Composites Design and Manufacture (Plymouth University teaching support materials) Thermoplastic polymers.

Lecture PowerPoint

Review papers

Subject Index

Useful resource:

• Periodic Table of Thermoplastics (Tangram Technology)

Thermoplastic polymer components can be produced in a heat-form-cool cycle and hence thermoplastic composite materials can potentially be recycled at the end-of-life.  However, it is likely to be difficult to effectively deply the layers of a laminate and hence the material will perhaps be granulated (at high energy cost due to the material toughness arising both from the matrix and from its reinforcement with fibres) for extrusion or injection moulding and the material properties of continuous fibres composites will be severely degraded in the second cycle of use.

A variety of thermoplastic polymers (the list below is not exhaustive) find use as the matrix for composite materials, including:

• Polypropylene - normally with glass fibres as in random Glass Mat Thermoplastics (GMT) or unidirectional Plytron prepreg
• Polyamides - intermediate properties and used with most types of fibre
• Polyesters - intermediate properties and used with most types of fibre
• Poly aryl ether ether ketones - normally associated with carbon fibres as in APC2 (advanced polymer composites of AS4 fibres in a PEEK matrix)

Typical properties of some common (and some specialist) thermoplastics are listed in the table below. The Society for the Plastics Industry (SPI) in the United States of America proposed the Voluntary Plastic Container Coding System in which an equilateral triangle formed of three curved arrows encloses a number (as in column three of the Table) with the acronym below the triangle.  The six specified generic materials cover 95% of the current domestic plastic waste produced.  The number 7 is allocated to all other polymers:

Black plastic packaging, when coloured using carbon black pigments, cannot be easily identified by the optical/near-infrared (NIR) sorting systems in plastics/material recovery facilities (MRF).

In-situ polymerisation for liquid composite moulding (LCM) processes

Molten thermoplastic polymers typically have viscosities far in excess of those used for LCM.  However, in recent years there has been increasing use of in-situ polymerisation to produce thermoplastic matrix composites during Resin Transfer Moulding or Resin Infusion under Flexible Tooling, albeit usually at elevated temperatures.  The principal systems are:

References

1. DSC Transitions of Common Thermoplastics, accessed 29 March 2019.
2. Thermal Transitions of Homopolymers: Glass Transition & Melting Point, accessed 29 March 2019.
3. Caprolactam, https://cameochemicals.noaa.gov/chris/CLS.pdf, accessed 29 March 2019.
4. AD La Rosa, I Blanco, DR Banatao, SJ Pastine, A Björklund and G Cicala, Innovative chemical process for recycling thermosets cured with Recyclamines^® by converting bio-epoxy composites in reusable thermoplastic - an LCA study, Materials, 2018, 11(353), 1-14.
5. E Louisy, F Samyn, S Bourbigot, G Fontaine and F Bonnet, Preparation of glass fabric/poly(L-lactide) composites by thermoplastic resin transfer molding, MDPI Polymers, 2019, 11(2), 339.
6. Y Qin, J Summerscales, J Graham-Jones, M Meng and R Pemberton, Monomer selection for in situ polymerization infusion manufacture of natural-fiber reinforced thermoplastic-matrix marine composites, Polymers, 2020, 12(12), 2928.
7. TJ Corden, IA Jones, CD Rudd, P Christian and S Downes, Initial development into a novel technique for manufacturing a long fibre thermoplastic bioabsorbable composite: in-situ polymerisation of poly-ε-caprolactone, Composites Part A: Applied Science and Manufacturing, June 1999, 30(6), 737-746.
8. P Christian, IA Jones, CD Rudd, RI Campbell and TJ Corden, Monomer transfer moulding and rapid prototyping methods for fibre reinforced thermoplastics for medical applications, Composites Part A: Applied Science and Manufacturing, July 2001, 32(7), 969-976.

Further reading

• Gert Strobl, Crystallization and melting of bulk polymers: New observations, conclusions and a thermodynamic scheme, Progress in Polymer Science, 2006, 31(4), 398-442.
• SP Nalawade, F Picchioni and LPBM Janssen, Supercritical carbon dioxide as a green solvent for processing polymer melts: Processing aspects and applications, Progress in Polymer Science, 2006, 31(1), 19-43.
• Andrzej Galeski, Strength and toughness of crystalline polymer systems, Progress in Polymer Science, 2003, 28(12), 1643-1699.
• ML Di Lorenzo and C Silvestre, Non-isothermal crystallization of polymers, Progress in Polymer Science, 1999, 24(6), 917-950.
• Yu Long, Robert A. Shanks and Zbigniew H. Stachurski, Kinetics of polymer crystallisation, Progress in Polymer Science, 1995, 20(4), 651-701.