Ask Dr. Dave | Adhesives & Sealants Industry

Ask Dr. Dave

Ask Dr. Dave’s Greatest Hits

Dave Dunn has retired as a columnist following 20 years of monthly contributions.

February 21, 2022

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.

Ask Dr. Dave

Alternative Cure Systems for RTV Silicone Sealants

We use RTV silicones in our assembly operations, and our workers keep complaining about the strong vinegar smell. Somebody told me that we might be able to get low-odor, low-volatile silicones. What issues should we be aware of?

Dave Dunn Ph.D.

January 25, 2022

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.

Ask Dr. Dave

Bonding Polystyrene to Glass

Can you recommend an adhesive for bonding a polystyrene part to glass for a consumer product? The adhesive needs some good strength, and it must be clear, cure quickly, and be easily used by relatively non-skilled operators. The final product will be used indoors and might suffer occasional impacts.

Dave Dunn Ph.D.

December 17, 2021

Many adhesives will probably do the job, such as tough acrylics and epoxies. The simplest to source and start with might be a clear 5-min epoxy, dispensed from a twin-syringe and fitted with a static mixer.

Ask Dr. Dave

Bonding Polystyrene Foam

We want to bond sheets of polystyrene foam to steel and to wood. What adhesives would you recommend that will be effective and safe to use?

Dave Dunn Ph.D.

November 19, 2021

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.

Ask Dr. Dave

Vibration- and Shock-Resistant Adhesives

Which adhesives can resist serious vibration and shocks?

Dave Dunn Ph.D.

October 20, 2021

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

Ask Dr. Dave

Bonding Fluoroplastic Parts to Metals

We manufacture PTFE and other fluoroplastic parts. We have been requested to make parts that can be bonded to metals. Is there a good adhesive, some sort of additive to the PTFE, or a surface treatment that we can use?

Dave Dunn Ph.D.

September 21, 2021

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.

Ask Dr. Dave

Bonding with Differing Coefficients of Thermal Expansion

We have a problem maintaining adhesion to two steel surfaces at divergent temperatures because of the response of materials to thermal conditions when going through heating and cooling cycles.

Dave Dunn Ph.D.

August 17, 2021

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?

Ask Dr. Dave

Adhesives for Fiberglass Bonding

What are the best adhesives for bonding fiberglass components?

Dave Dunn Ph.D.

July 20, 2021

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.”

Ask Dr. Dave

Moisture-Sensitive Urethane Adhesives and the Pros and Cons of Epoxies

Dr. Dave tackles two questions this month, one related to package stability for moisture-sensitive urethane adhesives, and the other regarding epoxy adhesives.

Dave Dunn Ph.D.

June 15, 2021

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.

Ask Dr. Dave

Packaging Moisture-Sensitive Sealants

Can you recommend suitable materials for packaging a sealant that is sensitive to atmospheric moisture? Additionally, we can do accelerated humidity testing of filled packages, but how do we correlate these with shelf life?

Dave Dunn Ph.D.

May 17, 2021

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.