Effects of Polymerization Temperature on Structure

Structure-Property Relationships for Neoprene Type W

“…Further, the results shown in Table II indicate that Neoprene Type W is more homogeneous than the other neoprenes examined, Types GN and CG, as well as the "cold" rubber, GR-S X-478. It has been reported that low polymerization temperatures give more uniform molecular weight distribution (16). Such a trend is illustrated by the results for Neoprenes Type GN and Type CG, and by comparison of the data given in Table II for GR-S X-478 (made at 5°C .)…”

“…Crystallization in high polymers requires a certain degree of symmetry and uniformity of structure. Vulcanizates of Neoprene Type W showed greater increase of durometer hardness on standing than do comparable Neoprene Type GN vulcanizates, indicating greater crystallization (3,4)• Neoprenes Type W and Type GN have been examined by means of an x-ray spectrometer and the areas above background under the crystalline and amorphous spectrometer curves were determined (7,16). This is a rough measure of relative crystalline contents of the polymers.…”

“…Since Neoprene Type W is different from other neoprenes in some of its properties, an investigation of the molecular structure of Type W was undertaken. Some properties of elastomers are influenced markedly by average molecular weight and molecular weight distribution (8,16). For example, optimum processing properties for a series of sodiumcatalyzed polybutadienes were reported for a polymer having a moderately high average molecular weight and relatively narrow molecular weight distribution (2).…”

Miniemulsion and conventional emulsion copolymerization of styrene and butadiene: Effect of process on gel content

“…The main influence was the polymerization temperature. Although the composition of the copolymers was not affected by temperatures between 30 and 70°C, below 0°C, a minimum in the styrene content in the copolymer composition was reported 5–7. Such a minimum would seem inconsistent with copolymerization theory, but was ascribed to the differences in the solubilities of the two monomers in the polymer particles.…”

Polymerization

“…They also compare the properties of their products with standard GR-S. Johnson, Brown, and Bebb (126) discuss the effect of low temperature polymerizations, using redox catalysts and glycerol as an antifreeze, on the properties of butadiene-styrene copolymers. The effect of reducing the temperature of copolymerization of butadiene and styrene was investigated by Meyer (169). He found that lowering the temperature increased the structural regularity, gave less branching, and produced a smaller proportion of low molecular weight polymers.…”