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991.
Thermal and flammability performance of polypropylene composites containing melamine and melamine phosphate‐modified α‐type zirconium phosphates 下载免费PDF全文
Deng Liu Guipeng Cai Juan Wang Xiaofang Tan Hongdian Lu Shiyun Zhang Qingqing Dai 《应用聚合物科学杂志》2014,131(10)
In this article, melamine (MA) and melamine phosphate (MP) have been intercalated into α‐type zirconium phosphate (α‐ZrP) interlayer spaces. The structure and thermal properties of the corresponding powders, MA‐ZrP and MP‐ZrP, were ascertained by X‐ray diffraction, Fourier transform infrared spectra, X‐ray photoelectron spectroscopy measurement, and thermogravimetric analyses (TGA). Furthermore, polypropylene (PP) and its intumescent flame retardant (IFR) composites containing the two organically modified α‐ZrP powders using maleic anhydride‐grafted PP (JPP) as compatibilizer were fabricated by melt blending. The results from TGA and cone calorimetry demonstrated that PP/JPP and PP/JPP/IFR composites containing MA‐ZrP and MP‐ZrP exhibited better thermal stability and burning behavior in comparison with their corresponding counterparts, PP/JPP and PP/JPP/IFR, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40254. 相似文献
992.
The crystallization morphology evolution of polyoxymethylene/poly(ethylene oxide) blend micropart prepared under microinjection molding conditions 下载免费PDF全文
This article is the first study on the microinjection molding and the effects of the microprocessing parameters on the crystallization and orientation of polyoxymethylene/poly(ethylene oxide) (POM/PEO) blend, which has better toughness and self‐lubricity compared with the neat POM and therefore is a better candidate material for making microparts like microgears with higher performances. The crystalline and phase morphologies were investigated by polarized light microscope (PLM), differential scanning calorimeter (DSC) and scanning electron microscope (SEM). The crystalline orientation of the microparts was evaluated by two‐dimensional wide‐angle X‐ray diffraction (2D‐WAXD) and Herman's orientation function. The experimental results showed that both POM and POM/PEO microparts prepared by microinjection molding exhibited three distinct layers, i.e., skin layer, shear layer and core layer, while the latter had thicker shear layer but thinner skin layer and core layer. PEO was well dispersed in POM matrix. The spherulite size, the melting point as well as the crystallinity of POM in the POM/PEO blend decreased due to the interference of PEO in the crystallization of POM. A shish‐kebab structure was observed in the shear layers of the POM/PEO microparts. The effects of processing parameters on the thicknesses of different layers of the POM/PEO microparts were investigated. With increase of the injection speed or decrease of the mold temperature, the skin layer and the core layer became thicker, while the shear layer and the oriented region became thinner. However, the influence of the injection pressure was not obvious. Also, the processing parameters affected the crystalline orientation of the POM/PEO microparts. With increase of the injection speed or decrease of the mold temperature, the orientation function f decreased, indicating a lower degree of orientation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40538. 相似文献
993.
Curing characteristics,morphology, thermal stability,mechanical properties,and irradiation resistance of methylethylsilicone/methylphenylsilicone rubber blends 下载免费PDF全文
Methylethylsilicone rubber (MESR)/methylphenylsilicone rubber (MPSR) blends were cured with 2,5‐dimethyl‐2,5‐di(tert‐butylperoxy)hexane. The curing characteristics, morphology, thermal behaviors, mechanical properties at different temperatures, radiation resistance, and thermal aging resistance of the MESR/MPSR blends were investigated. The results show that a high MPSR content could decrease the optimum curing time and improve the scorch safety. Dynamic mechanical analysis revealed that the glass‐transition temperature of the blends increased slightly with the addition of MPSR. Scanning electron microscopy showed that MESR and MPSR had good compatibility in the blends. Thermogravimetric analysis indicated that the thermal stability of the blends increased with increasing quantity of MPSR. The blends had excellent mechanical properties at low temperatures. However, these properties were significantly reduced when the temperature was increased. Moreover, changes in the mechanical properties decreased with increasing MPSR content at high temperatures, especially at temperatures higher than 100°C. In addition, the radiation resistance and thermal aging resistance of the blends increased with increasing MPSR content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40529. 相似文献
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995.
Subsolidus pyrochlores with the proposed formula, Bi3+(5/2)xMg2−xNb3−(3/2)xO14−x (0.14≤x≤0.22) were successfully synthesised at the firing temperature of 1025 °C using conventional solid-state reaction. The excess Bi3+ charge was offset by removal of relative proportion of Mg2+ and Nb5+ together with creation of oxygen non-stoichiometry in order to preserve electroneutrality of the system. These samples were crystallised in cubic structure with space group of Fd3m, No. 227 and their refined lattice parameters were in the range of 10.5706 (3)–10.5797 (7) Å. The surface morphologies of the samples as confirmed by scanning electron microscopy analysis were of irregular shaped grains while their crystallite sizes of ~30–85 nm were calculated using the Scherrer equation and the Williamson–Hall method. No thermal event was discernable indicating these pyrochlores were thermally stable within a studied temperature range of ~30–1000 °C. The recorded dielectric constants of Bi3+(5/2)xMg2−xNb3−(3/2)xO14−x (0.14≤x≤0.22) subsolidus pyrochlores were generally above ~160 and their dielectric losses were in the order of 10−4–10−3 at the frequency of 1 MHz and temperature of ~30 °C. Meanwhile, these ceramic samples also exhibited negative temperature coefficient of relative permittivity between −528 and −742 ppm/°C in the temperature range of ~30–300 °C. 相似文献
996.
There are growing evidences that Sr-containing calcium phosphate biomaterials can promote better osteo-precursor cell attachment and proliferation than pure calcium phosphate biomaterials. In this study, attempts were made to fabricate two kinds of Sr-substituted calcium phosphate (Ca–Sr–P) coatings on pure magnesium in electrolyte solutions with differing amounts of Sr(NO3)2 for biomedical application. The surface microstructure, composition and chemistry of the coatings were characterized by Scanning Electron Microscope (SEM), Energy-dispersive X-ray Spectroscopy (EDS), and X-ray Diffractometer (XRD), respectively. In addition, electrochemical and immersion tests were performed to evaluate the corrosion resistance of the Ca–Sr–P coated magnesium in phosphate buffered saline solution (PBS). 相似文献
997.
Y.S. Lim Y.P. Tan H.N. Lim N.M. Huang W.T. Tan M.A. Yarmo Chun-Yang Yin 《Ceramics International》2014
A simple method based on potentiostatic polymerization was developed for the preparation of ternary manganese oxide-based nanocomposite films. The ternary nanocomposites, which were characterized using x-ray diffraction spectroscopy and x-ray photoelectron spectroscopy, showed that the manganese oxide within the film consisted of MnO2 and Mn2O3. Electrochemical measurements showed that the ternary nanocomposite electrode exhibited high specific capacitance (up to 320.6 F/g), which was attributed to the morphology of a polypyrrole/graphene/manganese-oxide (PPy/GR/MnOx) ternary nanocomposite. The experimental approach maximized the pseudocapacitive contribution from redox-active manganese oxide (MnOx) and polypyrrole (PPy), as well as the electrochemical double layer capacitive (EDLC) characteristic from graphene (GR) sheets. Long cyclic measurements indicated that the specific capacitance of the ternary nanocomposite film could retain 93% of its initial value over 1000 charge/discharge cycles, in the potential range of −0.2 to 0.7 V versus silver/silver chloride electrode (Ag/AgCl). 相似文献
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999.
1000.
文章阐述了剂油比在催化裂化中的重要地位,分析了剂油比对反应过程的影响以及提高剂油比的手段,并通过上述方面对实际操作过程中如何合理调节这一重要参数提出指导性意见,以求达到平稳、合理的控制催化裂化的目的。 相似文献