Cellular Bi 2 O 3 /natural rubber composites for light-weight and lead-free gamma-shielding materials and their properties under gamma irradiation

Abstract

This work investigated the effects of a radiation-protective filler, namely bismuth oxide (Bi₂O₃), and blowing agents, namely azodicarbonamide (ADC) and oxy-bis (benzene sulfonyl) hydrazide (OBSH), on gamma attenuation and the mechanical, physical, and morphological properties of cellular natural rubber (NR) composites for potential use as light-weight and lead-free gamma-shielding materials. The contents of Bi₂O₃ were varied from 100 to 300 and 500 parts per hundred of rubber by weight (phr) and the contents of ADC or OBSH were varied from 0 to 8 and 16 phr. The results indicated that the addition of Bi₂O₃ enhanced the overall gamma-shielding ability, density, tensile modulus, and hardness (Shore OO), but lowered the tensile strength and elongation at break. On the other hand, the addition of ADC or OBSH resulted in decreases in the density, linear attenuation coefficient (μ), and overall tensile properties but an increase in the mass attenuation coefficient (μ_m), with ADC producing better mechanical properties than samples with OBSH. In addition, investigations on the properties of the cellular Bi₂O₃/NR composites under additional 35 kGy and 70 kGy gamma irradiation revealed that the irradiated samples had increased density, tensile modulus, and hardness (Shore OO), but decreased tensile strength, elongation at break, and μ_m after such ageing. In conclusion, the overall results suggested that the developed cellular Bi₂O₃/NR composites not only had efficient and promising gamma-shielding and mechanical properties but also offered comfort and light-weight to users, which could potentially reduce discomforts caused by wearing heavier conventional radiation-protective equipment.