{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,13]],"date-time":"2026-04-13T05:23:43Z","timestamp":1776057823300,"version":"3.50.1"},"reference-count":46,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2023,1,31]],"date-time":"2023-01-31T00:00:00Z","timestamp":1675123200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e Tecnologia","doi-asserted-by":"publisher","award":["UIDB\/00481\/2020"],"award-info":[{"award-number":["UIDB\/00481\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e Tecnologia","doi-asserted-by":"publisher","award":["UIDP\/00481\/2020"],"award-info":[{"award-number":["UIDP\/00481\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e Tecnologia","doi-asserted-by":"publisher","award":["CENTRO-01-0145-FEDER-022083"],"award-info":[{"award-number":["CENTRO-01-0145-FEDER-022083"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100014717","name":"Programa Operacional Regional do Centro","doi-asserted-by":"publisher","award":["UIDB\/00481\/2020"],"award-info":[{"award-number":["UIDB\/00481\/2020"]}],"id":[{"id":"10.13039\/501100014717","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100014717","name":"Programa Operacional Regional do Centro","doi-asserted-by":"publisher","award":["UIDP\/00481\/2020"],"award-info":[{"award-number":["UIDP\/00481\/2020"]}],"id":[{"id":"10.13039\/501100014717","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100014717","name":"Programa Operacional Regional do Centro","doi-asserted-by":"publisher","award":["CENTRO-01-0145-FEDER-022083"],"award-info":[{"award-number":["CENTRO-01-0145-FEDER-022083"]}],"id":[{"id":"10.13039\/501100014717","id-type":"DOI","asserted-by":"publisher"}]},{"name":"European Regional Development Fund","award":["UIDB\/00481\/2020"],"award-info":[{"award-number":["UIDB\/00481\/2020"]}]},{"name":"European Regional Development Fund","award":["UIDP\/00481\/2020"],"award-info":[{"award-number":["UIDP\/00481\/2020"]}]},{"name":"European Regional Development Fund","award":["CENTRO-01-0145-FEDER-022083"],"award-info":[{"award-number":["CENTRO-01-0145-FEDER-022083"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>Single-use plastics are a matter of convenience in everyday life, with the majority allocated to packaging production. However, it comes with a high environmental price as its mass recycling is challenging due to the heterogeneity of composition, contaminations of different kinds, and degradation caused by service and processing. This study aims to ascertain the impact of removing contaminants from post-consumer recycled polypropylene (rPP) on its degradation and properties by implementing a systematic approach for decontamination by washing. Four lots of recycled plastics with different degrees of contamination were evaluated via Fourier transform infrared, melt flow indexer, and differential scanning calorimetry and tested for tensile strength. Degradation of the rPP was manifested by the deterioration in ductility, resulting in 14.58% elongation at break (unwashed rPP) compared with 191.41% (virgin PP)) and a significant reduction in oxidation induction time. In the unwashed rPP sample, a wave intensity peak at 1730 cm\u22121, assigned to the saturated C = 0 stretch of the carbonyl functional group, was detected. This peak was gradually disappearing with an increase in the cleaning efficiency of rPP, highlighting the role of contaminants as degradation catalysts. The cold-washing method showed similar processing and mechanical performance improvement results compared with the other washing methods, while being more environmentally friendly and energy efficient.<\/jats:p>","DOI":"10.3390\/ma16031198","type":"journal-article","created":{"date-parts":[[2023,1,31]],"date-time":"2023-01-31T01:35:45Z","timestamp":1675128945000},"page":"1198","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":17,"title":["Assessment of the Impact of Superficial Contamination and Thermo-Oxidative Degradation on the Properties of Post-Consumer Recycled Polypropylene"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5288-7908","authenticated-orcid":false,"given":"Laura","family":"Prior","sequence":"first","affiliation":[{"name":"Department of Mechanical Engineering, Centre for Mechanical Technology and Automation (TEMA), University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6190-1238","authenticated-orcid":false,"given":"M\u00f3nica S. A.","family":"Oliveira","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, Centre for Mechanical Technology and Automation (TEMA), University of Aveiro, 3810-193 Aveiro, Portugal"},{"name":"LASI\u2014Intelligent Systems Associate Laboratory, 4800-058 Guimaraes, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2150-6241","authenticated-orcid":false,"given":"Tatiana","family":"Zhiltsova","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, Centre for Mechanical Technology and Automation (TEMA), University of Aveiro, 3810-193 Aveiro, Portugal"},{"name":"LASI\u2014Intelligent Systems Associate Laboratory, 4800-058 Guimaraes, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2023,1,31]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Carraher, C.E. (2013). Introduction to Polymer Chemistry, CRC Press.","DOI":"10.1201\/b13684"},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Francis, R. (2017). Recycling of Polymers: Methods, Characterization and Applications, John Wiley & Sons.","DOI":"10.1002\/9783527689002"},{"key":"ref_3","unstructured":"(2022, July 12). European Commission A European Strategy for Plastics in a Circular Economy 2018. Available online: https:\/\/www.europarc.org\/wp-content\/uploads\/2018\/01\/Eu-plastics-strategy-brochure.pdf."},{"key":"ref_4","unstructured":"(2022, September 24). Plastics Europe Plastics\u2014the Facts 2021 An Analysis of European Plastics Production, Demand and Waste Data. Available online: https:\/\/plasticseurope.org\/knowledge-hub\/plastics-the-facts-2021\/."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"35","DOI":"10.2174\/1876400201003010035","article-title":"Post-Consumer Polyolefins (PP-PE) Recognition by Combined Spectroscopic Sensing Techniques","volume":"3","author":"Serranti","year":"2010","journal-title":"Open Waste Manag. J."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Karaagac, E., Jones, M.P., Koch, T., and Archodoulaki, V.-M. (2021). Polypropylene Contamination in Post-Consumer Polyolefin Waste: Characterisation, Consequences and Compatibilisation. Polymers, 13.","DOI":"10.3390\/polym13162618"},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Garofalo, E., Di Maio, L., Scarfato, P., Pietrosanto, A., Protopapa, A., and Incarnato, L. (2021). Study on Improving the Processability and Properties of Mixed Polyolefin Post-Consumer Plastics for Piping Applications. Polymers, 13.","DOI":"10.3390\/polym13010071"},{"key":"ref_8","first-page":"2368","article-title":"Compatibilization Efficiency in Post-Consumer Recycled Polyethylene\/Polypropylene Blends: Effect of Contamination. Polym","volume":"55","author":"Kazemi","year":"2015","journal-title":"Eng. Sci."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"31","DOI":"10.1016\/S0141-3910(02)00379-8","article-title":"Evaluation and Identification of Degradative Processes in Post-Consumer Recycled High-Density Polyethylene. Polym","volume":"80","author":"Cruz","year":"2003","journal-title":"Degrad. Stab."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"75","DOI":"10.1016\/j.wasman.2019.07.005","article-title":"Closing the Loop for PET, PE and PP Waste from Households: Influence of Material Properties and Product Design for Plastic Recycling","volume":"96","author":"Eriksen","year":"2019","journal-title":"Waste Manag."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"110868","DOI":"10.1016\/j.marpolbul.2019.110868","article-title":"Evaluation of Polypropylene Plastic Degradation and Microplastic Identi Fi Cation in Sediments at Tambak Lorok Coastal Area, Semarang, Indonesia","volume":"151","author":"Khoironi","year":"2020","journal-title":"Mar. Pollut. Bull."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"703","DOI":"10.1016\/j.polymdegradstab.2010.12.004","article-title":"Degradability of Linear Polyole Fi Ns under Natural Weathering","volume":"96","author":"Ojeda","year":"2011","journal-title":"Polym. Degrad. Stab."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"6389","DOI":"10.1016\/S0032-3861(97)00214-0","article-title":"Crystallisation and Melting Behaviour of Photodegraded Polypropylene\u2014II. Re-Crystallisation of Degraded Molecules","volume":"38","author":"Rabello","year":"1997","journal-title":"Polymer (Guildf)"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"12","DOI":"10.1016\/j.polymdegradstab.2020.109434","article-title":"Probing into the Microstructural Evolution of Isotactic Polypropylene during Photo-Oxidation Degradation","volume":"183","author":"Wu","year":"2021","journal-title":"Polym. Degrad. Stab."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"2912","DOI":"10.3390\/polym6122912","article-title":"The Effect of Multiple Extrusions on the Properties of Montmorillonite Filled Polypropylene","volume":"6","author":"Delva","year":"2014","journal-title":"Polymers"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"509","DOI":"10.1016\/j.polymdegradstab.2003.08.010","article-title":"Changes in the Crystalline Phase during the Thermo-Oxidation of a Metallocene Isotactic Polypropylene. A DSC Study","volume":"83","author":"Elvira","year":"2004","journal-title":"Polym. Degrad. Stab."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"3622","DOI":"10.1021\/ma0116248","article-title":"Crystallisation of the \u03b1 and \u03b3 Forms of Isotactic Polypropylene as a Tool to Test the Degree of Segregation of Defects in the Polymer Chains","volume":"35","author":"Auriemma","year":"2002","journal-title":"Macromolecules"},{"key":"ref_18","unstructured":"Scott, G. (2012). Mechanisms of Polymer Degradation and Stabilisation, Springer."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"145","DOI":"10.1002\/masy.19890280111","article-title":"Localization of Oxidation in Polypropylene","volume":"28","author":"Billingham","year":"1989","journal-title":"Makromol. Chemie. Macromol. Symp."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"24","DOI":"10.1016\/j.wasman.2017.07.044","article-title":"Van Mechanical and Chemical Recycling of Solid Plastic Waste","volume":"69","author":"Ragaert","year":"2017","journal-title":"Waste Manag."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"109390","DOI":"10.1016\/j.polymdegradstab.2020.109390","article-title":"Thermo-Mechanical Degradation of Polypropylene (PP) and Low-Density Polyethylene (LDPE) Blends Exposed to Simulated Recycling","volume":"182","author":"Saikrishnan","year":"2020","journal-title":"Polym. Degrad. Stab."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"63","DOI":"10.1016\/S0142-9418(98)00008-7","article-title":"Odour Reduction on Plastics and Its Measurement","volume":"18","author":"Bledzki","year":"1999","journal-title":"Polym. Test."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"104907","DOI":"10.1016\/j.resconrec.2020.104907","article-title":"Development and Application of an Analytical Method to Quantify Odour Removal in Plastic Waste Recycling Processes","volume":"161","author":"Demets","year":"2020","journal-title":"Resour. Conserv. Recycl."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1500","DOI":"10.1002\/jssc.201601077","article-title":"Characterization of Odorous Contaminants in Post-Consumer Plastic Packaging Waste Using Multidimensional Gas Chromatographic Separation Coupled with Olfactometric Resolution","volume":"40","author":"Strangl","year":"2017","journal-title":"J. Sep. Sci."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"999","DOI":"10.1080\/02652030500157742","article-title":"Post-Consumer Contamination in High-Density Polyethylene (HDPE) Milk Bottles and the Design of a Bottle-to-Bottle Recycling Process","volume":"22","author":"Welle","year":"2005","journal-title":"Food Addit. Contam."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"1237","DOI":"10.1016\/j.polymertesting.2013.08.002","article-title":"Effect of Residual Contaminants and of Different Types of Extrusion Processes on the Rheological Properties of the Post-Consumer Polypropylene","volume":"32","author":"Garcia","year":"2013","journal-title":"Polym. Test."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"3474","DOI":"10.1007\/s10924-022-02447-9","article-title":"Thermal Stability and Crystallisation Behavior of Contaminated Recycled Polypropylene for Food Contact","volume":"30","author":"Veroneze","year":"2022","journal-title":"J. Polym. Environ."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"121104","DOI":"10.1016\/j.jclepro.2020.121104","article-title":"Odor Characterization along the Recycling Process of Post-Consumer Plastic Film Fractions","volume":"260","author":"Strangl","year":"2020","journal-title":"J. Clean. Prod."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"341","DOI":"10.1016\/0141-3910(95)00088-4","article-title":"Degradation of Contaminated Plastics: A Kinetic Study","volume":"48","author":"Day","year":"1995","journal-title":"Polym. Degrad. Stab."},{"key":"ref_30","unstructured":"(2022, July 04). The Association of Plastics Reciclers Polyolefin Standard Laboratory Processing Practices. Available online: https:\/\/plasticsrecycling.org\/images\/Design-Guidance-Tests\/APR-O-P-00-olefin-practices.pdf."},{"key":"ref_31","unstructured":"(2004). Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer (Standard No. ASTM International D 1238-04)."},{"key":"ref_32","unstructured":"(2004). Standard Test Method for Transition Temperatures of Polymers by Differential Calorimetry (Standard No. ASTM D 3418-03)."},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Ehrenstein, G.W., Riedel, G., and Trawiel, P. (2004). Thermal Analysis of Plastics, Hanser Publishers.","DOI":"10.3139\/9783446434141.fm"},{"key":"ref_34","unstructured":"(2015). Standard Test Method for Oxidative-Induction Time of Polyolefins by Differential Scanning Calorimetry (Standard No. ASTM D3895-14)."},{"key":"ref_35","unstructured":"(1996). Plastics\u2014Determination of Tensile Properties\u2014Part 2: Test Conditions for Moulding and Extrusion Plastics (Standard No. ISO 527-2)."},{"key":"ref_36","unstructured":"(2012). Plastics\u2014Determination of Tensile Properties\u2014Part 1: General Principles (Standard No. ISO 527-1)."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"182","DOI":"10.1016\/j.polymertesting.2018.05.008","article-title":"Correlating Different Techniques in the Thermooxidative Degradation Monitoring of High-Density Polyethylene Containing pro-Degradant and Antioxidants","volume":"69","author":"Antunes","year":"2018","journal-title":"Polym. Test."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"462","DOI":"10.1016\/j.polymdegradstab.2010.01.013","article-title":"Gamma Polymorph and Branching Formation as Inductors of Resistance to Electron Beam Irradiation in Metallocene Isotactic Polypropylene","volume":"95","author":"Cerrada","year":"2010","journal-title":"Polym. Degrad. Stab."},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Karger-Kocsis, J., and B\u00e1r\u00e1ny, T. (2019). Polypropylene Handbook-Morphology, Blends and Composites, Springer.","DOI":"10.1007\/978-3-030-12903-3"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"91","DOI":"10.1007\/s10924-019-01579-9","article-title":"Reprocessing and Solid State Polymerization on Contaminated Post-Consumer PET: Thermal and Crystallisation Behavior","volume":"28","author":"Fitaroni","year":"2020","journal-title":"J. Polym. Environ."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"494","DOI":"10.1007\/s10924-021-02214-2","article-title":"The Role of Residual Contaminants and Recycling Steps on Rheological Properties of Recycled Polypropylene","volume":"30","author":"Paiva","year":"2022","journal-title":"J. Polym. Environ."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"119","DOI":"10.1016\/S0141-3910(03)00172-1","article-title":"Catalyst Residue Effects on the Heterogeneous Oxidation of Polypropylene","volume":"82","author":"Goss","year":"2003","journal-title":"Polym. Degrad. Stab."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"117978","DOI":"10.1016\/j.jclepro.2019.117978","article-title":"Mixed Post-Consumer Recycled Polyolefins as a Property Tuning Material for Virgin Polypropylene","volume":"239","author":"Curtzwiler","year":"2019","journal-title":"J. Clean. Prod."},{"key":"ref_44","doi-asserted-by":"crossref","unstructured":"Smith, B.C. (2018). Infrared Spectral Interpretation: A Systematic Approach, CRC Press.","DOI":"10.1201\/9780203750841"},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Karger-Kocsis, J. (1998). Polypropylene: An A-Z Reference, Kluwer Academic Publishers.","DOI":"10.1007\/978-94-011-4421-6"},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Wang, K., Peng, Y., Matadi Boumbimba, R., Bahlouli, N., Pessey, D., Ahzi, S., Addiego, F., and R\u00e9mond, Y. (2019). Constitutive Modeling of the Tensile Behavior of Recycled Polypropylene-Based Composites. Materials, 12.","DOI":"10.20944\/preprints201906.0177.v1"}],"container-title":["Materials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1944\/16\/3\/1198\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T18:20:31Z","timestamp":1760120431000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1944\/16\/3\/1198"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,1,31]]},"references-count":46,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2023,2]]}},"alternative-id":["ma16031198"],"URL":"https:\/\/doi.org\/10.3390\/ma16031198","relation":{},"ISSN":["1996-1944"],"issn-type":[{"value":"1996-1944","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,1,31]]}}}