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Since vinyl ester resins must be pre-accelerated with amine accelerator or cobalt, their processing time at room temperature is shorter than with epoxy-based prepregs. Catalysts (also called hardeners) include peroxides such as methyl ethyl ketone peroxide (MEKP), acetyl acetone peroxide (AAP) or cyclohexanone peroxide (CHP).
Renewable precursors to vinyl ester resins have been developed. [2] Vinyl resins are often used in repair materials and laminating because they are waterproof and reliable. Bisphenol A is a precursor in production of major classes of resins, including the vinyl ester resins along with epoxy resins and polycarbonate. This application usually ...
Methyl ethyl ketone peroxide (MEKP) is an organic peroxide with the formula [(CH 3)(C 2 H 5)C(O 2 H)] 2 O 2. MEKP is a colorless oily liquid. It is widely used in vulcanization (crosslinking) of polymers. [3] It is derived from the reaction of methyl ethyl ketone and hydrogen peroxide under acidic conditions.
Thus, organic peroxides are useful as initiators for some types of polymerization, such as the acrylic, unsaturated polyester, and vinyl ester resins used in glass-reinforced plastics. MEKP and benzoyl peroxide are commonly used for this purpose. However, the same property also means that organic peroxides can explosively combust.
An intermediate case involves a mixture of resin and additives that requires external stimulus (light, heat, radiation) to induce curing. The curing methodology depends on the resin and the application. Particular attention is paid to the shrinkage induced by the curing. Usually small values of shrinkage (2–3%) are desirable. [2]
Vinyl ester resins made by addition reactions between an epoxy resin with acrylic acid derivatives, when diluted/dissolved in a vinyl functional monomer such as styrene, polymerise. The resulting thermosets are notable for their high adhesion, heat resistance and corrosion resistance.
The price of the vinyl ester resin is similar to that of the polyester resin. It utilizes the same hardeners as polyester resin (at a similar mix ratio). It doesn't degrade much over time, when compared to polyester resin, and is more flexible. Generally, vinyl ester resin is considered as fuel resistant.
Styrene, for example, is distilled at temperatures above 100 °C whereupon it undergoes thermal polymerisation at a rate of ~2% per hour. [1] This polymerisation is undesirable, as it can foul the fractionating tower ; it is also typically exothermic , which can lead to a runaway reaction and potential explosion if left unchecked.