Unique Additives for High-Performance Industrial Protective Coatings

By Yong Zhang, Bridgette Hendrix

Two-component (2K) epoxy coatings have long been used for industrial
protective applications due to their excellent adhesion to a wide range of
substrates, superior chemical resistance, and good mechanical properties. Today,
those in the industry who are looking for innovations that can boost coating
performance heavily prioritize high performance and productivity in particular.
Their main goal is to extend coating life service time and use the fewest coating
layers possible. Additives, or performance boosters, are commonly used for this
purpose in a formulation. One example of an additive is tougheners, which are
used in many high-performance industrial protective coatings to improve their tough-
ness, flexibility, adhesion, and long-term performance.

Phenoxy resins are unique polymer-based additives that have become available
to formulators. Phenoxy resins are the product of bisphenol A and epichlorohy-
drin, with the epoxide ring opened. They are a tough and ductile thermoplastic
material with high cohesive strength and good impact resistance. The backbone ether
linkages and pendant hydroxyl groups promote wetting and bonding to polar
substrates and fillers. 

The structure of the phenoxy resin is a polyhydroxyether with terminal alpha-
glycol groups. Weight-average molecular weights range from approximately 25,000
to above 60,000, with n ranging from 30 to above 60. This long chain linear
polyhydroxylether structure allows for excellent adhesion, impact and abrasion
resistance, flexibility, and chemical resistance in coating applications.