HARD / SOFT OVERMOLDED PARTS WITH KRAIBURG TPE THERMOLAST K: MATERIAL COMBINATIONS, PROCESSING, TESTING OF ADHESION

摘要

The influence of material combination and processing on the adhesion in overmolded parts made from hard thermoplastics and soft thermoplastic elastomers will be discussed. A method for testing the adhesion and examples for applications are presented. In contrast to standard SEBS products, adhesion modified THERMOLAST K thermoplastic elastomers (TPE's) provide excellent adhesion to a broad range of commodity and engineering grade thermoplastics. The overmolding adhesion is demonstrated, highlighting the strong influence of processing parameters on adhesion performance. For optimum results, high TPE melt temperature and injection speed are extremely important. For high-melting semi-crystalline thermoplastics, the insert molding process can be difficult. The effect of tool temperature and holding pressure on the adhesive force are comparatively less important, however it is proven that the holding pressure should be as low as possible for an optimized bond. Humidity has a strong negative influence on the adhesion characteristics between TPEs and polar thermoplastics. The adhesive force can often depend on the hardness of the TPE. Injection molding machine processing parameters can greatly improve adhesion results. Guidelines for users are given.