Early-age tensile properties of structural epoxy adhesives subjected to low-temperature curing

The early-age mechanical property development of structural adhesives during low temperature curing is critical for the outdoor construction of engineering structures, such as bridges or buildings. Construction of these structures is also carried out during winter time at low curing temperatures. Experimental investigations showed that the development of the tensile properties of a commercial structural epoxy adhesive strongly depended on the curing temperature. Lower curing temperatures significantly decelerate the process and consequently the rate of development of mechanical properties. At 0 degrees C, curing was inhibited or did not initiate at all. Tensile strength and stiffness developed at the same rate, although the former was slightly delayed compared to the latter. Significant development of the mechanical properties began only after the onset of material vitrification. This was in contrast to the development of the glass transition temperature, which increased particularly before vitrification. A proposed analytical model predicted the development of mechanical properties well, particularly under low isothermal and cyclic temperature conditions. (C) 2012 Elsevier Ltd. All rights reserved.