Gamma-ray induced deterioration of natural rubber vulcanizates

We would like here to report the effect of radiation on purified NR vulcanizates which do not contain any fillers. RSS No.1 was used as natural rubber for vulcanizations. It was mixed with reagents to obtain a mainly monosulphide-crosslinked vulcanizate, S1, a mainly polysulphide crosslink, Ssub(x) and the carbon black stock, B. Experimental details are given. Stress-strain curves of NR vulcanizates before and after 100 kGy irradiation are shown. A figure shows the changes with dose of network-chain density (ν), tensile modulus at 50% elongation (M50), tensile strength (Tsub(B)) and elongation at break (Esub(B)) for NR-Ssub(x) vulcanizate. The NR-S1 vulcanizate showed very similar results. Both Tsub (B) and Esub(B) decrease much by irradiation. M50 and ν remain constant in spite of the increase of γ-ray dose. The results are discussed. (U.K.)