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The traditional processing technology of shape memory polymer composites is complex and the cost of high performance filler is high. Therefore, low-cost high density polyethylene (HDPE) was introduced into trans-1,4-polyisoprene (TPI) matrix as reinforcing phase, and a novel shape memory polymer was prepared by mechanical melt blending, which fully exerted the excellent properties of plastic and rubber. Because of the difference in molecular chain distribution between different blend ratios of TPI/HDPE hybrid SMPCs specimens, the change of the blend ratio of the two components affects the thermodynamic and shape memory properties of the SMPCs. A series experimental results show that the TPI/HDPE hybrid SMPCs with the blend ratio of 80/20 has excellent thermodynamic and shape memory properties. And we believe that the relevant conclusions of this study can provide valuable design reference for the development of high-performance TPI SMPCs. 相似文献
43.
Shape memory polyurethanes (SMPUs) have attracted much attention in the biomedical field because they can easily control the transition temperature (Ttrans) to shape memory and are biocompatible. In this study, a shape memory polyurethane with both biocompatibility and a Ttrans close to the body temperature was synthesized by using natural derivatives of isosorbide and castor oil in place of petroleum-based materials. Isosorbide and castor oil were used to form net points, and polycaprolactone diol (PCL diol) acted as the switching segment. The synthesized four polyurethane (PCL diol/isosorbide/castor oil, PICU-1, 2, 3, 4) with different isosorbide contents exhibited desired thermal and mechanical properties. In the thermo-cyclic shape memory testing experiment, the PICU series demonstrated good shape memory property, with more than 95% shape recovery ratio (Rr) and more than 90% shape fixity ratio (Rf), and PICU-3 recovered its shape within 20 s in a 37 °C water bath. In addition, the PICU series proved to be safe materials with excellent biocompatibility, as indicated by the observed C2C12 cells viability and proliferation. The stent made with the PICU-3 film showed near complete magnetization at 37 °C within 18 s and proved to be a suitable self-expanding stent. 相似文献
44.
Fengling Liu 《大学化学》2020,35(2):88-91
The shape of an atomic orbital not only depends on the azimuthal quantum number l, but also associates with the magnetic quantum number m. We discussed about how to derive the shape of an atomic orbital from the numbers and shapes of the angular nodal planes, and the symmetries of distribution of all angular nodal planes when l and|m|are known. According to the|m|, the compatibility of the symmetry of an atomic orbitals have also been also discussed. 相似文献
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采用化学还原法合成Pd纳米立方体,并将其作为晶种,进一步合成大尺寸的纳米Pd立方体以及具有不同{100}和{111}晶面比例的纳米Pd多面体.将形貌和尺寸可控的纳米Pd溶胶应用于1,4-丁炔二醇催化加氢的反应中,反应结果表明,纳米Pd的催化性能取决于其尺寸和形貌.{111}晶面的催化活性高于{100}晶面,PVP稳定的Pd胶体对1,4-丁烯二醇均具有较高选择性,具有适当{100}和{111}晶面比例的纳米Pd多面体对1,4-丁烯二醇的选择性可达96%. 相似文献
48.
Intense investigations have been attracted to the development of materials which can reconfigure into 3D structures in response to external stimuli. Herein we report on the design and self-folding behaviors of hydrogels composed of poly(ethylene glycol) methyl ether methacrylate (OEGMA) and 2-(2-methoxyethoxy) ethyl methacrylate (MEO\begin{document}$_{2}$\end{document} MA). Upon immersion into a variety of solvents at room temperature, the resulting P(MEO\begin{document}$_{2}$\end{document} MA-co-OEGMA) hydrogel sheets self-fold into 3D morphologies, and the observed transformation in shape is reversible. We further show that composition of the gel, gaseous environment, and preparation procedure play important roles in the self-folding behavior of the resulting hydrogels. This work provides a facile approach for fabricating self-folding hydrogels. 相似文献
49.
Dong S. Yang David R. Fazzini Timothy I. Morrison Larc Trger Grant Bunker 《Journal of Non》1997,210(2-3)
A commonly used expression for modeling the XAFS of highly disordered systems is shown to generate substantial systematic errors in the coordination number in many cases of practical interest. This expression is corrected and generalized. Further, a simpler and more flexible model distribution is proposed, and the corresponding XAFS expression is derived. Comparison with experimental and simulated data show that the new expressions are useful in cases of high disorder for which the cumulant expansion loses its utility, and they explicitly account for the k-dependence of the mean free path. 相似文献
50.
David L. Henann 《Journal of the mechanics and physics of solids》2010,58(11):1947-1962
Recent experiments in the literature show that micro/nano-scale features imprinted in a Pt-based metallic glass, Pt57.5Ni5.3Cu14.7P22.5, using thermoplastic forming at a temperature above its glass transition temperature, may be erased by subsequent annealing at a slightly higher temperature in the supercooled liquid region (Kumar and Schroers, 2008). The mechanism of shape-recovery is believed to be surface tension-driven viscous flow of the metallic glass. We have developed an elastic-viscoplastic constitutive theory for metallic glasses in the supercooled liquid temperature range at low strain rates, and we have used existing experimental data in the literature for Pt57.5Ni5.3Cu14.7P22.5 (Harmon et al., 2007) to estimate the material parameters appearing in our constitutive equations. We have implemented our constitutive model for the bulk response of the glass in a finite element program, and we have also developed a numerical scheme for calculating surface curvatures and incorporating surface tension effects in finite element simulations. By carrying out full three-dimensional finite-element simulations of the shape-recovery experiments of Kumar and Schroers (2008), and using the independently determined material parameters for the bulk glass, we estimate the surface tension of Pt57.5Ni5.3Cu14.7P22.5 at the temperature at which the shape-recovery experiments were conducted. Finally, with the material parameters for the underlying elastic-viscoplastic bulk response as well as a value for the surface tension of the Pt-based metallic glass fixed, we validate our simulation capability by comparing predictions from our numerical simulations of shape-recovery experiments of Berkovich nanoindents, against corresponding recent experimental results of Packard et al. (2009) who reported shape-recovery data of nanoindents on the same Pt-based metallic glass. 相似文献