Studies On Syntheses And Properties Of Self-corsslinking Poly Vinyl Acetate Emulsions

In this work,poly（vinyl acetate）copolymer emulsion was prepared by ketone-hydrazine crosslinking,silicone crosslinking system,and soap-free emulsion and core-shell emulsion polymerization.The effects of emulsifier,initiator,crosslinking monomer amount and polymerization method on the polymerization process and emulsion performance were studied,and the latex film was characterized by FT-IR,TG,DSC,TG.The research contents and results are listed as following:（1）Firstly,ketone-hydrazine self-crosslinkable poly（vinyl acetate）emulsion was prepared with diacetone acrylamide（DAAM）-adipate dihydrazide（ADH）as crosslinking monomer,octylphenol polyoxyethylene ether（OP-10）as emulsifier,ammonium persulfate/sodium bisulfite as initiator system,polyvinyl alcohol（PVA）as protective colloid.The optimal polymerization condition of latex was 5wt%OP-10,5wt%PVA,0.5wt%ammonium persulfate/sodium bisulfite（molar ratio=3:1）,2wt%DAAM.The wet shear strength of emulsion increased from 1.06 MPa to 1.36 MPa,and the water absorption rate of latex film decreased from 52.36%to 26.81%.the FT-IR spectra showed that the appearance of C=N at 1675cm^-1,which indicates that crosslinking reaction has occurred between the ketone carbonyl group and hydrazide group;the TEM showed that particle size of emulsion was 300nm,and the dispersion was uniform without obvious agglomeration;the DSC showed that the T_gof the latex film（2wt%DAAM）was 22.37℃,which is 3.84℃higher than T_gof the uncrosslinked latex（18.53℃）;the TG showed that the initial decomposition temperature of the latex film（2wt%DAAM）was 280.9℃,which was 10.1℃higher than the initial decomposition temperature（270.8℃）of the uncrosslinked latex film.（2）Secondly,silicone self-crosslinking poly（vinyl acetate）emulsion synthesized by pre-emulsion method using vinyl triethoxysilane（VTES）as modified monomer,DNS-628 as emulsifier.The storage time of the emulsion was shortened,the wet shear strength increased from 1.31MPa to 1.75MPa,and the water absorption ratio decreased from 38.18%to 12.37%;the peak intensity of 1020cm^-1and 802cm^-1displayed by FT-IR spectra indicates that the silicone monomer has formed a cross-linked structure;the TEM showed that silicone self-crosslinking emulsion particles are combined with each other in a dumbbell shape,and their size distribution was 400nm;the DSC showed that the T_gof the emulsion（5wt%VTES）was 26.17℃,which is 7.64℃higher than T_gof the uncrosslinked latex（18.53℃）;the TG showed that the initial decomposition temperature of the latex film with 5wt%VTES was 286.6℃,which was 15.8℃higher than the initial decomposition temperature（270.8℃）of the uncrosslinked latex film.（3）Finally,Soap-free ketone-hydrazine crosslinked core-shell type poly（vinyl acetate）emulsion prepared by pre-emulsion and seed emulsion polymerization using DNS-86 as reactive emulsifier,DAAM-ADH as cross-linked system;when DNS-86 amount was 4wt%,the wet shear strength of the emulsion is 2.41MPa,and the water absorption rate of latex film was 6.84%;the FT-IR spectra showed that:the ketocarbonyl group and the hydrazide group are reacted;the TEM showed that the emulsion particles had clear core-shell structure and particles were evenly distributed;the DLS showed that as the amount of DNS-86 increased,the latex particle size first decreased and then increased;the DSC showed that latex has two T_g:T_g1=-5.05℃,T_g2=34.8℃,consistent with the conclusion of core-shell structure observed by TEM;the TG showed that the initial decomposition temperature of the latex film made by DNS-86 was 293.5℃,which was 12.6℃higher than the initial decomposition temperature（280.9℃）of the latex film made by OP-10.