Vinyl Ester Mechanism

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Vinyl ester mechanism. Vinyl ester resins are typically formulated from styrene and a condensation product of methacrylic acid with an epoxy. Essentially they comprise a base of polyester resin strengthened with epoxy molecules in the backbone of the molecular chain. 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. Vinyl ester resins offer increased strength corrosion resistance and durability and are used in a wide variety of applications.

Vinyl esters undergo homopolymerization via a radical mechanism. Vinyl alcohol containing polymers are prepared by hydrolysis of the corresponding vinyl acetate polymers. Vinyl ester resins are produced by the reaction esterification between an epoxy resin and an unsaturated monocarboxylic acid. Vinyl ester monomer contains two vinyl end groups that allow cross linked structure to form during the reaction.

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. Methyl ethyl ketone peroxide mekp is one such hardening agent. Vinyl ester or vinylester is a resin produced by the esterification of epoxy resin with unsaturated monocarboxylic acid. There are numerous types of reactants that make up the vinyl esters so that each resin has its own characteristic properties.

Chemical structure of the vinyl ester resin monomer. Vinyl acetate is not as hydrolytically stable in polymers as are the structurally similar acrylic esters. 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 aliphatic claisen rearrangement is a 3 3 sigmatropic rearrangement in which an allyl vinyl ether is converted thermally to an unsaturated carbonyl compound.

Vinyl esters have enhanced mechanical properties compared to polyesters with physical strength better impact and thermal shock resistance. The most widely used member of the category is vinyl acetate. 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. 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.