Polyvinylidene fluoride melting temperature

We can think of the strain as inducing melting. At the melting temperature TM we would expect the volume fraction of each phase to be equal to 0.5. We could argue that this happens where the storage and loss moduli are equal. Given these assumptions we can calculate the amount of solid and liquid-like material present as a function of strain. The apparent volume fraction of liquid is shown for a polyvinylidene fluoride latex in Figure 6.17. 

PVC, another widely used polymer for wire and cable insulation, crosslinks under irradiation in an inert atmosphere. When irradiated in air, scission predominates.To make cross-linking dominant, multifunctional monomers, such as trifunctional acrylates and methacrylates, must be added. Fluoropolymers, such as copol5miers of ethylene and tetrafluoroethylene (ETFE), or polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), are widely used in wire and cable insulations. They are relatively easy to process and have excellent chemical and thermal resistance, but tend to creep, crack, and possess low mechanical stress at temperatures near their melting points. Radiation has been found to improve their mechanical properties and crack resistance. Ethylene propylene rubber (EPR) has also been used for wire and cable insulation. When blended with thermoplastic polyefins, such as low density polyethylene (LDPE), its processibility improves significantly. The typical addition of LDPE is 10%. Ethylene propylene copolymers and terpolymers with high PE content can be cross-linked by irradiation. ... 

Fluoropolymers, such as copolymer of ethylene and tetrafluoroethylene (ETFE), polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), are widely used in wire and cable insulations. They are relatively easy to process and have excellent chemical and thermal resistance, but tend to creep, crack and possess low mechanical stress at temperatures near their melting points. Radiation has been found to improve their mechanical properties and crack resistance.36... 

Fluoropolymer manufacturers and suppliers have developed time-temperature-shear-rate data for melt viscosity or melt flow rate (index) to provide an assessment of the thermal stability of these polymers. Figures 6.1 and 6.2 show the melt viscosity of a few commercial grades of polyvinylidene fluoride as a function of temperature at a fixed shear rate. The relationships between melt viscosity and shear rate, and shear stress versus shear rate, are presented in Figs. 

Plastication unit design. The role of the plastication part of the machine is to mix and melt the polymer and the additives, homogenize, pressurize, and feed the melt to the transfer section of the cylinder through the check valve. Plastication takes place at elevated temperatures (230°C-400°C) depending on the type of the plastic. Polyvinylidene fluoride is injection-molded at the lowest end of the temperature range while PFA is processed at the highest. 

Kawai s (7) pioneering work almost thirty years ago in the area of piezoelectric polymers has led to the development of strong piezoelectric activity in polyvinylidene fluoride (PVDF) and its copolymers with trifluoroethylene and tetrafluoroethylene. These semicrystalline fluoropolymers represent the state of the art in piezoelectric polymers. Research on the morphology (2-5), piezoelectric and pyroelectric properties (6-70), and applications of polyvinylidene fluoride 11-14) are widespread in the literature. More recently Scheinbeim et al. have demonstrated piezoelectric activity in a series of semicrystalline, odd numbered nylons (75-77). When examined relative to their glass transition tenq>erature, these nylons exhibit good piezoelectric properties (dai = 17 pCTN for Nylon 7) but have not been used commercially primarily due to the serious problem of moisture uptake. In order to render them piezoelectric, semicrystalline polymers must have a noncentrosynunetric crystalline phase. In the case of PVDF and nylon, these polar crystals cannot be grown from the melt. The polymer must be mechanically oriented to induce noncentrosynunetric crystals which are subsequently polarized by an electric field. In such systems the amorphous phase supports the crystalline orientation and polarization is stable up to the Curie temperature. 

Many high-performance polymer fibres are used in filter media to meet various specific requirements in diverse filtration applications. Filters made from fluoropol-ymer (Polytetrafluoroethylene (PTFE), Polyvinylidene fluoride (PVDF), and Per-fluoroalkoxy alkane (PFA)) fibres, and membranes have inherent, chemical-resistant, and flame-retardant properties, and they are widely employed to filter aggressive chemicals and acids in the manufacture of wafers and microchips in the microelectronics industry. Ethylene ChloroTriFluoroEthylene (E-CTFE) melt blown fabrics have a unique ability to coalesce difficult liquids and can withstand the piranha effect in filtering ozone enriched ultrapure water. Polyphenylene sulfide (PPS) fibres are also chemical resistant, stand high temperature, and are suitable for making baghouse filters. Eilter media made from other high-performance polymer fibres, such as polyamide-imide, polyetherimide (PEI), Polyimide P84 fibre,polyetheretherke-tone, and liquid crystal polymers also appear in the filtration and separation market. 

Preparation of oriented fibers from mixtures of polyvinylidene fluoride with different inherent viscosities (molecular weight) has been reported. [" 1 In one example, two types of PVDF polymers with inherent viscosities of 1.49 and 0.95 dl/g were blended together at a weight ratio of 70%/30%. The mixture had an inherent viscosity of 1.33 dl/g. After pelletization, the PVDF blend was melt spun into monofilaments with a diameter of 520 pm. A single-screw extruder (32-mm diameter) was used to spin the filaments at a temperature of 300°C. Birefringence, which is defined as the difference in refractive index in two selected perpen-... 

Nanocomposites prepared with Cloisite 30B and polyvinylidene fluoride [39] provide an unexpected perspective of the mechanical properties of polymer-montmorillonite nanocomposites. Polyvinylidene fluoride has geminal fluorines on alternate carbons of a polyethylene chain. The polyvinylidene fluoride (PVDE Kynar 721 manufactured by Atofma Chemical Co.) was premixed as a powder with Cloisite 30B at 5 wt.% with a Elack-Tek DAC-150EV speed mixer. The extrusion of the melt-compounded composite was accomplished with a small DSM twin-screw extruder (capacity 5 cm ) that was utilized with the SMA and SAN meltblending work earlier. The temperature of the extruder was 200 °C. 

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