Multifunctional polylactic acid biocomposite film for active food packaging with UV resistance, antioxidant and antibacterial properties

Electrospun polylactic acid nanofibers membrane with copper ion-loaded clay nanotubes for fresh-keeping packaging

The plastics derived from fossil fuels for food packaging results in serious environmental problems. Developing environment-friendly materials for food packaging is urgent and essential. In this study, polylactic acid (PLA) composite nanofibers membranes were prepared with good biocompatibility and antibacterial property. Cu2+ loaded in the natural halloysite nanotubes (HNTs) was used for the antibacterial agent. Cu2+ was loaded in the HNTs and was confirmed by the X-ray photoelectron spectroscopy (XPS). PLA nanofibers with different HNTs-Cu content were continuous nanofibers with the nanoscale range. HNTs-Cu entered into the nanofiber successfully. Thermal analysis results showed composite nanofibers had good thermal stability. Composite nanofiber membranes had the good hydrophobic property. HNTs-Cu improved the mechanical property of composite nanofibers than pure PLA nanofibers. Tensile strength and elasticity modulus of composite nanofibers with 4 % HNTs-Cu content were the most outstanding. L929 cells were cultured on the nanofiber membranes for biocompatibility evaluation. Cell viability of nanofiber membranes was above the 90 %. Cell live/dead staining results showed L929 cells was seldom dead on the nanofiber membranes. PLA/HNTs-Cu nanofiber membranes exhibited excellent antibacterial effects on S. aureus and E. coli. The inhibitory rates against S. aureus and E. coli were 98.31 % and 97.80 % respectively. The fresh-keeping effects of nanofiber membranes were evaluated by the strawberry preservation. Strawberries covered by nanofiber membranes exhibited better appearance, lower weight loss and higher firmness than control, PLA and PLA/HNTs groups. It promised that PLA/HNTs-Cu composite nanofiber membranes have the significant potential application for active food packaging.

Preparation of polylactic acid (PLA) films plasticized with a renewable and natural Liquidambar Orientalis oil

Polylactic acid (PLA) is a brittle biodegradable thermoplastic due to its relatively high glass transition temperature (Tg ∼ 60 °C). This Tg limits the using of PLA in flexible applications, for example packaging films. In this study, it has been shown for the first time that the Liquidambar Orientalis (LO) oil as a nontoxic, environmentally friendly, and green additive can be successfully used as a natural, renewable, and sustainable plasticizer to produce flexible PLA parts and improve its thermal and physical properties and application potential. Natural oil obtained from Liquidambar Orientalis tree was introduced into PLA (as 10, 20, and 30 phr) by melt compounding (MC) and solution mixing (SM) methods. Effect of LO oil amount on the glass transition temperature, melt and cold crystallization behaviors, and degree of crystallinity values of samples were determined with differential scanning calorimetry (DSC). In addition, solid state viscoelastic properties of PLA films were also characterized with dynamic mechanical analysis (DMA) tests. Results showed that LO oil significantly reduced the Tg and storage modulus (E') value of PLA and LO oil showed an excellent plasticizing effect for PLA due to reducing strong hydrogen bonds and secondary interactions between PLA chains.