M. A. Abd El-Ghaffar

Preparation and characterization of polystyrene and styrene-butyl acrylate copolymer latices

Abstract Emulsion polymerization of styrene (S) and emulsion copolymerization of styrene with butyl acrylate (BuA) using potassium persulfate (KPS)/different aromatic aldehydic sodium bisulfite adducts as developed redox pair initiation systems were investigated at variable initiator, emulsifier concentrations and feed monomer compositions for studying the morphological characteristics of the obtained latices. It was found that the developed redox pair initiation system increased the number of polymer particles per unit volume of water (Nt) more than the classical system. Also, Nt, decreased with increasing initiator concentration, but increased with increasing emulsifier concentration for both the classical and developed ones. The volume-average particle diameter D v was found to be dependent on the different redox initiators: potassium persulfate/methylbenzaldehyde sodium bisulfite (KPS/MeBSBS), potassium persulfate/chlorobenzaldehyde sodium bisulfite (KPS/CBSBS), potassium persulfate/methoxybenzaldehyde sodium bisulfite (KPS/MBSBS), potassium persulfate/benzaldehyde sodium bisulfite (KPS/BSBS) and potassium persulfate/sodium bisulfite (KPS/SBS) to the powers 0.15, 0.27, 0.30, 1.80 and 0.70, respectively, while Nt, is dependent on emulsifier concentration to the powers 0.48, 1.00, 2.08, 3.33 and 4.41 with respect to the different redox systems KPS/SBS, KPS/MBSBS, KPS/CBSBS, KPS/BSBS and KPS/MeSBSB. The polydispersity index ( D w D w ) for the emulsion latices prepared using different emulsifier concentrations was found to be in the range 1.00–1.29, i.e. they are relatively narrow. This means that the emulsion polymerization of styrene was not in the so-called induction period. Increasing BuA ratio in the feed monomer composition of the prepared S/BuA copolymer lattices led to a decrease in Nt.

Effect of some free and chelated iron ions on the aqueous polymerization of methyl methacrylate

The aqueous polymerization of methyl methacrylate was carried out in absence and in presence of some inorganic iron salts and complexes using sodium bisulphite as a producer of initiator radicals. Polymerization in absence of iron salts or complexes resulted in the highest average molecular weights formation and the least reaction rates, while using salts in which the iron is ionizable lowered both the apparent energy of activation (Ea) of the system and the obtained average molecular weights and increased the initial rates. On the contrary, when the iron is chelated, as in case of potassium ferrocyanide and potassium ferricyanide, a retardation or complete inhibition of the polymerization reaction took place, respectively. Die wasrige Polymerisation von Methylmethacrylat wurde in Abwesenheit und in Gegenwart einiger anorganischer Eisensalze und Komplexe unter Verwendung von natriumbisulfit als Bildner fur Initiatorradikale durchgefuhrt. Die polymerisation in Abwesenheit von Eisensalzen oder Komplexen fuhrte zur Bildung des hochsten durchschnittlichen Molekulargewichts und der niedrigsten Reaktionsgeschwindigkeit, wahrend die Verwendung von Salzen mit freien Eisenionen sowohl die scheinbare Aktivierungsenergie des Systems als auch die erhaltenen mittleren Molekulargewichte herabsetzte und die Anfangsreaktionsgeschwindigkeit erhohte. Im Gegensatz dazu wurde fur komplexiertes Eisen in kaliumferro- und -ferricyanid eine Verzogerung bzw. vollstandige Inhibierung der Polymerisation beobachtet.