Adhesives in the cured and uncured state can be affected by climate. So it is important to establish a proper work environment.
Every country in the world undergoes seasonal changes, some more extreme in range than others. Global transportation methods encounter changes in the environment as well. The result is variable and inconsistent levels of heat and humidity.
Heat and humidity differences exist in both time and space. Time: it is not unexpected to see 30% relative humidity at 70°F in winter jump in the summer to 80% humidity at 70°F in the mid-Atlantic states of the US, for example. Space: A given day in June in the northern hemisphere will have warm weather, while there will be cool weather in the southern hemisphere.
The following advice will help you to make appropriate decisions.
Follow the manufacturer’s recommended storage guidelines for the best results with any chemical product.
You can usually find this information on the label. For example, a warehouse or refrigerator maintained between 45°F and 75°F or refrigerated at 40°F-45°F.
The work environment is just as important as proper storage, perhaps even more so. In this context, we are concerned with two measurable properties – heat and relative humidity – and their impact on the adhesive application and cure.
For example, there was a multinational company with basically the same manufacturing plants set up in Mexico and Eastern Europe. They wanted to simplify the supply chain by specifying a single product for use in all plants.
Shortly after both plants went into full production, QC tests reported a high number of component failures from the plant in Mexico. After comparing all the possible reasons for the difference in product performance, the native climate of the facility was found to be the overlooked factor in choosing the adhesive.
One location is a very cold, low-moisture country, while the other is very hot and humid. In this example, the adhesive spec’ed was a cyanoacrylate (instant) adhesive. These adhesives cure by reacting with trace amounts of moisture in the substrates. In the case of a high humidity environment, the adhesive begins to cure before the components can be fully assembled.
Many adhesive formulas are based on a “moisture-cure” reaction, not just the instant cyanoacrylates. These moisture-cure products include some of the polyurethanes, silicones, and modified epoxies, to name a few. Humidity also affects adhesives with long open times (for precise assembly.)
Each application should be carefully considered in all stages and tested across the full range of expected environmental conditions.
Measuring the environment with calibrated equipment and monitoring the work area regularly to maintain a constant temperature and relative humidity is important. It may be as simple as installing a fan or dehumidifier unit. This investment of time and money up front will ensure consistent cure speeds low reject rates.
If you’re supplying factories in a few different parts of the world, be sure to have new adhesive choices tested in each location. Don’t neglect to confirm that satisfactory storage arrangements are available.
Armed with the knowledge of the local climate and the application process, it is often possible to choose one adhesive that will meet all the requirements. For challenging conditions, contact the manufacturer, who will have a technical support staff to provide recommendations.
