Starch/poly(butylene adipate-co-terephthalate) blown antimicrobial films based on ε-polylysine hydrochloride and different nanomontmorillonites.

With increasing awareness on environmental protection and food safety, the development of biodegradable antimicrobial packaging materials has been paid growing emphasis. In this work, starch/poly(butylene adipate-co-terephthalate)/ε-polylysine hydrochloride films were prepared by extrusion blowing, and five commercial organically modified nanomontmorillonites (OMMT, including DK1, DK2, DK3, DK4, and DK5) were used as reinforcing agents. Intercalated structures were formed in the nanocomposite films, especially for those with DK3 and DK4 owing to their higher hydrophobicity and larger interlayer spacing. Adding OMMT weakened hydrogen bonds and the gelatinization/plasticization degree of starch. Morphology analysis revealed that the agglomeration of OMMT occurred in the films, but the film containing DK3 still showed a relatively homogeneous microstructure. Loading OMMT enhanced the strength, deformation resistance, thermal stability, surface hydrophobicity, but decreased barrier properties and water sensitivity of the films. Antimicrobial activity showed that the OMMT and ε-polylysine hydrochloride possessed a synergistic effect against Staphylococcus aureus and Escherichia coli. The maximum inhibition rate was observed in that with DK4, approaching 100 %. Findings supported the application of commercial OMMT in manufacturing biodegradable antimicrobial blown films.

Effects of adding methods and modification types of cellulose on the physicochemical properties of starch/PBAT blown films.

This study revealed the relationship between cellulose types/adding methods and film properties, in which sodium carboxymethyl cellulose (CMC), hydroxypropyl methyl cellulose (HPMC), and microcrystalline cellulose (MCC) were added into starch/PBAT blown films in powder, aqueous solution, and emulsion forms, respectively. Cellulose interacted with starch networks via hydrogen bonds, and those added in emulsion form made more homogeneous film morphologies. MCC emulsion enhanced the film strength (40%) and modulus (149%) to the greatest extent, while comprehensively, HPMC emulsion possessed better reinforcement effects on the films, which increased mechanical properties (31% ~ 100%), moisture barrier (20%), oxygen barrier (93%), surface hydrophobicity (20%), as well as water resistance (12% ~ 76%). Findings supported the application of cellulose in high-throughput biodegradable films, and the high-content starch/PBAT blown films reinforced by HPMC emulsion had great potential in commercial packaging fields.