The effects of the cross‐linking mechanism of low doses of gamma irradiation on the mechanical, thermal, and viscoelastic properties of the natural rubber latex/poly(styrene‐<i>block</i>‐isoprene‐<i>block</i>‐styrene) block copolymer blend
Nurul Hakimah Lazim, Norsyahidah Mohd Hidzir, Naim Syauqi Hamzah, Takenaka Mikihito, Siti Aisyah Shamsudin
Abstract
Abstract Natural rubber latex (NRL) is a natural polymer with versatile properties. However, uncured NRL has low strength and limited practical use. Therefore, we utilized low‐dose gamma irradiation to induce cross‐linking in blended NRL/poly(styrene‐ block ‐isoprene‐ block ‐styrene) (SIS). Blends were prepared in various ratios, and the 70 NRL /30 SIS blend gave optimal mechanical properties. The 70 NRL /30 SIS blend was then irradiated from 4 to 16 kGy. An exposure of 12 kGy led to the highest tensile strength (4.49 MPa), Young's modulus (0.41 MPa), gel content (45%), and cross‐link density (12.18 × 10 −5 mol·cm −3 ). The results of study show irradiation has improved the crystallinity of the polymer blend, which has been determined by the formation of a new NRL crystal peak at 31.2° and the decrease of the crystallization temperature from 58 to 19°C due to strain‐induced crystallization. Moreover, the radiation has transformed the 70 NRL /30 SIS blend irradiated at 12 kGy from liquid‐like to an elastic state that degraded at a higher temperature (392.01°C). The presence of a singlet alkyl radical peak was detected in the electron spin resonance. Therefore, the cross‐links are proposed to be C‐C bonds formed via the radiation technique. Irradiation is an effective technique to improve the performance of NRL/SIS blends without introducing any chemical cross‐linking additive.