A series of lectures given in the Dept of Polymer Engineering to students at UMIST

S F Bush and J M Methven

Aim

To allow the student to make strategic choices of material and process for polymer-based products.

Learning Outcomes

In the context of applications to the aerospace, automotive, construction and engineering sectors:

• To be able to understand and use the concepts of Utility and Scale in the materials and process selection stage of design;
• To recognise the main features of the various available manufacturing processes and the way in which the shape of product narrows the choice of process;
• To understand the main forms of reinforcement and additive used in polymer composites and their uses in products;
• To understand the application of rapid prototyping and rapid tooling in the making of small quantities of pilot products.

Syllabus

Concept of Utility[1] as a guide to selecting materials. Influence of production scale on process choice. Examples taken from aerospace, automotive and consumer applications using standard production processes including extrusion, injection moulding, resin transfer, filament winding and autoclave moulding.

Continuous and discrete fibre composites:[2] relative advantages and disadvantages. Design of structural components using continuous fibre reinforcements by pultrusion. Control of fibre placement. Composite failure mechanisms. Design of sandwich panels and honeycomb laminates, rubber products: seals, gaskets, springs. Applications to aerospace, building and piping systems.

Concept of Fibre Management[1] for different processes and products. Distinction between thermoplastic and thermoset composites and between speciality and bulk polymers. Common types of polymer and of fibre and their advantages and disadvantages. Minimising weight and maximising recycle in automotive and packaging applications. Mould design considerations in injection moulding applications to aerospace and other panel forms.

Fibre reinforced sheet moulding compounds[2] and processes and their application to large area panels in construction and land transport. Polymer composites made by resin transfer moulding. Lotus cars example. Polymer composites made by continuous fibre pultrusions including microwave assisted methods and their application in fibre optic cabling for terrestrial and aerospace application.

Rapid prototyping and pilot tooling[3] for metal as well as polymeric products. Prototyping techniques based on CAD and Stereolithography; 3-D printing, (laminated object manufacture and laser sintering.) Examples of surgical instruments made this way. Use of silicone moulds as short run production tools.

References

[1] Prof S F Bush

[2] Dr J M Methven

[3] S F Bush/J M Methven

Invited paper published in the Proceedings of the Institution of Mechanical Engineers: Process Mechanical Engineering, volume 214, Part E, 2000, Special Millenium issue, ISSN 0954-4089.

S F Bush

Abstract

From slow beginnings in the 1860s, the evolution of the polymer industry has been marked in the second half of the twentieth century by rapid increases in the scales of production, by increasing power to control order at the molecular level, and by the variety and complexity γ of the resultant processes and products. The paper reviews some of the key developments over the last 100 years or so with a view to identifying themes likely to be of continuing importance in the new century.

A general model for the cost of a processing technology is proposed in terms of the factors Q and γ involved in producing a given artefact. Particular technologies are discussed in terms of the order in which basic processing functions are carried out. A major trend likely to continue into the twenty-first century is the way in which the supramolecular organization of the polymer chains is increasingly being brought under control, either directly by processing or indirectly by self-ordering properties of the polymers themselves. Self-organization of reinforcing fibres during processing to produce optimal performance of polymer composites is a parallel trend also likely to develop further into the next century. To illustrate these ideas the paper draws on examples from major polymer processes: extrusion, injection moulding, film blowing, reaction moulding, thermoforming, fibre making and coating.

Paper to 16th Annual Meeting, Polymer Processing Society, Shanghai, China, 18th-23rd June 2000

S F Bush

Introduction: Market Needs and the Role of Polymer Processing

While there will always be room for serendipity in research, nonetheless ‘chance favours prepared minds’. Research opportunity will increasingly flow from a preparedness to respond to market needs. Particular goals will be achieved by the interaction of polymer science, polymer processing and product design.

The needs which the polymer industry responds to may be summarised under the following eight headings:

• The elimination or reduction of routine personal services, (e.g. easy-care textile fabrics, dirt-resistant decorative coatings and laminates)
• More efficient living space, (e.g. foamed insulation, corrosion resistant pipework)
• Fuel efficient, and more secure transportation, (e.g. weight reduction through polymeric components, elastic end sections for moving vehicles)
• Increased variety and quality of food and drink, (e.g. multilayer film packaging, lightweight bottles)
• Leisure, (e.g. lightweight, moisture repellent clothing and textiles)
• Economising on natural resource usage, (e.g. reduced energy in materials procesing, hardwood substitutions)
• Improved health-care, (e.g. contact lens, polymer prostheses, implants, drug delivery systems)
• Ever more powerful information technology, (e.g. compact disks, polymeric display systems)

Pressure is also unremitting to reduce the time between recognition of a market need and manufacture of the final product for sale. The future growth of the polymer industry will depend in part on how well it is able to respond to this imperative. It is the role of polymer processing to translate the desired features of the polymer architecture into a shaped artefact which meets a market need. Superimposed on all of these needs is the need to recycle by re-use or reprocessing.