Introduction

The aim of this chapter is to describe a range of industrial processing technologies for reactive polymer systems, and specifically to

• characterise the process and highlight important processing-quality-control tests, process variables and typical systems used,

• highlight applications of chemorheology in the process and

• examine the use of chemorheology in modelling of the production process.

In this way we will be bringing the concepts and understanding from all subsequent chapters into practical processing applications in order to aid acquisition of deeper understanding of these processes.

Casting

Process diagram and description

Casting is a relatively simple process (Figure 6.1) involving the pouring of a thermosetting liquid into a mould, where the liquid hardens into a solid, dimensionally-stable shape.

Examples of products include rod stocks, spheres, gears, bushings and complex moulded items. In casting applications structural properties such as hardness, toughness, dimensional stability and machinability are of most interest.

Quality-control tests and important process variables

Important process variables include

1. cost

2. viscosity

3. reaction exotherm

4. shrinkage

5. pot life

Cost is typically reduced by minimizing the amount of resin used (either via incorporation of fillers or modifiers, or by foaming). Viscosity is critical for casting operations, in which requirements concerning ease of processibility and large loadings of fillers need to be optimized. Exotherms typically pose processing problems for large casting masses since the cure reaction evolves >100 kJ/mol (Section 3.2.2), which may be reduced by incorporation of fillers, modifiers and the correct curing agent at an optimum concentration.