Antimicrobial packaging films have been widely used in various applications. However, because of concerns regarding safe food and consumer demands for preservative-free products, the antimicrobial agents applied to packaging have to be highly effective and the leaching effect is not allowed. In the present work, the antimicrobial agent polyhexamethylene guanidine hydrochloride was compounded with starch to prepare antimicrobial thermoplastic starch (ATPS). ATPS was then melt-blended with linear low-density polyethylene (LLDPE) to prepare the novel antimicrobial packaging film. The resultant LLDPE/ATPS films exhibited excellent antimicrobial properties against Escherichia coli in the shaking-flask test. The ring-diffusion test further confirmed the nonleaching effect of the films. However, the addition of ATPS decreased the crystallinity of LLDPE. Both rheological analysis and scanning electron microscopy images indicated that a high ATPS content might result in poor compatibility even in the presence of a compatibilizer.

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.