Question: We use an acrylic UV adhesive to bond and coat a complex medical device, and get areas where there is incomplete curing. How can we improve this?
Answer: First, you need to ensure that you measure the intensity of the UV light in various parts of the device and ensure that you use the optimum dose of radiation (intensity x time). Special versions of UV adhesives incorporate additives, such as isocyanate functionality, which cure by atmospheric moisture to solve those “shadow” areas where the UV radiation might not reach. One technique that I have seen used successfully is to cure the part in an enclosure that has mirrored surfaces. This way, the reflected UV light can often reach areas that direct radiation might miss.
Question: What is the best way to store my epoxy and acrylic adhesives to maximize their shelf life?
Answer: In general, storing at low temperatures will be the solution. Low temperatures reduce molecular mobility and stop catalysts from reacting prematurely. Temperatures from 0°C down to -20°C will make adhesives like cyanoacrylates or acrylics last for years, but it’s important to warm them up to room temperature before using them to achieve the original viscosity and cure speed.
The same technique can be used for epoxies, but be careful about storing them in poorly heated warehouses (~ 0-10°C), as crystallization might occur if they are not properly formulated. Crystallization can be reversed by heating the adhesives, but many users do not know this and assume that the adhesive has solidified permanently. ASI
Any views or opinions expressed in this column are those of the author and do not represent those of ASI, its staff, Editorial Advisory Board or BNP Media.