Study of the degradation and recyclability of polyethylene and polypropylene present in the marine environment Kauê Pelegrini , 1 Thuany Garcia Maraschin, 2 Rosmary Nichele Brandalise, 1 Diego Piazza 1 1 University of Caxias do Sul, Caxias do Sul-RS, 95.070-560, Brazil 2 Pontifícia Universidade Católica, Porto Alegre-RS, 90.619-900, Brazil Correspondence to: K. Pelegrini (E-mail: kaue_pel@hotmail.com) ABSTRACT: Polypropylene (PP) and polyethylene (PE) are two of the most widely used polymers in the world, and consequently the main polymer waste that contributes to the pollution of the oceans. Because they are considered inert to degradation, such waste becomes a threat to marine life. In this study, it was possible to collect data on the recyclability of PP and PE waste collected from the Great Pacific Garbage Patch. First, the degradation conditions suffered by these materials were evaluated. The Fourier transform infrared spectroscopy assays presented different levels of carbonyl in different layers below the surface of each material and scanning electron microscopy tests showed cracks and microorganisms. The mechanical and rheological properties were evaluated in order to evaluate the recyclability of samples exposed to the marine environment. From the study, it can be concluded that, despite the levels of degradation of the samples, it is possible to obtain satisfac- tory properties for mechanically recycled products. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48215. KEYWORDS: degradation; marine environment; polyethylene; polypropylene; recycling Received 5 January 2019; accepted 19 June 2019 DOI: 10.1002/app.48215 INTRODUCTION One of the biggest environmental problems today is the accumulation of polymeric waste in the oceans. It is estimated that, in the year 2010, 4.8–12.7 tons of polymer waste were generated on land and had as their destination the oceans. 1 When present in these environ- ments, polymeric waste can cause negative impacts on wildlife. 2–4 Polyethylene (PE) and polypropylene (PP) are the most widely employed polymers due to their good properties, easy processing, low cost, and for being recyclable. However, due to improper disposition of this material after use, and for being considered inert to degrada- tion, PE and PP can stay in our environment for many years. 5 For being constituted of carbon and hydrogen, polyolefins should not degrade; however, the presence of chromophoric groups resulting from the synthesis and processing can leave the polyolefin susceptible to degradation such as photooxidation. 6 By absorbing the UV rays, free radicals are produced, and from these, oxidation can occur which is indicative of degradation of the material. Oxidation occurs more slowly in the marine environment com- pared to materials exposed to air, because this environment pro- vides a lower temperature. 7 The degradation of a polymer can be verified by alterations of the chemical, thermal, morphological, rheological, and mechanical properties, among others. One of the techniques used to measure the degradation of a polymer is Fourier transform infrared spec- troscopy (FTIR), with which it is possible to identify possible changes in the composition of the material, as well as other func- tional groups generated by the degradation. The rheological properties of the polymeric materials can also be affected by the degradation. Oxidative degradation of the polymers may cause the polymers to undergo mainly chain breaks, crosslinkings, and branching. Chain breaks can cause a decrease in the molar mass of the polymers and consequently change their melt flow index. 8 Degradation can lead to loss of mechanical strength, mainly due to the rup- ture of the polymer chains and the formation of cracks on the material sur- face. 9 Therefore, degradation from exposure of the polymers to the weather and the degradation caused by the processing steps lead the recycled poly- mers to have their mechanical properties aggravated. According to some studies, after photooxidation the polymer may fragment, absorb water from the environment, and then begin the biodegradation process. 10 In view of the above, the objective of this work is to evaluate the deg- radation of post-consumer PE and PP samples present in the marine environment, as well as their recyclability regarding mechanical recycling. A further objective of this study is to find the maximum carbonyl content limiting the recyclability of the polyethylene (PE) and PP waste present in the marine environment. MATERIALS AND METHODS Materials For this work, samples of PE and PP collected in the marine environment of the Great Pacific Garbage Patch, which has its © 2019 Wiley Periodicals, Inc. 48215 (1 of 7) J. APPL. POLYM. SCI. 2019, DOI: 10.1002/APP.48215