Recycle

Research and Development of PP Fibre-reinforced Thermoplastic Composite Materials, Processing Techniques and Applications

The RECYCLE project was formed to develop the processing, joining and finishing technologies that will allow the UK automotive industry to use novel self-reinforced polypropylene (SRPP) composites.

Objectives
The project aimed to address the main technical obstacles limiting the widespread use of SRPP, such as tooling systems for low-volume manufacture, joining techniques, especially welding, manufacturing of sandwich panels, finishing methods, including paint and foils. The project also assessed the sustainability and recycling of SRPP.

Partners

Results

Forming techniques and tooling
The project investigated high and low pressure forming techniques, identified optimum process conditions and developed new tooling systems. Matched-tool stamping was the preferred route as it was rapid and robust.

Joining and finishing techniques

The most suitable joining techniques for SRPP were established, including adhesive bonding and welding. The chosen finishing technique for exterior parts was spray painting and for interior parts was co-moulding with PP fabrics and TPO foils. SRPP has a particularly good surface finish direct from the mould so class A finishes are relatively easy to obtain. The painted panels passed environmental tests.

All-PP sandwich panels

The project developed processes for laminating and forming sandwich panels consisting of SRPP skins with PP honeycomb and EPP foam cores and mechanical testing was performed.  

Material design criteria

The effect of processing conditions, such as temperature, soak time, press closing speed and forming pressure, on mechanical properties was assessed. Tooling with challenging features such as variable draw depth and radii was used to identify the forming limits of SRPP and strain analysis was used to assess the strain limits.

Recycling techniques

It was found that up to 50% post-manufacture SRPP waste can be re-used in the SRPP manufacturing process. Post-processing waste is likely to reprocessed as regular PP in injection moulding of commodity items. The project used shredded SRPP waste as a fibrous reinforcement in PP, retaining the value-added properties of SRPP. At end-of-life, SRPP parts should be disassembled and reprocessed. Paint can be removed using proprietary agents.

Exterior case studyAn exterior case study, a Lotus Elise front access panel, was designed, prototyped and tested. The new part was 57% lighter than the existing part and passed environmental durability tests. A stiffening bracket for the panel was also developed in SRPP and bonded to the front access panels to obtain all-PP assemblies.

Interior case study

Work was conducted on a number of interior parts including an LTI TXII knee bolster, a load floor and a cover panel. Covers were produced with a variety of finishes including fabrics and foils and tested for bond durability.

 

Sustainability Assessment

The project conducted an in-depth sustainability assessment for SRPP in automotive applications. SRPP has good environmental and social performance during material and component manufacture when compared with traditional composites. Cost modelling indicated that the SRPP parts were cost-neutral compared to current production solution. SRPP has lower density than glass fibre-reinforced composites so offers good potential for fuel savings, thereby reducing CO2 emissions and running costs during the use phase of a vehicle.

Next Steps

Following this successful project, the partners are now taking steps to exploit the results and have begun applying the technology in a number of applications in the automotive sector and other industries.

Acknowledgements

The project was part-funded by the DTI and EPSRC through the SMMT-backed Foresight Vehicle initiative.

Contacts

For more information, please contact Gordon Bishop of NetComposites by email or telephone +44 (0)1246 541918.