Soil burial biodegradation of antimicrobial biodegradable PBAT films

Recently, biodegradable polymers have been broadly used in various applications, including antimicrobial biodegradable composite materials. However, the biodegradability of such polymers in the presence of antimicrobial agents has barely been investigated. Moreover, whether the antimicrobial property of the material would be compromised or affected by the microorganisms in the soil is still unclear. In this work, the biodegradation behavior and antimicrobial property of the novel antimicrobial biodegradable poly(butylene adipate-co-terephthalate) (PBAT)/thermoplastic starch films before and after a three-month soil burial test have been investigated. The weight retention data showed that both PBAT and starch were still able to degrade even in the presence of the antimicrobial substance, polyhexamethylene guanidine hydrochloride (PHGH). However, the biodegradation rate was retarded. The antimicrobial films exhibited excellent growth inhibition against E. coli before biodegradation test. The film with the coupling agent 2,2′-(1,3-phenylene)-bis(2-oxazoline) (PBO) and less starch content presented a growth inhibition over 99% even after the three-month biodegradation test, due to a better PHGH retention. The semi-crystalline PBAT did not show any significant crystal structure change in the DSC analysis. Both SEM images and mechanical properties demonstrated the biodegradation of the films from the macro-scale.