Study on the degradation of biodegradable poly (glycerol maleate) (PGM) microbeads

Abstract

Plastics contributed from personal care products and plastic fragments are considered as one of the most common pollutants in the ocean since 1970s. In this study, poly (glycerol maleate) (PGM) is applied as the alternative of microbeads due to its high degradability in the water and the relatively low cost compared to other biodegradable polymers. The proposed PGM microbeads are fabricated via solvent evaporation methods with average diameter around 30 +/- 13 mm and polydispersity index around 0.2 to 0.3. To identify the degradability of PGM microbeads in different water solutions, samples were examined in buffer solution with different pH values, DI water, sea water and enzyme solution through total organic carbon (TOC) analyzer/UV-Vis spectrometry, microscopy, and SEM. These microbeads were completely degraded in 45 min in alkaline solution (pH 10). In contrast, 60% of PGM microbeads were degraded in 30 days in the acidic solution (pH 4). It revealed that the base catalysis of hydrolysis was quicker than acid catalysis. 50% more of PGM microbeads were degraded in the refreshed DI water in a month. However, only 36% of microbeads were degraded in synthetic sea water. The high salinity was suspected to obstruct the hydrolysis of PGM microbeads and slow down the degradation rate. Lipase solution is conducted to examine the possibility of bio-accumulation once PGM microbeads ingested inside the living organism, and the result shows that PGM microbeads degrade mostly in seven days. It is worthy to note that PLA microbeads only degrade at pH 10 in this study. With the comparison between PGM and PLA microbeads, PGM is more easily degraded and affordable, and it is thought to have great potential for being the alternative to plastic microbeads.