Low Shrinkage Adhesives

Epoxy adhesives have been found to have a lower degree of shrinkage in comparison to other reactive polymeric adhesive systems. It is important to note that even 100% reactive formulations exhibit some shrinkage upon curing. To lower the rate of shrinkage a variety of fillers including aluminum powder, silica, calcium carbonate, aluminum oxide can be added to the formula. Volumetric and linear shrinkage will be dramatically reduced in comparison to unfilled epoxy resin materials. The use of these fillers while lowering the degree of shrinkage can alter the performance properties of these compounds. They can also significantly increase the viscosity of these materials which will effect the dispensing characteristics of these products. Different types of curing agents are used for specific grades to satisfy the most desirable low shrinkage requirements in many applications.

The value of low shrinkage adhesives can not be underestimated and will have a direct impact on the longevity/effectiveness of bonded joints under multiple environmental conditions. They provide exact alignment, minimize stress which can cause cracks/voids in the bond line and offer optimization in reliability upon long term aging. Higher shrinkage can occur during heat cure polymerization because of the increased cross links density from thermal exposure during cure. Master Bond has made notable progress in developing new adhesive compositions to decrease polymerization shrinkage stress. Silicone adhesive systems have been often employed in delicate electro optic bonding on account of their minimal shrinkage rates, even lower than many epoxy products. Additionally low shrinkage UV/visible light cure adhesives deliver fast cures for high volume assembly usage.