Abstract:

Highly shear-stable copolymer dispersions with high solid contents of methyl methacrylate(MMA)and butyl acrylate(BA)were prepared using the semicontinuous emulsion polymerization,with thiol-ended poly(vinyl alcohol)(PVA-SH)as the protective colloid.FTrIR spectrum shows that PVA-SH mostly copolymerizes with MMA to form the grafting polymer PVA-g-PMMA at the first stage of the emulsion polymerization. TEM images sh0w that.when SDS(Sodium Dodecyl Sulphate)is added to the emulsion at the stage of shell formation,the particles are large in size and the PVA-SH shell is not integrated.However,when SDS is added at the stage 0f monomer droD-ping,the particles turn smaller in size and the PVA-SH shell becomes integrated. It is also indicated that the addi-tion of triethanolamine resuhs in a lower polydispersity index and an average relative molecular mass in nunaber 0f 50000 or so.Moreover,with the help of the drying assistant SiO₂,the acrylic dispersions with 0. 8% t0 1.5%(mass fraction)of PVA-SH can be spray-dried into highly dispersible powders that are easy to form sec0ndary dis-persions with a particle size distribution similar to that of the original dispersion

Key words: polyacrylate dispersion, thiol-ended poly(vinyl alcohol), protective colloid, redispersible p0lymer powder, property