TABLE OF CONTENTS This chapter is split into three sections covering processing of thermosets, elastomers (specifically LSR) and briefly ceramic and metal powder injection mouldable materials.
Thermoset plastics are chemically setting synthetic resins. Thermoset plastics set in the hot mould by crosslinking (chemical process), as opposed to thermoplastic freezing in a sufficiently cold mould (physical process). Synthetic resins tend to form shrinkage cracks, since a plastic deformation is practically impossible. The various resin types are shown in Table 7.1. Phenolic resins may also be referred to as Bakelite (after the chemist Baekeland who invented phenolic resin).
| PF | Phenol-formaldehyde resins | Phenoplasts | Polycondensate, i.e., crosslinking by elimination of H2O |
| UF | Urea-formaldehyde resin | Aminoplasts | |
| MF | Melamine-formaldehyde resin | ||
| UP | Unsaturated polyester resins | Crosslinking by polymerisation or addition, without formation of fission products | |
| DAP | Diallyl phthalate | ||
| EP | Epoxide (epoxi-, ethoxyl) resins |
Thermoset plastics are almost always processed with fillers and reinforcing materials. This is done to extend and reinforce synthetic resin and especially to minimise shrinkage. Examples of common fillers and reinforcing materials are shown in Table 7.2.
| Form | Powder flour | Fibre | Pellets | Chips | Mats Webs | Weave | |
|---|---|---|---|---|---|---|---|
| Inorganic | Stone | X | |||||
| Asbestos | X | X | X | X | |||
| Glass | X | X | X | X | |||
| Organic | Wood | X | |||||
| Cellulose | X | X | X | ||||
| Textiles | X | X | X |
