Shape memory thermosetting polyurethane (SMPU) composites containing different amount of multiwalled carbon nanotube (MWCNT) ranging from 0 to 0.250 phr were prepared. The shape memory behavior, tensile stress, and recovery stress were determined by using conventional thermomechanical cycle; however, the modified thermomechanical cycle designated as progressive stretch-relax-stretch (PSRS) cycle was also employed to create shape memory effects in studied composites. The test was carried out in water bath which was equipped with an electric heater, temperature controller, and tensile stress and strain measuring setup. The recovery and tensile stresses both were showing higher values for PSRS samples as compared with conventional samples. Loading of MWCNT improved the recovery stress of SMPU, thereby confirming reinforcing effect. The maximum recovery stress of 2.17 MPa for 0.188 phr MWCNT loading was observed as compared with 1.09 MPa of unreinforced SMPU specimen. The recovery time was also improved on reinforcement as demonstrated in this article. The morphology of fractured surface and degree of dispersion of MWCNT was studied using Field Emission Scanning Electron Microscope. The impact on glass transition temperature was also observed for MWCNT reinforcement on SMPU, which depends on the degree of dispersion and loading of MWCNT in the specimen. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44389.
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机译：制备了0-0.250 phr不同量多壁碳纳米管（MWCNT）的形状记忆热固性聚氨酯（SMPU）复合材料。采用常规热机械循环测定形状记忆行为、拉伸应力和恢复应力;然而，修正的热机械循环被指定为渐进式拉伸-松弛-拉伸（PSRS）循环，也被用于在所研究的复合材料中产生形状记忆效应。测试在配备电加热器、温度控制器以及拉伸应力和应变测量装置的水浴中进行。与传统样品相比，PSRS样品的回收率和拉伸应力均显示出更高的值。MWCNT的加载改善了SMPU的恢复应力，从而证实了增强效果。在0.188 phr MWCNT载荷下，最大回收应力为2.17 MPa，而未增强SMPU试样的最大回收应力为1.09 MPa。如本文所示，加固的恢复时间也得到了改善。采用场发射扫描电子显微镜研究了MWCNT的断裂表面形貌和分散程度。还观察到MWCNT增强对SMPU的玻璃化转变温度的影响，这取决于MWCNT在试样中的分散程度和负载程度。（c） 2016 Wiley Periodicals， Inc. J. Appl. Polym.科学 2017， 134， 44389.
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