Effect of SiO₂on rheology, morphology, thermal, and mechanical properties of high thermal stable epoxy foam

A series of highly thermostable epoxy foams with diglycidyl ether of bisphenol‐A and bisphenol‐S epoxy resin (DGEBA/DGEBS), 4,4′‐diaminodiphenyl sulfone (DDS) as curing agent have been successfully prepared through a two‐step process. Dynamic and steady shear rheological measurements of the DGEBA/DGEBS/DDS reacting mixture are performed. The results indicate all samples present an extremely rapid increase in viscosities after a critical time. The gel time measured by the crossover of tan δ is independent of frequency. The influence of SiO 2 content on morphology, thermal, and mechanical properties of epoxy foams has also been investigated. Due to the heterogeneous nucleation of SiO 2 , the pore morphology with a bimodal size distribution is observed when the content of SiO 2 is above 5 wt %. Dynamic mechanical analysis (DMA) reveals that pure epoxy foam possesses a high glass transition temperature (206°C). The maximum of specific compressive strength can be up to 0.0253 MPa m 3 kg −1 at around 1.0 wt % SiO 2 .