Structural conditions of processing and application of elastomers
Polimery 2001, No 2, 100
The main structural conditions affecting processing and application properties of elastomers are discussed. It is shown that there are some antagonisms between the structural requirements for the processing and application of rubber. Firstly the great antagonism exists between the structural requirements needed for high elasticity and low temperature properties of polar elastomers and their resistance to non-pol ar media. There is also the antinomy concerning the crystallization of rubber, if the strength and mechanical properties of elastomers are analyzed contrary to their elasticity and properties at low temperature. The high average molecular weight required for go od dispersion of reinforcing fillers and high strength and mechanical properties of cured elastomers are antagonistic from the point of view of the incorporation of fillers into the rubber and the processing of rubber mixes, i.e., for low elasticity and viscosity of rubber mixes, low energy consumption during processing, low calender effect and die swell of extrudate. The basic structural antinomy concerns the existing high chemical reactivity of unsaturated general purpose rubbers needed for their vulcanization on the one hand and low chemical activity required for safe manufacturing and processing of rubber mixes and for the high ageing resistance of rubber goods on the other hand. AIso various functional properties of elastomers depend on their crosslinking degree and kind of crosslinking bonds (Fig. 1). These antagonistic effects of structural parameters on the processing and properties of elastomers mean that the rule of technological and technical moderation and the rule of technical adequacy in the rubber technology are of great importance.
Keywords: rubbers, elasticity, chemical structure, crystallinity, molecular weight, viscosity, chemical reactivity, crosslinking degree, properties, processing