Preparation And Foaming Of PLA-based Biodegradable Food Package Material Reinforced By NCC

Biodegradable poly(lactic acid)(PLA)-based material can replace petroleum-based plastics and be used in food packaging, agriculture and forestry, medical health and other consumer goods. Pure PLA material has relatively low crystallization rate, low melt-strength and brittle property, which luckily can be effectively weakened by adding the filling agent-nanocrystalline cellulose (NCC). Therefore, biodegradable food package material based on PLA and NCC is not only a kind of green material which can alleviate the resources shortage and ecological problems, and improve the utilization of by-products of agriculture, but also a kind of reliable material which has good performance and can be widely applied in life.In this paper, the filling particle-NCC-in PLA-based composite was prepared from microcrystalline cellulose (MCC) by acid hydrolysis, centrifugation and ultrasonic treating orderly. Firstly, the appearance of MCCs and NCCs was observed by the scanning electron microscope (SEM) and transmission electron microscope (TEM) respectively. The transverse diameter of NCCs was20-30nm and the length was200-400nm mostly. Secondly, the crystallinity and thermal stability of MCC and NCC were analyzed through X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Finally, the process of NCC was optimized by using single factor and orthogonal tests.PLA-based composite reinforced by NCC was prepared by preparing the polyethylene glycol (PEG)/NCC composite fillers and melt-blending the mixture. On the one hand, the distribution of particles in the section, the molecular structure of the material and rheological property were analyzed by the field emission scanning electron microscopy (FESEM), infrared spectrometry (FTIR) and advanced rheological extended system (ARES), and the network formed between the filling particles-NCCs in composite was analyzed and discussed further. On the other hand, the thermal performance and mechanical properties of the composite were investigated and it was indicated that the adding of NCC and PEG in the composite promoted the configuration of PLA in melted composite and improved the crystallization of melted PLA. At the same time, the tensile strength of the composite was enhanced by adding the filling particle-NCC, the interfacial adhesion between PLA and NCC was promoted by the compatibilizer-PEG and thus the ductility of the composite was improved.Finally, PLA-based micro-porous foaming material was prepared by using supercritical CO2in this paper, it was investigated that the effect of the content of the filling particles-NCCs and the compatibilizer-PEG in the composite on the foam form and the influence of different soak time in supercritical CO2and foaming temperature on the foam form. It was implied that the content of NCC in the composite has a significant influence on foam form, the best sample was PLA-P-N-8and an ideal micro-porous foaming material with a bubble density of3×1010can be obtained at a foaming temperature of100℃and being soaked in supercritical CO2for4h using the sample of PLA-P-N-8.