polyvinyylidene

Polyvinylidene is a family of polymers derived from vinylidene monomers, in which each repeating unit contains a methylene carbon attached to a substituted second carbon (−CH2−C(R)2−). The best-known examples are polyvinylidene chloride (PVDC, from vinylidene chloride, CH2=CCl2) and polyvinylidene fluoride (PVDF, from vinylidene fluoride, CH2=CF2).

Production of polyvinylidene polymers occurs by free-radical polymerization of the respective vinylidene monomers. PVDC is typically produced by aqueous emulsion polymerization, yielding polymer particles that can be coagulated into pelletized resin or used as coatings. PVDF is commonly produced by suspension or solution polymerization to yield solid beads or films. Copolymers and terpolymers (for example PVDF copolymers with hexafluoropropylene) are used to tailor crystallinity, flexibility, and processing properties.

Properties and applications vary by monomer. PVDC offers exceptionally low permeability to gases and moisture, making it a popular barrier coating for food packaging and agricultural films. PVDF provides high chemical and thermal resistance, good mechanical strength, and, in certain grades, piezoelectric or ferroelectric properties, which are valuable in sensors, actuators, protective coatings, membranes, and chemical processing equipment. PVDF copolymers enable tailored flexibility and processability, expanding use in tubing, coatings, and filtration membranes. PVDC is film-forming but can be relatively brittle without plasticizers; PVDF generally exhibits better weathering and UV resistance.

Safety and environmental notes cover the chlorine content of PVDC and the persistence of fluoropolymers like PVDF. Processing and disposal require appropriate controls, and recycling options exist but can be complex and rate-limited by material and form.