Bonding and overmolding

Bonding

VESTAMID^® compounds are easily bonded, but the bonding surfaces must be clean and free of grease. The use of mold release agents should be avoided in production of molded parts that are subsequently to be bonded. Moreover, the bonding strength is improved if the surface is pretreated by roughening, primer application, or corona or flame treatment. The relevant safety regulations must be observed in every case.

Suitable adhesives are those based on

• Epoxide: one- or two-component (gap-filling) adhesives can be used for larger bond areas; the results are often better at higher temperatures.
• Polyurethane: reactive one- or two-component adhesives and hot-melt adhesives (gap-filling, flexible adhesives, often with fairly long pot lives and cure times); suitable for larger bond areas.
• Cyanoacrylate: single-component adhesives (with very short cure times); suitable for thin bonded joints and smaller bond areas.
• Specialty polyamide adhesives are suitable for bonding of VESTAMID^® E compounds.

Overmolding

The elastomers of the VESTAMID^® E series are particularly well suited to overmolding. All VESTAMID^® elastomers can be welded to one other and to VESTAMID^® L (PA 12). This applies particularly to overmolding of compounds of different hardness or color.

This property is exploited particularly often in the production of multicomponent and multicolored parts of sporting goods such as specialty sports shoe soles and ski boots. A higher melt temperature of up to 300°C, high injection speed, and high holding pressure are recommended for overmolding. Better adhesion between the hard and soft components of the composite can be obtained if the mold temperature is raised up to 100°C. For more transparent overmolding, on the other hand, a lower processing temperature can be useful.

VESTAMID^® elastomers can also be bonded to a number of other polymers by overmolding.