Effect of draw ratio and triggering temperature on properties of hydrothermal responsive shape memory microcomposite filaments

This paper investigates the production of hydrothermal responsive shape memory filaments with different draw ratios (0.8, 2.0 and 3.2) using microcrystalline cellulose (MCC) as a filler and shape memory polyurethane (SMPU) as a matrix. A mechanical-thermo-aqueous programming test was conducted to study the shape-memory properties of the microcomposite filaments. The effect of draw ratio and triggering temperature on mechanical, physical, thermal, morphological, and shape memory properties was thoroughly studied. Among the microcomposite filaments, SMPU-MCC with a draw ratio of 2.0 exhibited the highest tenacity value of 0.91 cN/dtex in its original shape with an elongation of 385.2%. The differential scanning calorimetry results showed that the glass transition temperature (T_g) of the filaments increased as the draw ratio increased from 0.8 to 3.2, ranging from 38.35 to 41.02 °C. The crystallinity percentages obtained for pure SMPU, SMPU-MCC-0.8, SMPU-MCC-2.0, and SMPU-MCC-3.2 were 27.10%, 30.68%, 38.72%, and 36.88%, respectively. In addition, an optimum draw ratio led to a degradation temperature rise from 372.5 to 391.3 °C which shows the thermal stability of the filaments was significantly influenced by the intermolecular bonding between MCC and SMPU, which intensified as the draw ratio increased from 0.8 to 2.0. Moreover, the filaments exhibited excellent mechanical and thermal properties in six cycles at the optimum draw ratio and triggering temperature indicating their future application for repeated use without experiencing major changes in shape memory properties.