Ultrasonic Vibration-Induced Shape Memory Polymer (Polyurethane)/Graphene Nanoplatelets Composite

Abstract

Ultrasonic vibration (UV)-induced shape memory polyurethane (PU) and composite containing 1 phr (part per hundred) graphene nanoplatelets (GNPs) were prepared through ex situ polymerization by using microcompounder. Atomic force microscopy and field emission scanning electron microscopy were used for the characterization of surface morphology, surface roughness, and graphene nanoplatelets dispersion in the polyurethane matrix. The thermomechanical properties (storage modulus, loss modulus, energy dissipation factor, and glass transition temperature) were determined by using the dynamic mechanical analyzer. The thermomechanical properties, shape memory stretch and recovery strength, shape fixity, tensile strength, and UV-induced shape recovery are enhancing for a composite having 1 GPU (1 phr GNPs in PU matrix). Shape memory and mechanical properties were improved for composite sample as compared to pure polyurethane. 1 GPU composite sample shows ultrasonic vibration-induced shape recovery, whereas pure polyurethane sample has no shape recovery. The UV-induced shape recovery strongly depends on the dispersion of GNPs and frequency of ultrasonic vibration. For composite sample (1 GPU), embedded GNPs in the PU matrix may absorb the UV frequency and converted into heat energy (lattice vibration of GNPs and heat is transfer through conduction) which is responsible for shape recovery. With increase in the frequency of UV, the shape recovery also increases for the composite. Glass transition temperature (Tg) was influenced with the addition of GNPs into neat polyurethane matrix. UV-induced shape recovery test was carried out in an ultrasonic vibration transducer with variable frequency (0–40 kHz).