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.

U ovom radu proučavana je biodegradacija kalemljenih kopolimera kukuruznog skroba i polistirena i kukuruznog skroba i poli(metakrilne kiseline) u rečnoj vodi. Ovi kopolimeri su sintetisani u prisustvu različitih aminoaktivatora. Sintetisani kopolimeri i produkta biodegradacije su karakterisani FTIR spektroskopijom i SEM mikroskopijom. Biodegradacija je praćena gubitkom mase uzoraka, a broj mikroorganizama Kohovom metodom. Stepen biodegradacije obe vrste kopolimera raste sa vremenom. Kalemljeni polimeri skroba i poli(metakrilne kiseline) potpuno se razgrađuju za 21 dan, dok se polimeri na bazi skroba i polistirena delimično razgrađuju nakon 27 dana (45,8-93,1 % od ukupne mase). Razlike u stepenu biodegradacije su posledica različite strukture uzoraka, a postoji i značajna negativna korelacija između udela polistirena u kopolimeru i stepena biodegradacije. Stepen kalemljenja polistirena (udeo polistirena u kopolimeru) koji sprečava biodegradaciju iznosio je 54 %. Na osnovu eksperimentalnih dokaza, predloženi su mehanizmi oba biodegradaciona procesa i ustanovljeni su uticaji količine skroba i sintetske komponente kopolimera na biodegradaciju.