Vinyl Ester Mechanism

Chemical structure of the vinyl ester resin monomer.

Vinyl ester mechanism.

Methyl ethyl ketone peroxide mekp is one such hardening agent. Vinyl esters undergo homopolymerization via a radical mechanism. Vinyl ester is dissolved in a monomer or reactive diluent usually styrene the result is a low viscosity liquid having a solids content of 36 39. Vinyl ester resins vers are high performance unsaturated resins derived by the addition reaction of various epoxide resins with α β unsaturated carboxylic acids.

These resins have always been. Vinyl ester resins are typically formulated from styrene and a condensation product of methacrylic acid with an epoxy. Vinyl acetate is not as hydrolytically stable in polymers as are the structurally similar acrylic esters. This condensation product acts as a crosslinking agent and to improve adhesion to glass fibers.

Vinyl ester resins are produced by the reaction esterification between an epoxy resin and an unsaturated monocarboxylic acid. Vinyl alcohol containing polymers are prepared by hydrolysis of the corresponding vinyl acetate polymers. Vinyl ester resins are epoxy based thermosetting resins that are cured by free radical initiation of polymerization similar to the curing mechanism of conventional polyester resins. The aliphatic claisen rearrangement is a 3 3 sigmatropic rearrangement in which an allyl vinyl ether is converted thermally to an unsaturated carbonyl compound.

The curing process is radical initiated. The peak heat release rate decreases by 16 9 and 39 3 and total heat release decreases by 20 1 and 36 4 for ver pepabfr and ver dopobfr systems. The loi increases to 29 3 and 30 7 with incorporation to 15 wt pepabfr and 15 wt dopobfr from the 20 3 corresponding to pure vinyl ester resin ver. The most widely used member of the category is vinyl acetate.

There are numerous types of reactants that make up the vinyl esters so that each resin has its own characteristic properties. Vinyl ester monomer contains two vinyl end groups that allow cross linked structure to form during the reaction. Essentially they comprise a base of polyester resin strengthened with epoxy molecules in the backbone of the molecular chain. While vinyl ester resins are classified as polyester based formulations they are actually an intermediate between a polyester backbone and epoxy terminations on the ends of the molecules.