Mar 21 2007
Thanks to a revamped machine design, BASF experts have shown how to greatly simplify the processing of their high temperature-resistant plastic Ultrason® E, a polyether sulfone (PESU). During the injection-moulding process, a special de-gassing screw serves to remove not only any residual moisture but also entrained air. Consequently, customers can manufacture very high-quality products without having to pre-dry the material.
Particularly in the case of injection-moulded headlight reflectors made of Ultrason E, excellent surface quality is required since they are coated with an ultra-thin metal layer over the course of their subsequent processing. As a result, surface flaws are not concealed, but rather exacerbated by the high metallic gloss. In view of these extreme requirements, if the plastic is not sufficiently dried in advance, or if air enters the plastic melt during the plasticizing process, streak formation and high reject rates occur with conventional screws.
Rainer Klenz, a specialist at BASF’s injection-moulding technical laboratory, explains the advantages of the new screw, “We have configured the geometry of this screw with an eye towards the melting behaviour of Ultrason. In spite of the presence of a de-gassing opening, this screw can be employed for a wide range of shot weights and, due to the extraordinary hydrolysis resistance of Ultrason, no damage occurs to the material, even with a high initial moisture content.” The entire process becomes more stable since moisture and entrained air can be reliably removed, thus accounting for fewer problems when the machine is started up again after a standstill. Processors using Ultrason E now have the possibility to process this material into complex components much more efficiently and cost-effectively than before.