The effect of electron beam irradiation and fillers on natural rubber prepared by latex mixing: A Small and Wide Angle X-ray scattering study

Abstract

The natural rubber (NR) cured by electron beam (EB) irradiation prepared by latex mixing was studied via small angle and wide angle x-ray scattering (SAXS and WAXS) techniques for the first time. In this study, the effect of EB irradiation doses (100–250 kGy) and fillers (graphene nanoplatelets (GE), mixture of silica and graphene nanoplatelets (TSi/20%GE) on the mean distance of crosslink and strain-induced crystallization were investigated. The SAXS experiments revealed that the maximum position of the plot (qmax) was increased from 1.76 nm to 1 to 1.99 nm-1, indicating that the mean distance between crosslinks of NR decreased due to the occurrence of crosslink networks after EB irradiation processes. It was found that the mean distance between crosslinks of all EB-irradiated NR was insignificantly different (qmax ∼ 1.94–1.99 nm−1) although the higher crosslink density was found in NR with the higher EB dose. Likewise, the addition of fillers did not also affect the mean distance between crosslinks of NR. The discussion led to the conclusion that the mean distance of NR depended on the type of crosslink networks. The WAXS study revealed that the intensities of crystallinity reflection peaks increased in the function of EB irradiation dose. It can be seen in all NR types that molecular chains of NR were still in amorphous regions although the high stretching was applied. Additionally, the crystallinity percentage of EB-irradiated NR in stretching mode was always lower than that in retraction mode, which the highest crystallinity percentage was found in the case of NR250 (41.89% crystallinity at 500% strain). Based on WAXS results, the conclusions were in agreement with NR cured by other vulcanization systems. Finally, it was found that addition of TSi/20%GE in NR pulled down the level of strain – induced crystallization, which the crystallinity percentage was 27.75% at 500% strain, while the crystallinity percentage of NR added GE was 36.19% at the same strain.