Thermo-viscoelastic properties and creep response of two commercial, ambient temperature cure epoxy structural adhesives were analyzed and compared. The adhesives were formulated by the same manufacturer and appeared to have the same base chemistry; however, one system contained accelerators to shorten its cure time. In the laboratory, dynamic mechanical temperature/frequency sweeps were performed on both systems to generate dynamic mechanical data and predict creep compliance master curves using time-temperature superposition principles. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and moisture sorption analysis were also used to assess the thermal and hygroscopic properties of the materials. Differences were observed in the thermal, hydrolytic and dynamic mechanical properties of the two adhesive systems as well as in their estimated creep compliance behavior, which were attributed to differences in the curing agent(s) and accelerator(s) used in the adhesive systems. In most cases the differences in the epoxy properties were small, but a few properties, particularly the predicted creep behavior, exhibited very large differences. Laboratory creep testing was carried out which confirmed the predicted difference in creep behavior. The data also suggest that dynamic mechanical testing combined with time-temperature superposition may be a useful metrology for predicting trends for in-service creep behavior from short term tests.
Citation: Journal of Adhesion
Pub Type: Journals
epoxy, adhesives, moisture sorption analysis, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical thermal analysis, time-temperature superposition, creep compliance, adhesive anchors