Enhancing Mechanical and Shape Memory properties in hyperbranched epoxy Shape Memory Polymers

摘要

Shape Memory Polymers (SMP) are a kind of materials that are capable of change its shape when an external stimulus is applied. The polymer can be processed into their permanent shape by conventional techniques and can be deformed in a second or temporary shape in a step calling programming [1]. In recent years some studies have reported shape memory epoxy-based thermosets (SMEP) with excellent shape memory properties, thus enabling the use of SMPs in more mechanically demanding applications such fold-deployment space structures [2]. However there are still some limitations in SMEPs that greatly limit their use as shape memory materials and should be improved, such as the brittle behavior and low elongation at break. Some studies have focused on overcoming this limitation by choosing suitable shape-memory thermal programs and through chemical composition adjustments [3-5] and, although the toughness of epoxies is greatly improved, the mechanical properties in terms of tensile strength may remain a limitation. Thus, it is necessary to explore new kind of SMEPs, with greatly improved toughness, and that combine high values of tensile strength and maximum deformation above and below room temperature. For this purpose, in this study the use of hyper-branched polymers as crosslinking agents for epoxy-based SMPs is proposed in order to determine the effect of hyper-branched structure on SMEP's thermo-mechanical properties; specifically, to mechanical resistance depending on the testing temperature and to its shape memory performance.