Paper

S F Bush with F G Torres

Abstract

Thermoforming is a major process with a wide range of applications in several fields. One of the most interesting possibilities is the thermoforming of PP. It is well known that Long Glass Fibre (LGF) composites present better mechanical properties than unreinforced PP. In addition to that, long fibres increase the thermal stability and the melt strength of the unreinforced polymer. In this paper, the thermoformability of LGF reinforced PP is studied using dynamic mechanical analysis (DMA), hot tensile tests, sheet sag tests, and microscopical techniques for the characterisation of the fibre mat deformation process. DMA is used to characterise the anisotropy and the softening behaviour of the LGF extruded sheets. Hot tensile testing is used for assessing stretchability. Sheet sag studies under Infra-red (IR) conditions showed that LGF reinforced materials present a much lower degree of sag and a higher resistance to localised heating than the unreinforced polymers. Finally, scanning electron microscope (SEM) pictures are presented to verify the mat deformation processes occurring during thermoforming.

Prosyma Research Ltd report to CaMac Corporation

S F Bush

Summary

A visit was made to CaMac’s factory at Bristol, Virginia, during the week 5-9 July 1993. Subsequently one day was spent checking on some of the polymer mechanisms and systems which the visit suggested might have a bearing on the operations involved.

Given the complexity of the operations at CaMac, and the short time expended, this assessment risks being superficial. Nonetheless in accordance with the brief the scope is broad. Comments are made on organisation, the performance of the three new fiber-making processes (Nylon 6, Nylon 6.6, Polyester (PET) and Polypropylene (PP)), the relation of technology to markets, color and the application of a systems approach to production control and product quality.

My thanks are due to the many CaMac staff I talked to and to Drs Britton and Studholme from CTC, all of whom unfailingly did their best to answer my questions.

Prosyma Research Ltd report to Nueva AG

S F Bush

The overall objectives of the projects over the six months to 30th June 1990 are:

1. Provide the process data for optimising the strength performance of the scale up pipe process, in particular for HD-Hostalen 5010. Part of this objective is to define, if possible, the conditions under which fibre loadings above 2.5 v/v do or do not give broadly proportionate increases in strength and stiffness (SAFIRE A).
2. Provide input to the scale-up design so that the results of objective 1 can be readily implemented (SAFIRE B).
3. Complete the development of the Mark IV granulation head so that the SAFIRE granules can be made in the relevant fibre concentrations (4 – 10% v/v) for the Olefine polymers of main interest (HD, PP, LD) (SAFIRE C).
4. Continue the testing programme to support objectives 1 and 3, in particular focussing on fracture behaviour. Carry out creep experiments for SAFIRE Hostalen at 2% and 3% v/v at 23 and 60 ^oC (SAFIRE D).

Report 6 from a series of 5 Prosyma Research Ltd reports to Ametex AG, 15th February 1989 to 14th January 1990.

Report 6 dated 31st May 1989, Report 7 dated 11th July 1989, Report 8 dated 24th July 1989.
S F Bush

Summary: Part 1

1. During the period under review, SAFIRE project A has followed up the breakthrough in finishing technology achieved in the previous six-month period.
2. On the process itself follow-up has concentrated on establishing the design and operating parameters which determine acceptable and indeed exceptional finish with the new technology, at the same time making many metres of pipe for burst and creep testing.
3. Both polypropylene (PP) and HDPE SAFIRE pipe can be made with fine finishes on a routine basis. While not of direct benefit to the project, the finishing technology gives quite remarkable mirror finishes to virgin pipe.
4. In the period under review, SAFIRE project C has concentrated on producing SAFIRE granules in a wide range of combinations of fibre and polymer, and evaluating these for use in pipes.
5. The signs are that the evaluations made for this purpose will also give a good indication of the commercial potential for SAFIRE granules in combination with Fibre Separating Devices (FSD) sold in their own right. The significance of this potential has become clear from recent information on present commercial products.

Paper to the 6th Plastics and Rubber Institute Conference on Pipes, York, UK, 25th-27th March, 1985.

S F Bush with W G Harland and S Bilgin

Abstract

In an earlier paper[1] the principle of extruding short (around ½ mm) glass fibre reinforced poly-propylene in pipe form, using a rotating mandrel and stationary outer die, was described, together with the results shown in the first section of the Table below. Generally, desirable increases in both hoop strength and hoop modulus were obtained at relatively low (around 10 rpm) rates of mandrel rotation. This improvement was ascribed to two factors (a) elimination of the weld line (this particularly affects hoop strength) and (b) partial alignment of the figures in the hoop (circumferential) direction (this particularly increases hoop modulus, and reduces longitudinal crack propagation).

The present paper reports work which extends the earlier results in three directions. These are (i) use of a wider range of fibre lengths, (ii) use of other polyolefine matrices including rubber modified types, (iii) development of the die system design. The object of (i) and (ii) has been primarily to improve further the strength-modulus-toughness combination while (iii) is aimed at enabling (i) and (ii) to be carried out and also at improving the surface quality. A third objective under (iii) has been the design of a rotating die system which is easy to install on standard machines. Basically the results indicate that a commercially applicable process for making tubes with an attractive combination of properties has been developed.

The polymer systems investigated include PP, HDPE, mixtures of the two, and PP containing a proportion of EPDM, together with varying amounts and lengths of glass fibre. The process systems investigated include inner and outer die rotation together with an optimised cooling profile. The effects of different process configurations on pipe surface finish as well as on the primary mechanical properties have been assessed. Fibre orientations have been determined as a function of process parameters and compared with model predictions. Other measurements made comprise fibre length distribution in the pipe, burst strengths and dart impact resistance, as functions of the combined polymer-process system. The results obtained for two of the many matrix-fibre combinations investigated are shown in the Table with earlier values for comparison. While not as yet quantified, the results obtained under dart impact with the latest fibre-matrix-process system are especially noteworthy: the tendency for cracks to propagate and collapse the pipe specimen is greatly if not entirely inhibited.

Key: SGF – short glass fibre; NF – new fibre; CA – coupling agent.

Ref 1: S F Bush, W G Harland, S Bilgin, “Extrusion of Fibre-reinforced Thermoplastic Pipe”, 233, SERC Polymer Engineering 2nd Biennial Review Meeting, Loughborough, 13th-15th April 1983.