In recent years, there have been many new advances in the performance of LFT materials, LFT molding and processing processes: the more popular materials used can be broadly categorized as LFT-G and LFT-D. The more mature molding technologies are compression molding and injection molding. This needs to be selected according to the specific technical requirements of the product, cost, production scale and other factors.
LFT-G is the result of the technical innovation of short glass fiber thermoplastic granule (FRTP) material. Although the length of early FRTP pellets can reach 5-6mm, the final length of fiber in the product is often less than 1mm after mixing, cutting, plasticizing and injection molding processes, which can only increase the rigidity of the product as a filler, and the improvement of tensile strength and impact resistance is very limited. Therefore, at that time, FRTP was not a mainstream composite material. In order to give full play to the advantages of high production efficiency and low cost of injection molding, and to strive to minimize the degree of fiber breakage, LFT-G was born in the early 1980s.
LFT-G's raw materials are about 3mm in diameter and 12mm and 25mm in length, of which 12mm or so is mainly used for injection molding, while 25mm or so is mainly used for compression molding. In the process of LFT-G injection molding, although the injection molding machine has undergone many improvements, limited to the injection molding process, the fiber in the finished product can only reach 3.2 ~ 6.4mm. Although this length is longer than the fiber of FRTP injection molding, the impact resistance of the product is also significantly improved, but it is shorter than the fiber of LFT-D injection or compression molding, and the strength and impact resistance are also worse than LFT-D.
LFT-D is a process technology for the direct production of products from long fiber reinforced thermoplastic composites. The key factor that distinguishes it from GMT and LFT-G is that the semi-finished step is eliminated and there is more flexibility in the choice of materials. In LFT-D technology, not only the fiber content and length but also its matrix polymer can be adjusted directly to the requirements of the final part.
The advantages of LFT-D are mainly in two areas.
First, it reduces the cost. Because it is a one-step production, the cost of large structural parts produced by LFT-D is 20% to 50% lower than that of GMT or LFT-G pressed parts produced by the two-step process.
LFT-D compression molded products have slightly lower impact resistance than GMT, with an average fiber length of 19mm to 50mm. The low plasticization requirement of LFT-D improves the fiber breakage condition. Parts with a molding cycle of more than 1 min can be molded in 30 s with LFT-D injection molding equipment. Another advantage of D-LFT injection molding is that it avoids the large punching of parts and the resulting scrap; the ultimate fiber length of D-LFT injection molding is 7mm to 12mm, which is shorter than compression molding, but longer than that obtained by injection molding long glass fibers on standard machines.
Either injection or compression molding of D-LFT has the advantage of being able to easily recycle punching trim and scrap, which is a major advantage for molders who produce using both processes.
Whether it's LFT-D or LFT-G, MDC Mould can help you run your business smoothly. We know all the ways to mold composite LFTs, whether injection molding or compression molding. Contact us today to order LFT molds.
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