Comparison on properties of composites prepared by four kinds of biological glues and wheat straw

In order to compare mechanical properties and moisture absorption properties of wheat straw/biological glue composites prepared by the biological glues (sodium alginate, guar gum, starch gum, plant protein adhesive) and wheat straw, infrared spectra of four kinds of biological glues and wheat straw were analyzed, mechanical properties and moisture absorption properties of wheat straw/biological glue composites were tested, and their microstructure were observed. The results show that four kinds of biological glues have stretching vibration absorption peaks of -CH and -OH, plant protein adhesive has stretching vibration absorption peak of -NH₂ and absorption peak of -O-. The mechanical properties of the composites prepared by plant protein adhesive are good, and moisture absorption rate is small. The tensile strength of composites prepared by plant protein glue is 436%, 93%, 416% higher than that of composites prepared by sodium alginate, guar gum and starch gum, the bending strength is 922%, 49%, 963% higher, the elastic modulus is 714%, 678%, 254% higher, and the absorption rate is 42%, 17%, 16% smaller, respectively. Wheat straw are wrapped preferably by matrix in wheat straw/plant protein adhesive and wheat straw/guar gum composites, and the two phase interface between plant protein adhesive-wheat straw and guar gum-wheat straw are fuzzy, which combine well. However, wheat straw/sodium alginate and wheat straw/starch gum composites have more holes and flaws in the two phase interface. The interface between wheat straw and matrix is obvious, the combination with wheat straw is worse. Wheat straw/plant protein adhesive composites are equivalent to the plastic-based composites in mechanical properties, but the moisture absorption property needs to be improved.