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New branched polymers will open up more applications for PVDF |
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Polyvinylidene Fluoride (PVDF) is a highly non-reactive and pure thermoplastic fluoropolymer. PVDF is a specialty plastic material in the fluoropolymer family - a specialty plastic that has alternation of hydrogen and fluorine atoms on the molecular chain providing additional properties like abrasion resistance, radiation stability and a lower melting point than most fluoropolymers, which allows for lower processing temperatures similar to those of polyolefins. Other benefits are lower density than most fluoropolymers and good tensile strength at up to 150�C. PVDF is used generally in applications requiring the highest purity, strength and resistance to solvents, acids, bases and heat and low smoke generation during a fire event. Compared to other fluoropolymers, it has an easier melt process because of its relatively low melting point of around 177�C. It has a low density (1.78) and low cost compared to the other fluoropolymers. It is available as piping products, sheet, tubing, films, plate and an insulator for premium wire. It can be injected, molded or welded and is commonly used in the chemical, semiconductor, medical and defense industries, as well as in lithium ion batteries. Despite this impressive property profile, PVDF has struggled to shake its niche status. Several key PVDF makers are doing extensive development work to broaden its use.
Arkema Inc has done development work to alter homopolymer PVDF with the aim of improving processing efficiency. Kynar High Melt Strength (HMS) PVDF grades are chain-branched polymers that exhibit high melt strength and sag resistance during extrusion, making them excellent candidates for extrusion blow molding, thermoforming, and blown film extrusion. The ability to modify polymer architecture to balance melt viscosity with elasticity allows these PVDF polymers to be cost-competitive while maintaining the material�s performance attributes. They exhibit balanced rheological properties, which allow them to be used in many more processes and applications than conventional PVDF polymers. They combine good melt strength and draw-down ratio with sag resistance and strain hardening. They are specifically recommended for extrusion blow molding, thermoforming, and blown film extrusion and can also be used in rigid foam extrusion and potentially in fiber spinning. Furthermore, their mechanical and physical properties remain comparable to those of conventional Kynar polymers.
In blown film, Kynar HMS expands the processing window and maintains PVDF polymer properties such as tensile strength, impact resistance, and chemical resistance. It offers excellent balance between melt strength and elongation, high sag resistance at low viscosity, and high die swell. These enhanced properties were obtained by the introduction of long-chain branching. One of the key applications is fire-resistant extrusion coatings for aircraft interiors.
The other PVDF available in the market include:
Solef PVDF and Hylar PVDF homopolymers from Solvay are used to make durable, long-lasting membranes. Their toughness, chemical resistance and oxidative stability allow membranes to tolerate a wide variety of feed streams and cleaning methods. These materials are soluble in conventional processing solvents to make hollow fiber and flat sheet membranes by DIPS and TIPS processes.
Solef PVDF homopolymers are made using a suspension-type polymerization process which provides a linear, gel-free product. They are available in powders and pellets that cover a wide range of molecular weights. High molecular weight grades improve fiber strength and minimize fiber breakage.
Hylar PVDF is a broad MWD grade of PVDF with low crystallinity and physical properties of standard homopolymers. Hylar 460 also has a relatively high concentration of chain branches that give it unique resistance properties in certain applications
Their key features include high purity, broad chemical resistance, excellent mechanical properties, continuous use up to 150�C, excellent resistance to aging, easy processing by solution, broad molecular weight and high branching, physiologically harmless and approved for contact with food products. These materials find application in Low pressure water filtration, Wastewater treatment, RO/NF pre-treatment.
DyneonTM PVDF (a polymer of vinylidene fluoride) is ideal for multiple applications across a wide array of industries. PVDF Homopolymers are ideal for a variety of applications such as pumps, valves, sheet products, pipes, tubes and fittings needing excellent chemical resistance and operating temperatures up to 150�C (302�F). Various grades are available that can be processed by injection molding, compression molding, blow molding and extrusion. Features include Continuous service temperatures up to 150�C (302�F), excellent mechanical strength, good chemical resistance, excellent abrasion resistance, smooth, anti-fouling surfaces, excellent aging resistance, resistance to UV and nuclear radiation, excellent flame resistance, good permeation resistance.
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