A robust biaxially stretching strategy for fabrication of biodegradable and antimicrobial PBAT-based composite films

In this study, the biaxially stretching and reactive blending strategies were combined to fabricate the high-performance antimicrobial biodegradable polybutylene adipate-terephthalate (PBAT)/polylactic acid (PLA) based composite film with polyhexamethylene guanidine hydrochloride (PHMG) being as the efficient antimicrobial agent. Various measurements, including scanning electron microscopy (SEM), Fourier transform infrared (FTIR) analysis, 2D-small angle X-ray scattering (2D-SAXS), gas barrier test, mechanical property test, antimicrobial activity test, etc., were employed to carefully characterize the obtained films. The experimental results showed that the biaxially stretching could induce the orientation of polymer molecular chains and formation of submicron-thick layered thin-lamella structures of PLA dispersed phases in PBAT matrix in the presence of initiator dicumyl peroxide (DCP) and PHMG, thus significantly enhancing the crystallinity and mechanical properties of the obtained film, as well as improving the gas barrier and hydrophilicity-oleophobicity characteristics. At a stretching ratio of 3.5 × 3.5, the tensile strength of the prepared film could reach 61.9 MPa, and meanwhile the oxygen and water vapor permeability rates were reduced to 3.1 × 10 −14 and 5.1 × 10 −14  g/(cm s Pa), respectively. In addition, the incorporation of PHMG endowed the film with highly efficient antibacterial properties, e.g. a film with 1.0–1.5 wt% PHMG content could achieve a 100 % inhibition rate against Escherichia coli (E. coli) and a 99.9 % inhibition rate against Staphylococcus aureus (S. aureus). The further lychee preservation experiments demonstrated that the PHMG incorporating PBAT/PLA composite film remarkably extended the preservation time of fruit (40 % longer). The prepared antimicrobial PBAT/PLA/PHMG film exhibited the high safety and economic benefits, thus showing the promising application prospects in the field of food packaging.