Basic Polymer Chemistry Thermosets

In the previous chapter we talked about linear polymers and have mentioned the concept of cross-linking only in passing. Linear polymers are usually thermoplastic they soften or melt when heated and will dissolve in suitable solvents. They can be remelted and shaped into their finished product with no further chemical reactions. Thermoset resins, those having elaborately cross-linked three-dimensional structures, set or harden by undergoing a chemical reaction during the manufacture of finished products. They decompose on heating and are infusible and insoluble. Their chemistry and physical properties are quite different from thermoplastic polymers. The important ones are now discussed. 

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VINYL ESTER RESINS. The vinyl ester resins are a relatively recent addition1 to thermosetting-polymer-chemistry. Superficially, they are similar to unsaturated polyester resins insofar as they contain ethylmic lmsaturation and are cured throngh a free-radical mechanism, usually in the presence of a vinyl monomer, such as styrene. However, close examination of the chemistry and structure of the vinyl ester resins demonstrates several basic differences which lead to their unique characteristics. 

Aqueous Thermosetting Emulsions. The basic concept of a thermosetting emulsion is a logical extension of solvent-based thermosetting chemistry (22. 23). Reaction functionality is copolymerized into the polymer backbone, and after application, the... 

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