Estimation of Creep and Recovery of Carboxyl-terminated Butadiene Acrylonitrile-epoxy Shape Memory Polymers under Tensile Loading

The creep and recovery of 5% carboxyl-terminated butadiene acrylonitrile (CTBN) modified epoxy shape memory polymers (SMP) was studied. The results were compared with those for the unmodified epoxy SMP. The glass transition temperatures (Tg) were determined using Advanced Rheometric Expansion System (ARES). The creep behavior of the unmodified epoxy and 5wt.% CTBN modified epoxy SMP were studied through short-term tensile creep test. These tests were carried out at different temperatures ranging from glassy, viscoelastic, and rubbery regimes and different loading conditions. It was observed that Tg is slightly reduced by the addition of CTBN in the SMP. For both the SMPs, the creep strain increases with increasing temperature and shows a maximum in the vicinity of the Tg. Furthermore, creep strain increases with increasing load in the glassy and rubbery regimes. A mutual comparison revealed that the creep strain was higher for unmodified epoxy SMP than that of 5% CTBN modified epoxy SMP at all the temperatures considered. A higher percentage creep recovery was noticed in the case of the CTBN modified epoxy SMP as compared to the unmodified epoxy SMP.