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Reactive adhesives include epoxides, urethanes, phenolics, silicones, and acrylates. Epoxides. Introduced in the early 1940s, these depend on three-membered epoxy or oxirane rings at the end of carbon chains with pendant hydroxyl groups, all of which react with various second components to produce thermoset polymers.

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All matter in this Universe is made up of different kinds of elements. There are about 100 types of elements. Elements are in turn made of atoms. These atoms are so tiny that they cannot be seen with the naked eye. Only a powerful microscope will reveal these atoms. In fact a pinhead contains about 10,000 atoms.