LOW TEMPERATURE CHARACTERISTICS OF SOME BLENDED RUBBERS

PART IV. LOW TEMPERATURE BEHAVIOR OF RUBBER VULCANIZATES

Abstract

The mutual solubility of the elastomer blendings used popularly were studied with behavior of relaxation modulus at low temperatures. In addition, the improvement on the low temperature characteristics of CR and NBR was studied by blending with rubbers having cold resistance.
The elastomer blends studied in this paper were as follows, NBR-NR, NBR-SBR, NBR-BR. CR-NR, CR-SBR, CR-BR. SBR-NR and BR-SBR.
Electron microscopic studies of the replication method on cut section of frozen NBR-NR blend revealed a micro-ununiform dispersion, and the island-phase of NBR particles having several μ in diameter afloated on the sea-phase of NR, and also showed the phase displacement in the range of 0.60.8 blending ratio of NBR.
Considering from the time-dependence of relaxation modulus, it apparently seemed that there was phase separation in the blend. But the behavior was slightly different from that of the simple mechanical blended materials. The phase separation similar to NBR-NR was observed in the blends such as CR-NR, NBR-BR, NBR-SBR, CR-SBR, and CR-BR, whereas SBR-BR blend showed better mutual solubility, and NR-SBR blend slightly good.The practical method preventing the hardening due to the crystallization of NR or CR at low temperature is not found yet to date, however, the blending of non-crystallizing rubber having good mutual solubility with NR or CR remarkably decreased the crystallization rate of them.