Structure of FKM and its influence on properties influence of fluorine monomer. The bond energy of the carbonfluorine bond,is at 442KJ/mole, substantially higher than that of the carbon-hydrogen bond at 376KJ mole. It is also higher than the bond energy of carbon with other atoms. Like chlorinc. For this reson,and because of the shielding of the ploymer chain by the larger fluorine substitwents,as compared with non-substitwents chains,FKM has a very hight heat and chemical resistance [3.621]. Because of certain dehydro fluorination reaction, and florinated hydroxarbons are,howvere,dithiols,or aromatic diphenyl compounds,like bisphenol AF. FKM grades with 65 to 67% fluorine can only be crosslinked with great difficulty,and they give very low states of cure.