Studying On The Preparation And Performance Of A.pernyi Silk Powder,Silk Fibroin/Polylactic Acid Composite Materials

The material basis of the development of modern food packaging is packaging materials. However in today, paper, plastic, metal and glass are the protagonist of food packaging materials, in which plastic products occupy an irreplaceable position in food packaging materials for its low cost, stable and excellent quality, and convenient (Wang xuerong et al,2008). But the major issues facing the industry are the shortage of oil resources, prices soaring, white plastic pollution and others. Choosing cheap and easy to get selected agricultural products and by-products to chemical extraction and then synthesis degradable green packaging materials is an effective way to solve the above problems. Extraction of starch in some renewable plants as corn, potato, straw and so on, then transforms starch to glucose, and glucose turns sour into lactic acid, and further polymerization of green plastic polylactic acid(PLA).PLA is a rapidly developed biodegradable polymer materials in recent decades (ShenYiding et al,2007). It is considered to be the most promising polymer materials, has attracted attention at home and abroad (Ann Christine Albertsson et al,2001). At present, PLA is mainly used in the medical field (Kricheldorf H R,2001).But PLA has some weak points such as hard and brittle quality, high production costs, thermolabile, degrades slowly in the natural environment limit this species in a wide range of applications in food packaging (R G Sinclair,1996). In this study, cheap and easy to get Antheraea perny cocoon shell as raw materials, and Antheraea perny silk powder(ApSP) and Antheraea perny silk fibroin(ApSF) are obtained by physical and chemical methods, and then adding ApSP and ApSF to PLA matrix,blending modification in order to improve the above-mentioned drawbacks of PLA. This test mainly explored the conditions of preparation of ApSF,ApSP/PLA composite materials. The mechanical properties, the composite effect, the heat resistance, the antibacterial properties, the UV resistance and the degradation of this composite has been measured, so as to provide experimental evidence for the practical application of improved plastic varieties.The main conclusions of this paper are as follows:(1)The preparation conditions of the composite film was:drying temperature is 35℃, phosphate hydrolysis time is 3h, ApSF mass fraction was 2% and its content is 0.3mL, PEG(400) addition is 30%-40%, the comprehensive performance of this composite film is better;(2)The ApSF mass fraction should be less than 4%, otherwise the tensile strength and the tensile strain of this composite film will decline;(3)An excellent composite effect of the ApSF/PLA film is proved by IR test results and x-ray test results;(4)The ApSF-PLA film exhibites the best UV-shielding effect in UV-B range when ApSF mass fraction of 4% and phosphoric acid hydrolysis time of 1h, and the UV transmittance of the prepared composite film at the optimal conditions is 9.4%-12.7%.;(5)The composite film which is prepared by adding ApSF to PLA matrix through solution blending method has good antibacterial activity, especially against E.coli, saccharomyces,cerevisiae and candida tropicalis;(6)The ApSF which in particle size of 5μm and 15μm can improve the tensile strength of PLA, when the ApSF mass fraction is 5% and PEG(400) addition amount is 0%, the composite film has the maximum value of tensile strength, they are 14.53MPa,15.4MPa, increase than that of pure PLA by 166.7%,182.6%;(7)The ApSP in different particle size can improve the heat resistance of PLA, with the addition of ApSP increased, the heat resistance of composite film enhances. The ApSP which in particle size of 5μm improves the heat resistance of the composite film better, when its addition is 15%, the heat resistance of composite film is 107℃;(8)The SEM of the cross-sectional of the ApSP/PLA composite chip illustrates:adding 5%,5μm ApSP/ PLA has better composite effect, and has no obvious phase separation;(9)Adding ApSP to PLA matrix can promote the degradation rate of PLA in the phosphate buffer solution. which the mass loss of 15%,5μm ApSP/PLA composite chip can be achieved 22.3% after 48 days.