermore, due to the complexity of this type of J. Compos. Sci. 2024, 8, 156 molecule, other possible degradation products result. 14 of 21 Figure 10. Mechanism of formation of 2,4-di-tert-butylphenol. 3.3.3. Mechanism of Formation of the Bis(di-tert-butylphenyl) Pho sphate Product FigFiugrure 10. Mechanism of formation of 2,4-di-tert-butylphenol.Ine 1F0ig. Mureec h1a1n, itshme odf efogrrmadataitoino no fp 2r,4o-ddui-ctetr (t-Ibrguatyflopsh Pen-1o6l.8 Phosphate) is also the starting p3o.i 3 3n .3t..3. M.3. TMhe ec ec han hparo i nc s ise m mss o f Form obfe Fgoin ation of the Bis(di-tert-butylphenyl) Phosphate Product In Figure 11, the degrm s watiitoh a homolytic cleavage between the carbon of the R group and the oxygen, which leraaddast itoon n porfo dthuec tB(Iirsg(adfio-stePr-t1-6b8uPthyolpsphheantey)li)s Pahlsoostphehate Product point. The process begins with a ho mthoely rtieclcelaeasvea ogef bthetew aeelknythl egcraorbuopn ionf tthheeR fgorr smtar oting In Figure 11, the degradation product (Irgafos P-168 Phosphate)o uisp aan f da radical (R·) and t lso the starting pothine hoex yogxeyng, ewnh iachttalecahdesdto ttoh ethreel epahseoosfpthhoe raulksy lagtoromup aisn athneoftohremr orfaadricadailc. aAl t(R t·h)iasn pdoint, hydro- genth (eHto.· x)Ty rhgaeedn piacrtatoalcsce hssetsda bbtoieltighzien psbh owotshipt hhrao ardu ihscoamtlosm,o floaysrtmiacn iocntlgheea Brvirasag(ddeici -abtlee. trAwtt-betheuinsty ptlohpienh tec,nahrybdl)or opngh eoonfs tphhea Rte .g roup an(Hd ·t)hraed oicxaylsgsetanb,i lwizehibcohth leraaddicsa tlso, ftohrem rinegleBaiss(ed io-tfe trht-beu atylklpyhle gnryol)upph oisnp hthatee .form of a radical (R·) and the oxygen attached to the phosphorus atom as another radical. At this point, hydro- gen (H·) radicals stabilize both radicals, forming Bis(di-tert-butylphenyl) phosphate. Figure 11. Mechanism of formation of Bis(di-tert-butylphenyl) phosphate. Figure 11. Mechanism of formation of Bis(di-tert-butylphenyl) phosphate. 3.3.4. Mechanism of Formation of the Mono(di-tert-butylphenyl) Phosphate Product 3.3.4. MInecFhigaunreis1m2, tohfe Ffoorrmmaatitoinonm eocfh tahneis mMboengoin(ds fir-otemrtt-hbeuptryelvpiohuesnpyrlo)d P uhctoBsips(hdai-tteer Pt-roduct Figbuutryel p1h1e. nMyel)cphhaonsipsmha toef; finortmheaptiroense onfc eBoisf(tdhie-therytd-brougteynlprhadenicyall)a pnhdohsipghhatteem. perature, aJ. Compos. Sci. 2024, 8, x hFOoIRmn Po EFlEyRitg iRcuEcVI rleeEa W1v 2ag, ethoecc fuorrsmbeatwtieoenn mtheecChoafnthisemR gbreoguipnasn fdrothme o txhyeg epnr,erevlieoasuins gparnoodt1h5u eocrft 2B2 is(di-tert- b3u.t3Ry.4glp.r ohMuepen,cybhola)t hnpiohsfomws phoihcf haFtaoerr;e misntaa tbthiioleizn ep dorfew stiehthnec hMey doorfno gtohe(nde riha-tdyeidcratr-losb.guTethnye lrpdaehdgeirncaadylal t)ai oPnndhpo hrsoipdghuhca tteoemf Pproedrautcutr e, a homintoelryesttica ncdleaavdai-gteert o-bcuctuylrpsh beentywl aereeno bthtaein Ced o. f the R group and the oxygen, releasing another R grouInp ,F bigouthr eo f1 2w, hthiceh f oarrme sattaiboinli mzeedc hwainthis hmy dbreogginesn frraodmic tahlse. pTrheev dioeugsr apdraotdiounct p Briosd(duic-tt eorft - inbtuetryelspt haenndy al) dpih-toesrpt-hbauttey; lipnh tehney pl raersee onbctea oinf etdh.e hydrogen radical and high temperature, a homolytic cleavage occurs between the C of the R group and the oxygen, releasing another R group, both of which are stabilized with hydrogen radicals. The degradation product of interest and a di-tert-butylphenyl are obtained. Figure 12. Mechanism of formation of Mono(di-tert-butylphenyl). Figure 12. Mechanism of formation of Mono(di-tert-butylphenyl). 3.3.5. Mechanism of 2-Tert-butylphenol Product Formation In Figure 13, this time in part of the product 2,4-di-tert-butylphenol, under the same conditions set out above, a homolytic cleavage occurs in the tert-butyl group in the posi- tion para, so the degradation product of interest and a tert-butyl group are obtained. Figure 13. Mechanism of formation of 2-tert-butylphenol. 3.3.6. Mechanism for Obtaining the Product 4-Tert-butylphenol The last mechanism illustrated in Figure 14 for the formation of the 4-tert-butylphe- nol product involves the loss of a tert-butyl group in the (ortho) position, so it begins with the 2,4-tert-butylphenol molecule, which undergoes a homolytic cleavage between the ring carbon bond and the tert-butyl carbon, resulting in the product of interest 4-tert-bu- tylphenol and a tert-butyl group. Figure 14. Mechanism of the formation of the 4-tert-butylphenol product. J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 15 of 22 J. C ompos. Sci. 2024, 8, x FOR PEER REVIEW 15 of 22 Figure 12. Mechanism of formation of Mono(di-tert-butylphenyl). 3F.3i.g5u. rMe e1c2h. aMniescmha onfi s2m-T eorft f-obrumtyaltpiohnen oofl M Proondou(dcti- Fteorrtm-bauttiyolnp henyl). J. Compos. Sci. 2024, 8, 156 In Figure 13, this time in part of the product 2,4-di-tert-butylphenol, under the sa1m5 eof 21 co3n.3d.5it.i oMnse csheta onuistm ab oofv e2,- Ta ehrot-mboultyytlipc hcleenavoal gPer oocdcuucrts Fino rthmea tteirot-nb utyl group in the posi- tion para, so the degradation product of interest and a tert-butyl group are obtained. In Figure 13, this time in part of the product 2,4-di-tert-butylphenol, under the same co3n.3d.5it.iMonesc hsaent iosmut oafb2o-Tveer,t -ab uhtoymlpohleyntoicl PcrloedavuactgFeo ormccautriosn in the tert-butyl group in the posi- tion paInraF,i gsou rteh1e3 d, tehgirsatdimaetioinnp parrot dofutchte opfr iondtuercet s2t, 4a-ndid-t ear tte-brut-tbyulpthyel ngorlo,uupnd aerret hoebtsaaimneed. conditions set out above, a homolytic cleavage occurs in the tert-butyl group in the position para, so the degradation product of interest and a tert-butyl group are obtained. Figure 13. Mechanism of formation of 2-tert-butylphenol. 3.3F.6i.g Murec1h3a. nMisemch afnoirs mObotfafionrimnagt itohneo Pfr2o-tdeurtc-bt u4t-yTleprhte-bnuolt.ylphenol 3.3T.6h.eM laesct hmanecishmanfiosrmO iblltuasintriantgedth ien PFriogduurec t144- Tfoerr tt-hbeu tfyolrpmhaetnioonl of the 4-tert-butylphe- nFoilg purroed 1u3c.t M inevcohlavneiss mth eo lfo fsosr mofa at itoenrt o-bf u2t-ytel rgt-rbouutpy lipnh tehneo (lo. rtho) position, so it begins with thep 2ro,4d- T ute h cr e tt-inb lausvot tymlvlp ehcehnaones thel i smmoillloss oe lu fc s au tlrea,t ewdhintert-buitch F iyl gu gur rnod ee1uprg 4 ino feosr tah ehofomrmolayttiiocn colefathvaeg4e- tebrett-wbueteynl pthheenol 3.3.6. Mechanism for Obtaining the Product 4-tTheer(to-brtuhtoy)lppohseitnioonl , so it begins with t he rin2g, 4c-atrebrot-nb ubtoyldp haenndo tlhme otelerct-ublue,tywl hcaicrhbounn, dreesrguolteinsga ihno tmheo lpyrtoicduclceta ovfa ignetebreetswt 4e-etnertth-beur-ing tylpcahrebTnoohnle ba olnandsd ta a mtnedertct-hbeaunttyeirls tmg-br ouiultlypul.sc tarrabtoend, riens uFlitginugrien 1th4e fporro tdhuec tfofrmintaetrieosnt 4o-tfe trht-eb u4t-ytleprht-ebnuotlylphe- noaln pdraotdeurtc-bt uintyvloglrvoeusp t.he loss of a tert-butyl group in the (ortho) position, so it begins with the 2,4-tert-butylphenol molecule, which undergoes a homolytic cleavage between the ring carbon bond and the tert-butyl carbon, resulting in the product of interest 4-tert-bu- tylphenol and a tert-butyl group. Figure 14. Mechanism of the formation of the 4-tert-butylphenol product. Fig3u.r4e. 1V4a. lMideacthioanniosfmP roofp tohsee fdoMrmeacthioann iosmf tshe 4-tert-butylphenol product. It is widely recognized in scientific circles that quantum chemistry offers an effective m ethod for understanding processes occurring in chemical reactions. This allows for the calculation of charge distribution, molecular properties, and potential energy surfaces associated with these reactions. Numerous studies have supported the utility of Density Functional Theory (DFT) as a powerful tool for predicting trajectories, kinetics, and sec-Fiognudrea r1y4.p Mroedcuhactnsisomf coofm thpeo fuonrmdsatoiof nin otef rtehset 4u-tnedrte-rbusptyelcpifihecneonlv pirroondmucetn. tal conditions, as documented in the scientific literature. Therefore, we have chosen to employ computational to ols to validate the formation of proposed degraded products in the preceding section. This will further support our conclusions and enhance our understanding of the underlying processes in the studied chemical reactions. Based on the results provided in Table 3, it can be concluded that all analyzed formation mechanisms and products exhibit negative values for both the delta of Gibbs free energy (∆G) and the delta of enthalpy (∆H), indicating the favorable thermodynamic nature of the reactions under study. Significant differences are observed between the values of ∆G and ∆H among the different mechanisms, with the mechanism for obtaining the 4-tert- butylphenol product standing out as the most spontaneous with the most negative value of ∆G. The close relationship between ∆G and ∆H suggests that enthalpy plays an important role in the spontaneity of reactions, although other factors also have an influence. J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 16 of 22 3.4. Validation of Proposed Mechanisms J. Compos. Sci. 2024, 8, x FOR PEER REVIEIWt is widely recognized in scientific circles that quantum chemistry offe16r so fa n22 effective method for understanding processes occurring in chemical reactions. This allows for the calculation of charge distribution, molecular properties, and potential energy surfaces as- so3c.4ia. tVeadlid watiiotnh otf hPersoepo rseda Mctieochnasn. isNmus merous studies have supported the utility of Density FunctiIot insa wl iTdheleyo rreyc o(gDnFizTe)d a isn asc ipeonwtifiecr fcuirlc lteoso tlh afot rq uparnetduimct cinhgem trisatjreyc otoffreiress a, nk ienffeetcitcivs,e and sec- onmdeathryod p froor duuncdtesr sotaf ncdoimngp poruoncedss eos fo cincuterriensgt iun ncdhemr iscpael creifiact ieonsv.i Trohnism alelnowtasl fcoor nthdei tions, as docaclucumlaetniotne do fi cnh athrgee sdciisetrnibtiufitcio lni,t emroalteucruel.a rT phreorpeefrotirees,, waned hpaovteen tciahlo esneenr gtyo s eumrfapcleosy a sc-omputa- tiosoncaial tetodo wlsi ttho thveasleid raetaec ttiohnes .f oNrummaetrioouns osft updrioesp ohasveed sduepgproardteedd t hper oudtiulitcyt so ifn D tehnes itpyr eceding seFcutinocnti.o Tnahli sT hweoilrly f u(DrtFhTe) ra ss uap ppoowret rofuulr t ocooln fcolru psiroendisc tainngd teranjhecatnorciee so, ukirn uetnicdse, rasntda nsedci-ng of the unonddearrlyy ipnrgo dpuroctcse ossf ecso minp tohuen sdtsu odfi eindt ecrhesetm uincdael rr esapcetciiofinc se.n vironmental conditions, as docuBmaseendte do nin t hthee rsecsiuenlttsifi pc rloitveriadteudre . Therefore, we have chosen to employ computa-tional tools to validate the formation oinf pTraobploes e3d, idt ecgarnad beed cporondculucdtse idn tthhae tp arlelc eadnianlgy zed for- msaetcitoionn m. Tehcish awnilils fmurst haenrd s upprpoodrut cotusr ecxohnicbluits inoengs aatnidv ee nvhaaluncees ofourr ubnodther tshtaen ddienlgta o of ft hGei bbs free enuenrdgeyrl y(ΔinGg )p aroncde stshees idne tlhtae sotfu ednietdh achlpemy i(cΔaHl r)e,a icntidonicsa. ting the favorable thermodynamic na- ture oBf athseed r oena ctthioe nress unltsd epr osvtuiddeyd. iSni gTanbifilec 3a,n it dcaiffn ebree ncocnecsl uadre do bthsaetr valel da nbaeltywzeede nfo trh- e values ofm ΔaGtio ann mde ΔchHan aismmosn agn dth per oddiuffcetrse enxth mibiet cnheagnatiisvme sv,a wluietsh f othr eb omthe tchhea dneisltma o ffo Gr iobbsta firneein g the 4- teernt-ebrguyty (lΔpGh)e annodl tphreo ddeultcat o sf teanntdhainlpgy o(ΔuHt )a, si ntdhiec amtinogs tt hsep foanvotaranbeloe uthse wrmitohd ythnaem mico nsat -negative J. Compos. Sci. 2024, 8, 156 vatuluree ooff t hΔeG re. aTchtieo ncsl ousned reer lsattuidoyn.s Shigipn ibfiectawnte deinff eΔreGn caens da rΔe Hob sseurgvegde sbtest wtheaetn ethneth vaallpueys plays an 16 of 21 imofp ΔoGrt aanntd rΔoHle aimn otnhge tshpe odnifftaenreenitt ym oefc hraenaicstmiosn, ws,i tahl tthhoe umgehc hoatnhiesmr f faocrt oobrsta ainlsinog h thaev e4 -an influ- tert-butylphenol product standing out as the most spontaneous with the most negative envcaelu. e of ΔG. The close relationship between ΔG and ΔH suggests that enthalpy plays an Tabimlepo3r.taGnti brobles ifnr etheee snpeonrgtayneaitnyd ofe rneathctaiolnpsy, aflothrotuhgeh potrhoepr foascetodrsd aelsgor haadvae taino ninflmu-echanisms. Taebnlcee .3 . Gibbs free energy and enthalpy for the proposed degradation mechanisms. Table 3. Gibbs free energy and enthalpy foGr ithbeb psr GoFprioebseeb d sdeFgrraedeation mecha∆nGism os.f the ∆∆HG of the Mechanism Structure Energy Enthalpy of the ∆H of the Mechanism Structure Ener(gHy Enthalpy Gibbs Free artree∆) Reaction RReeacatcitoino n Reaction (Hartree) G o(fH( tkhacera tlr/eme∆o)Hl) of th(ke cal/mol) Mechanism Structure Energy (HEanrtthraelep)y (kcal/mol) (kcal/mol)(Hartree) Reaction Reaction (Hartree) (kcal/mol) (kcal/mol) −2279.7−620 279−.7226709.614 −2279.614 −2279.760 −2279.614 MechMaencihsamn iosmf of formfaotrimona toiofn 2 o,4f -2,4- di-tert- −744.23 − 744.23− 732.30 −732.30 di-tert- butyblpuhtyelnpohel.n ol. Mechanism of formation of 2,4-di- −744.23 −732.30 tert-butylphenol. −1659.277 −1−6156599.2.17717 −1659.171 J. Compos. Sci. 2024, 8, x FOR PEER REVIEW −1659.277 −1659.171 17 of 22 J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 17 of 22 J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 17 of 22 J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 17 of 22 −621.669 −621.610 −621−.666291 .66−96 2612.611−.066 6219.610 −621.610 −621.669 −621.610 −2279.760 −2279.614 −−22227799.7.−766020 2 7−92−.722762970.96.1641 4 −2279.614 −2279.760 −2279.614 Mechanism of formation of the Mechanism oBfis(di-tert- formatiMech −761.17 −747.99 oMnecohfaantbnhiuissetmylp ohofef nyl) −1734.514 −1734.404 Bis(ffodorirm-m phosphate teaarttitMio-onenc ohofaf n tthiseme of pr −761.17 −747.99 butylphBBieisns(f(dyodirli-m)-tteaertrti oto-d-nu octf the Bis(di-tert- −7−6716.17.1 7 −7−474.979.9 9 phosphatbebuupttyyrlolppdhheuencnytyll)) butylphenyl) −−11773344.5.−511414 7 3−41−.57131743.4.0440− 47 61.−171 734.4−07447.99 pphhoosspphhaattee −1734.514 −1734.404 phosphate pprroodduupccrtot duct −546.459 −546.402 −546.459 −−546.4.4025 9 −546.402 −−554466.4.45599 −5−4564.64.0420 2 Mechanism of formation of the Mono(di-tert- butylphenyl) −1734.514 −1734.404 −760.54 −747.99 phosphate Mecphraondiusmct of formation of the MMeecchhaaMnnioissnmmo( d ooif-f t ert- ffoorrmmaattiiobonunt yoolfpf ththhene −1734.514 −1734.404 −760.54 −747.99 e y l) MMoonnoo((ddpiih--toteesrprtth--ate bbuutt p yyllpphhee rnoydlunyl)) ct −−11773344.5.51144 −1−713743.44.0440 4 −7−6706.054.5 4 −7−4774.979.9 9 pphhoosspphhaattee p prroodduucctt J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 17 of 22 −621.669 −621.610 −2279.760 −2279.614 Mechanism of formation of the Bis(di-tert- butylphenyl) −761.17 −747.99 −1734.514 −1734.404 phosphate product J. Compos. Sci. 2024, 8, 156 17 of 21 Table 3. Cont. −546.459 −546.402 Gibbs Free ∆G of the ∆H of the Mechanism Structure Energy Enthalpy (Hartree) (Hartree) Reaction Reaction (kcal/mol) (kcal/mol) Mechanism of formation of the J. ComMpoosn. oS(cdi. i2-0t2e4r,t -8, x FOR PEER REVIEW −1734.5−114 734butylphenyl) −.5117344.404 −17−37640.4.5044 −747.99 18 of 22 J. ComJ p J. C. C os. Sci. omompposo.s .S 2S0c2i.4 2, 082, 4x FORci. 2024, ,8 8, ,x x F F P OO E RR ER R PPEEEE ERVR RR IE EVV W II EEW 181 8o f 22 W 18 o f of 22 2 J. Comphpoos.s Spchi. a2t0e2 4, 8, x FOR PEER REVIEW 18 of 22 product Mechanism of formation of the −1189.267 −1189.194 −1−118198.296.276 7 −1−118198.199.194 Mono(di-tert- −1−11819.8−296.1721 6879 −.2161−87191.1894. 41 9−4 1189.194 −760.54 −747.99 buty lphenyl) phosphate product −546.459 −−55−445664..4645.5495 9 −5− −554466.4046..40.4220 2 2 −546−.45496 .459−546.402− 546.402 −6−−26162.2161.66.966 699 −6−2−6162.62111.60.61 01 0 −62−16.2616−.96 66291 .6−692−16.2611.06 10− 621.610 MechM Me Manec e ich c sha hananinsiissmm f fofoorrr Mecohoboabtbnatatia m isninimin f niin n o gfgog r t r thtM h obtaineicnhgantihsem fhoee e r −87−88−.758817. 85.15 1 −86−3.ob product 4-tert- 8− 468536 .435.4 5 prodptouparbriconotdaid4nuugcct t t4 h4-e-tt ebutihn-ytienlprgth -teh erertt --nol −87−8.51 −878 878. 51 −86−3 ..5415 −863.45 bpurtohpbdyrbuuoluptcdhtthhu y4eycl-npltpeohhrleten- 863.45 t 4-tenrootl-l butbhuytlhpyhlepnhoeln ol −4−6446.46.6656 5 −4−6446.6418 −464−. 46654 .665−464.6.6181 8− 464.618 −46−44.6646.56 65 −46−44.6641.86 18 −158.403 −158.368 −−115588.−4.4010353 8 .40−3−115588.3.3686 8− 158.368 −15−81.5480.34 03 −15−81.5386.83 68 J. Compos. Sci. 2024, 8, 156 18 of 21 Table 3. Cont. J. CJ. oCmopmops o . sS. cSi.c i2. 022042,4 8, ,8 x, xF OFORR P PEEEERR R REEVVIEIEWW Gibbs Free 1Enthalpy ∆G of th19e 9 of J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 19 ooff 2 22 2 ∆H of the M echanism Structure Energy 22 (Hartree) (Hartree) Reaction Reaction (kcal/mol) (kcal/mol) −−662211.−.666699 −621.610 −621.6692 1.66−9−662211..661100 −621.610 MMecMehMce an ehccah insha m ain fo nsiimssmm f r o fforob o rr otaboiotb natiianngbtaiiinnin tgh gte hthe e product ofn2in-tge rtth-e −−779922.5.544 −792.54 −778.11prpporrdoouddcuutcc ott foo f2f -22t--ettreetrr-tt-- −792.54 −−−77777888..11.111 bubtuhbbtu yhltyphhenoluthlyypllphphehneenonolo ll −−446644−..55224996 4.529−−446644...444888222 − 464.482 −−115588.−..44001335 8.40−3−115588...336688 − 158.368 333.5..55. ..P PPeerercrcceenennttataagggeee A AAnnnaaallylyysssiiisss ooofff ttthhheee DDeeeggrrraaddaattiiioonn PPrroodduuccttss ooff IIrrggaafffooss PP---1166888 3.5. FPFFiegiirggucuurerrenee 1t 11a555g p peprrroAoovvvniiidaddleeeyssss a aiasnnn o iiinnfnttteeehrrrepprrDreettetaagttriiooannd aootffi tothhnee P vvaraorridiaauttiicootnnsss o iiinfn I I IIrrrggaaafffooosss P PP----111166668888 cc cooonnnccceeennnttrrtaraattiitooionnnss,,s , iliilllulluusstsrttFraraatitigtniinungggr te ththh1eee 5 s ssiipgiggnrnnoiiififivficcciaadannnettt s iiimmanppaaiccnctttt ooeffrf pddriiffffeeetarreetninott neexxottrfraatcchttiieoonnv mamreietatthhtoioddnsss,,s , s ssoioonllvlvvIeerenngnttsatss,,f ,aoa annsnddPd ff -oof1orr6mrmm8ss cs oo off n f centrations, CCC-P--PPPP/P//PPEEE. ..I ItIt tw wwaaasss o oobbbssseeerrrvvveeeddd ttthhhaaattt aallllll ddeeggrraaddaatttiiioonn pprroodduucctttss rreeaacchheedd t tthheeeiirirr h hhiigigghhheeessstt t pp peeerrcentages iwllustrating the signific rcceenntataggees s wwhhheeennn t ththheee m mmiiciccrrrooowwwaaavvveee e eexxxtttrrraa actniotni mtecphanciqtuoef wdaisff uesreedn itne cxotmrbcintaiotinonm weitth doidchs,losroolmveethtasn,ea nd forms of C-PP/PE. It was obseravccettidioont h tteacthanliilqudee gwraassd uassteido inin pcoromdbiuincatttsiioornne awciiththhe d ddiictchhhloelorirroomhmiegeththhaeansnete p ercentages aawan n hnd dde C CnC- -Pt- PPPPP//P/PPEEE i ininn t tthhheee fffooorrrmm ooofff fifilllmmsss... AAlllttthhoouugghh ttthhiiisss ttteeeccchhnniiiqquue involves short times and low tteemmppeerrahatteuurrmeessi,,c iirnno ttwhheeaoovrreyy,, e iitxt stshrhaoocuutlliddo nnoottte cccaahuunsseeiq ssuiiggenniwifificcaaasnntut sstterrud ee iiinnvcoollvvmeessb sishnhoaortrtit o ttinmimweess ia tahnnddd l iolcowhw lo romethane taetnrmadcpteCior-naPt uoPfr /edsPe, gEinra itdnheetdoh rpeyr,fo oidtr usmhctosou mfldafi ynl mobte cause significant str uuccttuurrs .beAc ctur aaalll c cchhaannggeess;; tthhee ggrreeaatteerr eexx-- trtaracctitoionn o of fd deeggrraaddeedd pprroodduuccttss maayy bbee bbeeccaalatuuuhsssoeee uttthhhgeeeh sssataahmmippspllleteeesss c wwheenerrreieeq e euex hepaonisngevedso ;t lotvh heeis gghsrehearo tter ex-xpose peratures during the previous preparation stages, which could haxvpe ocsoe dd ttoo h higigher treetmmti--mes and low tepmeraptuerreast udruersin, gi nthteh peroervyio, uist pshreopuarladtionno tstcaageuss, e shiigchn icfiocualdn thasvteru ccotnnuttrrriiabbuted h etor ttehme - pdeergatruadreast iodnu roifn tgh eth Ireg pafroesv Pio-u16s 8p. Irte ipsa ervaitdioenn ts tthaagte tsh, ew shhaicphe coof uthlde Ch-aPvPe/ PcoEn atlrsib luutcethedda t notog t ehthsee; the greater dedexegtgrraaradcdatiatoitoinonn oo offf t thdhee Ig Irrggaaadffooessd P P--p116r68o8..d IItut iicss t eesvviimddeeannytt ttbhhaaett btthheeec ssahhuaasppee ootfhf tethhees CaCm--PPPpP/l/PePEsE a wls o influences the number of degraded products. Notably, the highest percentages of degraadls oeo ri neinflfleuxepncoesse d to higher ethme pnuemrabteurr oefs ddegurraidnegd tphroedpurcetsv. iNooutably, the highest percentages of degradaattiioonn uperondce-s thuec tns uwmerbee rfo oufn dde graded products. Not prod- ucts were found iinn CC--PPPP//PPEE fifillmmss,, wwhhiil aseb ptlhyre,e tppheeal rlheaitgt aihonendst g sprteoarugcnedns t,faowgremhs sioc sfh hdocewgoreuadld laotwhioaenrv pceorocndo- -ntributed to utchcetens twdraetgiroern afsod uoafn tdtiho iens eCo p-fProtPh/PeEI rfigl le the pellet ducts. Tmahfseo, sfiwlPhmi-l 1est 6rth8ue.c tpuIetrellises t eaanvnd ground forms showed lower con- centrations of these pr are l died sgesr nodtuenntshde a faotnrtdmh pse essrhmhoawepaebedle ol,o ffwatcehirlie tcaoCtn---PP/PE also ciinennflgtu roaextniyocgneessn o tdfh itffehuenssuieo mnp rbao oeddruuocctftssd.. TeThghere film structures are less dense and permeable, facilitat- ing oxygen diffusion anndd,, tthheerreeffoor afied,l meitds s rtpreuraoccttdiuournec stw sai.rtheN lIoestsa bdlere, its reaction with Irrggaaffoosy n ,Pste-h1 a6en8h.d iT gphheeresmes tefiaplmbelresc , aefranect iaalilgstaoet s- of degrada- itnlieogsn so pxryrogoteedncut edcditff saugwsaiioennrse ta enfnodvu,i rtnhodnermienfeonCrtea-,lP ietPlse /mrePeaEncttifiso slnmu cwshi, tawhs Irgafo ss P-16shuinleligthteP a-p1n6 88.. TThheessee fifilmlmss a arree a alslsoo lelesss sp prorotetecctetedd a aggaaiinnsstt eennvviirroonnmmeennttaall eelleemments such as sunlight an eddl hlheuutmmaiindddiittyyg,, wrwohhuiiccnhhd ccaafnon r ms showed laoaccwcceeellererrcaaotteen ddceeggnrrtaarddaaatttiiioon sproofcethsseese. Fpurothdeurmc etonsr.tesT, sChu-ecPhPfi /alPsmE sn processes. Furthermore, C-PP/PE ufisnltmrliusg chatrtu ea rmnedos rhaeur semusliecdesiptsytd,i bwelenh tsioce hma cena-n films are more suscep d permeable,afcachccaeilnleiitrcaaattlie ns dtgreegossrx adydugaretiinognd hpiafrnfoudceslisnosgen sd.a uFeu rtoth setrrmetcohrein, gC -oPr Pd/ePfEo rfimlmatsio anr ep mroocrees sseuss dceup tible to me- chanical stress during handling d ri tnibgl em taon mu-e- cfhaacntuicrainl gst, rweshsi cdhu irnincrge hasaensd tlhineigr dvu uneed ttoo, tsshttrreeerttecchhfoiinnrgge ,ooirrt sddeerfefooarrcmmtiaaottinioonnw ppirtrohocceIerssgsseaessf do dusurPrini-ng1g 6m m8a.anTnuuh--ese films are faaflacstcouturlirenisngsg,p wrohticehc tiendcreaagsaesi nthsetier nv uvullinnreoerrnaabmbiilleiittnyy t ttaool IIerrglgeaamffooses nPP-t-11s66s88u ddceehggrraaasddasation. , which increases their vulnerability to Irgafos P-168 degradauttiiononlni. .g ht and humidity, which can accelerate degradation processes. Furthermore, C-PP/PE films are more susceptible to mechanical stress during handling due to stretching or deformation processes during manufacturing, which increases their vulnerability to Irgafos P-168 degradation. J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 20 of 22 J. Compos. Sci. 2024, 8, 156 19 of 21 FiguFirgeu 1r5e.1 D5.eDgreagdraadtiaotino npprorodduuccttss ooff Irgaffoss PP--116688. . IntIenrteesretisntignglyly, , tthheem mosot sptr epdoremdinoamntindaengrta ddaetgiornapdraotdiounct wparos dMuocnto (wdia-tse rtM-boutnyolp(dhei-ntyelr)t-bu- tylpphheonspyhl)a tpeh, foosllpohwaetde,b fyoBllios(wdie-dte rbt-yb uBtiysl(pdhi-etneyrlt)-pbhuotysplphhateen. yTlh)i spihsoinstpehreasttein. gTshinisc eis, aicnctoerrde-sting sincineg, atocctohredliteratand 2,4 di-tienrgt- bto u re, wuttyhlpe hl hiteenrathteurdee,g wrahdeantio tnheo fdIerggarfaodsenol are frequently the produca Pt-tsi 1o6n8 oofc cIurgrsa, Iwith the hifgo rgsa Pfo-1s P-1hest pe6r8c 68 Phosphate eonctcaugres[,3 I6r,g37a]f.os P- 168T Phihsodsipschraeptea nacnydr a2is,4e sdeis-steenrtti-abluqtuyelpsthioennsoalb aoruet tfhreeqeuxaecnttdlye gtrhaed aptiroondmucetcsh awniisthm sthine thhieghest perpcreensteangcee [o3f6d,3if7fe]r. eTnhtisso dlviescnrtse.pOannctyhe raoitsheesr ehsasnedn,tdiaiclh qluoreosmtioetnhsa nabeoduemt tohnes etrxaatecdt dneogtarbaldyation mechhigahneirsmrecso vine rtyhrea tpesreosfednecger aodfa tdioiffneprreondtu cstoslvcoemntpsa. rOednt othLeim ootnhenr ehinanadll,t hdeictheclhonroiqmuesthane demusoends.trAagteadin ,nLoitmabolnye nheig, hasera rgerceoenvesroylv reantteso potfi odne,gsrhaodwastiiotsn epffreocdtiuvcetnse scsombypparroevdi dtion gLimo- nenleo wine raplel rtcheen ttaegcehsnoifqdueegsr audsaetdio. nApgraoidnu, cLtsimanodneexntera, catisn ga agcrceeepnta sbolelvaemnot uonptstioofnI,r gsahfoows s its effePc-t1iv68e.nTeshse sbeyr epsruolvtsidhiinggh lligohwtetrh epecorcmepnlteaxgietys ooff tdheegirnatedraatcitoionn psrboedtwucetesn aInrgda feoxstrPa-c1t6i8n,g ac- cepstoalbvleen tasm, aonudnetxst roafc tIirognacfoonsd Pit-i1o6n8s.a Tndhethsee urergsuenltcsy hoifgfihnldiginhgt athneo pctoimmapllbeaxliatnyc oefb tehtwe eiennterac- tionefficient additive recovery and minimal degradation. Furthermore, it highlights the criticalims pboertwtaneceeno Ifrcgaarfeofus lPly-1se6l8e,c tsionlgveexnttrsa,c taionnd ceoxntdriatciotinosnto cpornedseitrivoentsh eanindte tghreit yuorgf ethnecayd odfi -find- ingt aivne .oTphtiemsearle bsualltasnaclseo beemtwpheaesniz eeffithceieunrgt eandcdyiotifvceo rneticnouveedryre asenadrc mh tionicmonaslt adnetglyraimdaptrioovne. Fur- theermxtroarceti, oint hteicghhnliiqguhetss athnde mcriintiicmailz iemthpeodrteagnracde aotifo cnaoref ftuhellyp osleylmecetrisnagn edxtthreaicrtaiodnd ictiovneds.itions to preserve the integrity of the additive. These results also emphasize the urgency of con- tinu4e. dC ornecsleuasricohn sto constantly improve extraction techniques and minimize the degrada- tion of tThhee proeslyumltseorbst ainnde dthineitrh aisdsdtuitdivyessh. ow that the microwave extraction technique sur- passes the ultrasound and Soxhlet techniques in terms of effectiveness, reducing extraction 4. Ctiomnecsluasnidoninsc reasing the recovery efficiency of the compound of interest. Furthermore, ground C-PP/PE leads to notable improvements in the recovery of Irgafos P-168 compared toTCh-eP Pre/sPuEltps roebsetanitnateidon isn itnhitsh estfuodrmy sohfofiwlm tshaatn tdhpe emlleictsr.owThaevsee eimxtprarocvtieomne tnetcshanrieqaute- sur- pastsreibsu tthede tuoltthraesaoduvnandt aagneds iSnohxerhelnett toteucshinngiqgureosu nind Cte-rPmP/sP oEf, seuffcehcatsivaesnuebssst,a nretidaluicnicnrgea esextrac- tionin ttihmeecso natnadct isnucrrfeaaces,inmgo rtehex rceclloevnet rpye remffieacibeinlitcyy, tohfe tphres ceonmcepoof usmndal loefr pinatretircelests., aFnudrther- mogrere, agterrohuonmdo Cge-nPePit/yPEin ltehaedcso mtop onsoitiaobnleo fitmhepmroavtermiael.nTtos bine mthoere rperceocviseeriyn othf eIfirgnadfionsg sP, -168 combpyaarpepdly tion gCm-PiPcr/oPwEa pvreessfeonrt4a5timonins, iwni tthheth feorsmolv oefn fit dlmichs laonrodm peethllaentse. aTnhdeusesi inmg pgrroouvnedments are Ca-ttPrPi/bPuEteads taos tuhbes tardatvea, nthteagmeasx iinmhuemrernetc toov eursyinogf Igrgraofuons dP -C16-8PPis/PacEh,i esvuecdh, aosb taa isnuinbgstaantial incrpeearcseen itna gtheeo fc9o6n.0ta7c%t ;swuritfhacaed, umraotrieo nexocfe4l5lemnitn p, eursminegatbhielistoyl,v tehnet Lpirmesoennecnee oafn dsmgraolluenrd parti- clesC, -aPnPd/ PgEr,eaatreerc ohvoemryoogfe9n2e.8it3y% inis tahceh iceovmedp; oansidtiboyn uosfi nthgeth me autletrraisaol.u Tndo ebxet rmacotiroen pterechci-se in the findings, by applying microwaves for 45 min, with the solvent dichloromethane and using ground C-PP/PE as a substrate, the maximum recovery of Irgafos P-168 is achieved, obtaining a percentage of 96.07%; with a duration of 45 min, using the solvent Limonene J. Compos. Sci. 2024, 8, 156 20 of 21 nique for 90 min, with the solvent dichloromethane and ground C-PP/PE, a recovery of 91.74% and 89.71% with Limonene is obtained. However, the Soxhlet extraction technique, with a duration of 1440 min and using ground C-PP/PE, entails the lowest recovery of 78.64% with dichloromethane and 76.66% with Limonene. These results underline that the microwave extraction technique is the best choice when combined with ground C-PP/PE, providing the highest recovery percentages at noticeably shorter extraction intervals. Al- though dichloromethane exhibits some advantages in terms of recovery, the choice of Limonene as an alternative solvent is viable. It provides additional benefits, such as lower toxicity and reduced environmental impact. Author Contributions: Conceptualization, J.P.-M. and R.O.-T.; Data curation, R.O.-T.; Formal analysis, J.H.-F. and R.O.-T.; Funding acquisition, J.P.-M.; Methodology, J.H.-F. and R.O.-T.; Project administra- tion, J.H.-F.; Resources, J.H.-F., J.P.-M. and R.O.-T.; Software, J.H.-F.; Validation, J.H.-F.; Visualization, J.P.-M. and R.O.-T.; Writing—original draft, J.H.-F.; Writing—review and editing, J.P.-M. and R.O.-T. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Data Availability Statement: Data will be available upon request. Acknowledgments: The authors thank the Universidad de Cartagena for the providing equipment and reagents to conduct this research. Conflicts of Interest: The authors declare no conflicts of interest. References 1. Pfaendner, R. How will additives shape the future of plastics? Polym. Degrad. Stab. 2006, 91, 2249–2256. [CrossRef] 2. 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