| Currently traditional synthetic adhesives is the most widely used class of adhesives, but it has a non-renewable raw materials, large-scale production during transport pollution, long-term release of formaldehyde and other shortcomings when used.Therefore, the development of environmentally friendly, non-polluting new adhesive becomes market requirement.This paper used konjac flour as the main raw material,in order to overcome the shortcomings of common konjac starch pastes, such as poor stability and low binding ability, crosslinking, oxidation and esterification techniques were used to modify the macaroni, and then used infrared spectroscopy and viscosity measurement to study the macroscopic, microscopic differences of the pastes.The effects of different modification processes on the molecular structure, micro-surface and adhesive viscosity, thermal stability, water repellency and shear adhesion of konjac starch adhesive were investigated.The main results are as follows:(1)The konjac flour (KGM) was used as solute and deionized water as solvent,study on the appearance of each solution concentration, viscosity and shear adhesion force variations, identified as 20g/L?40g/L as the optimum concentration range of adhesive;then the konjak starch solution in this concentration range was gelatinized at different temperature and time,by appearance, viscosity and shear adhesion evaluation to determine the optimal gelatinization temperature of 50?55?, pasting time was 30min.(2)The gelatinized KGM solution was treated with sodium hexametaphosphate (SHMP) as crosslinking agent, potassium permanganate as oxidant, hydrochloric acid, sulfuric acid and acetic acid as acidifying and esterifying agent, and then using crosslinking, oxidation and esterification these three ways to modify it, and finally found that the crosslinking process could increase molecular weight of KGM, the degree of intermolecular aggregation while didn't destroy the molecular sugar ring structure; thereby enhancing the smooth surface of the film forming the glue, and also enhance the thermal stability of glue, viscosity and shear adhesion by the measurements of IR,13C NMR, gel permeation chromatography, scanning electron microscopy, thermogravimetric analysis, viscosity and shear adhesion measuring; oxidation process will destroy the molecular chain and glue film-forming microstructure, thereby reducing the relative molecular weight, glue viscosity and adhesion capacity, but significantly enhance the thermal stability of glue and water resistance; the esterification process can increase the molecular weight of KGM by forming the ester bond structure, and enhance the smoothness of the microfacial film formed by the glue, and further improve the thermal stability and water resistance of the glue with the crosslinking process, increase the viscosity and adhesion of the glue ability.After comprehensive comparison, we found that the better preparation process is as follows:KGM's additive amount is 30g/L, dissolving temperature between 10?30?, gelatinized at 50?55? and for 30 minutes, additive amount of crosslinking agent is 1.1 g/L, crosslinking KGM adhesive at 30? for 15 minutes, use acetic acid as esterifying agent,esterified at 30? for 15 minutes, maintain adhesive's pH between 2.5?3,stirring speed 300?350r/min. The average shear adhesive strength of this product is 1422.69N, which has the advantages of large viscosity, strong adhesive ability and zero formaldehyde emission, and has good prospects in home improvement applications. |
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