Synthesis And Application Of Crosslinking And Grafting Modified Starch Adhesive

Environmental problems have always been a very serious topic in Chinese chemicalindustry, in recent years, with the increasingly perfect environmental statutes ofenvironmentally friendly adhesives, non-toxic and environmentally friendly starchadhesives gradually replace "three formaldehyde adhesion"(urea-formaldehyde resinadhesive, phenolic resin adhesive, melamine-formaldehyde resin adhesive) of themarket in our country, starch can beas adhesive because starch is generated byamylopectin which can promote the starch paste and amylose which can promote thestarch gelatination, the starch adhesives can take the place of "three formaldehydeadhesion" becauseof the starch sources, low price, environmental protection andbiodegradation. But the water resistance, bonding strength andstorage stability of thestarch adhesive itself can not meet the need of plywood and panel production, so needto modified starch.This thesis usedoxidized corn starch as raw material, epichlorohydrin as crosslinkingagent, ammonium persulfate and sodium bisulfite (APS-NaHSO3)as initiator, butylacrylate and acrylamide as grafting monomer, we prepared a crosslinking and graftingmodified starch adhesive.Firstly we prepared a crosslinked modified starchwith epichlorohydrin as crosslinkingagent.With the dosage of epichlorohydrin, reaction temperature, reaction time and pHvalue as the experimental factors, with the cross-linking degree of crosslinking modifiedstarch as evaluation indicators, using L9(34) orthogonal test to choose the best way ofpreparation of crosslinked modified starch, the study found that when the dosage ofepichlorohydrinwas0.1wt%of oxidized starch, reaction temperature was30℃, reactiontime was3h, pH value was10, sedimentation volume was minimal, the smallest is0.37ml, degree of crosslinking reached the maximum.Then with butyl acrylate(BA) and acrylamide(AM) as grafting monomer, began tografting modification for crosslinking modified starch, with reaction temperature,reaction time, dosage of BA and AM, the dosage of initiator (APS and NaHSO3) forexperimental factors in orthogonal experiment design, with bonding strength and waterresistance as examining index, using L9(34) orthogonal test method to select the optimalconditions of grafting, the optimum reaction conditions of starch graft copolymerizationwere obtained in orthogonal experiment, the optimum reaction conditions: reactiontemperature was70℃, reaction time was3.0h, dosage of AM and BA (1:2) was 7.0wt%, dosage of APS and NaHSO3(1:1) was0.7wt%, bonding strength and waterresistance of modified starch had been greatly improved, bonding strength reached7.85MPa, water resistant time was up to50h.Finally through repeated tests studied the optimum adding amount of the additives,the optimum adding amount of stabilizer PVA was15.0wt%, emulsifier SDS was0.8wt%, defoaming agent BYK-024was0.1wt%, packing bentonite was8wt%,preservatives phenol was0.20wt%, plasticizer glycerin was2wt%, water resistance,bonding strength, the drying rate and antibacterial properties achieved the best.Through a series of analytical tests, includingFTIR verifying the grafting monomersuccessfully grafted on the molecular chain of starch,SEM verifying that modifiedstarch morphology changed a lot, DSC and TG/DTG analysis verifying that the heatresistance and thermal stability of modified starch was stronger,the samples have beencharacterized.In short, various properties of through crosslinking and grafting modified starchadhesive, such as water resistance, bonding strength, storage stability, viscosity and soon all conformed to the requirements of the production.