In general

bulk-crystallized FEP copolymer possesses spherulitic morphology. The extent of development and perfectness of the spherulites depends upon the molecular structure and crystallization condition of the copolymer. The size of spherulites of the polymer samples studied is in the range of several up to more than one hundred microns. The number of tie chains in the interdomain regions increases with molecular weight and with the decreasing of crystallization temperature of the sample

and has a pronounced effect on its craching behavior. The more the number of tie chains

the better is the service performance of the material. Annealing at a temterature near the melting point may improve the serviceability of FEP copolymer around 200℃.