Degradation Behavior of Rubber Materials for Elevator Safety According to Hydrothermal Aging

Abstract

The degradation behavior of vulcanized rubber in elevator cabins for reducing vibrations was investigated by morphological and spectroscopy analysis. Thermal (85℃) and hydrothermal aging (85℃ and 85% relative humidity) was performed to determine the effects of heat and humidity on the mechanical properties of rubber materials. The international rubber hardness degree (IRHD), tensile strength, and elongation percentage of rubber materials were measured to better understand the stiffening of the surface with the degradation time. The degradation mechanism of rubber materials was classified into two types: an increase in cross-links and chain scission. When rubber components were used for 96 hr under hydrothermal stress conditions, their mechanical characteristics deteriorated rapidly according to the results of the thermal aging test due to complex degradation behavior. Hydrothermal aging affects the increase in not only cross-links but also chain scission of the polymer segment. Fourier transform infrared (FT-IR) spectroscopy of the specimens of hydrothermal aging revealed improvement in C-H bonding at 2916 and 2848 cm?1, and an increase in the peak intensity in the 1080 cm?1 due to C-O-C bonding. The reduced C-C bonding was associated with the decomposition of cross-links and elastic modulus, which affected the degradation of the matrix near the surface. Therefore, the mechanical properties decreased more rapidly after hydrothermal degradation than after thermal degradation. (Received December 28, 2012).