Characterization of epoxy syntactic foams by dynamic mechanical analysis

Epoxy syntactic foams that are capable of withstanding use-temperatures in the range of 106 to 175°C were fabricated with DGEBA or novolac based epoxy resins and appropriate amine hardener materials. These foams were characterized for dynamic mechanical properties in single cantilever mode. The storage modulus, loss modulus and tan δ values were recorded over a wide temperature range. A typical density value of around 0.45 g/cm3 of the syntactic foams made respectively from a cycloaliphatic amine hardener, aromatic amine hardener-I, aromatic amine hardener-II recorded storage modulus (E′) values of 1354 MPa, 1500 MPa and 1530 MPa respectively and tan δ values of 0.0139, 0.0090, 0.01039 respectively at 30°C. The storage modulus values gradually decreased with increasing temperature while the loss modulus values showed corresponding gradual increase in the same temperature range. There is a steep variation in these values when the material softens in the vicinity of the glass transition temperature (T g) indicating the upper temperature limits to which they can be put in use. The reduction in the storage modulus values with increasing temperature and the glass transition temperature values are characteristic of the resin/hardener systems as well as the curing/post curing cycles employed.