Research On Key Technologies Of Fully-degradable Packing Materials

Serious environmental pollution, a lot of resource and energy consumption are major issues that restrict the sustainable development of the world in the 21st century. At present, in order to mount environmental and legislative pressure to reduce plastic and packaging wastes, various biodegraded materials become emerge as the time requires, which include starch based plastics, pulp molding packing materials and fully-degradable packing materials, etc. Nowadays, the fully-degradable packing materials are the best substitutes for plastic packaging materials in the world. Wide application of these materials can control or eliminate the increasing white pollution problems effectively in the world. The fully-degradable packing materials derived from starch and plant fiber, such as corn starch, straw fiber and bagasse fiber, which take advantage of full biodegradability, controlled degradation, enough raw materials, reuse and mass production. However, the fully-degradable packing materials have not been put into industrialization due to some crucial problems, such as immature compatibility, imperfect core equipments, few basic researches and insufficient evaluation criterion, etc. In this study, with the synthesis and refining of relevant researches at home and abroad, main efforts have been made on the methodology and key technologies of the fully-degradable packing materials, based on the strategy of"compatibility mechanism-forming process and mechanism-product performance"'Due to the immature compatibility of the fully-degradable packing materials, the forming process and mechanism of the fully-degradable packing materials were investigated on the basis of analysis of molecular structure and physical-chemical characteristic of plant fiber and corn starch. Combined with the working principle of core equipment mould, the technological parameters of forming process were studied. The technological process of fully-degradable packing materials was introduced, which established the foundation for the following study.Aiming at the imperfect design of core equipment molding, the hot-force coupling field of the mould in the working process was simulated. And the temperature field, the stress field and the strain field of the working surface of the molding were accomplished, which provided theoretical basis for the mould structure and processing parameters optimization.In this paper, the mechanical properties of the fully-degradable dishware were presented by tensile tests, which included Elastic Modulus, Poisson's Ratio and Tensile Strength. Finite element models of the fully-degradable dishware were established by using the experimental results of the mechanical properties. The rule of the stress and strain distribution of the plant fiber and starch dishware under outside load was found with finite element method, which was verified by the experimental results, and the force-deformation curve of the fully-degradable dishware was found The results were of significance to its design, transport and application. Meanwhile, The performance of the fully-degradable dishware was studied, which included gravimetry, volume, weight bearing experiment, dropping experiment, hot water resistance experiment, hot oil resistance experiment, fold experiment and moisture content, etc.The biodegradability of the fully-degradable dishware was studied by isolating funguses from compost. The fungal growth degree and the weight loss rate of these materials were analyzed in experimental period. The experimental results showed that the growth grade of these materials was the V grade and the weight loss rate was 41.59%. These results revealed the fast degradation of these materials in the presence of funguses. In addition, the experimental results indicated that the size of sample had no significant influence on the biodegradability of these materials. As a contrast, the biodegradability of other materials, such as pulp model dishware, starch-plastic dishware, cellulose filter paper and polypropylene, were also analyzed.The indexes system of green degree of the fully-degradable packaging materials was built and the Fuzzy Analytical Hierarchy Process (FAHP) methodology was employed to analyze and assess this system. The qualitative assessment gained by survey and the statistics theory were both employed to deal with the qualitative data. The pair-comparison matrix was built and the maximum characteristic root and vector were computed using the sum-product method. Then the relative importance degree of every influence factor was computed, and also the composite importance degree of every influence factor was gained. The membership function of every influence factor was established by logical reasoning assignment method, and then the membership degree was gained. According to the composite importance degree and the membership degree of every influence factors, the green degree of biodegradable packaging materials was generally assessed. Finally, Comparing with the green degrees of six kinds of biodegradable packaging materials with foamed plastics materials, we are convinced that the biodegradable packaging materials had wide development prospects.