PCTFE is a semicrystalline polymer with a helical polymer chain and a pseudohexagonal crystal. PVDF and equimolar ETFE are isomers but the latter has a higher melting point and a lower dielectric loss than the former.Similar to ETFE, ECTFE terpolymers (same termonomers) have better mechanical and abrasion and radiation resistance than PTFE and other perfluoropolymers.
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PCTFE Properties
PCTFE is a semicrystalline polymer with a helical polymer chain and a pseudohexagonal crystal. Crystal growth is spherulitic and consists of folded chains. Large size of chlorine constrains recrystallization after melting during processing. This resin has good properties at cryogenic temperatures relative to plastics in general, although they are inferior to other fluoropolymers except PVDF.
PCTFE has exceptional barrier properties and superb chemical resistance. It is attacked by a number of organic solvents.
PCTFE has low thermal stability and degrades upon reaching its melting point, requiring special care during processing.
ETFE Properties
PVDF and equimolar ETFE are isomers but the latter has a higher melting point and a lower dielectric loss than the former. ETFE crystallizes into unit cells believed to be orthorhombic or monoclinic. The molecular conformation of ETFE is an extended zigzag. This polymer is dissolved in some boiling esters at above 230 C, thus allowing determination of molecular weight (weight-average) by light scattering. ETFE has several transitions, alpha relaxation at 110 C (shifts to 135 C at higher crystallinity), beta at 25 C, and gamma relaxation at 120 C.
ETFE terpolymers have good mechanical properties including tensile and cut-through resistance and lower creep than perfluoropolymers. ETFE is more resistant to radiation than perfluoropolymers (modestly affected up to 20 Mrad) and can be crosslinked by radiation such as electron beam. Crosslinking is used to strengthen cut-through resistance of ETFE wire insulation.
ETFE has a dielectric constant of 2.6e3.4 and dissipation factor of 0.0006e0.010 as frequency increases from 102 to 1010 Hz.
ETFE terpolymers are resistant to stress cracking and chemical attack by most compounds. Strong oxidizing acids, concentrated boiling sulfonic acids, and organic bases (amines) attack ETFE and any chemical that affects PTFE, PFA, and FEP.
ECTFE Properties
ECTFE is semicrystalline (50e60%) and melts at 240 C. It has an alpha relaxation at 140 C, a beta at 90 C, and gamma relaxation at 65 C. Conformation of ECTFE is an extended zigzag in which ethylene and CTFE alternate. The unit cell of ECTFE’s crystal is hexagonal.
Similar to ETFE, ECTFE terpolymers (same termonomers) have better mechanical and abrasion and radiation resistance than PTFE and other perfluoropolymers.
Dielectric constant of ECTFE is 2.5e2.6, and independent of temperature and frequency. Dissipation factor is 0.02 and much larger than ETFE’s.
ECTFE is resistant to most chemicals except hot polar and chlorinated solvents. It does not stress crack dissolve in any solvents. ECTFE has better barrier properties to SO2, Cl2, HCl, and water than FEP and PVDF.
Post time: Mar-14-2018