Лако-красочные материалы — производство

All adhesives display changes in their bulk properties when the temperature changes. This change is particularly marked (as with many engineering plastics) when the glass transition temperature (Tg) is passed. The Tg of a cyanoacrylate is of the order of 120 °C whereas a UV acrylic generally has a lower Tg (50-80 °C). These changes in adhesive properties above and below Tg will affect the stress distribution pattern in the adhesive joint. This can be important if the adhesive is to be used to transmit power directly through shear loading.

When materials with different coefficients of thermal expansion (CTE) are joined, shear stresses result when the assembly is heated or cooled. Many engineering plastics have a CTE value in the range 80-100 x 10-6 mm/mm/°C but sometimes differences can occur. For example, liquid crystal polymer has a CTE of 10 x 10-6 mm/mm/°C, whereas acrylic has a CTE of 80 x 10-6 mm/mm/°C, and if these two substrates were to be bonded with a cyanoacrylate (CTE = 80 x 10-6 mm/mm/°C [5]) then the adhesive could be subjected to some quite severe stresses at the extreme operating temperature range. In this case a thicker bond line and more compliant or flexible adhesive (e. g., a flexible UV acrylic) may reduce problems.