Curing agents, epoxy polysulphides

Among the countless number of applications of polymers, the construction industry is one which utilises several polymeric materials. In this book I cover those polymeric materials which are single or bicomponent systems and are cured at ambient temperature either with the aid of curing agents or atmospheric moisture. The various polymers used in manufacturing such products include epoxies, polyurethanes, acrylics, silicones, polysulphides, alkyds and polyesters. As a result of innovation, new technologies exist which utilise more than one polymer in a single product. Such systems are discussed in Chapter 10, on hybrid polymers. 

Polysulphides. Polysulphides are used as curing agents for epoxies in the presence of tertiary amines which accelerate the cure such cured systems exhibit good flexibility and tensile strength at ambient temperature. In a real sense they are flexibihsers for epoxy systems. Specific applications are for the crack injection system (for moving cracks) and coatings (Chapter 10). 

Modifiers that may also be reactive as curing agents (such as polysulphides, triphenyl phosphite, and some polyamides) can be used. Polysulphide polymers used on their own will react slowly with expoxies. One to three parts of an active catalytic amine or amine salt can be used to accelerate cure. Triphenyl phosphite reduces viscosity and lowers cost. Ratios up to 2 5 phr appear to have no severe effect on physical properties at room temperature. Although reactive with epoxy, triphenyl phosphite is not an effective curing agent by itself it needs also a polyfunctional amine. About 75% of the normal stoichiometric amount of amine gives optimum results when 2 5 phr triphenyl phosphite is used with a resin such asDER331. 

In this book I have confined discussion to those polymeric materials which are cured by chemical reaction and which have found widespread application in the construction industry. As such, the book covers materials based on epoxies, polyurethanes, silicones, polysulphides, alkyds and polyesters. In addition, there is a chapter on hybrid polymer systems and one on acrylics. It is true that acrylic emulsions are not strictly thermosetting polymer systems, but their widespread use and importance made their exclusion difficult. These materials find use as coatings, sealants, adhesives, grouts, flooring compounds, repair compounds and waterproofing agents. 

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