What Does Phenoxy Resin Mean?
Phenoxy resin is a thermoplastic polymer derived from bisphenol A ((CH3)2C(C6H4OH)2) and the epoxy, epichlorohydrin (Cl-CH2-(C2H3O)). From its starting materials, phenoxy resins may be classified as a polyepoxy, but after reactions during polymerization, the resin has virtually no epoxide functional groups remaining. As such, phenoxy resins can be classified as a polyether due to the chain of ether functional groups across its backbone. Alcohol functional groups are also present, allowing for further modifications with cross-linking reactions with isocyanates, anhydrides, or other chemicals. Phenoxy resins have the following basic repeating form:
Phenoxy resins have a large variety of applications in industry ranging from molded parts, coatings, inks and adhesives. Specific formulations of phenoxy resins may have specific enhanced properties such as increased adhesion, flexibility and chemical resistance.
Corrosionpedia Explains Phenoxy Resin
The molecular weight of phenoxy resins depends on the ratio of bisphenol A to epichlorohydrin during reaction. If two equivalents of epichlorohydrin to bisphenol A are used, the reaction ends with the diepoxy molecule, bisphenol A diglycidyl ether (DGEBA, (CH3)2C(C6H4-O-CH2(C2H3O))2). To create polymerization, the equivalents of epichlorohydrin is decreased, allowing for other unreacted bisphenol A alcohol groups to react with the epoxy functional groups, creating a chain. A phenoxy resin is formed when these conditions are modified to create a high molecular weight polymer around 30,000-70,000 g/mol. Phenoxy resins are transparent and are soluble in methyl ethyl ketone.
Other properties of phenoxy resins vary by formulation, with melt indexes at 200°C (392°F) ranging from 4-70 g/10 min and glass transition temperatures ranging from 80-100°C (176-212°F).
Phenoxy resins are used for both flexible coatings on wires and rigid coatings on printed circuit boards (PCBs) and metal piping. They can be used for structural adhesions, composites and molded plastics. Hybrid material types are also available with modified properties for specific applications.