Study On Preparation And Properties Of Modified Cassava Starch Adhesive For Wood

As the continuous development of wood processing industry in our country,the demand of wood adhesive is also increasing.At present,the most applied wood adhesive is“three formaldehyde glue”,that is,phenolic resin adhesive,urea formaldehyde resin adhesive and melamine formaldehyde resin adhesive.When“three formaldehyde glue”is used,it will emit poisonous gas such as formaldehyde and phenol,which will cause serious harm to human body and the environment.Starch adhesive is a cheap,non-toxic and environmental friendly adhesive.It has a wide application prospect.But the starch has poor water resistance,adhesive strength and stability,it is limited in practical application.This paper adopts cassava starch as raw materials,and it was through oxidation,gelatinization,grafting copolymerization and blending which can improve the starch performance to prepare modified cassava starch adhesive for wood.The main research and results are as follows:The cassava starch was oxidized by hydrogen peroxide to prepare oxidized cassava starch,and then gelatinized.Using ammonium persulfate,butyl acrylate,acrylamide as initiator,a soft monomer,and a hard monomer respectively,to prepare starch adhesive.Monomer and starch mass ratio,acrylamide and butyl acrylate mass ratio,ammonium persulfate content,and reaction temperature were investigated to study the effects on the properties of starch adhesive.The results showed that when starch content was 25 g,monomer and starch mass ratio was 1.0:1.0,acrylamide and butyl acrylate mass ratio was 0.5:1.0,ammonium persulfate content was 0.25 g,and reaction temperature was 60?,the starch adhesive properties reach the best,and the shear adhesive strength in dry state and wet state were 4.59 MPa,2.51 MPa,respectively.In order to further improve the starch adhesive bonding strength and water resistance,adding vinyltriethoxysilane in the latex in later stage of the starch/butyl acrylate/acrylamide reaction to prepare vinyltriethoxysilane modified cassava starch adhesive.Vinyltriethoxysilane content,ammonium persulfate content,emulsifier content and reaction temperature were as the variables.The results showed that when starch content was 25 g,vinyltriethoxysilane content was 8%?based on the adhesive solid content?,ammonium persulfate content was 0.3 g,lauryl sodium sulfate content was 0.6 g,and reaction temperature was 50?,the adhesive strength in dry state and wet state of starch adhesive could reach 6.52 MPa and 3.57 MPa respectively,the viscosity was 1.35 Pa.s.FT-IR and XPS spectra demonstrated vinyltriethoxysilane,acrylamide and butyl acrylate had grafted onto starch.TGA curves showed that when adding vinyltriethoxysilane,it plays a cross-linking agent,and can improve the starch adhesive thermal stability.Adding three different kinds of compound emulsifiers respectively to study the effect on the properties of starch adhesive.Blending three different morphology of light calcium carbonate particles which were made in lab with starch adhesive respectively to improve the starch adhesive bonding strength and water resistance.The results showed that with the non-ionic emulsifier content increase,the viscosity of the starch adhesive decrease.When the amount of cubic calcium carbonate was3%?based on the adhesive mass?,both the shear strength in dry state and wet state reach the maximum with the value of 7.23 MPa and 3.83 MPa,respectively.And SEM showed that the calcium carbonate particles was uniformly dispersed in the starch adhesive.Using sodium dodecyl sulfate and alkyl phenol polyoxyethylene as compound emulsifier,vinyltriisopropoxysilane as silane coupling agent.The starch adhesive was prepared through vinyltriisopropoxysilane,starch,butyl acrylate and acrylamide graft copolymerization.The results showed that when starch content was 25 g,compound emulsifier content was 1.17%,vinyltriisopropoxysilane content was 10%?based on the adhesive solid content?,reaction temperature was 60?,and ammonium persulfate content was 0.3 g,the adhesive strength in dry state and wet state of starch adhesive could reach 6.11 MPa and 3.05 MPa respectively,the viscosity was 1.15 Pa.FT-IR and ¹³C-NMR demonstrated that vinyltriisopropoxysilane and monomer had grafted onto starch successfully.TGA curves showed that starch adhesive thermal stability was improved after vinyltriisopropoxysilane was adding.In conclusion,the cassava starch can via oxidation,gelatinization,grafting copolymerization and blending to prepare the starch adhesive.And the prepared starch ashesive has good performance,green and environment-friendly.So it has great market prospect and popularization value.