Preparation And Performance Study Of Starch/EVA Foam Composite Materials

Starch foam composite material can partly replace the non-biodegradable plastic foam for its good biodegradation function, which is beneficial to relieve "white pollution" and "oil shortage" problem. So the promotion of this material is beneficial to the added value of starch and the agricultural economy. In this research, use starch and EVA (ethylene vinyl acetate) as matrix resin, and add some processing agents, such as plasticizer, foaming agent, then prepare the foaming composite materials through extrusion or injection foaming method. Having explored the interface combined theory, the internal and external lubricant balance theory, the starch plasticization theory,the flux theory and the foaming theory of the starch/EVA composite material. At the base of those, studied the extrusion molding process and machining performance research, discussed the influence of raw material type and content on mechanical properties, rheological properties, microstructures and degradationThe results showed that:(1) When the screw speed is120r/min, die temperature is130℃, material moisture content is14%, the extrusion process is smooth and the extrusion shape is good, and the expansion ratio of the foam composite material reach a larger value.(2) When the lubricant content (the ratio of the internal and external lubricant is3:2) is5%, the surface of the foam composite material is smooth. Discovered that the glass transition temperature of the foam composite material is66.4℃and the processing temperature is132.1"C by thermal analyzation.(3) By comparing the different kinds of coupling agent and nucleating agent, found that the silane coupling agent and the nano calcium carbonate nucleating agent have a better effect to increase mechanical properties of the foam composite material. The tensile strength of the composite will reach a larger value when the starch content is45%and the glycerin content is10%. When the cross-linking agent content is0.6-0.9%, the mechanic performance of the foam composite material is good. However, when the content of NaHCO3is3%, the tensile strength of foam composite material reach a lower value, but the elongation at break and the resilient rate reach a larger value.(4) The melt shear viscosity of the composite decreased with the increase of the rotate speed, which shows the shear thinned behavior.(5) Through the microstructure observation, discovered that the interface effect of the glycerin plasticizing composites was fine, and the internal structure fusion effect of the composite material adding the silane coupling agent is better than which of using other coupling agent. When the NaHCO3foaming agent content is3%, the molding temperature is140℃, the injection frequency is10s-1and the injection pressure is70Mpa, the number of the bubble hole is bigger and the cell morphology is better.(6) Buried by soil degradation experiment after45days, the degradation performance of the foam composite material with15%glycerin is better.