Influence of Ultraviolet Radiation on Mechanical Properties of a Photoinitiator Compounded High Vinyl Styrene–Butadiene–Styrene Block Copolymer

Abstract

Ultraviolet curing of elastomers is a special curing technique that has gained importance over the conventional chemical crosslinking method, because the former process is faster, and thus, time-saving. Usually, a suitable photoinitiator is required to initiate the process. Ultraviolet radiation of required frequency and intensity excites the photoinitiator which abstracts labile hydrogen atoms from the polymer with the generation of free radicals. These radicals result in crosslinking of elastomers via radical–radical coupling. In the process, some photodegradation may also take place. In the present work, a high vinyl (~50%) styrene–butadiene–styrene (SBS) block copolymer which is a thermoplastic elastomer was used as the base polymer. An attempt was made to see the effect of ultraviolet radiation on the mechanical properties of the block copolymer. The process variables were time of exposure and photoinitiator concentration. Mechanical properties like tensile strength, elongation at break, modulus at different elongations and hardness of the irradiated samples were studied and compared with those of unirradiated ones. In this S-B-S block copolymer, a relatively low exposure time and low photoinitiator concentration were effective in obtaining optimized mechanical properties. Infrared spectroscopy, contact angle and scanning electron microscopy were used to characterize the results obtained from mechanical measurements.

The Influence of Freeze-Dried Alcohol-Water Extracts from Common Yarrow (Achillea millefolium L.) and German Chamomile (Matricaria chamomilla L.) on the Properties of Elastomer Vulcanizates

“…Post-curing occurs due to the recombination of free radicals into branched structures that expand the internal spatial network of the polymer. Moreover, it can be related to the influence of elevated temperature or UV radiation, which may lead to the activation of the remaining cross-linking system compounds used in the rubber mixture and also contribute to the formation of new network nodes [ 80 , 81 ]. On the other hand, elastomer mixtures based on natural rubber are more likely to degrade due to the uncontrolled and irreversible changes in cis-1,4-polyisoprene structure including chain scissions and the formation of chain molecules, which leads to the reduction of elastomer molecular weight.…”

System for Precision Measurement of Environmental Parameters in an Installation for Uv Exposure on Rubber Products and Plastics

“…Система автоматизированного детектирования параметров световой и климатической сред для установки: «Установка ультрафиолетового воздействия на резинотехнические изделия и пластмассы» разработана с использованием современных программно-аппаратных средств и алгоритмы математического анализа систем [5].…”