This One Surprising Ingredient Helps Our Adhesives Cure

What you will learn from this article:

What are Polyurethane Adhesives
H2O's Role in the Curing Process

Many of our conversations with construction professionals across the country begin with this question: “I want to use your Subfloor Adhesive for (insert general subfloor-related application here), will it work?”

Assuming the application involves general construction materials (OSB, plywood, etc.), then the answer will be yes. We will, however, ask some follow-up questions in order to give some additional guidance. Where in the country are you located? What is the weather like there right now?

The primary reason we ask this is: Humidity impacts the curing process for our adhesive products. If the applicator is based in a dry location (especially during the winter, when this article was written), we will recommend that humidity be introduced to the substrate in order to help the adhesive fully cure.

What are Polyurethane Adhesives?

There are many types of adhesives manufactured today. You could break down the adhesives market into two main segments: Natural and Synthetic. Natural adhesives are made from animals or vegetables. Our adhesives are a part of the synthetic category, falling into the polyurethane subsegment (others subsegments that you may be familiar with include epoxies, acrylics and silicones).

“Most important adhesives are synthetic. Adhesives based on synthetic resins and rubbers excel in versatility and performance. Synthetics can be produced in a constant supply and at constantly uniform properties… Structural adhesives are adhesives that generally exhibit good load-carry capability, long-term durability, and resistance to heat, solvents, and fatigue… ,” (Pike).

“Polyurethanes are a class of extremely versatile polymers that are made into flexible and rigid foams, fibers, elastomers, and surface coatings. They are formed by reacting an isocyanate (a compound having the functional group NCO) with an alcohol (having the functional group OH).” (Britannica).

H2O's Role in the Curing Process

See how our Product Manager describes the curing process:

But how does the water in the air start the curing process?

It happens in five steps: 1) Water in the air attacks the isocyanate. 2) The isocyanate removes the hydrogen from the water. 3) The nitrogen removes the other hydrogen. This makes an amine and carbon dioxide. 4) This new amine attacks another isocyanate, just like in the first step. 5) The isocyanate takes a hydrogen from this amine, and so on, (Polymer Science Learning Center).

See below for a graphic break down:

As the carbon dioxide begins to expel, the weight of the adhesive starts to increase. The adhesive becomes more and more viscous. Eventually, carbon dioxide bubbles become trapped. When it solidifies, the bubbles stay there. These are the bubbles that form our squeak-stopping Subfloor Adhesive. This structure allows the expansion of the adhesive to fill the gap between the subfloor and the joist.

The below image shows the Subfloor Adhesive curing on the left, and on the right you can see the fully cured bubbles:

Consider how the Handbook of Adhesive Technology describes PMDI technology and the relationship with water:

“The isocyanate group in PMDI is characterized by high reactivity towards all substances which contain active hydrogens. The main hardening reaction proceeds via reaction with water to the final amide group, while at the same time CO2 is split off. The water necessary to induce the hardening reaction is applied together with the PMDI (spraying together with the PMDI or spraying of an aqueous dispersion of PMDI in water) or is present in the wood in sufficient amount,” (Dunky).

If you are interested in learning more about our polyurethane foam adhesives or have questions about a specific application, please reach out to your local TYTAN Professional Representative. You can also give us a call at (817) 381-4427.