The Effects Of Chemical Exposure On Adhesives

Interview conducted by G.P. ThomasOct 24 2013

Robert Michaels, Vice President of Technical Sales at Master Bond, discuss some of the issues surrounding chemical exposure on adhesives and the role of chemically resistant adhesives.

What are some of the considerations with respect to evaluating the effects of chemical exposure on adhesives?

There are almost thousands of combinations of adhesives, substrate materials and chemical agents to consider. The variables typically include the exposure type that can range from a splash to continuous immersion. The interaction of adhesive systems with specific chemicals can also vary substantially based on the frequency, duration and temperature at which the exposure might take place. The key challenge is to precisely determine how this chemical exposure would impact the adhesive.

Which adhesive families have a broad resistance to many types of chemicals?

One must note that there may not be a universal solution from an adhesive standpoint that can be used as the ideal choice for every chemical environment. It is a fact that certain adhesive families are known for having a broad resistance to different types of chemicals. Epoxies tend to be the most popular. Even though there are certain types of polyurethanes, silicones, UV curables and polysulfides that offer acceptable chemical resistance against a more limited range of chemicals, they cannot stand up to nearly as many chemical environments as certain chemically resistant epoxies.

Adhesive chemistries can change substantially even in a family. Individual adhesive grades can have several different functional additives and curing reactions that will affect their ability to withstand chemicals. It is always essential to consider the resistance of individual grades to specific chemical exposures.

What are the different types of exposures and how should they be considered with respect to the application?

At the fundamental level, exposures can be characterized by the intensity of contact with a chemical agent. Low intensity exposures are best considered as a splash.

Higher intensity exposures will involve immersion that can be continuous or intermittent. It is also important to factor the exposure frequency. Note that exposures can potentially involve vapors, in addition to liquids.

Chemical exposure at high temperatures is more aggressive than the corresponding room temperature exposure. Adhesives that hold up well at room temperatures may not qualify automatically for resisting the same chemical at elevated temperatures.

What can happen if the type of exposure is mischaracterized?

In case the intensity of the exposure or the severity of the load is understated, adhesive products don’t perform as well as expected, perhaps even to the point of failure. However, overstating exposure or load can all pose an issue by limiting the number of suitable adhesive products for a given application.

For any potentially harmful chemical agent, there are many more adhesives that can resist splashes at low temperatures compared to adhesives that can resist continuous immersion at high temperatures.

How does one typically test a chemically resistant adhesive for an application?

Based on the eventual operating conditions that the adhesive is subjected to, testing can be performed in the form of short/long term soak/spray tests or in the form of accelerated tests under varying conditions. The key properties that one monitors would typically include the weight change and degradation in the physical properties of the cured adhesive.

Does Master Bond have any testing data?

Master Bond has a unique data base for long term chemical exposure data. Some of this chemical exposure data comes from immersion tests. The long- term data covers numerous combinations of adhesives and chemicals, including many organic and inorganic acids, alcohols, chlorinated compounds, hydrocarbons, solvents and more.

About Robert Michaels

As an integral part of the foundation of Master Bond, Robert Michaels has served as the Vice President of Technical Sales for over 25 years.

Master Bond is a leading manufacturer of high performance adhesives, sealants, coatings, potting and encapsulation compounds and impregnation resins. Their line of products consists of:

• Epoxy Systems
• Silicone Systems
• UV Curable Systems
• Polyurethanes
• Polysulfides

Master Bond custom formulates products with specific performance properties designed for unique applications. These compounds exhibit the advanced properties required for a number of different industries, including the aerospace, medical, optical, electrical, electronic and other manufacturing industries.