technology | LFTs
testing and commissioning of a tailor-made LFT pultrusion plant. We design plants for fibre contents of up to 60 wt% and throughputs of up to 1,200 kg/h.”
Above: An LFT production line developed by PolymersNet, which was acquired by Protec last year
products with a high torque demand, such as engineer- ing plastics or high-temperature applications; the STS Mc11 series is for standard plastics such as polypropyl- ene and polyethylene. Coperion K-Tron equipment is used for feeding. Following impregnation, the fibre- polymer strands are cooled in a water bath and pelletized. Coperion Pelletizing Technology’s pelletizer is equipped with a special chopping rotor for this task. ProTec has developed an impregnation die head that it claims cannot clog with filler material. “Moreover, roving unwinding with rotating coils, as well as roving pre-warming with individual fibre spreading, enable the best possible impregnation,” Coperion claims. Support and development of customer-specific formulations can take place in ProTec’s testing centre in Bensheim. ProTec says the plant’s impregnation die is designed in such a way that, even using recycled material contents of up to 10% in the melt, consistently high qual- ity impregnation of the fibre filaments is achieved. The various different creels required for unwinding glass and carbon fibres in the pultrusion plant are also available. Last June, ProTec acquired PolymersNet, giving it
ownership of a pultrusion plant for producing LFTs. At the time, it said PolymersNet was the only independent company in Europe manufacturing state-of-the-art machines for high volume production of LFT pellets. The plant has since been rebuilt and extended at ProTec’s process and materials development technology centre, where it can also be used for carrying out specific customer tests. The plant uses a 26-mm twin-screw extruder, while upstream is a Somos Gramix S gravimetric nine-component dosing system (Somos is a ProTec brand). “With focused know-how along the entire LFT
process chain, ProTec has established an efficient structure for this high-performance technology,” said Peter Theobald, the company’s Managing Director when he announced the development. “We are now a one-stop shop, offering everything from materials development to
36 COMPOUNDING WORLD | May 2016
Alternative approaches Depending on the process, the design of the extruder can play a larger or smaller part in production of LFTs. For example, with the traditional pultrusion and “wire-coating” processes, since the melt and fibres only come together in the die head, the purpose of the extruder is largey to melt the polymer and mix and disperse other additives. However, with some other processes, such as one developed by Fraunhofer Institute for Chemical Technology (ICT) and Leistritz, the fibres are introduced about half-way down the extruder, making flight design crucial in ensuring that fibre length is retained. Leistritz says its ZSE MAXX extruders offer the
necessary broad process window, facilitated by a screw geometry optimized for the application. It points out that a continuous well-controlled intake of glass fibres into the extruder is an essential factor in this process, and says it developed a special roving monitoring system for this. The process shares some features in common with the LFT-D process for moulding directly after com- pounding. Jan Diemert, Head of Polymer Engineering at Fraunhofer ICT, says the technology provides more flexibility than the more traditional ways of making LFTs in terms of the polymers and fibres that can be used. However, it does yield granules with a much greater variation in fibre length, which may rule it out for use in some automotive applications that have strict specifica- tions on minimum fibre length. Trials have shown that some fibres may be as long as 40 mm, but others will be just as short as in conventional short-fibre com- pounds. Development work continues at the institute.
In-line solutions LFT users also have the option of in-line LFT com- pounding and part production, either using injection moulding or compression moulding. Much of the development work for these integrated processes has also been carried out at Fraunhofer ICT. The institute has even developed a process that combines LFT compounding and in-line injection moulding technology (which it calls LFT-D-IM) with Trexel’s Mucell physical foaming technology. This combination yields particularly light and stiff parts. Fraunhofer ICT worked closely with Dieffenbacher, a
leading producer of hydraulic press systems and supplier of fully automated production lines, on the process technology for inline compression moulding of LFTs
www.compoundingworld.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94
