Sunlight and marine weathering of poly(oxymethylene): Evolution of the physico-chemical properties

Abstract

Plastic pollution is now an environmental problem that affects all environmental compartments. The study of plastic degradation in terrestrial, marine and other freshwater environments is emerging. Research is mainly focused on plastic fragmentation into microplastics. In this contribution, an engineering polymer, poly(oxymethylene) (POM), was studied under different weathering conditions using physico-chemical characterization techniques. A POM homopolymer and a POM copolymer were characterized by electron microscopy, tensile tests, DSC, infrared spectroscopy and rheometry tests after climatic and marine weathering or artificial UV/water spray cycles. Natural climatic conditions were the most favorable for POM degradation, especially under solar UV, as evidenced by the strong fragmentation into microplastics when subjected to artificial UV cycles. The evolution of properties with exposure time was found to be non-linear under natural conditions, in contrast to artificial conditions. Two main stages of degradation were evidenced by the correlation between strain at break and carbonyl indices.

Keywords: Marine weathering; Photodegradation; Plastic pollution; Polyoxymethylene; Solar weathering.