Study On Water Resistance Of PVAc Emulsion Adhesive

PVAc is an ideal substitute for traditional wood adhesives because of its advantages of formaldehyde-free,environmental protection and low price.However,the water resistance of PVAc adhesive is poor,which limits the development prospects of it.In view of the poor water resistance of PVAc,the paper use copolymerization and modification methods to modify the adhesive.The water absorption,dry compression compressive strength and wet compressive strength of the adhesive were used to characterize the water resistance of the adhesive.The main research fingdings are as follows:（1）PVAc was synthesized by emulsion polymerization using PVA as the main raw material,BA as soft monomer,AA as functional monomer,PVA-1799 as protective colloid,SDS as anionic emulsifier,OP-10 as nonionic emulsifier,Na HCO₃as p H buffer and APS as initiator.,Under the condition of controlling the solid content of emulsion,investigating the effects of the content of PVA,the content of compound emulsifier,the ratio of compound emulsifier,the content of soft monomer and the content of functional monomer on the water resistance of PVAc adhesive.Through the orthogonal test and result analysis,a better formulation of PVAc adhesive with good water resistance is found.The dry compressive strength of the adhesive prepared by the formula is5.55MPa and the wet compressive strength is 1.37MPa.（2）Then,based on the formulation above,inorganic particles is added to the adhesive.Four kinds of inorganic particles,such as CaCO₃,Si O_2,TiO₂and nano TiO₂,are chosen to be added.The ratio of inorganic particles is 2%,4%,6%,8%and 10%.Through dry compressive strength and wet compressive strength,the effects of the type,and particle size of the added components on the water resistance of the adhesive were characterized,then a modified PVAc emulsion adhesive was selected.Through the comprehensive analysis,it is found that the water resistance of the adhesive is the best when the content of nano TiO₂is 6%.The dry compressive strength of the adhesive is7.18MPa,29.4%higher than that before modification,and the wet compressive strength is 2.35MPa,71.5%higher than that before modification,which achieve the standard of winter-used PVAc emulsion wood adhesive.