Grafting Reaction In The Emulsion Polymerization Of Vinyl Acetate With Poly (Vinyl Alcohol) As Protective Colloid

The grafting reaction during the emulsion polymerization of vinyl acetate (VAc) with partially hydrolyzed poly(vinyl alcohol) (PVA) used as protective colloid and ammonium persulfate as initiator was investigated in this paper . During the emulsion polymerization, the VAc reacted with PVA forming PVA-graft-PVAc. Since particle formation and therefore the properties of the final latex, such as viscosity, solid content and adhesive strength, will depend on the degree of grafting. It is important to quantify and to characterize the grafting reaction.In this work, the study and characterization of the latex samples being polymerized by different recipes were carried out by a two-step selective solubilization of the latex, first with sulfate solution to break the latex, then with water to separate the water-soluble PVA, followed by methanol to solute the PVAc homopolymer. After the separation, the water-insoluble and methanol-insoluble materials were desolved by DMSO to separate the DMSO-insoluable inpurities, and were characterized by 13C -NMR.The effects of polymerization temperature , the initator amount, thedegree of polymerization and viscosity of the protective colloid and the conversion of VAc on grafting reation were also studied in this paper. It is concluded that the amounts of PVA-graft-PVAc increased with polymerization temperature and the amounts of initiator. The best polymerization temperature was 90 C, and the high grafting efficiency of initiator occured at (NH4)2S2O8/VAc=0.370/o, The amounts of grafted PVAc, followed the same recipes, increased with conversion, and the grafting of PVA was nearly stopped by the time when monomer droplets feeding nearly finished (about 40% conversion in this paper). Another, the higher degree of polymerization( > 2000) and viscosity of PVA acting as protective colloid, the less VAc was grafted.Finally, The emulsion polymerization of vinyl acetate with PAM, CMC and EC in place of PVA as protective colloid were studied. It is concluded that PAM and EC could be used as protective colloid in the emulsion polymerization of vinyl acetate. However, the physical and chemisty properties of the latex have not been studied indetail yet.