High Performance Plastics in the Chemical Industry

June 2022

Because of their superior properties, fluoropolymers have been rapidly replacing metal alloys for corrosion inhibition in chemical processing equipment.

Most Fluoropolymers have an excellent resistance to acids, solvents and bases, which means that they can remain in contact with these substances without any detectable chemical reaction.

This makes them the material of choice for applications where excellent corrosion protection is needed. Applications include water treatment plants, where harsh sanitising chemicals are used, or in purified water generation plants which produce the highly pure water for pharmaceutical requirements.

The chemical inertness of PTFE is outstanding because of the chemical structure, however, the challenges in processing PTFE led to the development of other fluoropolymers with a focus on preserving the full fluorination of the backbone chain for chemical resistance, while being melt-processable for ease of processing.

The first melt-processable fluoropolymer developed was FEP or fluorinated ethylene propylene, developed in 1956 by DuPont. FEP is fully fluorinated and melt-processable. The full fluorination preserved the essential chemical inertness of PTFE and the changes in structure lead to it being melt processable but as a result there is some slight loss in high temperature properties.

Other melt processable polymers including PFA, ETFE, ETCFE and PVDF do not have the full fluorination of the backbone chain that is seen in PTFE and as a result these polymers do not achieve the same chemical resistance.

PEEK is a semicrystalline thermoplastic with excellent mechanical and chemical resistance properties that are retained to high temperatures. It is highly resistant to thermal degradation as well as attack by both organic and aqueous environments.

PEEK is attacked by halogens and strong acids as well as some halogenated compounds and aliphatic hydrocarbons at high temperatures. It dissolves completely in concentrated sulfuric acid at room temperature.