COMPETENce in Joining MATERIALs
Welding, adhering, Overmolding
In the bonding of plastics, whether to one another or to other materials, our considerable expertise in the finishing of molding compounds ensures that, for example, these bond to metal to protect metal pipes against corrosion, bond inseparably to various rubbers in the plastic-rubber process, or form a secure weld seam in high-pressure gas pipes.
VESTAMID® compounds can be welded by all the conventional techniques. These typically include:
Hot plate butt welding: The use of hot plates coated with PTFE prevents adhesion of the molding compound to the hot plate (for hot plate temperatures of up to 270°C).
Ultrasonic welding: A weld seam contour such as an energy director or pinch-off weld should be used. Far-field welding of molding compounds with low elastic modulus is possible only with difficulty.
Friction welding is possible by rotation or vibration.
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.
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.