Dave Dunn Ph.D.

After more than 20 years of sharing his expertise and wisdom in the monthly Ask Dr. Dave column, Dave Dunn has retired as a columnist. Here we share some of his most popular columns over the years.

Room-temperature vulcanizing (RTV) silicones are well-known for their extreme durability. They are convenient one-component sealants that cure by reaction with moisture from the atmosphere.

Bonding polystyrene foam to steel and wood is an application that was traditionally done with contact cements or other solvent-based adhesives. Due to health and flammability concerns, however, the modern trend is to use 100% reactive systems.

You have a wide range of possibilities here. Normally, you would require an adhesive that has been toughened with a rubber for this.

Polytetrafluoroethylene (PTFE) is a high-performance plastic used in a variety of industries, particularly for its heat and chemical resistance and “non-stick” properties. However, PTFE has a low surface energy that does not allow adhesives to wet its surface and subsequently bond.

We are using epoxy adhesives to bond steel substrates that are exposed periodically to both 150˚C and as low as 0˚C. Our problem is in maintaining adhesion to the two steel surfaces at such divergent temperatures because of the response of materials to thermal conditions when going through heating and cooling cycles. Do you have any suggestions?

Called thermoset polyesters, these materials are glass fiber-reinforced unsaturated polyesters. They are also often referred to as “sheet molding compounds” (SMCs), “fiber-reinforced plastics” (FRPs), or simply “fiberglass.”

Question: My colleague and I are working on a unique challenge of trying to find a solution for manufacturing urethane-based adhesives that are quite sensitive to moisture exposure.

You can obviously package your moisture-sensitive sealant in glass or metal cans or tubes, which will totally prevent moisture ingress. Aluminum tubes are widely used for this type of product, as long as you have good crimps.