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Rubber to substrate bonding (RTSB) is common in many industries, including automotive and medical. Successful bonding depends on selecting the right adhesive.
You spend a good amount of time selecting and purchasing the best RTSB material for your application. However, improper storage can damage or compromise product integrity. This can weaken the bond and cause safety issues. Similarly, improper storage can damage the rubber itself, even if the adhesive remains strong.
Below are some tips on how to properly store your rubber and RTSB materials to get the best possible bonding result.
1. Control the Storage Temperature
Rubber can change based on the temperature to which it is exposed. This is because rubber has a high coefficient of friction, meaning it has more friction force relative to normal force. Higher temperatures will soften it, while colder temperatures will stiffen it. The best practice is to store rubber between 40℉ and 80℉.
Rubber should also be stored away from sunlight, which can eventually lead to damage. You can do this by storing it in a cardboard box or another container that blocks the sun.
2. Control Humidity
Materials like rubber can absorb moisture, so their performance can be affected by humidity. When storing these products, make sure to keep humidity under 75% and avoid condensation.
3. Avoid Evaporation
When storing adhesives, it is important to avoid any evaporation. Cans that are partially open or not tightly sealed can compromise the product by letting contaminants in and allowing liquids to evaporate. For example, water will evaporate from MEGUM W and ROBOND TR bonding-agents if the top is not totally closed. Evaporation will be slower with solvent-based products.
Though evaporation will not immediately decrease product effectiveness, the increase of dry solids can coagulate products, rendering them useless.
Similarly, exposure to oxygen or ozone (O3) can seriously damage rubber products. If rubber products sit next to high voltage equipment electrical equipment, the ozone can break the carbon backbone polymer chain into smaller chains. So, like adhesives, you should store these in air-tight containers.
4. Agitate Before Use
Many bonding agents use products that settle during storage. For example, MEGUM, ROBOND and THIXON™ bonding-agent products contain dispersed solids that can settle.
Bonding agents should be agitated using an electric or air-driven motor with a propeller. However, avoid using equipment like paint shakers that will cause the product to foam. Foam is bad for the product because it takes a long time to dissipate. By the time it does, you will have to agitate again.
Some adhesive products come with their own internal agitators. Because solvents are not used, explosion-proof equipment is not required.
5. Proper Stirring Time
Stirring time depends on the amount of settlement and on the stirring technique you use. Flat stirrers about half the diameter of the container are more effective than propellers. The goal is to stir just long enough to make the product homogeneous.
When stirring, the product should be around room temperature.
Overall, you should store rubber and RTSB materials in a way that keeps the products safe and ready to use when you need them. If you find that your products are consistently getting damaged during storage, you should re-evaluate your storage plans and practices.
Experts at H.M. Royal can help you select the best adhesive from DuPont for your project based on its performance with your specific elastomer. They can also help you with any questions or concerns about storing and using these products.