Synthesis of curing agent for epoxy resin based on halogenophosphazene

Effect of Cyclotriphosphazene-Based Curing Agents on the Flame Resistance of Epoxy Resins

Epoxy resins are characterized by excellent properties such as chemical resistance, shape stability, hardness and heat resistance, but they present low flame resistance. In this work, the synthesized derivatives, namely hexacyclohexylamino-cyclotriphosphazene (HCACTP) and novel diaminotetracyclohexylamino-cyclotriphosphazene (DTCATP), were applied as curing agents for halogen-free flame retarding epoxy materials. The thermal properties and combustion behavior of the cured epoxy resins were investigated. The obtained results revealed that the application of both derivatives significantly increased flame resistance. The epoxy resins cured with HCACTP and DTCATP exhibited lower total heat release together with lower total smoke production compared to the epoxy materials based on conventional curing agents (dipropylenetriamine and ethylenediamine). Comparing both derivatives, the HCACTP-cured epoxy resin was found to provide a higher flame resistance. The designed novel class of epoxy materials may be used for the preparation of materials with improved flame resistance properties in terms of flame spreading and smoke inhibition.

Effect of different silane coupling agents on cryogenic properties of silica-reinforced epoxy composites

Epoxy-based composites containing silica modified by various silane coupling agents (SCAs) were prepared. The effect of the SCAs and the silica content on the thermal, mechanical properties, and fracture toughness of the nanocomposites was investigated. The particle size and dispersion state of the modified silica particles in the matrix were determined by transmission electron microscopy. The modification of silica with SCAs was verified by Fourier transform infrared spectroscopy. The specific tensile properties at ambient temperature (AT, 298 K) were compared with those at cryogenic (LT, 77 K) condition for silica content of 1−5 wt%. The effect of certain types of coupling agents on the thermal properties of the composites was also investigated. The Tg of all amino-silane-modified composites tended to be improved at low silica contents, while that of epoxy-silane-modified composites seemed to be enhanced further at high silica content. The tensile properties of the nanocomposites both at AT and LT tended to be enhanced at lower silica content, especially the failure strain. The fracture toughness ( KIC) turned out to be better enhanced by coupling agents at LT. The difference of the toughening mechanism at AT and LT was examined according to the morphology of the fracture surfaces using the scanning electron microscopy.