The Plasticization of Butadiene-Styrene Rubber

1. The kinetics of the plasticization of a butadiene-styrene copolymer on a cold laboratory mill was studied. It was established that, at temperatures of 20–30° C, the plasticity rises steadily and that, consequently, under these conditions a monodirectional destructive process takes place. 2. The kinetics of plasticization of a butadiene-styrene copolymer was investigated in a laboratory banbury at 140° C, both with and without a plasticization aid (chemical). Plasticization at a high temperature is accompanied by the simultaneous operation of the two reactions of destruction and structure formation proceeding at cross-purposes, and may be described by a kinetic equation of the type: P=P0 (1+a⋅m)(1−b⋅n) 3. Plasticized rubbers obtained by breakdown on a cold mill have a smaller capacity for recovery than those obtained by treatment in a boiler or a banbury at temperatures above 120° C. 4. Plasticized rubbers obtained by milling on a cold mill give stocks with higher tensile strength and higher relative elongation than rubbers plasticized by hot treatment. 5. The high recovery capacity of rubbers plasticized at elevated temperatures and the lowering of the physical and mechanical properties of vulcanizates of those rubbers are explained by the branched molecules which they form during structure formation.