Issue of Epoxy-Based Coatings System Crystallization and Effect of Partial Crystallinity on Mechanical Parameters

Abstract

Crystallization of bisphenol A-based and bisphenol F-based epoxy resins is the common property of the oligomers. However, producers of paints, coatings and other systems based on these epoxy resins are making efforts to slow down the crystallization process as much as possible. Thereby the shelf life is prolonged, while improving the competitiveness of their products. The main topic is the generalization of factors influencing the crystallization process of bisphenol A-based and bisphenol F-based epoxy resins, the validation of new approaches to possibility of influencing their crystallization process, and the determination of possibility of using a certain degree of crystallinity of bisphenol A-based and bisphenol F-based epoxy resins when preparing and producing paint and coating systems. Two types of the epoxy resins in formulations of paint and coating and other systems, namely: diglycidyl ether of bisphenol A (DGEBA) and diglycidyl ether of bisphenol F (DGEBF) were used. The tendency to crystallize not only for the pure epoxy resins, but also various mixtures with reactive diluents, fillers, etc. was determined according to the standard ISO 4895 Plastics – Liquid epoxy resins – Determination of tendency to crystallize. Furthermore, the crystallinity of individual samples was determined. The effectiveness of potentially active nucleating agents such as precipitated calcium carbonate, DGEBA, and DGEBF crystals, etc. was selected and tested according to the ISO 4895 standard. The effectiveness of potentially active admixtures with crystallization retardation effect was selected and tested according to the ISO 4895 standard. Selected samples of the epoxy resins with a specified degree of crystallinity were cured with 3-aminomethyl-3,5,5-trimethylcyclohexylamine (IPD) based crosslinking agent. Mechanical parameters such as compressive strength and flexural strength were determined. The influence of crystallinity on selected mechanical parameters was also observed.