Environmental effects on epoxy adhesives employed for restoration of historical buildings

Fiber-reinforced composites based on epoxy resins are used in the restoration of historical buildings, for example, in the restoration of the Basilica di S. Francesco (Assisi, Italy). In this study, the epoxy resin that served as a matrix in the composite was analyzed, focusing attention on the factors that could affect its durability in service. The curing process of the epoxy resin was monitored. Thermal, chemical, and mechanical properties were measured on samples exposed, after curing, to levels of humidity, temperature, and water above the ordinary values. The properties of the cured resin were calculated before and after the treatments. The thermal treatments led to an increase in glass-transition (T-g) temperature and a strengthening of the system; the exposition to moisture or water yields a reduction in T-g, while it does not affect considerably the mechanical properties of the resin; the effects of thermohygrometric treatments are more complex.