The tendency in the automotive industry to use smaller engines has resulted in a situation where lubricating oils are exposed to higher operating temperatures. This is especially the case in countries where there is no restriction on highway speed. Amine-based additives present in the oils (e.g., as dispersants and corrosion inhibitors) tend to slowly attack the conventional fluorocarbon elastomer seals under these conditions. As a result of that attack, the seal becomes brittle and eventually fails. A novel fluorocarbon elastomer of vinylidene fluoride, tetrafluoroethylene, and propylene has shown excellent aging behavior in the laboratory toward many aggressive engine oils at elevated temperature. Its improved resistance as compared to conventional fluorocarbon elastomers is attributed to the replacement of hexafluoropropylene with propylene.
The effects of percent fluorine, filler, and cure systems on the thermal and acid resistance of fluoroelastomers were evaluated over temperature ranges that would be typical of actual flue duct installations and accelerated conditions such as 275°C for thermal resistance and 149°C for concentrated sulfuric acid resistance. FKM 2176, which contains 65% fluorine by weight, became hard and brittle after two weeks of accelerated air aging at 275°C. The balance of physical properties of FKM 2176 were good when aged at 200°C. FKM 4894, which contains 67% fluorine by weight, retained useful properties after six weeks of accelerated air aging at 275°C. This indicates this material has improved properties for flue duct applications compared to FKM 2176. FKM 4894 filled with MT carbon black had improved retention of tensile strength after aging at 232°C relative to the FKM 4894 filled with SRF/HAF black, Austin Black and litharge. FKM 2176 was totally degraded after aging three days at 149°C in concentrated sulfuric acid. Aging of FKM 4894 in concentrated sulfuric acid at 149°C resulted in a loss of approximately 75 percent of the original tensile and an increase in the elongation, and the appearance of the exposed surface did not indicate chemical attack. Although FKM 4894 was superior to FKM 2176 when aged in sulfuric acid at 149°C, there was little difference between FKM 4894 and FKM 2176 when aged at 121 °C for up to four weeks or after eight weeks at 100°C in concentrated sulfuric acid. Austin Black showed the best retention of tensile of the four filler systems evaluated after aging at 100°C in concentrated sulfuric acid. FKM 4826, which contains 69% fluorine and is vulcanized using organic peroxide and triallyl isocyanurate, has indicated a compatibility with fiberglass that is superior to all fluorocarbon elastomer gums that were tested.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.