Engineers must consider many factors when selecting adhesives for industrial laminating applications, and oftentimes chemical exposure is not given the careful evaluation it deserves. A quick review of a chemical resistance chart or a couple of data sheets may be all the effort put into evaluating adhesives for use with specific chemical exposure. This half-hearted approach will not cut it for adhesive and sealant applications that must perform as expected in many aerospace, automotive, medical, and industrial applications.
Know How an Adhesive Will Respond Given All Variables
It can be challenging for engineers who know exactly how an adhesive will respond to all variables that can impact the effects of chemical exposure. All polymers, including adhesives, can be vulnerable to chemical exposure, which can degrade physical characteristics. The interaction of substrates, adhesives, and chemical agents could have endless combinations.
In adhesives, chemical resistance can also be substantially affected under different thermal and mechanical loads. High heat and high stress can affect how well an adhesive will perform in service. The type of exposure must also be considered, such as continuous immersion or an occasional splash. It can be time-consuming and challenging to understand how an adhesive will perform under all variables.
Some basic guidelines for selecting adhesives that will hold up and chemical environments include understanding the chemical interactions, the exposure variables, and testing strategies.
Understanding Chemical Interactions
Different adhesive families provide a broad resistance to many chemical types. Epoxies provide broad resistance, whereas silicones, UV-curable coatings, polyurethanes, and polysulfides provide resistance to a more limited range of chemicals. Chemical and thermal resistance are closely connected, with adhesives with a higher Glass Transition Temperature (Tg) able to withstand high heat and greater chemical exposure.
Engineers must also consider that within each adhesive family, there are many substantial variations of chemistries, and individual grades can display very different properties when it comes to chemical exposure. It is, therefore, critical for engineers to consider how individual grades will resist exposure to specific chemicals.
Understand All Variables with Chemical Exposure
Determining which adhesives to use when exposed to specific chemicals is a good starting point, although many other factors must be considered. The type and intensity of exposure to a chemical agent, whether low, high, or intermittent, should be considered. Underestimating the type of chemical exposure is one of the most common mistakes with the most serious consequences.
It is also critical to evaluate the mechanical and thermal loads when selecting adhesives for chemical exposure. High temperatures can cause many adhesives to decline in their ability to resist chemicals. High physical stress can also cause adverse effects on the ability of adhesives to hold up in a chemical environment. Misunderstanding the severity of physical or thermal loads could result in poor adhesive performance or failure.
Engineers must be careful not to overcompensate for chemical resistance that is not necessary. This can limit the choices for possible adhesives in an application as those that must have resistance to high stress, high temperatures, or continual immersion are fewer than adhesives that can resist low stress, low temperatures, and low to intermittent exposure. Overprotecting against chemical exposure could cause engineers to miss out on other adhesive properties for chemical resistance that the application does not need. More chemical-resistant adhesives could also be more challenging when carrying and mixing and can increase costs.
Understand Adhesive Functional Testing
It is crucial for engineers to know that their industrial adhesives have been properly tested by chemical and industrial adhesive suppliers. There are several types of industry-specific tests aimed at capturing functional bonding requirements. ASTM D896 is one of the most commonly used standards for testing adhesive chemical resistance, although it does not distinguish between penetration at the interface of the substrate and adhesive or adsorption in the bulk adhesive.
Working with an experienced industrial adhesive supplier will help you to understand all of these critical considerations regarding chemical interactions, exposure, and testing to select the best adhesive for your process.
Universal Chemicals & Coatings, UNICHEM, is an industry-leading supplier of quality industrial adhesives tested for reliability and performance. We offer more than 50 years of experience in solving problems and delivering high-quality adhesive solutions that improve your products and processes. Contact us to learn more about selecting the best industrial adhesives with the right level of chemical exposure for your application.