Shape memory and mechanical properties of cross-linked polyethylene/clay nanocomposites

Shape memory polymer (SMP) such as cross-linked low-density polyethylene (XLDPE), can return from its temporary shape to the original (permanent) shape upon heating. SMP in comparison with shape memory alloy (SMA) and shape memory ceramic (SMC) has lower stiffness, so generates lower recovery force when it is being used as an actuator. Also, when SMP is reinforced with traditional micro-fillers, it often loses its shape memory effect due to the high weight fraction of filler (20–30%). To overcome these disadvantages, nanoclays can be used. The smart resultant nanocomposite, even in small clay loading level (0–10 wt.%), shows higher modulus, strength, and the other physical properties such as higher recovery force, required to act as an actuator. In this work, the effect of modified montmorillonite on mechanical and shape memory properties as well as the force generation of a shape memory cross-linked low density polyethylene were investigated. The results show that the modulus of elasticity, the recovery temperature, the recovery force and force recovery rate increase with increasing organoclay in nanocomposites, but final recovery strain decreases slightly.