WEB EXCLUSIVE: Ticona, Florence, Ky., has developed a new blend technology that is said to overcome issues with previous impact-modified acetals. This has resulted in a next-generation UV-stabilized, impact-modified line with improved mechanical properties and processing behavior, the company says.
Various impact modifiers have been used to improve the impact strength of acetal but at the expense of lower stiffness and tensile strength. Acetal has proved to be difficult to modify due to its high level of crystallinity and its incompatibility with most impact modifiers. Furthermore, coloring of impact-modified grades can be more difficult due to increased light scatter. In automotive interior applications, these conventional impact-modified formulations have exhibited more color change than typical UV-stabilized acetal without impact modification.
Ticona says it has improved the compatibility between the acetal polymer matrix and the impact modifiers with its new blend technology. By incorporating functional groups such as hyroxyls groups into the polymer chain, the resin is able to react via multifunctional coupling agents with impact modifiers such as TPU. The chemical coupling results in compatibilization between the acetal and the impact modifier. This improved phase adhesion leads to better mechanical properties of the blends, particularly impact strength and weld-line performance. In melt processing, there is less phase separation in molding, resulting in less mold deposit and delamination. Improved compatibility allows for higher levels of impact modifiers than can be used with conventional toughened acetal. According to Ticona, using typical levels of impact modifier, the new technology can achieve up to 75% higher Charpy notched impact strength than comparable standard impact-modified acetal, while still maintaining similar stiffness and tensile strength. Potential applications include carpet clips (shown), hard trim (visor clips), instrument panel trim (bezels), and door trim.