Comparison of Hydrogenated Bisphenol A and Bisphenol A Epoxies: Curing Behavior, Thermal and Mechanical Properties, Shape Memory Properties

Abstract

Hydrogenated bisphenol A epoxy resin was cured using different kind of curing agents, resulting in epoxy networks with better shape memory properties than bisphenol A epoxy networks. The non-isothermal curing kinetics investigated by differential scanning calorimetry (DSC) demonstrated that hydrogenated bisphenol A epoxy showed lower curing reactivity than bisphenol A epoxy, while it still could be cured well. The thermal and mechanical properties as well as shape memory properties were studied by dynamic mechanical analysis (DMA), DSC, thermogravimetric analysis (TGA), three-point bending test and U-type shape memory test and cyclic stretch test using DMA. Results manifested that hydrogenated bisphenol A epoxy systems exhibited lower shape transition temperature (lower T g ), slightly higher modulus, better toughness, much faster shape recovery rate, and better elongating ability at temperature above T g than bisphenol A epoxy systems, which was due to the rigidity of cyclohexane ring from its steric hindrance and favorable segmental mobility when absorbing external energy such as heating or bending. Moreover, the shape fixity and shape recovery ratio of all the samples were as high as 96.3~98.5% and 100% and their cycling stability during shape memory test was excellent. Although lower than bisphenol A epoxy networks, hydrogenated bisphenol A epoxy networks possessed high thermal stability with initial degradation temperature (Td5%) of >305 °C.