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Discussion centers on elastomeric material used for liners in automotive air conditioning systems. The following facts must be taken into consideration: the ambient temperatures may reach greater than 120 C there will be a move towards R 134a or R 22 as substitutes for the refrigerants now in use. The three materials that are discussed are NBR, HNBR and CM (an example of heat-resistant elastomers containing chlorine, CM). HNBR is a heat-resistant alternative to NBR and withstands both R 12 and R 134a. HNBR has good low-temperature bending behavior. It, therefore, has the widest, most useful temperature range of all the elastomers tested. Where NBR is in use at present, the introduction of R 134a does not necessitate the use of a different elastomer. However, CM is a more suitable elastomer for R 22.