Ask Dr. Dave: What's a safe adhesive for bonding plastics?
It is not difficult to find an adhesive that is strong enough that the plastics break when tested.
Question: We manufacture high volumes of clear polystyrene and acrylonitrile butadiene styrene (ABS) parts, and would like to bond them with a safe adhesive that’s stronger than the plastics. Can you provide any insight?
Answer: It is not difficult to find an adhesive that is strong enough that the plastics break when tested. Solvent cements will bond these plastics, but I assume you would prefer not to use flammable or toxic solvents. I would recommend that you contact a manufacturer of 100% reactive acrylic adhesives for two reasons: 1.) to avoid using toxic or flammable solvents and 2.) to obtain a fast assembly technique that is suitable for your high-volume production.
The acrylic adhesives are available as two-part adhesives, or can be single-component UV-cured systems. In your case, with your parts being clear, I would suggest that a UV system would give you tremendous advantages over a two-part system in terms of productivity.
Question: We are a manufacturer of large steel panels and would like to replace welding and bolting of our 1/8- and
½-in.-thick stainless steel panels by adhesive bonding. What adhesive would you recommend?
Answer: Adhesive bonding has always been an alternative to traditional fastening systems. In your case, it seems that you really need a structural high-strength adhesive. It is very important that you choose a system that will: give reliable bonding to the steel, cure quickly to give high strengths, and will have the durability to maintain the weight of the panel during the lifetime of the panels. You really need to know what loads the assemblies will carry.
The necessity for high strength and loadbearing capability will preclude many adhesives. I would avoid thermoplastic systems like cyanoacrylates or hot melts, which will creep under prolonged loading. In your case, a high-performance two-component epoxy adhesive will be an obvious candidate. These adhesives can be formulated to give highly crosslinked thermoset systems that will resist creep under load for long periods of time. In addition, their cure speed can be varied to suit your assembly process. For example, a system that might take 24-72 hours to cure fully at room temperature can often be spot-heated to fixture and hold the parts together in a minute or two. The only drawback is that these epoxy adhesives tend to be somewhat rigid and brittle.
Ensure that you work with your adhesive supplier to do some testing. Depending on your specific requirements, alternative adhesives could be reactive acrylics or polyurethanes. These two types of adhesives will give you toughness and impact resistance at the expensive of the highest tensile shear strength.
Any views or opinions expressed in this column are those of the author and do not represent those of ASI, its staff, Editorial Advisory Board or BNP Media.