Catalytic effect of various kaolinite forms on the emulsion polymerization of vinylacetate using acetone sodium bisulfite as initiator

Kaolinite was intercalated with N-methylformamide (NMF) and dimethylsulphoxide (DMSO), separately. The intercalation of these species expanded the basal space of kaolinite from 0.72 to 1.08 and 1.13nm, respectively as shown by the X-ray diffraction (XRD). Emulsion polymerization of vinylacetate (VAc) was carried out at different temperatures (60-80 degrees C) using acetone sodium bisulfite as initiator in the absence and presence of untreated as well as the modified forrms of kaolinite (K-NMF, K-DMSO). The results revealed that the presence of kaolinite decreased the rate of polymerization (Rp) by factor of 4 at 60 and 70 degrees C and 7 at 80 degrees C and also the activation energy of polymerization (E-a) was decreased from 43.35 x 10(4) to 10.32 x 10(4) Jmole(-1) if compared with the polymerization of VAc in absence of kaolinite. Using the modified forms of kaolinite (K-NMF, K-DMSO) enhanced the Rp and reduced effectively the E-a to-27.92 and-55.78, respectively. Conversely to untreated kaolinite, the Rp was declining with increasing the temperature in these cases. In all cases, Rp was the highest in the absence of any kaolinite form but in the same time the E-a was also the highest. These results were discussed and explained on the basis of the catalytic activity of the different forms, radical scavenging nature of the kaolinite, and chain transfer.