BASF Develop Low Warpage Grade of PBT

Product developers at BASF have augmented the PBT range (PBT: polybutylene terephthalate) by a particularly new low-warpage type. The latest addition to this already low-warpage Ultradur S4090 family is the plastic Ultradur S4090 GM11, which is reinforced with glass fibers and minerals and which offers low warpage levels that had not yet been available on the market.

Large plastic parts may suffer from warpage, if their shrinkage behavior is different in two spatial directions. The new Ultradur® S4090 GM11 is a very low-warpage version within BASF’s PBT product range: It shows almost no warpage at all, so that plastic parts remain straight and planar.

Homogeneous shrinkage - minimal warpage

The determining factor for the warpage is the ratio of the shrinkage (according to ISO 294) in the lengthwise and crosswise directions of the material flow. Whereas the closely related Ultradur S4090 GM13, which is likewise an PBT/ASA reinforced with minerals and glass fibers, already displays an excellent ratio of 0.70/0.80, the new product reaches the astonishing ratio of 0.95/1.0. Thus, the shrinkage in both spatial directions is almost the same, as a result of which the warpage is minimal. In combination with its good mold-removal behavior from the injection mold and its good surface quality, this property is of particular interest when it comes to manufacturing large-surface parts for automobile interiors.


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