Opitimization Of Production And Study Of Properties Of Starch-based Wood Adhesive

On the research basis of starch-based wood adhesive in our lab, this study has prepared a new kind of starch-based wood adhesive with better compressive shear strength, fluidity and storage stability by choosing optimal starch material, using vinyl acetate (VAc) and butyl acrylate (BA) as monomer to modify starch in grafting coplymerization, and adding cross linking agent.Firstly, waxy corn starch was chosen as the optimal raw material to prepare starch-based wood adhesive, and the process was improved to prepare a adhesive with better properties by reducing viscidity in the way of acid-modification and oxidation, using polyvinyl alcohol (PVA) as protective colloid, grafting coplymerization of starch with VAc and BA, and adding cross linking agent.Secondly, the effect of grafting coplymerization and cross linking agent on the stength properties of the prepared adhesive were studied. the experimental results showed the optimal reaction conditions as follows: the concentration of waxy corn starch slurry was 30%(w/w); ammonium persulfate as initiator was added 1.8% (w/w, base on the dry starch weight) at the beginning of acid-modification and oxidation, following the second addition of 0.45% (w/w, base on the dry starch weight) after 1.5 h grafting reaction; the acid-modification and oxidation time was 45 min; the temperature and pH value of grafting reaction were 75℃and 2.5, respectively; 80% (w/w, base on the dry starch weight) of VAc and BA monomer (24/16, v/v) was used to modify starch, and the monomer-dripping time and grafting reaction time were 3.0 h and 3.5 h, respectively. The adhesive prepared in these conditions showed higher compressive shear dry strength, reaching 6.76 MPa, and compressive shear wet strength of 1.82 MPa. The conditions of adding two kinds of cross linking agents were obtained by singer-fact test. Using compressive shear wet strength as guide line, the orthogonal experiment showed the optimal conditions as follows: No.1 cross linking agent's adding dosage was 0.8% (w/w, base on the monomer weight), and the adding time was 90min; No.2 cross linking agent's adding dosage was 0.5% (w/w, base on the monomer weight), and the adding time was 60 min. The compressive shear dry strength and compressive shear wet strength of adhesive prepared in these conditions were 7.34 MPa and 3.46 MPa, respectively.Thirdly,Adhesive's storage property was studied. Type of polyvinyl alcohol (PVA),the mass of initiator,urea can effect the adhesive's storage property.PVA1788, mass of ammonium persulfate as initiator of 1.8% (w/w, base on the dry starch weight) at the beginning of acid-modification,mass of urea of 22%( w/w, base on the dry starch weight) can be used to product adhesive which have better storage propertyFinally, the properties of adhesive prepared in the optimal conditions were studied and the costing was estimated. The improved adhesive has higher compressive shear dry strength, shorter initial dry time, better surface wetting and higher stability, reaching the property level of polyvinyl acetate adhesive in middle-high grade. Besides, the improved adhesive has lower cost than polyvinyl acetate adhesive despite of costing a little higher than adhesive prepared in our lab before. Thus, the improved adhesive can be well applied in wood industry.