A facile method to prepare triple-shape memory polymers was developed by blending polyurethane and polylactide–polytetramethylene with well-separated glass transition temperatures. The thermal properties of the blends were characterized using modulated differential scanning calorimetry and differential scanning calorimetry. Field emission scanning electron microscopy, Fourier transform infrared spectroscopy and wide-angle X-ray diffraction were used to characterize the microstructures and crystal structures of the blends. The mechanical properties were also evaluated. The versatile triple-shape memory effect and quantitative shape memory response were evaluated by consecutive thermal mechanical experiments based on a two-step programming process and subsequent progressive thermal recovery. The results show that the blends have phase-separated microstructures resulting in an ability to fix two temporary shapes independently and can recover to their original shapes sequentially. The blends have excellent triple-shape memory properties and may have some applications in multi-shape coatings, adhesives, films and temperature sensing or actuating elements. © 2015 Society of Chemical Industry

Polypropylene (PP) nanocomposites filled with the pristine multi-wall carbon nanotubes (CNTs) and the purified CNTs were prepared by melt blending. The microstructure and linear viscoelastic properties wereinvestigated using rheological and morphological measurements. The results show that the purified CNTs disperse uniformly in the PP matrix. At low frequencies, frequency dependence of modulus weakens clearly with the addition of the CNTs, indicating that the long-range motion of the polymer chains is restrained by the presence of the CNTs. Percolation networks form when the loading levels achieve up to 3 and 1.5 wt% for the composites with the pristine CNTs (PPCNTs) and the purified CNTs (PPcCNTs), respectively. The linear relaxation modulus increases with increasing loading level. And for composites with loading levels above percolation concentration, the modulus appears to reach a plateau at long time scales due to the formation of percolation network. Tensile strength and impact strength are simultaneously improved with the addition of the CNTs. The better the dispersion of the CNTs, the greater the improvement of the tensile strength and the impact strength. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

Polylactide (PLA) and calcium carbonate (CaCO₃) were melt blended using a twin-screw extruder. The morphology of PLA/CaCO₃ composites was observed by scanning electronic microscopy. The linear and nonlinear shear rheological behaviors of PLA/CaCO₃ melts were investigated by an advanced rheology expended system. The results show that the CaCO₃ particles are evenly dispersed in the PLA matrix. The incorporation of low CaCO₃ content (<20%) causes the reduction of the storage moduli, loss moduli, and dynamic viscosities whereas high CaCO₃ content (>30%) leads to the increase of the storage moduli, loss moduli, and dynamic viscosities. The composites with high CaCO₃ content show pseudo-solid-like behaviors at low frequency. High CaCO₃ content also results in a significant increase of flow activation energy and a dramatic decrease of flow index n, which is in consistent with the more serious shear-thinning tendency of high-filled PLA composites melts. The particular rheological responses might be attributed to the formation and destruction of the percolating network. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009