Unplasticized CTFE, because of the presence of chlorine in the polymer chain, exhibits several differences in properties from those FLUOROPOLYMERS previously discussed. Most important is probably the effect on the useful temperature range. While CTFE can be used at temperatures almost as low as PTFE, FEP and PFA, its maximum continuous use temperature drops off below that of FEP to 390°F. CTFE, like PFA, is melt processible. Electrical insulation properties are good, but not as good as PTFE. With the presence of chlorine, tensile properties are enhanced with only a slight loss of impact properties over PTFE, FEP and PFA. CTFE has very good chemical resistance; is unaffected by all corrosive inorganics including oxidizing acids; but is swelled slightly by halogenated materials. Like the other FLUOROPOLYMERS it is non-flammable, shows no effect from outdoor weathering and sunlight exposure. CTFE posesses a very low water-vapour transmission rate making it an excellent gas and liquid barrier. CTFE, due to its ability to melt, will heat seal to itself. But, like the previous FLUOROPOLYMERS, cannot be bonded to other materials without treatment. This is due to its inertness toward adhesives. CTFE is available with as much as 25% plasticizer, but such products are not used in tube, rod or sheet. CTFE is a very dimensionally stable material with respect to temperature. Its coefficient of linear thermal expansion is only double that of Aluminum and rivals those of many filled polymers. Thus machining tolerances can be held on CTFE more easily than other unfilled FLUOROPOLYMERS.