EFFECT OF STYRENE CONTENT AND ZNO-STEARIC ACID ON THE MECHANICAL-PROPERTIES OF RADIATION-VULCANIZED STYRENE-BUTADIENE RUBBER (SBR)

The effect of styrene content on the properties of electron irradiation-vulcanize SBR loaded with carbon black was pronounced only at low irradiation doses where the crosslinking densities were not so high. At high doses, no effect was observed especially for SBR containing ZnO. It was also observed that ZnO (3 phr) increased the tensile strength of SBR containing 23.5 wt.-% styrene by 20% at 20 kGy irradiation dose, compared to 5% at higher doses for SBR containing 46 wt.-% styrene. However, the increase in tensile strength by ZnO for loaded SBR (23.5%) was almost 17% at all irradiation doses. Besides, tear strength, abrasion resistance and elongation at break were remarkably improved. The high efficiency of ZnO toward SBR (23.5%) may be attributed to the higher butadiene content. The behavior of SBR (46%) at 20 kGy was surprising, since both tensile strength and elongation at break were almost maximum.