The use of both granule LFT PP (LFT-G) and direct compounding and moulding in-line of LFT PP (LFT-D) along with its use by vehicle around the world has been discussed in a report by AMI Consulting. The result is a comprehensive analysis of LFT PP by application, OEM and geographical region. Glass fibre and PP have long been combined to make car parts. Short glass fibre compounds are the best known products and they are used widely in under-the-hood components. They offer price advantage versus polyamide and PBT, but do not have the same high temperature benefits as engineering plastics. Glass Matt Thermoplastics (GMT) is another long established PP-based product. The product is produced as a sheet and is typically shaped by compression moulding. The resulting product is very stiff and has been used quite extensively in applications such as under body shields and spare wheel wells. Amongst the best known GMT brand names are Azdel and Symalit.
Since the late 1990s two new families of PP based products have been gaining an increasing role in automotive design: LFT-G and LFT-D. LFT-G (Long Fibre Thermoplastic PP) refers to a product sold as a granule, whereas the name LFT-D is used to describe the process in which an LFT is compounded and moulded in-line or directly. LFT-G PP is made in conventional compounding equipment but with modified dies: the long fibre length is achieved by using either wire coating or pultrusion technology. There are a number of variants in the LFT-D process but in essence fibre length is maintained because, rather than granulating the product it moves through an open die directly into the mould. The first successful promoter of this technology was Dieffenbacher which makes compression moulding machinery, but more recently Krauss Maffei has emerged as the largest supplier of in-line injection moulding machinery. The in-line compression moulding process is particularly suitable for 2-D parts and the in-line injection moulding process suitable for more complex 3-D parts. LFT-D's economic benefits lie where the moulder is producing high volumes of relatively large parts. In other circumstances LFT-G PP is the preferred choice. While the two processes compete with each other their proponents also report differences in performance depending on part design. Indeed the technical and commercial performance of the finished part relies deeply on its design. LFT PP is now used widely in automotive front end carriers, instrument panel carriers, door panel supports, consoles, pedals, under body shields and a number of other applications. The exciting feature of many of these applications is that LFT PP is permitting automotive engineers to either replace steel and thereby reduce weight and improve fuel efficiency, or replace more expensive engineering plastics. The parts made in LFT PP are routinely so large that a moulding may weigh 3-4 kg although wall thickness below 1mm is also found in some designs. An excellent example of LFT-D PP in practice is the under body shield moulded by Polytec Group for the VW A5/PQ35 platform (that's the platform which includes Audi A3, Volkswagen Golf, SEAT León, Škoda Octavia and quite a lot of other vehicles).
The production plant in Germany has capacity to make 2.4 mln mouldings/year enough to supply to VW plants making these models around the world. An equally impressive application, but this time using LFT-G PP is the instrument panel carrier for the new BMW 7 Series which is made from an LFT-G grade supplied by Borealis. The LFT-G PP contains 20% glass fibre whereas the same part on the prior model used a PPE/PS blend containing 10% glass fibre. The largest producers of LFT-G include Ticona with its Celstran brand, Sabic which markets the product using both Stamax and Verton brands and Chisso which is now JNC Corporation and linked with Japan Polypropylene and Mitsubishi. Demand for LFT PP been growing strongly in most applications and in most regions of the world and is predicted to grow at double digit rates during the coming years. To date the penetration of LFT PP varies significantly by OEM within the various applications and as design experience builds there is plenty of evidence that LFT PP will become a material of choice for automotive designers.