Dual-Curing Systems of Epoxy Resin for Using in Prepreg Manufacturing

Nowadays, the use of prepregs has accelerated the composite manufacturing and has facilitated their processing. To prepare the epoxy prepregs, it is necessary to cure the resin slightly in order to maintain the overall shape of the prepreg and to hold the fibers together. Since epoxy resins require heat for curing and heat is release during the curing reaction, it is always difficult to control the degree of cure in the precuring stage. The progress of precuring reaction determines the mechanical properties and processability of the prepregs. One of the methods to control the degree of cure of epoxy resin for use in prepregs is to use two different curing systems with different conditions for each stage called dual curing system. In this article, while introducing the types of dual curing systems used for epoxy resin such as epoxy-acrylate, epoxy-phenol, epoxy-thiol, epoxy-siloxane, epoxy-sulfonium salt and epoxy-amine, the application of each system is reviewed. Due to the diversity of dual curing systems, different systems can be used to control the prepregs properties such as viscosity, curing percentage, shelf life and also improve the properties of the final composite. Studies show that, in order to increase the shelf life of prepregs using the click reaction with an optical initiator to perform the reaction of the first stage of curing and the thermal click reaction for the second stage of curing are most effective.