Biodegradation of starch-graft-polystyrene and starch-graft- poly(methacrylic acid) copolymers in model river water

Abstract

In this paper, a biodegradation study of grafted copolymers of cornstarch and polystyrene (PS) and cornstarch and poly(methacrylic acid) in model river water is described. These copolymers were obtained in the presence of different amine activators. The synthesized copolymers and products of degradation were characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). Biodegradation was monitored by mass decrease and the number of microorganisms by the Koch method. Biodegradation of both copolymers advanced with time, the starch- -graft-poly(methacrylic acid) copolymers had completely degraded after 21 day, and the starch-graft-polystyrene had partially degraded (45.8-93.1 % mass loss) after 27 days. The differences in the degree of biodegradation are the consequences of the different structures of the samples, and there was a significant negative correlation between the share of polystyrene in the copolymer and the degree of biodegradation. The grafting degree of PS necessary to prevent biodegradation was 54 %. Based on experimental evidence, the mechanisms of both biodegradation processes are proposed, and influence of degree of starch and synthetic component of copolymers on the degradation of the samples were established. Copyright ©2013 SCS.