Adhesives play a crucial role in various industrial processes throughout different sectors. They are lightweight and offer practical solutions for secure bonding, sealing and coating applications for various materials. As a result, they are extensively used in sectors like aerospace, automotive, electronics manufacturing, food processing, marine, and construction.
However, the adhesives used in most of these industries are subjected to extreme temperatures, humidity, and other environmental factors. These dynamic environmental conditions affect adhesive performance and reliability. The varying temperature and humidity in different industries and applications affect the mechanical and chemical properties of the adhesives, weakening their bond strength over time. In this blog, we will dive deeper into how temperature and humidity affect the adhesive and how you can ensure optimal performance.
A] Role Of Temperature In Adhesive Performance
Adhesives require a specific temperature for curing, bonding and providing optimal adhesion throughout their life. Industrial applications require accurate temperature control to provide the best results and longevity. It is crucial to discuss the adhesive’s properties, like curing temperature, thermal resistance and conductivity, and electrical resistance and conductivity with the adhesive manufacturer before applying the adhesive.
1. Effects Of Low Temperatures On Adhesives
At a lower temperature, certain adhesives do not bond as effectively as they would at room temperature. Most pressure-sensitive adhesives lose their stretchability and become brittle in cold. This can affect the flexibility and bonding strength of the adhesive, compromising effectiveness and longevity. Low temperatures can also increase the thermal residual stresses. Thermal residual stress increases the adhesive’s volume, decreasing the adhesive bond strength.
Hot melt adhesives specifically require higher temperatures to cure effectively. If the curing temperature is not high enough, the adhesive does not spread and cure as intended, leading to weak bonds between substrates. This adversely affects the result and drives up the cost and time required. To tackle this issue, you can use adhesives that are specifically created to withstand cryogenic temperatures and thermal cycling. These adhesives do not deteriorate or get brittle in low temperatures.
2. Effects Of High Temperatures On Adhesives
Adhesives can have a shift in mechanical and physical properties when exposed to high temperatures. Adhesives that cure under high temperatures could melt and return to a viscose state when extreme temperatures are applied. Most adhesives lose their integrity and can no longer hold onto the substrates. High temperatures are responsible for adhesive failure in many industries where the adhesives are subjected to temperatures higher than they can handle.
Heat-curing two-part epoxies can benefit from high temperatures as they become more viscose and mix better. However, certain adhesives can get too thin, risking the contamination of water molecules. Adhesives with special fillings can crystallise and become stiff at higher temperatures; this makes the adhesives prone to cracking, rendering them useless.
B] Role Of Humidity On Adhesive Performance
Humidity is the level of moisture present in the environment. Applying adhesives without damaging the composition can be tricky in the presence of moisture. Humidity can make a curing agent softer and foamy, impacting its quality and serviceability.
Certain adhesives can resist the effects of humidity to an extent; however, extreme humidity can create a layer of condensation over the substrate surface, reducing bond strength. This makes it necessary for you to ask certain questions while selecting adhesives. In this case, you should check if the adhesives are resistant to humidity. In order to further understand this, let’s take a look at how low and high humidity can affect adhesive performance.
1. Effects Of Low Humidity On Adhesives
Humidity a little lower than average usually does not affect the performance of the adhesives. However, extremely low humidity, such as during winter or in a refrigerated environment can cause various problems. Low humidity can make the epoxy resin hard and brittle, leading to cracks in the adhesive layer.
Low humidity can impact adhesive’s bonding strength and serviceability. Water-based adhesives could take more time to cure and set in low humidity and might require special methods to maintain their moisture.
2. Effects Of High Humidity On Adhesives
High humidity can be problematic for creating strong bonds between substrates. At high humidity conditions, the moisture condenses and forms a barrier between the substrate and the adhesives. Needless to say, this reduces the adhesive bond strength. It is important to maintain the right humidity for successful adhesive bonding. However, in applications where humidity levels are challenging to control, it may be necessary to use a humidity-resistant adhesive.
Specially designed moisture-curing adhesives are available in the market for high humidity conditions. These water-based adhesives can be used in moisture-rich industrial applications for bonding various substrates like wood, plastic and metal with strong adhesion.
C] How To Store Adhesives To Prevent Damage From Temperature and Humidity
Storing adhesives at the right temperature can be vital to maintaining their consistency, texture and chemical and mechanical properties. Storing adhesives in conditions where the temperature is not too high or cold and the moisture is at an appropriate level, can increase the shelf life of the adhesive and reduce waste.
To minimise the impact of temperature on adhesives and prevent the adhesive from becoming too dry or too viscose, you must store it between 10℃ and 50℃. You must also consider the effects of weather on the adhesive’s physical properties and take appropriate measures to maintain the right temperature.
To avoid the effects of humidity on adhesives, you should store the adhesive away from direct sunlight and above the ground. It is advisable to read and understand the manufacturer’s instructions on the container for optimal results.
D] How Temperature And Humidity Affect Curing Time Of Adhesives
Adhesives with faster curing properties are essential for meeting the demands of shorter manufacturing cycles. Every adhesive is different in composition and will act differently to high or low temperatures and humidity. Mostly, adhesives cure faster in high temperatures and create strong cross-polymer bonds. However, if the temperature is too high or the adhesive is not built to withstand the heightened temperature, it will lose its consistency and be useless. On the other hand, low temperatures can decrease the speed of curing, which leads to weak adhesion between the adhesive and the substrate.
High humidity can also decrease the adhesive’s curing time, especially moisture-cure adhesives, so you need to ensure the adhesive is spread correctly before it becomes solid. On the other hand, low humidity decreases the curing time, making it difficult to form strong bonds. Special measures need to be taken according to the adhesive being used to optimise the curing time under high or low moisture conditions.
Conclusion
Environmental factors like temperature and humidity can affect an adhesive’s curing time and bond strength and alter its chemical and physical properties. These environmental uncertainties are not optimal for maintaining the reliability of the adhesive for industrial use. You must understand the environment where the adhesive will be used and choose the adhesive appropriately. There are various adhesives available that are custom-built to serve in dynamic environments like extreme humidity and temperature.
To purchase adhesives that are tailor-made to suit your business needs, feel free to contact us any time! Kohesi Bond is a leading manufacturer and supplier of custom-made adhesives for various industries and applications.
