The effect of Tinuvin derivatives as an ultraviolet (UV) stabilizer on EPDM rubber

Abstract

Ethylene-propylene-diene monomer (EPDM) is one of the most widely used synthetic rubbers, especially in the automotive industry. Despite its many benefits, the chief weakness of EPDM has been the color change occurring in its products due to ultraviolet (UV) rays. It is recognized that UV energy causes the dissociation of bonds (mostly CC and C-H) in EPDM materials as well as cracks and color changes on the surface. The aim of this study was to investigate the effect of the Tinuvin derivatives widely used as UV stabilizers in the plastics industry on EPDM rubber. The EPDM rubber plates were prepared by adding Tinuvin-P, Tinuvin-213 and Tinuvin-234 as UV absorbers (UVAs) and Tinuvin-123 as hindered amine light stabilizer (HALS) material at a ratio of 1.0 phr (parts per hundred parts of rubber) to an available EPDM formula. The effects of the Tinuvin derivatives were investigated by the internationally recognized Florida outdoor aging test. The surfaces of the EPDM plates were visually scrutinized and surface morphological changes were examined via scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and Fourier transform infrared (FTIR) spectrometry analyses. The results obtained showed that, unlike in the plastic industry, not all Tinuvin derivatives could be used as UV stabilizers for EPDM products. Of all the tested Tinuvin derivatives, the Tinuvin-123 compound was the most effective, indicating it to be suitable for use as a protective UV stabilizer for EPDM rubber applications. Thus, an important issue such as the UV resistance of sealing profiles made by EPDM rubber has been contributed about the suitability of Tinuvin derivatives.

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“…This can be expected to further enhance the stability and robustness, as the molecular organization is fixed, showing no temperature dependence (up to decomposition, which for the materials we are considering here is at least up to about 200 • C), and reduced sensitivity to humidity and light. Nevertheless, for outdoor applications, light stability can be further improved by the addition of photo-stabilizers [80], such as benzotriazoles [81], which are basically colorless inert dyes that do not disturb the liquid crystal order during the production phase.…”