The outline of a Course given in the Department of Polymer Engineering to 3rd and 4th year students at UMIST

S F Bush and J M Methven

Aim

To equip the student to analyse the properties and processes needed to design and manufacture polymer composite artefacts.

Learning Outcomes:

• Understand the meaning of Integrated Design and Manufacture for polymer composite products.
• To be able to analyse for impact, fatigue, fracture, creep, thermal conduction, gaseous permeation, in polymer products.
• To analyse the behaviour of fibre reinforced composites in their various forms.
• To be able to apply the concepts and analysis to practical examples in the engineering, construction, automotive, electrical, and packaging sectors.

Syllabus

Integrated Design and Manufacture:[1] the main choices of process and material types; design rules for relating process to product; process pathways and “order of processing steps” principle; design methodology exemplified by thermoplastic gas pipe distribution system: six design stages including screening out unsuitable materials. Failure modes: impact, fatigue, fracture and creep analysis. Stress analysis, thermal conduction, permeation of gases and application to packaging and gas containment generally.

Fibre reinforcement:[1] distinction between continuous, long, and short discrete fibres. Control of fibre orientation. Fibre touch and composite strength equations. Applications to thermoplastic injection mouldings, pipe and sheet extrusions and blow-mouldings: practical examples from automotive, textiles, drinks sectors.

Lightweight materials for design of sandwich panels:[2] classes of cellular plastics – for thermoset and thermoplastics. Manufacture of foams – materials, reaction injection moulding, thermoplastic (structural) foams. Structure and properties of foams – stiffness, thermal conductivity. Compounding for cost reduction and property enhancement: applications in automotive and electrical sectors. Manufacture of dough moulding compounds and sheet moulding compounds: mechanical properties from rule(s) of mixtures applied to 3 components (resin, filler and fibre).

Assessments

90% by written exam

Pre-requisites

Second year Engineering Materials

References

[1] Prof S F Bush

[2] Dr J M Methven

US Patent: 5,264,261, 23rd November 1993

S F Bush

Abstract

Fibrous network structures are produced within liquid polymer resins by passing the fiber-containing resin along a channel having a plurality of sets of flow modifying elements which establish a regulated succession of velocity profiles for the principal flow direction and the two directions perpendicular thereto.  The individual velocity profiles persist over distances which are small compared to the channel dimension over which they are established and are such that there is substantially no net deviation from the principal flow direction.  The velocity profiles superimpose on each other to cause rotation and sliding of the fibers so that a coherent network structure is built up which persists through extrusion dies and molds into the solid state.  By means of a large number of touches per fiber the structures thereby established confer efficient mechanical reinforcing properties and enhanced thermal properties on the polymer composition.

To see the patent in full, go to US Patent Office. On the first page click on USPTO Patent Full-Text and Image Database (PatFT), then under the heading “Searching Full Text Patents (since 1976)”, click on Patent Number Search and enter the patent number (with or without commas) into the “Query” box, then click on “Search”. To search for another US patent, click on Pat Num in the red display at the top of the page.

Also Australian Patent 602948, 7th December 1987, based on UK patents 8629216, 6th December 1986, and 8713513, 10th June 1987.

Paper to the Polymer Processing Society European Regional Meeting, Palermo, Sicily, 15th-18th September 1991.

S F Bush with C A Benson

Introduction

The design of reaction injection moulding processes requires knowledge of the system chemistry, an evaluation of the possible mixing processes which can be used, and characterisation of the subsequent in-mould behaviour of the reacting mixture. Mixing times are required to be a few milliseconds, moulding filling times typically a few seconds, and cycle times from one to three minutes.

The major problems in handling the phenolics chemistry for process design are how to characterise the variety of resins used and how to reduce the complexity of the chemical mechanisms to manageable proportions.

Phenolic reinforced reaction injection depends on rapid mixing of two or more unequal reactant streams with flow rate ratios typically somewhere in the range from 1 to 20 to 1 to 3. The major stream may contain reinforcing fibres of lengths up to 1.5 mm. The work reported here has concentrated on phenolic foams of densities up to about 500 kgm^-3. Fibre reinforcement at about 5% of final part weight can increase strength and modulus by about 50% for foams in the range 300 to 400 kgm^-3. On the basis of the chemical and mixing models an RRIM machine and mixhead have been designed and built for maximum shot volumes of 3 litres and an injection rate of 1 litre s^-1. This gives for instance a 1 m x 0.5 m x 19 mm foam moulding of 400 kgm^-3 density.

See also the section on Development of New Products and Processes.