Accelerated Aging and Thermal Analysis Testing on Neoprene and EPDM Blend Rubber Materials used in the Microgravity Science Glovebox (MSG) on International Space Station (ISS)

摘要

The Microgravity Science Glovebox (MSG) was built for the National Aeronautics and Space Administration (NASA) by the European Space Agency (ESA), and was launched to the International Space Station (ISS) in July 2002. Th The MSG will e remain in orbit until at least 2012. The MSG utilizes several types of rubber seals, each of which is mounted against a nickel nickel-plated or anodized aluminum surface. Most of the MSG seals are bonded to the metal MSG assembly with an epoxy adhesi adhesive. Until 2005, ve. MSG seals were made of Nor Norsorex?, a polynorbornene rubber. It was found in 2005 sorexthat Norsorex would no longer be manufactured because of obsolescence. Therefore, the Norsorex was replaced with an EPDM blended with some natural rubber for use on MSG seals. The EPDM blend is a fai fairly soft material, with a Shore A hardness of 30 compared rly to 25 for Norsorex. The Norsorex seals had a 3 to 5 year shelf life, and the seals tended to surface crack within that time. The EPDM blend has a shelf life of 5 to 10 years (1, 2). Gloves used I inside the MSG are made of neoprene rubber. The gloves are nside stressed at the junction of the glove to metal glove ring, not to mention repeated stress from the user putting on or removing the gloves. The gloves have a minimum shelf life of five years, provi provided the gloves are stored free from stress or deformation and at an ded average temperature and relative humidity of 23°C and 65%, respectively (3). Because of unknowns about use of the EPDM blend as a replacement rubber seal material for MSG, the Materials T Test Branch/EM10 at Marshall Space Flight Center est (MSFC) was asked to perform accelerated aging testing on the EPDM blend and neoprene for predicting useful lifetimes. Tensile dog bones were stamped out of flat sheets of EPDM blend and neoprene. Approximat Approximately 20 tensile specimens each of the ely two rubber materials were conditioned at 25, 32, 42, 52 and 60°C for times up to 325 days. A 10% change in the tensile product (TP, ultimate stress x ultimate strain) was used to represent a significant change in mater material properties as the basis (along with the ial Arrhenius rate equation) for a useful life prediction on each rubber material. Tensile peel specimens of the EPDM blend bonded to anodized aluminum with epoxy adhesive were subjected to the same temperature cond conditioning. The highest temperature of 60°C was itioning. Chosen for the aging test because this is considered the maximum continuous use temperature of the epoxy adhesive.The accelerated aging test data resulted in predicted lifetimes of approximately 10 years for the neoprene and 5 years for the EPDM blend. Some thermal analysis testing was performed on these materials as well.