| The graft copolymerization of mixed grafting monomers such as vinyl acetate and ethylacrylate, vinyl-acetic ester and butyl acrylate onto grafting skeleton of corn starch have beeninvestigated respectively using ammonium persulfate as initiator, starch based wood adhesiveprepared by in emulsion synthesis have green material, superior property, low cost.The effectsof various factors on the graft copolymerization were studied such as reaction time, reactiontemperature, initiator concentration, match of mixed monomers, monomers concentration andPVA concentration.Reaction of graft copolymerization of vinyl acetate and ethyl acrylate onto corn starchusing ammonium persulfate as initiator was investigated. By single-factor tests, the optimumgraft copolymerization conditions with higher grafting efficiency and grafting percent ratiocorrespond to the reaction time of 3h, the graft polymerization reaction temperature of about65℃, the initiator concentration of 9.7×10-3mol/L, the mixed grafting monomersconcentration of 1.2mol/L, the volume ratio of VAc to EA of 6: 4, the PVA concentration of0.15 mol/L. By orthogonal experiment based on single-factor tests, results showed that thecondition of reaction was the best when the concentration of initiator was 0.010mol/L, thereaction of time was 3h, the volume ratio of VAc to EA was 6:4, the concentration of PVAwas 0.15mol/L. With extreme difference analysis, the influence of factors on shear strength inthe following order: the concentration of PVA＞the concentration of initiator＞the reaction oftime＞the volume ratio of the mixed grafting monomers. Under optimal directions, viscosityand compressive shear strength were 131 mm2/s and 19.2MPa., respectively.A study of graft emulsion copolymerization of vinyl acetate and butyl acrylate onto cornstarch was carried out. The experimental results showed that the grafting rate and graftingefficiency are preferable when the optimal reaction time is 3h, the graft polymerizationreaction temperature is about 60℃, the initiator concentration is 9.7×10-3mol/L, the mixedgrafting monomers concentration is 1.2mol/L, the volume ratio of VAc to BA is 6:4, thePVA concentration is 0.20 mol/L. By orthogonal experiment based on single-factor tests, results showed that the condition of reaction was the best when the concentration of initiatorwas 0.010mol/L, the reaction of time was 3h, the volume ratio of VAc to BA was 5: 5, theconcentration of PVA was 0.20mol/L. With extreme difference analysis, the influence offactors on shear strength in the following order: the concentration of PVA＞the concentrationof initiator＞the volume ratio of the mixed grafting monomers＞the reaction of time. Underoptimal directions, viscosity and compressive shear strength were 130 mm2/s and 19.4MPa. The graft copolymers of starch were characterized by IR, XRD and DTA. IR spectra ofgraft copolymers existed the carbonyl group characteristic absorption peak at 1730～1740cm-1 besides the characteristic absorption peak of starch. The several dispersion peaks ofXRD showed that the graft copolymers were the concomitant product of a little crystallineregion and amorphous state.Production of starch based wood adhesive was white or cream white emulsion paste,excellent emulsive properties. It has a good high temperature stability, good adhesiveness,good cold endurance and good stability for storage. All properties of starch based woodadhesive reached national standard HG/T2727-95 of polyvinyl acetate wood adhesive.Especially compressive shear dry strength was over the national standard enormously.
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