| Résumé : |
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.1 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 toughness, flexibility, adhesion, and long-term performance.
Phenoxy resins are unique polymerbased additives that have become available to formulators. Phenoxy resins are the product of bisphenol A and epichlorohydrin, 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 typical phenoxy resin structure is shown in Figure 1.
The structure of the phenoxy resin is a polyhydroxyether with terminal alphaglycol 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.
Phenoxy resins are soluble in a variety of materials, including ketones, glycol ethers, and glycol ether esters. This article discusses the use of a phenoxy solvent solution, in a solventborne zinc-rich primer formulation. A performance comparison with a commercially available zinc-rich primer will also be discussed, specifically comparing adhesion, dry time, hardness, impact resistance, and salt spray corrosion resistance. |
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Unique additives for high-performance industrial protective coatings in COATINGS TECH, Vol. 20, N° 3 (05-06/2023)
