Crystallization in Binary Blends of Polytetrafluoroethylene with Perfluorinated Tetrafluoroethylene Copolymer

Abstract

ABSTRACT:Miscibility and crystallization were studied for two binary blends of polytetrafluoroethylene (PTFE) with poly(tetrafluoroethylene-co-10 mol % hexafluoropropylene) (FEP) and poly(tetrafluoroethylene-co-2 mol % perfluoropropylvinyl ether) (PFA), using DSC and X-Ray diffractometry. In FEP/PTFE blends, FEP and PTFE components were separately crystallized to form their own crystallites, while in PFA/PTFE blends, PFA and PTFE components were cocrystallized to form PTFE-type crystallites incorporating tetrafluoroethylene segments of PFA and PTFE. The crystallization behavior in both blends is discussed in terms of chemical structure, molecular weight, crystallization rate, blending method (how the two components are blended) and comonomer concentration. [DOI 10.1295/polymj.36.716] KEY WORDS Polytetrafluoroethylene / Poly(tetrafluoroethylene-co-10 mol % hexafluoropropylene) / Poly(tetrafluoroethylene-co-2 mol % perfluoropropylvinyl ether) / Blends / Crystallization / Polytetrafluoroethylene (PTFE) is a polymer with good thermal stability up to 720 K, excellent chemical resistance to many solvents, low surface energy, and good electric insulation.1 However, PTFE used industrially is generally required to have high molecular weight (for example, Teflon 3170 has an average number molecular weight, M n , of about 3:6 Â 10 5 ) enough to avoid excess crystallization, but the high molecular weight results in the high melt viscosity, and hence special processing technology such as powder sintering and paste extrusion is required to reform PTFE powders, for example, into sheets. To overcome the above undesirable properties of PTFE, fluorinated copolymers of tetrafluoroethylene (TFE), such as poly-(tetrafluoroethylene-co-hexafluoropropylene) (FEP) and poly(tetrafluoroethylene-co-perfluoroalkylvinyl ether) (PFAVE), have been developed. These copolymers are semicrystalline polymers and their melt viscosities are in general lowered by the introduction of comonomer, compared with those of PTFE, allowing their molding by usual melting extrusion and injection molding technologies.Recently, scientific interest has been paid to miscibility and crystallization in binary polymer blends.2 In particular, it is important to clarify how and why miscibility and crystallization occur in semicrystalline polymer/semicrystalline polymer blends. Miscibility and crystallization behavior has been investigated for several binary blends of PTFE with perfluorinated TFE copolymers.3-7 Runt et al. 3 studied miscibility and crystallization for binary blends of PTFE (Teflon 3170) with poly(tetrafluoroethylene-co-perfluoropropylvinyl ether) (trade name Teflon PFA335, but simply called PFA in this paper), using dynamic mechanical (DM) spectroscopy and differential scanning calorimetry (DSC), where the perfluoropropylvinyl ether (PVE) content of the PFA was 1-2 mol %. DM spectra as a function of temperature showed two peaks labeled and , which were related to reorientational motion of long segments above the glass transition temperature (T g ) and r...

Modification of carbon nanotubes with fluorinated ionic liquid for improving processability of fluoro-ethylene-propylene

“…Three diffraction peaks of (100), (110), and (200) could be observed in the 2-D diffraction patterns which were attributed to the typical crystal structure of FEP [7,26,27],…”

Tribological, Mechanical and Thermal Properties of Fluorinated Ethylene Propylene Filled with Al-Cu-Cr Quasicrystals, Polytetrafluoroethylene, Synthetic Graphite and Carbon Black

“…The structure of such blends was investigated in [ 40 , 41 , 42 , 43 , 44 ]. Analysis of such blends using differential scanning calorimetry and X-ray diffraction shows that FEP and PTFE are immiscible and coexist as separate phases over a wide range of blend concentrations, and no co-crystallisation effect was observed [ 40 , 41 , 42 , 43 ]. Chemical bonds between these two fluoropolymers can form only as a result of crosslinking under irradiation [ 44 ].…”