Preparation And Application Of Poly Lactic Acid Based Nano Laponite Composite Films

Poly lactic acid(PLA) is a kind of biodegradable polymer material, which has good biodegradability and biocompatibility, but also having a mechanical strength compared to common plastics, therefore Poly lactic acid is considered an ideal alternative to common plastic products, it has broad application prospects in the field of medical equipment, packaging materials, especially in the field of film materials. However, Poly lactic acid is severe brittle, which film material with poor flexible gas permeability and thermal stability, low tensile strength, and its melt temperature is 185-190 °C, it is easy to thermal degradation at high temperature, these drawbacks make it difficult in the general plastic processing equipment on the stability of blown film formation, and these shortcomings have limited the development and application of Poly lactic acid film materials and their products. In this paper, by adding other biodegradable polymer materials and fillers in order to improving and enhancing mechanical, thermal stability, barrier properties and anti-bacterial / anti-oxidant properties of PLA based composite film, and expand the range of package field of PLA based composite filmIn this paper, we select Poly trimethylene carbonate(PTMC) and Nano Laponite as the filler of PLA, prepared by solvent casting to obtain PLA / PTMC / Laponite composite film, and the microscopic appearance, mechanical properties, barrier properties, thermal properties of the composite film were characterized and analyzed. And focusing on the effect of composites’ properties and the postharvest preservation of Agaricus bisporus with the content of Laponite(0, 1, 2 and 3 wt%). In the study we found the toughness and water vapor permeability of composite significantly enhanced, the differential scanning calorimetry(DSC) curve shows the degree of crystallinity is improved, with scanning electronic microscopy the fracture surface of composites appeared a large number of pores, with the increasing of Laponite content. We use PLA / PTMC / Laponite composite film and low-density polyethylene(LDPE) film as the packaging materials for the postharvest preservation of Agaricus bisporus under the temperature of 4 ± 1°C for 12 days. The weight loss, hardness, color, overall acceptability of mushroom and the gas content of O2, CO2 inside the packaging were measured three days interval. The results show that under the same conditions, with the passage of time, PLA / PTMC / Laponite composite film can effectively alleviate the rotting of mushrooms, the mushroom maintaining color and overall acceptability, and it retards the mushrooms become soft, but not effectively retards weightlessness. The gas permeability of PLA / PTMC / Laponite composite is better than LDPE film, CO2 content of the composite film package significantly lower than LDPE film packaging, and all O2 content is similar, it is capable of inhibiting anaerobic respiration In the 12 days, mushroom within the PLA / PTMC / L2 and PLA / PTMC / L3 composite film packaging can still remain the level of sale. These results indicate that PLA / PTMC / Laponite composite film can be effectively applied in mushroom preservation process.In addition,Poly lactic acid(PLA) and Poly trimethylene carbonate(PTMC) as matrix, Oregano essential oil as an active additive to prepare PLA / PTMC / OEO active composite film by solvent casting method, then the microstructure, mechanical properties, thermal properties, antibacterial properties and anti-oxidant properties of composite were characterized. We study the effect of oregano essential oil content(0, 3, 6, 9, and 12 wt%) on performance of composite. Scanning electron microscopy(SEM) showed that with oregano essential oil content increases, the cross-section of the composite film becomes rougher, differential scanning calorimetry(DSC) curve indicates that the degree of crystallinity of Poly lactic acid decreased, but does not affect the composite thermal stability of the composite film, and the water vapor permeability(WVP) increased slightly. Since the OEO has good antioxidant and antibacterial properties, such composite have significant antibacterial and antioxidant properties, it can effectively inhibit the propagation of E. coli and Listeria, while a highly efficient radical scavenging.