Carbamate containing acrylates

A widely used method of cross-linking paint films consists of reacting of hydroxyl containing acrylates or carbamate containing acrylates with melamine-formaldehyde resins or urea-formaldehyde resins [100-102]. Crosslinking is carried out at ca.l30 °C and is effected by acid catalysis (Fig. 7-5). The paints exhibit outstanding gloss and durability [103]. 

The kinetics of ultrafast polymerization of acrylic monomers exposed to UV radiation or laser beams has been investigated by IR spectroscopy. An 8 fold increase of the cure speed was observed by using diphenoxybenzophenone as photoinitiator instead of benzophenone. llie reactivity of polyurethane-acrylate or epoxyacrylate systems was markedly improved by adding acrylic monomers that contain carbamate or oxazolidone groups and which impart both hardness and flexibility to the cured polymer. Time-resolved infirared spectroscopy was used to directly record the actual polymerization profile for reactions taking place within a fraction of a second upon UV or laser exposure. Comparison with other techniques of real-time analysis show the distinct advantages of this method for an accurate evaluation of the important kinetic parameters and of the dark polymerization which develops just after the irradiation. 

Chart 11.1 Chemical structures of acrylates containing carbamate (left) or oxazolidone groups (right) [20]. 

Vulcanization of the epichlorhydrin rubbers is normally brought about by reaction of the chloromethyl group with diamines and polyamines or their derivatives such as hexamethylene diamine carbamate, with 2-mercaptobenzimidazoline, with lead oxide and lead phosphite, and with ammonium salts. The processes are analogous to those used with the polychloroprenes and with those acrylic rubbers containing a halogenated cure site. A sulphur-curable grade was announced in late 1977. 

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