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Study on Preparing of Antiseptic Formaldehyde-free Plywood

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Tutor: MeiChangTong
School: Nanjing Forestry University
Course: Wood Science and Technology
Keywords: soy-based wood adhesive,two-components formaldehyde-free adhesive,woodpreservati
CLC: TS653.3
Type: Master's thesis
Year:  2013
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Abstract:
Presently,Urea formaldehyde resin (UF),phenol formaldehyde resin (PF) and MalemineUrea formaldehyde resin(MUF) are widely used in plywood industry.however,these resins arederived from non-renewable oil resources,and will release toxic formaldehyde when plywoodmanufacturing and using.So there is much interest in developing environmental friendlybio-based adhesive in wood-based panel industry.The main research works and results in thisstudy were as follows.Because of the very low solid content and high loading rate of soybean protein adhesivewhen applied time plywood manufacturing,the moisture content of the veneer met can be prettyhigh and would cause some problems,such as blow and delamination,during the hot-pressingprocess. In this study, the mat was pre-pressed at certain temperature (80¡æ) in order to controlthe moisture content of the mat before hot-pressing.Through orthogonal experiment, physicaland mechanical properties test results proclaimed that the optimal parameters of soybeanprotein adhesive plywood prepairing were hot-pressing temperature160¡æ, pressure1.2MPa,resin loading rate450g/m2£¬hot-pressing time80s/mm, and the temperature had significantinfluence on the soybean-based plywood properties.A two components formaldehyde-free adhesive system was adopted and studied in thispaper. Polyvinyl acetate emulsion(PVAc) was as the major constituents, and theMethylenediphenyl Diisocyanate (MDI) as the curing agent in the ashesive system. Theorthogonal experiment results showed that the optimal physical and mechanical properties ofthe plywood using the two components adhesive system were hot-pressing temperature130¡æ,hot-pressing time80s/mm, resin content200g/m2, and the ratio of PVAC and MDI was9:1. Analysis of variance proclaimed that the percentage of MDI in the two componentsadhesive system havd the most significant influence on the plywood properties.Antiseptic capacity of soy-based wood adhesive was studied by adding differentpreservatives at various concentrations. The preservatives used in this study were Zinc borate,CuSO4, sodium benzoate and BIT(1,2-benzeisot Hiazoline). antiseptic chemicals can disturb anddestroy metabolism of microorganism cells, and prevent the soybean-base adhesive to get mould.Through comparing with antisepsis effect,we found the Zinc borate and BIT is better than othersas antiseptic to restrain the growth of mould in soy-based wood adhesive,and the optimal dosageof Zinc borate and BIT is0.5%and0.1%respectively.Comparing the two preservatives in glue layer treatment of soy-based adhesive plywood,the Zinc borate and BIT had nothing different in anti-mould effect. Nevertheless, the zincborate had a significant influence on bonding strength.The more the additive amount of zincborate,the lower of the bonding strength of the plywood resulted. In contrast, BIT addition seemed have less impact on the bonding strength of plywood which were glued with treatedsoybean adhesive than Zinc borate.The effect of veneer pretreatment with preservative ACQ on anti-mould and bondingstrength of soybean-based adhesive plywood was also investigated in this study. The poplarveneer were impregnated by ACQ solution, which is environment-friendly preservative, undernormal condition. The weigth content of the preservative grew as increase of the concentration ofACQ solution. After pressed into plywood, the anti-mould performance and bonding strengthof the plywood were tested. The result showed that veneer ACQ pretreatment had a betteranti-mould effect than glue layer treated mehtod. Test result indicated that veneer ACQpretreatment had a little negative effect to the bonding strength of the plywood. Significancetesting proved that is not obvious.
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