Invited Paper to the Institute of Materials Conference “Advances in Blow Moulding”, Loughborough University, UK, 30th June-1st July 1998.

Published by the Institute of Materials, “Plastics, Rubber and Composites 1999” Vol. 28 No. 8 379, ISSN 1465-8011

S F Bush with M Dreiza and J D Tonkin

Abstract

Precompounded discrete fibres have long been used as reinforcement in injection moulding particularly with polypropylene and nylon matrixes. Usually the lengths of the fibres in the finished article have been in the range 0.2-1.00 mm and for convenience are labelled short glass fibres. The last 15 years has seen the development of precompounded long glass fibres, having lengths in the finished article of typically an order of magnitude longer than for short glass fibres.

The present paper describes experiments on the blow moulding of long glass fibre reinforced virgin and recycled polymers. The long glass fibre compounds have been made using in house technology, for which the matrix interface conditions are known and can be varied. Bottles of 2 L capacity with integral handles were blown as the primary testpieces for evaluating blowability of these new materials and for investigating the reinforcing structures obtained in the bottle walls. Mechanical properties were evaluated at room temperature before and after recycling and at elevated temperatures up to 100 ^oC, which are particularly relevant to the blow moulding applications envisaged. PRC/1523

Report to Morecroft, Dawson & Garnetts

S F Bush

Summary

This report enquires into matters relevant to the dispute between Big K Manufacturing Company and TWA Machinery (Plastics) Ltd over the supply and commissioning of a blow moulding machine and mould from November 2nd 1984 to March 1985. Relevant court pleading, invoices and correspondence have been examined, but an inspection of the machine was not possible as it was destroyed in a fire at the premises of Big K in early 1986.

The premises of Big K have been inspected however, in August 1985 (in connection with a dispute between Big K and another supplier of blow moulding equipment). Comment is made on the premises’ suitability for a blow moulding operation. In this connection an assessment is made of the sensitivity of blow moulding operations to the quality of machine supervision by the operators and to the quality of the key services required by the machine, notably water and air.

Paper to the Polymer Processing Society 12th Annual Meeting, Sorrento, Italy, 27th-31st May 1996.

S F Bush with J D Tonkin

Introduction

Continuing the work of processing long glass fibre reinforced thermoplastics, under the generic title of Self Assembling Fibre Reinforcement (SAFIRE), the blow moulding of 2-litre bottles has been achieved, complementing advances made using other major processing techniques (injection moulding and pipe and sheet extrusion).

The sample bottles were processed on a Latymer HYD6 accumulator head blow moulding machine. The initial problems encountered when processing the long fibres were the reduced levels of parison die swell compared with the unreinforced material. The thinner walled parison produced a thinner blown bottle and the narrower width parison resulted in the incomplete blowing of complex non-symmetrical geometries. To compensate for this reduced parison die swell, larger diameter dies with larger width annuli were used.

Besides a fully blown shape, a good quality SAFIRE glass fibre granule is required that allows the separation of fibre bundles into individual filaments that can form a network structure. Some characteristics that determine a quality granule include wetting the glass fibre-polymer interface and the presence of a coupling agent⁽¹, 2). In addition the use of a Fibre Separating Device (FSD)³, a mechanical unit that forces the fibre-bearing melt through narrow channels, using differences in flow velocities to cause separation of the filaments from the bundles, improves the final fibre network structure.

References

[1] S F Bush, F Yilmaz and P F Zhang, “Impact strengths of injection moulded polypropylene long glass-fibre composites, Plast Rubb Comp Proc, App 24, (1994) 139-147

[2] D R Blackburn and O K Ademosu, Poly Proc Soc 9th Ann Mtg (5-8 April 1993) paper 06-14

[3] S F Bush, “Filament Separation in Liquids”, Euro Pat 0355 116B1 (31 March 1993)

Paper to the Polymer Processing Society 9th Annual Meeting, UMIST, 5th-8th April 1993.

S F Bush with K R Large

Introduction

Cavity walled containers are of major interest because of their high flexural strength to weight ratios, insulation properties and protection of the contents against penetration. The use of a suitably designed I-beam type cross-section in a container wall has been shown to yield weight savings of up to 50% over an equivalent solid cross-section[1]. At the same time the insulation characteristics of these structures with air filled cavities have been calculated to extend the insulation times by about 75% over the equivalent solid walled containers. The inclusion of a double skin also lends protection to the container contents if the outside skin is accidentally pierced in use or transit, provided the inside skin remains intact.

A number of techniques already exist for the manufacture of such containers, but all depend on making the inner and outer walls separately and then assembling the container. A requirement was therefore envisaged for a process to manufacture these articles in a single operation. A design approach was adopted which broke the polymer process up into unit operations and this showed the economic advantage of blow-moulding a cavity-walled container. A novel prototype blow-moulding process was therefore designed incorporating an innovative die-head and parison inflation circuitry. The new process has been given the name Cavity Wall Blow Moulding (CWBM).

References

[1] K R Large, Design of a Novel Cavity Wall Blow Moulding Process, MSc Thesis, UMIST (1990).

[2] FIDAP Fluid Dynamics Package, Fluid Dynamics International, Illinois (USA).