Foaming Properties And Model Research Of Food Packaging Material Based On PLA/Corn Straw Fiber

The developing of food packaging material based on polylactic acid (PLA)/corn straw fiber not only solve the environment pollution caused by undegradable material but also remission energy shortage, otherwise it also improve the use ratio of agriculture by-product, follow the principle of sustainable development.PLA foams were prepared through melt mixing and hot pressing. Firstly MAH, TMA, PMDA and MAH were introduced as plasticizer and the effect of melt viscosity with different plasticizer on apparent density and expansion ratio of foams were measured as well, among these four plasticizers GMA was the optimal one. And then, the effect of GMA on the molecular and interfacial structures were discussed, it was revealed that there was a react between PLA and GMA. Besides, the apparent density, expansion ratio, void fraction, mechanical properties and thermal properties with different GMA content were investigated, it was showed that the foam of PLA need a suitable melt viscosity, High melt viscosity prevents the gas diffusion and the cell expansion while low viscosity accelerates gas loss and cell collapse phenomenon, the density and other properties reached maximum values while GMA mass was 4% and the melt viscosity was 233Pa.S.The effect of fiber introduction on molecular and interface structures of PLA/corn fiber composite foams were studied firstly. Then, the parameters of hot-pressing process were optimized. Moreover, the effect of corn fiber concentration on apparent density, expansion ratio, mechanical thermal and moisture properties of foams were investigated. It turned out that, to some extent compatibility between PLA and corn fiber was observed; the most optimal parameters were hot-pressing pressure 15MPa, temperature 200℃, keeping-time 5min and the most ideal materials were obtained when fiber content was 15%.A mathematical model for the bubble growth of PLA foams was established on the basis of classic foaming theory, cell-model, law of conservation of mass and conservation of momentum, ideal gas equation and so on. After compared with experiment data we got the conclusion that this model was suitable for PLA foam system, but when the foams were complicated it still need further calculation and simplification.