Catalytic Effect of Various Kaolinite Forms on the Emulsion Polymerization of Vinylacetate Using Acetone Sodium Bisulfite as Initiator

Abstract

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 1.13 nm, respectively as shown by the X-ray diffraction (XRD). Emulsion polymerization of vinylacetate (VAc) was carried out at different temperatures (60-80 C) using acetone sodium bisulfite as initiator in the absence and presence of untreated as well as the modified forms 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 C and 7 at 80 C and also the activation energy of polymerization (E a ) was decreased from 43.35Â10 4 to 10.32Â10 4 J mole À1 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 À27.92 and À55.78, 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.

Exfoliation of Kaolinite Nanolayers in Poly(methylmethacrylate) Using Redox Initiator System Involving Intercalating Component

“…The initial rate of polymerization (Rp) and apparent activation energy (Ea) were determined according to the procedure listed in a previous work conducted in our laboratory [13,21,22] . Briefly, the initial rate (Rp) of emulsion polymerization was determined by taking the slope of the conversion-time curves at the linear part of the very initial period of polymerization and substituting in Eq.…”

“…Lately, an attempt was conducted by Essawy et al [13] who prepared preintercalated Kaolinites with DMSO or NMF according to the procedure reported in the literature [14,15] and carried out emulsion polymerization of vinylacetate in presence of these species and in the presence of virgin Kaolinite as well for comparison. Unfortunately, polymer intercalation into the basal space was unsuccessful, on the contrary, the preintercalated NMF or DMSO species deintercalated back into the reaction medium and the interlamellar space collapsed.…”