MDI and TDI based polyurethanes with tunable mechanical and shape memory performance.

In this work nanocomposites based on poly (l‐lactide) (PLLA) and zinc oxide (ZnO) nanoparticles with a concentration up to 5 wt % have been prepared by solvent‐precipitation followed by compression moulding at 200 °C. Structural evolution of nanocomposites as a function of time and nanoparticle concentration has been monitored by differential scanning calorimetry (DSC). Results reveal a marked reduction of the enthalpy relaxation rate βH from 3.273 J/g for neat polymer to 0.912 J/g for its 0.25 wt % reinforced counterpart, revealing slower aging dynamics induced by zinc oxide. It is shown by field emission scanning electron microscopy (FE‐SEM) that concentrations larger than 1 wt % yield nanoparticle agglomeration. These large aggregates decrease the amount of nanoparticle surfaces exposed to PLLA chains, notably reducing the efficiency of ZnO nanoparticles to delay the physical aging of its hosting matrix. Mechanical tests show an increased stiffness upon ZnO loading as denoted by the increase in modulus from 2310 MPa to 2780 MPa for the 1 wt % nanocomposite. Obtained findings through this work lead the way for the development of nanocomposites based on renewable polymers and natural fillers to be used in packaging applications, where the use of nonbiodegradable materials for short‐term applications is extended. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43619.

Shape‐memory polyurethanes (SMPUs) represent a highly interesting class of materials due to their applications in different sectors such as biomedical, textile, and aerospace. Moreover, it is possible to synthesize a variety of polyurethanes with different molecular architectures just choosing properly the chemical structure of their components. In this work, it is described the influence of the soft segment on the thermomechanical properties and shape memory behavior of shape memory polyurethanes. The synthesis, based on two‐step polymerization, was prepared by two different soft segments: poly(oxytetramethylene) glycol (PTMG) or poly(ethylene glycol) (PEG). Depending on the molecular architecture achieved, the materials present different properties that were studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Furthermore, the shape memory response of thermally activated SMPUs is determined qualitative and quantitatively by visually monitoring the shape recovery process and by thermomechanical analysis (TMA), respectively. All developed compositions have shown good shape memory behavior, with recovery ratios higher than 99.8%. POLYM. ENG. SCI., 58:238–244, 2018. © 2017 Society of Plastics Engineers

In this work, thermoresponsive shape-memory polyurethane (SMPU) fibers were produced by melt spinning from different SMPU pellets. Afterwards, the knitted fabric samples were prepared by the obtained fibers. Some of the SMPUs used were synthesized previously in our laboratory whereas a commercial one, named DIAPLEX MM4520, was also evaluated in order to carry out comparative studies. All the SMPUs were characterized by different techniques, such as thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis and tensile testing. Moreover, the shape-memory capabilities of the fabrics were measured by thermo-mechanical analysis. The obtained results show that the synthesized SMPUs could be attractive candidates for potential applications such as breathable fabrics or moisture-management textiles.

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