p. 1115. Three-dimensional networks
- David J. WaltonDavid J. WaltonCoventry University
- and J. Phillip LorimerJ. Phillip LorimerCoventry University
Abstract
This chapter focuses on three-dimensional networks, which are the toughest and most rigid materials, since the polymer chains are linked together in all directions to give effectively a single giant molecule. Three-dimensional networks do not melt, although segments may go through phase changes with temperature. They are insoluble, although lightly cross-linked ones can be solvent-swollen. They are therefore prepared in two stages, the first giving a processable intermediate that becomes the intractable final product in the second one. These principles are demonstrated for several systems, including Bakelite (phenol-formaldehyde polymers) and fibre glass (linear unsaturated polyesters), and also the vulcanization of rubber. Polymers which set hard after heating, usually because of a thermal cross-linking reaction, are called thermosets. The chapter then looks at electron beam cross-linking and physical cross-linking.
