Paper to International Polymer Materials Engineering Conference, Shanghai, China, 18th-21st September 2005

S F Bush

Abstract

All successful process technologies are rate dependent^[1]. Generally speaking quality of product, however defined, decreases as processing rates increase, but the point at which quality is unacceptable varies with the polymer matrix, the nature and amounts of additives and any fibre reinforcement, and machinery use.

The efficiency of polymer processing, expressed in terms of the quantities of polymer and additives used to make a given amount of product also decreases as processing rates increase. Efficiency is also greatly affected by the manufacturing systems technology in which the polymer process is embedded.

The paper sets out to explore those factors in a polymer technology which determine the rate/quality and rate/efficiency boundaries; in a phrase, to answer the question, “How much faster can we go?” To do this, the paper splits the relevant factors affecting the answer into two groups:

• E – Equipment dependent mechanisms, principally bulkflow, mixing, and heat transfer (whose rates depend mainly on the power input)
• M – Molecular and supra-molecular mechanisms (whose rates depend primarily on temperature, pH and microflows).

 
The principal quality factors affected by factors E and M are also split into two groups: (A) Appearance (e.g. gloss, haze, texture, colour); (B) Bulk properties (i.e. impact and tensile strengths, creep and thermal resistances); (G) Geometrical factors (distortion, dimensional variability). For all these quality measures, uniformity is a basic requirement.

Data is reported from four quite different processes both in this Laboratory and in the factories of its partner companies. This data has been used to obtain some of the rate limiting steps in quantitative terms for a number of the common process technologies: organic/inorganic compounding/alloying, reaction injection moulding, pultrusion, and rotational moulding. These rate limiting values indicate where new developments in either E or M will facilitate increases of production rate at given quality levels.

Reference

[1] S F Bush, Scale, order and complexity in polymer processing, Proceedings of the Institution of Mechanical Engineers (200) 214 Part E, 217-232.