Ask Dr. Dave
QuestionNow that we are in the middle of winter, is there anything special that we should be doing with our adhesives and sealants?
AnswerWinter brings two major potential problem areas as far as adhesives and sealants are concerned, namely, low temperatures and low humidity. One of the critical things to do if you are using a water-based adhesive, such as an acrylic latex, is to ensure that you prevent it from freezing. You should check drums at the receiving dock to make sure the adhesive has not frozen during shipment - evidence of this is often in appearance, such as a "cottage-cheese"-like look. Also ensure that drums are not left on the receiving dock in very cold weather. Although many latex adhesives can be formulated to be freeze-thaw stable, the trend is away from this because the anti-freeze additives, such as ethylene glycol, are quite toxic.
If you are using adhesives and sealants outdoors, you should check carefully with your supplier because, at low temperatures, products cure more slowly. In fact many will not cure at all in very extreme weather.
Most assembly and sealing operations carried out indoors will be in a controlled environment, but you can sometimes see winter-related problems. I frequently get calls from medical-device manufacturers who are using the "instant" cyanoacrylate adhesives and are finding that they are not instant anymore! The most common cause of this is low humidity because moisture on surfaces is the catalyst that initiates the cure of cyanoacrylates. The solution to this problem is to create a high-humidity environment, such as humidifying a fume-hood or small room. The cure rate of other products such as RTV silicones and one-component polyurethanes can also be affected by low humidity.