High Energy Release-high Retraction Smart Polymer Fibers used in Artificial Muscle Fabrication

Shape-memory polymers (SMPs) could remember their original shape and then, return to their initial shape upon stimulus. So far, quantities such as fixity and recovery ratio of SMPs have been broadly reported. Nevertheless, one main issue is the existence and use of an appropriate approach to quantitatively estimate the SMPs released energy. In addition, it is hypothesized that the elastic behavior of SMPs plays an underlying role when SMP fibers need to exhibit high-tension and high-elongation capacity as required in synthetic muscles. Here, we present, for first time, SMP trinary bulk and filament systems of acrylonitrile butadiene styrene (ABS)/thermoplastic polyurethane (TPU)/ethylene vinyl acetate (EVA) fabricated under calendering intense shear mixing and hot pressing. A digital blocked force load cell was used to record specimens energy released. The results exhibited high retraction from the specimens secondary shape correlated to the tensile behavior. It was shown the blended system of 50, 25 and 25% of TPU, ABS and EVA, respectively, resulted in ~640% and 3900% increase in the elastic modulus and energy release compared to EVA/TPU systems. The double SMP filaments led to a 50% increase in the energy release compared to single fibers. Nevertheless, the blended binary specimens with the TPU/ABS ratio of 50/50 exhibited 600% increase in tensile strength. It was confirmed the elastic modulus, number of fibers and elongation at break govern the SMP stored. The findings of the research lightened a new class of SMPs to be used as fiber-based artificial muscles and orthodontic products.