Hydroxyl terminated polybutadiene-based shape memory polyurethane nanocomposites containing nano metal-oxide fillers for microfluidic valve actuator applications

Abstract

We report here a novel and unique thermo-responsive Shape Memory Polyurethane Nanocomposites (SMPUNCs) derived from Hydroxyl Terminated Polybutadiene (HTPB) and Poly Tetra Methylene Glycol (PTMG) blend encapsulated with nano metal oxides fillers such as CuO, NiO, Fe2O3, CuFe2O4, and Fe2NiO4 for possible use in polymer-based microvalve actuator systems. The synthesis methods adopted and the various characterization techniques employed are presented. The corresponding SMPUs are named PU−CuO, PU−Fe2O3, PU-NiO, PU−CuFe2O4, and PU-Fe2NiO4 respectively. HTPB and PTMG are used as the base polyols for reacting with isocyanates to form the polyurethane base matrix, named as PU-Neat for comparison. Different fillers were used to study the effect of these fillers on the enhancement of the shape memory properties of polyurethane. Morphological, thermal, mechanical, and shape-memory properties of the prepared SMPUs are fully characterized. Morphological studies confirm that all the nano-metal oxide fillers are uniformly dispersed within the SMPU matrix. The shape memory transition temperature (Ttrans), which plays an important role in the shape memory effect (SME), is obtained from DSC analysis. The results show that Ttrans is enhanced with the reinforcement of the nano-metal oxide fillers (resulting in about 10% enhancement in the shape recovery time). The metal oxide filler integrated samples show higher thermal stability as well as shape fixing and recovery performances than PU-Neat. The tensile test confirmed that the PU−Fe2O3 matrix possesses a high tensile modulus and is rigid when compared to other SMPUs. We also demonstrated a microvalve actuator system using PU−Fe2O3, as it possesses the optimum shape recovery and better shape fixing properties, compared to other prepared Shape Memory Polyurethane Nanocomposites. An improvement of 10% efficiency in the closing and opening of the valve for PU composite film was observed in the demonstrated actuator setup.