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81.
It has been found, in this study, that there is no close correlation between the tensile and nanoindentation moduli of polyamide 6 (PA6) at high temperatures. It is demonstrated that heat modifies the surface of PA6 specimens, but its effect on the nanomechanical properties is minor. The main spurious factor which affects the nanoindentation results is adhesion, especially at low indentation depths. The overestimation in the measured indentation moduli can be corrected by performing indentations with loads high enough so that the modulus is independent of the applied load. It is concluded that the lack of strict correlations between the tensile and indentation moduli (after corrections of adhesion) is caused by the shift in the glass transition temperature of PA6 owing to the hydrostatic stress imposed by the indenter. Further proof is given with two examples on hydrostatic pressure‐dependent polymers: polytetrafluoroethylene and polycarbonate. Copyright © 2011 Society of Chemical Industry 相似文献
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聚丙烯熔融特性与MDSC条件的相关性 总被引:1,自引:0,他引:1
用调制式差示扫描量热法研究了聚丙烯(PP)升温过程熔融特性与线性升温速率(β)、温度调制振幅(AT)和调制周期(p)的相关性。实验结果表明,在低β时,总热流部分PP熔融呈现双峰;β加快时,呈现单熔融峰。随β加快,不可逆热流部分熔融热(△H)增加;可逆热流部分出现明显的放热峰。随p延长,总热流部分和不可逆热流部分的熔融峰温(Tp)基本不变,起始熔融温度(Ton)降低;但△H前者不变,后者增加;可逆热流部分从吸热变成放热,放热峰温移向高温。总热流和不可逆热流部分的Tp和Ton不受AT的影响,但随AT增大△H前者不变,后者降低。 相似文献
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Gui‐Ying Liao Liang Chen Xiao‐Yong Zeng Xing‐Ping Zhou Xiao‐Lin Xie E‐Jun Peng Zhang‐Qun Ye Yiu‐Wing Mai 《应用聚合物科学杂志》2011,120(4):2154-2165
Polymer blending is one of the most effective methods for providing new, desirable biocomposites for tissue‐engineering applications. In this study, electrospun poly(L ‐lactide)/poly(ε‐caprolactone) (PLLA/PCL) blend fibrous membranes with defect‐free morphology and uniform diameter were optimally prepared by a 1 : 1 ratio of PLLA/PCL blend under a solution concentration of 10 wt %, an applied voltage of 20 kV, and a tip‐to‐collector distance of 15 cm. The fibrous membranes also showed a porous structure and high ductility. Because of the rapid solidification of polymer solution during electrospinning, the crystallinity of electrospun PLLA/PCL blend fibers was much lower than that of the PLLA/PCL blend cast film. To obtain an initial understanding of biocompatibility, adipose‐derived stem cells (ADSCs) were used as seed cells to assess the cellular response, including morphology, proliferation, viability, attachment, and multilineage differentiation on the PLLA/PCL blend fibrous scaffold. Because of the good biocompatibility and nontoxic effect on ADSCs, the PLLA/PCL blend electrospun fibrous membrane provided a high‐performance scaffold for feasible application in tissue engineering using ADSCs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
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To investigate the interfacial interaction of AI(OH)3/polypropylene (PP) composites modified by in situ‐functionalized polypropylene (FPP), AI(OH)3/polypropylene (PP) composites containing a low AI(OH)3 content, modified by in situ‐grafted acrylic acid, were prepared by a one‐step melt‐extrusion process. The effect of in situ FPP on the crystallization and melting behavior, crystalline morphology of the composites, and interfacial interaction between the filler and PP was investigated. The crystallization and melting behavior and crystalline morphology of PP in the composites depended upon the interfacial physical [heterogeneous nucleation of AI(OH)3; cocrystallization and compabilitization of PP with in situ FPP] and the interfacial chemical interaction between both the components in the composites. FTIR results indicated that there exists a chemical reaction between AI(OH)3 and in situ FPP. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 110–120, 2002; DOI 10.1002/app.10270 相似文献
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Composites based on isotactic polypropylene (PP) and sisal fiber (SF) were prepared by melt mixing and injection molding. The melt mixing characteristics, thermal properties, morphology, crystalline structure, and mechanical behavior of the PP/SF composites were systematically investigated. The results show that the PP/SF composites can be melt mixed and injection molded under similar conditions as the PP homo‐polymer. For the composites with low sisal fiber content, the fibers act as sites for the nucleation of PP spherulites, and accelerate the crystallization rate and enhance the degree of crystallinity of PP. On the other hand, when the sisal fiber content is high, the fibers hinder the molecular chain motion of PP, and retard the crystallization. The inclusion of sisal fiber induces the formation of β‐form PP crystals in the PP/SF composites and produces little change in the inter‐planar spacing corresponding to the various diffraction peaks of PP. The apparent crystal size as indicated by the several diffraction peaks such as L(110)α, L(040)α, L(130)α and L(300)β of the α and β‐form crystals tend to increase in the PP/SF composites considerably. These results lead to the increase in the melting temperature of PP. Moreover, the stiffness of the PP/SF composites is improved by the addition of sisal fibers, but their tensile strength decreases because of the poor interfacial bonding. The PP/SF composites are toughened by the sisal fibers due to the formation of β‐form PP crystals and the pull‐out of sisal fibers from the PP matrix, both factors retard crack growth. 相似文献