| Soy protein plastics have attracted more and more attentions for their renewable, biodegradable,low-cost features. However,soy protein plastics have some serious defects such as water sensitivity, poor processibility and mechanical properties. Blending is a handy and effective method to solve the above problems. In this work, soy meal, the byproduct of soy oil industry, was selected as raw material to prepare coal modified soy meal plastics, which have super mechanical properties and water resistance. On this basis, the interfacial interaction of the composites was characterized and investigated by mechanical properties test, water absorption test, FTIR, TG, DSC, SEM and model compound simulation. Firstly, soy meal was blended with fine coal powder, plasticized by glycerol. Thus a series of soy meal/coal composites with different coal content were obtained through compression-molding process. Then the effect of coal macromolecule on the mechanical properties and water absorption of soy meal plastics was investigated. The results indicated that the coal content in the range of 5% to 30% in the toal coal and soy meal content not only can enhance the composites' tensile strength and elongation at break obviously, but also can improve their water resistence and thermal stability. FTIR analysis indicated that certain chemical reactions took place between coal and soy protein. For the further study of the interaction between coal macromolecule and soy protein molecule, EAA was selected as model polymer accoding to the structure of coal, to simulate the interaction between coal macromolecule and protein molecule through investigating the interaction of EAA and protein in soy meal/EAA composite prepared by reactive extrusion . SEM analysis indicated that soy meal was well dispersed in the EAA matrix when soy meal content was 10% and 20%. DSC and FTIR analysis indicated that the -COOH groups in EAA reacted with the -NH2, and -CONH- groups in soy meal to result in the formation of substituted amide and hydrogen bond. On the basis of the above analysis, it is conjectured that the –COOH groups in coal macromolecule phase can react with soy meal protein by the same manner as that of EAA and soy meal. Coal/soy meal/EAA composites were prepared by EAA in soy meal/EAA composites partly replaced by coal powder and reactive extrusion technique to investigate the interaction among the other active groups of coal and the groups of soy meal protein. The results indicated that when EAA in soy meal/EAA composites was partly replaced by moderate content of coal powder ,the tensile strength was improved distinctly compared with pure soy meal/EAA composites and coal/EAA composites. Moreover,the water absorption of the composite was reduced with the increase of coal content. SEM analysis showed that interface of coal/soy meal/EAA composites was not so clear. It can be futher illuminated that there were interactions among the other active groups of coal and the groups of soy meal protein. There were 10%～23% small molecule phase in coal except for the macromolecule phase. For this reason,crylic acid was selected as the model compound to simulate the -COOH groups in the samll molecular phases of coal for investigating the roles of the small molecule phase on the interface interaction of coal and soy meal protein. Soy meal grafted with crylic acid was prepared by using ammonium persulphate as initiator,it was based on the experimental fact that there is amidate reaction between the –COOH groups in coal and soy meal protein. Then the interaction between coal macromolecule and protein molecule was studied through investigating the interfacial interaction of EAA and protein in soy meal/EAA composites, which were prepared by extruding the crylic acid grafted soy meal together with EAA. The results show that the tensile strength of modified soy meal/EAA composites was higher than that of the soy meal/EAA composites. DSC analysis indicated that the thermal stability of soy meal/EAA composites was improved by grafting soy meal with crylic acid. F...
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