{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,16]],"date-time":"2026-10-16T12:41:58Z","timestamp":1792154518763,"version":"4.4.0"},"reference-count":56,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2022,12,30]],"date-time":"2022-12-30T00:00:00Z","timestamp":1672358400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001691","name":"JSPS KAKENHI","doi-asserted-by":"publisher","award":["JK21K05146"],"award-info":[{"award-number":["JK21K05146"]}],"id":[{"id":"10.13039\/501100001691","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001691","name":"JSPS KAKENHI","doi-asserted-by":"publisher","award":["2021"],"award-info":[{"award-number":["2021"]}],"id":[{"id":"10.13039\/501100001691","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Fuji Seal Foundation","award":["JK21K05146"],"award-info":[{"award-number":["JK21K05146"]}]},{"name":"Fuji Seal Foundation","award":["2021"],"award-info":[{"award-number":["2021"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Polymers"],"abstract":"<jats:p>The purpose of this study is to investigate the thermo-oxidative degradation behavior of polypropylene (PP) by comparing three types of pristine PP granules (consisting of homopolymer, random copolymer, and block copolymer) with their corresponding oxidized analogues. These analogues were intensely oxidized under oxygen at 90 \u00b0C for 1000 h by using the electron spin resonance (ESR) spin trapping method that can detect short-lived radical intermediates during the degradation. The degrees of oxidation could be evaluated by chemiluminescence (CL) intensity, which was related to the concentration of hydroperoxide groups generated in the PP chain. In the pristine PP samples, a small amount of hydroperoxides were found to be formed unintentionally, and their homolysis produces alkoxy radicals, RO\u2022, which then undergo \u03b2-scission to yield chain-end aldehydes or chain-end ketones. These oxidation products continue to take part in homolysis to produce their respective carbonyl and carbon radicals. On the other hand, in the oxidized PP granules, because of their much higher hydroperoxide concentration, the two-stage cage reaction and the bimolecular decomposition of hydroperoxides are energetically favorable. Carbonyl compounds are formed in both reactions, which are then homolyzed to form the carbonyl radical species, \u2022C(O)\u2013. PP homopolymer produced the largest amount of carbonyl radical spin adduct; thus, it was found that the homopolymer is most sensitive to oxygen attack, and the presence of ethylene units in copolymers enhances the oxidation resistance of PP copolymers.<\/jats:p>","DOI":"10.3390\/polym15010200","type":"journal-article","created":{"date-parts":[[2023,1,2]],"date-time":"2023-01-02T02:44:03Z","timestamp":1672627443000},"page":"200","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":19,"title":["Spin Trapping Analysis of Radical Intermediates on the Thermo-Oxidative Degradation of Polypropylene"],"prefix":"10.3390","volume":"15","author":[{"given":"Thu Anh","family":"Nguyen","sequence":"first","affiliation":[{"name":"Doctor\u2019s Program of Materials Chemistry, Graduate School of Science and Technology, Kyoto Institute of Technology, Matsugasaki Sakyo, Kyoto 606-8585, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hui Ming","family":"Lim","sequence":"additional","affiliation":[{"name":"Undergraduate School of Applied Chemistry, Kyoto Institute of Technology, Kyoto 606-8585, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4342-3516","authenticated-orcid":false,"given":"Kenji","family":"Kinashi","sequence":"additional","affiliation":[{"name":"Faculty of Materials Science and Engineering, Kyoto Institute of Technology, Kyoto 606-8585, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0255-0861","authenticated-orcid":false,"given":"Wataru","family":"Sakai","sequence":"additional","affiliation":[{"name":"Faculty of Materials Science and Engineering, Kyoto Institute of Technology, Kyoto 606-8585, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8835-1347","authenticated-orcid":false,"given":"Naoto","family":"Tsutsumi","sequence":"additional","affiliation":[{"name":"Faculty of Materials Science and Engineering, Kyoto Institute of Technology, Kyoto 606-8585, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Satoko","family":"Okubayashi","sequence":"additional","affiliation":[{"name":"Faculty of Fiber Science and Engineering, Kyoto Institute of Technology, Kyoto 606-8585, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Satoru","family":"Hosoda","sequence":"additional","affiliation":[{"name":"Graduate School of Science & Technology, Kyoto Institute of Technology, Kyoto 606-8585, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tetsu","family":"Sato","sequence":"additional","affiliation":[{"name":"Tohoku Electronic Industrial Co., Ltd., Mukaiyama 2-14-1, Sendai, Miyagi 982-0841, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,12,30]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2006","DOI":"10.1021\/acs.accounts.8b00250","article-title":"The fate of the peroxyl radical in autoxidation: How does polymer degradation really occur?","volume":"51","author":"Smith","year":"2018","journal-title":"Acc. Chem. Res."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"609","DOI":"10.5254\/1.3543293","article-title":"Kinetic studies in the chemistry of rubber and related materials. II. The kinetics of oxidation of unconjugated olefins","volume":"20","author":"Bolland","year":"1947","journal-title":"Rubber Chem. Technol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"480","DOI":"10.1039\/C0OB00596G","article-title":"Revising the mechanism of polymer autooxidation","volume":"9","author":"Hodgson","year":"2011","journal-title":"Org. Biomol. Chem."},{"key":"ref_4","unstructured":"Moore, E.P. (1996). Polypropylene Handbook: Polymerization, Characterization, Properties, Processing, Applications, Hanser-Gardner."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"95","DOI":"10.1016\/0141-3910(93)90031-D","article-title":"The mechanism of the low-temperature oxidation of polypropylene","volume":"42","author":"Gijsman","year":"1993","journal-title":"Polym. Degrad. Stab."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"409","DOI":"10.1016\/0144-2880(86)90008-4","article-title":"Advantages and limits of hydroperoxide titration methods in solid polymers","volume":"7","author":"Gardette","year":"1986","journal-title":"Polym. Photochem."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1661","DOI":"10.1007\/s00289-011-0560-6","article-title":"Thermal degradation behavior of polypropylene in the melt state: Molecular weight distribution changes and chain scission mechanism","volume":"67","author":"Qian","year":"2011","journal-title":"Polym. Bull."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"355","DOI":"10.1016\/0141-3910(94)90205-4","article-title":"The oxidation mechanism of polypropylene: Contribution of 13C-NMR spectroscopy","volume":"45","author":"Vaillant","year":"1994","journal-title":"Polym. Degrad. Stab."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Corvaja, C. (2008). Introduction to Electron Paramagnetic Resonance. Electron Paramagnetic Resonance: A Practitioner\u2019s Toolkit, John Wiley & Sons, Inc.","DOI":"10.1002\/9780470432235.ch1"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"R\u00e5nby, R., and Rabek, J.F. (1977). ESR Spectroscopy in Polymer Research, Springer-Verlag.","DOI":"10.1007\/978-3-642-66600-1"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"21","DOI":"10.1016\/j.ymeth.2016.05.013","article-title":"Detection and characterisation of radicals using electron paramagnetic resonance (EPR) spin trapping and related methods","volume":"109","author":"Davies","year":"2016","journal-title":"Methods."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"907","DOI":"10.1021\/ed064p907","article-title":"Introduction to the interpretation of electron spin resonance spectra of organic radicals","volume":"64","author":"Bunce","year":"1987","journal-title":"J. Chem. Educ."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Eaton, G.R., Eaton, S.S., Barr, D.P., and Weber, R.T. (2010). Quantitative EPR, Springer.","DOI":"10.1007\/978-3-211-92948-3"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"31","DOI":"10.1021\/ar50037a005","article-title":"Spin Trapping","volume":"4","author":"Janzen","year":"1971","journal-title":"Acc. Chem. Res."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1289\/ehp.8564151","article-title":"Chemistry and biology of spin-trapping radicals associated with halocarbon metabolism in vitro and in vivo","volume":"64","author":"Janzen","year":"1985","journal-title":"Environ. Health Perspect."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"123416","DOI":"10.1016\/j.polymer.2021.123416","article-title":"Spin-trapping analysis for thermal degradation of poly(vinyl alcohol)","volume":"217","author":"Hayashi","year":"2021","journal-title":"Polymer"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"254","DOI":"10.1021\/acs.macromol.6b01942","article-title":"Spin-trapping analysis of thermal degradation reaction of poly(butylene terephthalate)","volume":"50","author":"Sono","year":"2017","journal-title":"Macromolecules"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1088","DOI":"10.1021\/acs.macromol.7b02654","article-title":"Spin-trapping analysis and characterization of thermal degradation of thermoplastic poly(ether\u2013ester) elastomer","volume":"51","author":"Sono","year":"2018","journal-title":"Macromolecules"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"109871","DOI":"10.1016\/j.polymdegradstab.2022.109871","article-title":"Spin trapping analysis of the thermal degradation of polypropylene","volume":"197","author":"Nguyen","year":"2022","journal-title":"Polym. Degrad. Stab."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"99","DOI":"10.1002\/pol.1961.1205015312","article-title":"Oxyluminescence from polypropylene","volume":"50","author":"Ashby","year":"1961","journal-title":"J. Polym. Sci."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"461","DOI":"10.1016\/0141-3910(94)90019-1","article-title":"Studies of chemiluminescence observed in photo-irradiated and weathered polypropylene in the early stages","volume":"43","author":"Osawa","year":"1994","journal-title":"Polym. Degrad. Stab."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"97","DOI":"10.1016\/0141-3910(88)90034-1","article-title":"Properties and chemiluminescence of polypropylene stored for a long period","volume":"22","author":"Osawa","year":"1988","journal-title":"Polym. Degrad. Stab."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"763","DOI":"10.1295\/polymj.22.763","article-title":"Chemiluminescence parameter for the degradation of polyolefins","volume":"22","author":"Kihara","year":"1990","journal-title":"Polym. J."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"263","DOI":"10.1016\/0141-3910(91)90122-8","article-title":"Chemiluminescence from peroxides in polypropylene. Part I: Relation of luminescence to peroxide content","volume":"34","author":"Billingham","year":"1991","journal-title":"Polym. Degrad. Stab."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"89","DOI":"10.1016\/0141-3910(96)00106-1","article-title":"Characterisation of polypropylene peroxides; their thermo-oxidative stability and reactivity towards dimethylsulfide","volume":"54","author":"Kron","year":"1996","journal-title":"Polym. Degrad. Stab."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"119","DOI":"10.1016\/0141-3910(96)00079-1","article-title":"Chemiluminescence from oxidation of polypropylene: Correlation with peroxide concentration","volume":"53","author":"Kron","year":"1996","journal-title":"Polym. Degrad. Stab."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"2680","DOI":"10.1016\/j.polymdegradstab.2013.09.031","article-title":"Thermal oxidative degradation of additive-free polypropylene pellets investigated by multichannel Fourier-transform chemiluminescence spectroscopy","volume":"98","author":"Yano","year":"2013","journal-title":"Polym. Degrad. Stab."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"109575","DOI":"10.1016\/j.polymdegradstab.2021.109575","article-title":"Chemiluminescence studies on the photooxidation of isotactic polypropylene","volume":"188","author":"Hosoda","year":"2021","journal-title":"Polym. Degrad. Stab."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"403","DOI":"10.1007\/s00723-018-0984-3","article-title":"Impregnation of Polycarbonate by Paramagnetic Probe 2,2,6,6-tetramethyl-4-hydroxy-piperidine-1-oxyl (TEMPOL) in supercritical CO2","volume":"49","author":"Akovantseva","year":"2018","journal-title":"Appl. Magn. Reson."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Gromov, O.I., Kostenko, M.O., Petrunin, A.V., Popova, A.A., Parenago, O.O., Minaev, N.V., Golubeva, E.N., and Melnikov, M.Y. (2021). Solute Diffusion into Polymer Swollen by Supercritical CO2 by and Chromatography. Polymers, 13.","DOI":"10.3390\/polym13183059"},{"key":"ref_31","unstructured":"Wunderlich, B. (1980). Macromolecular Physics, Academic Press. [3rd ed.]."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"203","DOI":"10.1002\/polc.5070070115","article-title":"Contribution to the study of ethylene-propylene copolymers by infrared spectroscopy. Distribution of monomeric units","volume":"7","author":"Bucci","year":"1964","journal-title":"J. Polym. Sci. Part C Polym. Symp."},{"key":"ref_33","unstructured":"Coates, J., and Meyers, R.A. (2006). Interpretation of infrared spectra, a practical approach. Encyclopedia of Analytical Chemistry: Applications, Heory and Instrumentation, John Wiley & Sons, Ltd."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1155\/2012\/382639","article-title":"Needleless melt-electrospinning of polypropylene nanofibers","volume":"2012","author":"Fang","year":"2012","journal-title":"J. Nanomater."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"478","DOI":"10.1049\/mnl.2016.0812","article-title":"Oxidative degradation and morphological properties of gamma-irradiated isotactic polypropylene films","volume":"12","author":"Mouaci","year":"2017","journal-title":"Micro Nano Lett."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"357","DOI":"10.1016\/0032-3861(61)90038-6","article-title":"The constitution of ethylene-propylene copolymers","volume":"2","author":"Duck","year":"1961","journal-title":"Polymer"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"442","DOI":"10.1590\/S1516-14392011005000080","article-title":"Degradation study of polypropylene (PP) and bioriented polypropylene (BOPP) in the environment","volume":"14","author":"Longo","year":"2011","journal-title":"Mater. Res."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"1475","DOI":"10.1016\/j.polymdegradstab.2012.05.005","article-title":"Analysis of thermomechanical reprocessing effects on polypropylene\/ethylene octene copolymer blends","volume":"97","author":"Wang","year":"2012","journal-title":"Polym. Degrad. Stab."},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Esmizadeh, E., Tzoganakis, C., and Mekonnen, T.H. (2020). Degradation behavior of polypropylene during reprocessing and its biocomposites: Thermal and oxidative degradation kinetics. Polymers, 12.","DOI":"10.3390\/polym12081627"},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Ng, H.M., Saidi, N.M., Omar, F.S., Ramesh, K., Ramesh, S., and Bashir, S. (2018). Thermogravimetric Analysis of Polymers. Encyclopedia of Polymer Science and Technology, John Wiley & Sons, Ltd.","DOI":"10.1002\/0471440264.pst667"},{"key":"ref_41","first-page":"1198","article-title":"Study of the thermo-oxidative degradation behavior of isotactic polypropylene with the varying ethylene content","volume":"46B","author":"Alam","year":"2007","journal-title":"Indian J. Chem. Sect. B"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"221","DOI":"10.3109\/10915818809014521","article-title":"Polypropylene: A literature review of the thermal decomposition products and toxicity","volume":"7","author":"Purohit","year":"1988","journal-title":"J. Am. Coll. Toxicol."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"5220","DOI":"10.1021\/ma00046a017","article-title":"Photoinitiated crosslinking of low-density polyethylene. 7. Initial radical reactions with model compounds studied by spin-trapping ESR spectroscopy","volume":"25","author":"Qu","year":"1992","journal-title":"Macromolecules"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"259","DOI":"10.1016\/S0891-5849(87)80033-3","article-title":"Spin Trapping: ESR parameters of spin adducts","volume":"3","author":"Buettner","year":"1987","journal-title":"Free Radic. Biol. Med."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"4306","DOI":"10.1021\/ja00746a044","article-title":"Spin trapping of short-lived free radicals by use of 2,4,6-tri-tert-butylnitrosobenzene","volume":"93","author":"Terabe","year":"1971","journal-title":"J. Am. Chem. Soc."},{"key":"ref_46","first-page":"35","article-title":"A spin-trapping study on crosslinks induced by \u03b3- and neutron irradiations of n-eicosane","volume":"27","author":"Tabata","year":"1986","journal-title":"Int. J. Radiat. Appl. Istrum. C Radiat. Phys. Chem."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"5215","DOI":"10.1021\/ma00046a016","article-title":"Photoinitiated cross-linking of low-density polyethylene. 6. Spin-trapping ESR studies on radical intermediates","volume":"25","author":"Qu","year":"1992","journal-title":"Macromolecules"},{"key":"ref_48","first-page":"369","article-title":"Spin trapping of carboxylic esters \u03b3-irradiated in solid and liquid phases","volume":"16","author":"Tabata","year":"1980","journal-title":"Radiat. Phys. Chem."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"559","DOI":"10.1016\/0014-3057(80)90087-7","article-title":"Hydrogen atom abstraction from polypropylene and polystyrene by t-butoxy radical site of radical attack studied by spin trapping","volume":"16","author":"Niki","year":"1980","journal-title":"Eur. Polym. J."},{"key":"ref_50","first-page":"200","article-title":"Photoinduced reactions of dibenzoyl peroxide as studied by EPR and spin-trapping","volume":"47","author":"Rosenthal","year":"1982","journal-title":"J. Magn. Reson."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"2709","DOI":"10.1016\/S0040-4039(01)96959-X","article-title":"Photolysis of polyhalomethanes in the presence of nitrosoalkanes formation of acyl alkyl nitroxides","volume":"12","author":"Hartgerink","year":"1971","journal-title":"Tetrahedron Lett."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"2095","DOI":"10.1007\/BF00953412","article-title":"Oxidation of secondary cyclic alcohols by Pb(OAc)4 catalyzed by Cu(II) compounds","volume":"37","author":"Kapustina","year":"1988","journal-title":"Bull. Acad. Sci. USSR Div. Chem. Sci."},{"key":"ref_53","doi-asserted-by":"crossref","unstructured":"Luo, Y.-R. (2002). Handbook of Bond Dissociation Energies in Organic Compounds, CRC Press.","DOI":"10.1201\/9781420039863"},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"217","DOI":"10.1016\/0079-6700(90)90029-Z","article-title":"Thermal oxidation of polyethylene and polypropylene: Effects of chemical structure and reaction conditions on the oxidation process","volume":"15","author":"Iring","year":"1990","journal-title":"Prog. Polym. Sci."},{"key":"ref_55","unstructured":"Zlatkevich, L. (1989). Luminescence Techniques in Solid State Polymer Research, Marcel Dekker, Inc."},{"key":"ref_56","doi-asserted-by":"crossref","unstructured":"Deblieck, R., Remerie, K., den Fonteyne, W.V., and Boerakker, M. (2021). A morphology-based model to describe the low-temperature impact behaviour of rubber-toughened polypropylene. Polymers, 13.","DOI":"10.3390\/polym13132218"}],"container-title":["Polymers"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2073-4360\/15\/1\/200\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T01:48:51Z","timestamp":1760147331000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2073-4360\/15\/1\/200"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,12,30]]},"references-count":56,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2023,1]]}},"alternative-id":["polym15010200"],"URL":"https:\/\/doi.org\/10.3390\/polym15010200","relation":{},"ISSN":["2073-4360"],"issn-type":[{"value":"2073-4360","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,12,30]]}}}