Water resistance is one of the most important barrier properties of a coating, and is mainly governed by the polymeric binder and by the nature of the monomers used to produce the binder. This large disparity in glass transition temperature between these vinyl neo-ester monomers allows the polymer formulator the latitude to develop very hydrophobic polymers with a broad latitude of possible Tgs.
VINYL ACRYLIC EMULSION PRICELIST SERIES
The result was a series of polymers with Tgs ranging from 10 ☌ to 119 ☌, leading to the conclusion that the higher Tg of polyvinyl neononanoate is a cumulative effect of the shorter chain length and the higher degree of branching within the various isomer mixtures. 4 This work evaluated the effect of chain branching by measuring the homopolymer Tg of a series of vinyl esters based on neononanoic acids with differing degrees of branching. The reason behind the striking difference in glass transition temperatures between these monomers was elucidated by the work of Scholten and Van Westrenen. The vinyl ester of neodecanoic acid has a homopolymer Tg of -3 ☌, making it a flexibilizing monomer, while the vinyl ester of neononanoic acid has a homopolymer Tg of 70 ☌.
The two most common vinyl neo-ester monomers are the vinyl ester of neodecanoic acid, which contains 10 carbon atoms, and the vinyl ester of neononanoic acid, which contains nine carbon atoms. Furthermore, these vinyl neo-esters exhibit strong resistance to hydrolysis and do not degrade under the influence of UV light. The branched tertiary structure with bulky and hydrophobic hydrocarbon groups provides neo-ester monomers (Figure 2) with a highly hydrophobic nature and low surface tension. The alkyl neocarboxylic group of these monomers is very resistant to degradation in alkaline conditions, as there is no hydrogen on the a-carbon atom. Their principal use is as hydrophobic co-monomers in vinyl and acrylic polymerization. Vinyl neo-esters are very hydrophobic monomers with a highly branched tertiary substituted a-carbon structure.
The neocarboxylic acid can be converted into its vinyl ester monomer by reaction with acetylene. Before the intermediate carbocation reacts with carbon monoxide, isomerization reactions are observed and, therefore, the resulting acid is composed of a number of isomers.
Herbert Koch from the Max Plank Institute in Mülheim, Germany, found that olefins may react with carbon monoxide and water under the influence of strong acids to form tertiary branched neocarboxylic acids (Figure 1).
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