Preparation And Performance Of Soy Protein Materials With Epoxy Compounds Modification

As a natural polymer material with several amino acids in it,soy protein has so many advantages such as abundant,renewable,versatile,processed and biodegradable.However,some disadvantages such as poor mechanical and waterresistance properties also exist,so we need to change it if more soy protein materials apply in wood adhesives,plastic films,fiberboard bonding and so on.In this work,the epoxidized oleic acid and epoxy resin are used as the modifying agents,sodium hydroxide and urea are taken to pretreat soy protein molecular,and the soy protein emulsions are prepared in appropriate conditions,which has shown some high comprehensive properties when the emulsions apply in wood adhesives,plastic films and fiberboards.(1)Epoxidized oleic acid was synthesized through epoxidation reaction,and the average epoxy value was 3.647%through chlorhydric acid-acetone method detection.Two kind of soy protein emulsions were prepared,one of the soy protein emulsion was modified by epoxidized oleic acid,and the other one was modified by both epoxidized oleic acid and epoxy resin,the optimal experiment conditions were reseached by testing the viscosity,dry shear strength and wet shear strength of the emulsions.The results showed that the soy protein should be pertreated by 280 mL 0.6 mol/L urea solution and the pH value of emulsion was about 10 for1 h firstly,and then 60%of epoxidized oleic acid was added to modify soy protein molecular,after 2 h with the reaction temperature maintained to 65?,the adhesive of modified soy protein had a better performance,the dry shear strength and wet shear strength of the adhesive had increased 52.4%and 410.8%,respectively,when compared to pure soy protein adhesive.And when the soy protein was modified by both epoxidized oleic acid and epoxy resin,the ratio of epoxidized oleic acid and epoxy resin should be 1:1,the amount of composite epoxy compounds should be 50%,and 3%of sodium dodecyl sulfate(SDS)also should be added to emulsify the epoxy resin,other experimental conditions just the same as the previous was ok,the modified adhesives in this coditions had a better performance than that modification adhesives before,the dry shear strength and wet shear strength had increased 65.2%and427%,respectively,when compared to pure soy protein adhesive.The Infrared spectrum(FTIR)results displayed that the epoxy groups had been reacted with amino groups in soy protein.(2)The soy protein emulsions modifed by epoxidized oleic acid were chosen as the raw materials,and the soy protein films were prepared through solution casting method,a series of test methods such as X-ray diffraction(XRD),scanning electron microscope(SEM),thermogravimetric analysis(TGA),contact angle,water uptake,degree of degradation and mechanical properties were used to test the properties of soy protein films.The XRD results showed that degree of crystallinity of the film had decreased because of the reaction between epoxidized oleic acid and amino groups in soy protein;the SEM results showed that flexibility of modified films were better than the pure film.TGA results indicated that the reaction between epoxidized oleic acid and SPI molecular could improve the thermal stability of films,however,because the urea had a low decomposition temperature,the thermal stability of the modified SPI films decreased totally.Mechanical properties,contact angle and water absorption results displayed that after modification the soy protein films had a better flexibility and water resistance properties,and the elongation at break of protein films decreased with the increasing addition of epoxidized oleic acid,the mechanical strength of modified films decreased a little when compared to the pure soy protein film.Degradation properties of the protein film also have been tested,the SEM pictures and degree of degradation data had showed that this films had a good degradation property,the degradation half life of these films was less than 30 days,and the film which had been modifed by epoxidized oleic acid had a better antiseptic ability.(3)Before making the straw fiberboard,straw fibres should be pertreated by 1%NaOH firstly,during this processing,the wax layer on straw surface could be damaged,and then two kinds of straw fiberboard were made with different modified soy protein adhesiveA and B.The modulus of rupture(MOR),modulus of elasticity(MOE),internal bonding(IB),water absorption(WA),and 24 h thickness swelling(TS)of the samples were researhed with different addition of adhesives,density of fiberboard,hot pressingtemprature and hot pressing pressure.The results showed that straw fibres pretreated by 1%NaOH,and more than 12%of adhesives were added,the density of fiberboard was 0.8 g/cm~3,and the hot pressing temprature and pressure were 140?and 6 MPa,respectively,mechanical and water resistance properties of the straw fiberboards had improved a lot.Both of the two kind straw fiberboards could meet GB/T 11718-2009 standard,and what's more,the staw fiberboard which was bonded by compsite epoxy compounds modified adhesive had a better comprehensive properties than the fiberboard bonded by epoxidized oleic acid modified adhesive.SEM pictures showed the close combination between staw fibres and adhesives.The curves of Tg showed that straw fibres with A and B adhesives bonding were beneficial to improvements in thermal stability.