ECTFE chains

The unit cell of alternating copolymers of ECTFE is hexagonal with a chain repeat distance of 0.502 mn.[57][58] pjjg (.gp contains three molecules and occupies a volume of 0.324 nm. f l The preferred morphology of ECTFE chains is similar to that of ETFE where chlorotrifluoroethylene units line up opposite ethylene in the adjacent chain. This structure has been credited for the relatively high melting point and physical properties of equimolar ECTFE. 

PCTFE has better mechanical properties than PTFE because the presence of the chlorine atom in the molecule promotes the attractive forces between molecular chains. It also exhibits greater hardness, tensile strength, and considerably higher resistance to cold flow than PTFE. Since the chlorine atom has a greater atomic radius than fluorine, it hinders the close packing possible in PTFE, which results in a lower melting point and reduced propensity of the polymer to crystallize.7 The chlorine atom present in ECTFE, a copolymer of ethylene and CTFE, has a similar effect on the properties of the polymer. 

Commercial ethylene-chlorotrifluoroethylene copolymer is an alternating polymer with 1 1 ratio of the comonomers. It is partially crystalline (50-55%) and melts at 240°C.[ ECTFE exhibits three second order transitions at 140°C (a), 90°C (/3), and at -65°C (7). The first and last transitions are ascribed to the motion of chain segments in the crystalline phase whereas the /3 transition is thought to relate to the motion of chain segments in the amorphous phase. 

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