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composites and LFTs | technology


Right: The seat pan for GM’s


Opel Astra OPC is moulded in a thermoplastic hybrid


composite


process using BASF Ultramid PA resin


thermoplastic composite part to be produced with tailored levels of performance in specific areas, especially creep and impact resistance, allowing cost to be minimised. It also shows that such a process could be operated on the cycle times required for medium to high volume production. In the study the part was moulded on a total cycle time of 70s but, as the actual moulding cycle was just 30s, Ticona believes this could be reduced considerably through process optimisation. Meanwhile, Japan’s Teijin announced in December


that the first carbon fibre reinforced thermoplastic com- posite parts had been manufactured at its new pilot component plant at its Matsuyama facility. The company claims that its proprietary manufacturing technology reduced part cycle times to less than 60s, which it says makes it suitable for high volume car production. In April last year, Teijin opened a composite techni-


cal centre at Auburn Hills in Michigan in the US where it is working together with General Motors to develop carbon fibre-based thermoplastic composite manufac- turing technologies.


Below: Woven carbon fibre fabrics from Oxeon were used in a joint Ticona, Fraunhofer and Fiberforge hybrid


thermoplastic composite development project


Polymerising in the mould Another option being considered for production of thermoplastic composite parts is in-situ polymerisation. This is similar in concept to the resin transfer moulding (RTM) techniques used in the thermoset composites sector, where a preformed reinforcement is placed into a mould which is then closed and impregnated with a liquid thermoset resin. However, while RTM results in a thermoset polymer matrix, in-situ polymerisation – sometimes designated as thermoplastic resin transfer moulding (T-RTM) – results in a thermoplastic matrix. Aside from improved damage resistance and easier


recyclability, in-situ polymerisation is said to offer the potential for shorter cycle times than traditional RTM. Parts can also be post-formed and welded if required to simplify ongoing assembly processes. Injection machinery maker Engel demonstrated in-situ polymerisation of a continuous glass fibre


reinforced PA6 automotive brake pedal insert during an open house last year at its large machine factory at St Valentin in Austria. The process uses two


ε-caprolactam raw materials (one containing a metal salt catalyst and the other a blocked diisocyanate


activator), which are solid at ambient temperature. The technology was developed jointly with Fraunhofer ICT, Lanxess and ZF Friedrichshafen. According to Peter Egger, who heads up Engel’s new


technology centre for lightweight composites, the prototype production system is based on a standard Engel e-Victory 120 Combi machine equipped with two electric injection units, which are inclined at 30˚ to the horizontal and use modified non-return valves because


of the very low viscosity of the ε-caprolactam feedstock at processing temperatures. The two components are combined in a mixing head, with the precision dosing injection units eliminating the need for the recirculating systems used in traditional reaction processing machinery. “The temperatures and pressures for the in-situ


polymerisation of caprolactam are lower than those required for PA6 processing, and this makes the process highly efficient. The maximum mould tempera- ture for in-situ polymerisation is 170°C,” says Egger. While Engel sees this technology being used


predominantly for thin parts for weight saving reasons, in-situ polymerisation is equally suitable for thick wall components. “Cast nylon parts with thicknesses well above several inches are industry standard and cycle times are much less governed by part thickness than with injection moulding,” Egger says. “Part geometry is


24 INJECTION WORLD | January/February 2013 www.injectionworld.com


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