Study on the onset mechanism of bio-blister degradation of polyolefin by diatom attachment in seawater

Abstract

It is essential to develop a mechanism for lowering the molecular weight of polyolefins to achieve biodegradation in seawater. In this study, a prephotodegradation treatment was applied to a blend sample to generate hydroperoxide groups in the polypropylene component of the blend to initiate autoxidation and generate carboxylic acid substances in the poly(lactic acid) component of the blend to promote autoxidation. However, the generated carboxylic acid substances were neutralized in seawater, which is alkaline, disabling the acid-activated autoxidation mechanism for developing biodegradability of the blend. Although aqueous Cl− was an effective inhibitor of autoxidation of polyolefins in seawater, autoxidation could be initiated using the dissociation of ClOH (called blister degradation) to lower the seawater pH. The blister degradation mechanism enabled autoxidation, even in seawater, by taking advantage of the ability of diatoms to secrete transparent exopolymer particles (TEP) to prevent direct contact between the surface layer of polyolefins and alkaline seawater. Bio-blister degradation induced by diatoms was characterized for a linear low-density polyethylene (LLDPE)/starch sample. SEM, IR, and DSC analyses showed that diatoms induced the disintegration of the LLDPE component of the blend sample in seawater.