PVDF is a specialty plastic material in the fluoropolymer family; it 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. It is also available as a crosslinked closed cell foam, used increasingly in aviation and aerospace applications.
Properties
Polyvinylidene fluoride has a glass transition temperature (Tg) of about −35 °C and is typically 50–60% crystalline. To give the material its piezoelectric properties, it is mechanically stretched to orient the molecular chains and then poled under tension. PVDF exists in several forms: alpha (TGTG'), beta (TTTT), and gamma (TTTGTTTG') phases, depending on the chain conformations as trans (T) or gauche (G) linkages. When poled, PVDF is a ferroelectric polymer, exhibiting efficient piezoelectric and pyroelectric properties. These characteristics make it useful in sensor and battery applications. Thin films of PVDF are used in some newer thermal camera sensors.
Unlike other popular piezoelectric materials, such as PZT, PVDF has a negative d33 value. Physically, this means that PVDF will compress instead of expand or vice versa when exposed to the same electric field.
Applications
PVDF is commonly used as insulation on some kinds of electrical wires, because of its combination of flexibility, low weight, low thermal conductivity, high chemical corrosion resistance, and heat resistance. Most of the narrow 30-gauge wire used in wire wrap circuit assembly and printed circuit board rework is PVDF-insulated. In this use the wire is generally referred to as "Kynar wire", from the trade name.
The piezoelectric properties of PVDF are used to advantage to manufacture tactile sensor arrays, inexpensive strain gauges and lightweight audio transducers. Piezoelectric panels made of PVDF are used on the Venetia Burney Student Dust Counter, a scientific instrument of the New Horizons space probe that measures dust density in the outer solar system.
In the biomedical sciences PVDF is used in immunoblotting as an artificial membrane, usually with 0.22 or 0.45 micrometres pore sizes, on which proteins are transferred using electricity (see western blotting). PVDF is resistant to solvents and, therefore, these membranes can be easily stripped and reused to look at other proteins, making it very convenient.
Polyvinylidene fluoride is used for specialty monofilament fishing lines, sold as fluorocarbon replacements for nylon monofilament. Optical density is lower than nylon, which makes the line less discernible. The surface is harder, so it is more resistant to abrasion and sharp fish teeth. It is also denser than nylon, making it sink faster.
More about: Polyvinylidene fluoride sale
Read more: Base chemicals
No comments:
Post a Comment