Recovery Stress and Storage Modulus of Microwave-Induced Graphene-Reinforced Thermoresponsive Shape Memory Polyurethane
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JMEPEG https://doi.org/10.1007/s11665-020-04568-5
Recovery Stress and Storage Modulus of Microwave-Induced Graphene-Reinforced Thermoresponsive Shape Memory Polyurethane Nanocomposites Ritesh Kumar Gupta, S.A.R. Hashmi, Sarika Verma, Ajay Naik, and Prasanth Nair (Submitted April 23, 2019; in revised form December 19, 2019) A special class of smart material was developed using shape memory polyurethane (SMPU) elastomer and graphene nanoplatelets (GNPs) via melt-blending process using micro-compounder. The shape recovery of the developed composites was studied under microwave irradiation. The nanocomposites were developed having 0.2, 0.4, 0.6, and 0.8 phr GNPs in the SMPU matrix. The effects of GNP reinforcement on morphology, shape memory effects, and viscoelastic properties of the composites were investigated. The recovery stress of virgin SMPU increased with reinforcement and maximized on the incorporation of 0.6 phr GNPs. The deformation-induced shape memory creation process influenced significantly the recovery stress of composites as compared to virgin SMPU. The recovery stresses of SMPU at 50, 75, and 100% strain were 1.5, 1.7, and 1.9 MPa, whereas the values of GNP-SMPU composites were 3.2, 3.4, and 4.1 MPa corresponding to 0.6 phr GNP reinforcement. The value of storage modulus above the glass transition temperature of SMPU increased from 9.2 to 15.1 MPa on the addition of 0.6 phr GNPs. The peak of the damping factor, tan d shifted toward higher temperatures with the increased GNP content. The morphological study confirms the uniform dispersion of GNPs in the SMPU matrix. The microwave-induced heating of 0.8 phr GNP composite shows 80% shape recovery in 60 s, which is faster than convectional heating. Keywords
dynamic mechanical analysis (DMA), graphene nanoplatelets (GNPs), recovery stress, shape memory thermoplastic polyurethane (SMPU), storage modulus
1. Introduction The shape memory polymers (SMPs) are nonmetallic shape memory materials (SMMs) with the ability to undergo a large recoverable deformation upon the application of an external stimulus (Ref 1, 2). SMPs have several advantages over shape memory alloy (SMAs) such as lightweight, low cost, ease in processability, high strain recoverability, tailorable switching temperature, and response to a wide range of stimuli (Ref 3). Various types of stimuli for SMPs are heat (Ref 4-7), electric field (Ref 8-11), magnetic field (Ref 12, 13), moisture (Ref 14, 15), pH value (Ref 16, 17), light (Ref 18-20), pressure (Ref 21), multi-stimuli (Ref 22), etc. The SMPs have several potential uses in biomedical engineering, control systems, smart textile, Ritesh Kumar Gupta, Academy of Scientific and Innovative Research (AcSIR), AMPRI Bhopal, Bhopal, India; S.A.R. Hashmi and Sarika Verma, Academy of Scientific and Innovative Research (AcSIR), AMPRI Bhopal, Bhopal, India; and CSIR-Advanced Materials and Processes Research Institute, (AMPRI) Bhopal, Bhopal, Madhya Pradesh, India; and Ajay Naik and Prasanth Nair, CSIR-Advanced Materials and Processes Research Institute, (AM
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