Bonding Plastics to Metal - Guidance from 3M

Posted on 8/9/2018 9:46:00 AM By ASC

Adhesives company 3M provides its insights into the knotty problems of bonding plastics to metals. Bond strength, says 3M, is among the key questions to consider. Non-structural adhesives have a bond strength below 1,000 psi, and structural adhesives will have bond strengths of 1,000 psi or more.

When components are not required to bear loads, 3M Ultra-Clean Laminating Adhesive 502FL will be suitable for use. The company says that its clients use the adhesive for membrane switches, electronics assemblies, or instrument clusters. The only surface preparation required is the wiping away of any dust that may have settled on surfaces. The metal substrate can even be lightly oiled, and low surface energy plastics are compatible with the product.

3m Scotch-Weld Structural Adhesives help manufacturers to bond load-bearing components. They can be used for bonding low or high surface energy plastics, eliminating the need for traditional fasteners. The company says that the two-part acrylic adhesives are even stronger than the materials they bond.

3M also recommends its VHB tapes as a simple solution. They can bond most plastics, and the foam tape will cushion bonds against impacts while damping vibration and dealing with thermal expansion or contraction.

The choice of adhesives to bond metal to plastics will depend on the plastics in question. Polycarbonate and ABS plastics are the easiest to work with, and polypropylene and polyethylene will present a greater challenge. In the latter instance, 3M recommends using a primer, as this will improve the bond strength achieved.

Ultimately, 3M recommends that designers and manufacturers should work in partnership with their adhesive suppliers to find the best solutions, particularly when choosing an adhesive that meets the challenge of bonding metals to plastics.

More information on adhesion/cohesion available HERE