Study of polypropylene degradation in aqueous environment

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Kemian tekniikan korkeakoulu | Master's thesis
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Date

2022-10-18

Department

Major/Subject

Functional Materials for Global Challenge

Mcode

CHEM3061

Degree programme

Master's Programme in Advanced Materials for Innovation and Sustainability

Language

en

Pages

70 + 1

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Abstract

Plastic waste in sea, originating from common synthetic polymers, is a major contemporary environmental concern. Even though degradation mechanisms of plastics in sea have already been studied and described, there is still more to be discovered about the resilience of many of the widely used polymers. Polyamide (PA), polyethylene (PE), and polypropylene (PP) account for 80.7 % of ocean plastics pollution (1). This document presents an experimental study on the degradation of PP immersed in seawater. Filament shaped samples were aged for a time varying from one to seven years in 3 different locations around the French coast. The samples were subjected to mechanical, morphological, and chemical analysis through traction tests, scanning electron microscopy (SEM) and infrared spectroscopy and compared to an appropriate control reference, that is, an unaged PP sample. The study focused on three degradation factors that are hydrolysis, sediment abrasion, and UV alterations. The role that microbial colonization may play in the degradation of the polymer by biofouling is also discussed. Results shows that PP is strongly durable in sea environment. While some surface degradation can be seen by SEM, the mechanical properties were not markedly altered. At times, even a 20% increase in Young’s modulus was observed after seven years in immersion. No chemical alterations were observed with IR spectroscopy but a more thorough study with MALDI-TOF analysis was suggested for the future to study degradation more in detail. An experimental protocol was also suggested in order to create a model for an in vitro accelerated ageing of polymers while reproducing a natural degradation environment. In a more applied context that triggered the research in this thesis, the results yielded important knowledge on how man-made plastic systems in sea can withstand natural conditions under prolonged time spans. Such systems include Roselière : PP strands attached to a strap that are introduced to coastal regions to protect native seagrass populations from hydrodynamic fluxes and provide shelter for juvenile fishes.

Description

Supervisor

Kontturi, Eero

Thesis advisor

Musnier, Alexandre

Keywords

aqueous, degradation, polypropylene, sea, water, pollution

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https://urn.fi/URN:NBN:fi:aalto-202210236200

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[dipl] Kemian tekniikan korkeakoulu / CHEM