Kynar PVDF (property of Arkema) is a high purity polymer that combines extreme-temperature performance, easy manufacturability, and durability in some of the harshest environments.
What is PVDF?
PVDF (polyvinylidene difluoride or polyvinyl fluoride) is a fluorinated thermoplastic resin that is classified as a specialty polymer whose brand names include Kynar (Arkema), KF (Kureha), and Solef or Hylar (Solvay). This engineering polymer can often be found in environments that involve high purity, hot acid, extremely high temperatures, and/or radiation.
Fluoropolymers are used in multiple industries, including aerospace, transportation, chemical and petrochemical processing, pharmaceutical, medical, telecommunications, and electronics where they are used for seals, gaskets, bushings, bearings, hoses, tubing, wiring, and even fiber optic cladding. There are multiple ways to manufacture parts and components made from fluoropolymers, and injection molding is one of them.
What Are Fluoropolymers?
Fluoropolymers, as the name no doubt implies, are polymers that are based on bonding between fluorine and carbon. The first fluoropolymer was PTFE (polytetrafluoroethylene), which is perhaps better known by its trade name Teflon. Other common fluoropolymers include ETFE (ethylene tetrafluoroethylene), PFA (perfluoroalkoxy alkane), PVDF (polyvinylidene fluoride), PVF (perfluoralkoxy), FEP (fluorinated ethylene propylene), and ECTFE (ethylene chlorotrifluoroethylene).
They are popular materials because of their properties that include resistance to high temperatures, chemical attacks, and electrical current. They are also low friction, non-toxic, exhibit minimal aging and leaching of chemicals, and non-stick. In addition, many fluoropolymers are biocompatible, making them ideal for medical applications.
Injection Molding Process
Injection molding is a manufacturing method for thermoplastic materials where the plastics are heated almost to their melting point and then fed into aluminum or steel molds at extremely high pressures using a powerful screw mechanism. There are several benefits to injection molding:
Can handle high-volume production
Labor costs are relatively low
Products highly accurate parts that can meet tight tolerances
Supports fairly complex designs with fine details
Produces an excellent surface finish
In many instances, the scrap can be recycled
The major cost involved in injection molding is the tooling: to achieve good results, the molds must be high-quality and well designed. However, molds can be configured to make multiple parts at one time with minimal post-processing.
Note that injection molding can be used to manufacture otherwise challenging components, including thin-walled parts. The feasible envelope for parts can typically range from 0.01 in³ to 80 ft³ (depending on the fabricators’ capabilities) and can achieve tight tolerances and smooth surfaces.
Injection Molding Fluoropolymers
While fluoropolymers can be challenging to injection mold, the process is not impossible for most materials. Some of the best fluoropolymers for injection molding include PFA and FEP, which are both melt-processable. Additional consideration may have to be given to the tooling for molding fluoropolymers, including a hot runner system to keep the polymer flowing easily as it moves through the mold.
PTFE, however, is challenging to injection mold because even when heated above its melting point because it simply will not flow like other thermoplastic polymers. It does soften, but not enough to make injection molding possible. Fortunately, there are several other options when it comes to manufacturing with PTFE, including machining, compression molding, cold extrusion, and isostatic pressing.
Fluoropolymers are widely used in many different industries and applications. If you are looking for an effective way to reliably manufacture components using a fluoropolymer, injection molding may be an excellent option.
The basic principles behind machining engineering plastics are the same as those behind machining metals, but there are some key characteristics of plastics that make machining them to tolerance an interesting challenge.