Elastomers in hoses for air-conditioning systems

This paper discusses the development of rubber compounds for air-conditioning hoses designed to meet the stringent demands of the automotive industry, The phasing out of chlorofluorocarbons (CFCs) as automotive refrigerants and the introduction of new refrigerant fluids requires a new approach to compounding. The paper focuses on halobutyl formulations for an inner tube based on a VW draft specification for the temperature range of 90 to 110 degrees C. The results given in this paper are the optimised rubber compounds and cover only part of an extensive study. In the search for an optimum compound, a study was made of the effect of the polymers, fillers and vulcanisation system on each of the properties required and particularly on the compression set. Chlorobutyl and bromobutyl rubber are shown to be excellent base materials for rubber compounds for automotive air conditioning systems. Vulcanisates based on these elastomers, when correctly compounded, meet the most stringent specification requirements.