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石蜡相变乳液是集储热与传热于一体的新型功能流体,具有广阔的应用前景。但石蜡相变乳液在降温时会出现过冷现象,极大降低了其储热与传热的性能。采用差示扫描量热法(DSC)测量石蜡相变乳液的过冷度受到升/降温速率的影响,且升/降温速率越大,测得过冷度越大。提出一种测量石蜡相变乳液过冷度的方法——平衡态比容法。该方法通过测量石蜡相变乳液在不同温度下的比容,以确定乳液中石蜡粒子在升/降温过程中的相变温度,并进一步求解石蜡相变乳液的过冷度。实验结果表明,本研究提出的平衡态比容法能准确测量石蜡相变乳液的过冷度,并从比容变化的角度揭示石蜡相变乳液过冷现象的机理。 相似文献
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石蜡乳液是集储热与传热于一体的新型功能流体,具有广阔的应用前景。但是石蜡乳液在降温时会出现明显的过冷现象,降低了其储热与传热的性能。针对这个问题,用镁-铝层状双金属氢氧化物(Mg-Al LDHs)代替化学表面活性剂,采用高速剪切乳化法,制备了石蜡含量为30%(质量)的O/W型Pickering乳液;分别采用扫描电子显微镜、激光粒度分析仪、流变仪、全能稳定性分析仪和差示扫描量热仪对所制得的石蜡Pickering乳液的微观形貌、粒度分布、黏度、稳定性和热力学性质进行了表征。结果表明,当Mg-Al LDHs的含量从1%(质量)增加到5%(质量)时,石蜡Pickering乳液的粒度减小,黏度升高,稳定性得到改善;在石蜡Pickering乳液中,Mg-Al LDHs纳米颗粒吸附在石蜡液滴表面,诱导石蜡在降温时异相成核结晶,从而抑制了其过冷现象;所制备的石蜡Pickering乳液的相变焓值约为56.6 J·g-1,在测试的温度范围内(30~70℃)的平均表观比热容为6.08 J·g-1·K-1,是纯水的1.45倍,具有良好的储热性能。 相似文献
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陈湘 《中国石油和化工标准与质量》2023,(1):63-65
采用差示扫描量热(DSC)技术,利用程序控温,测量热流变化,模拟GB/T2539—2008 《石油蜡熔点的测定冷却曲线法》的测试过程,实现了准确分析56号半精炼石蜡的熔点。与现行方法相比,该方法具有程序控温精准、分析用试样量少、重复性好、操作简单、分析时间短、化验员工作强度低等特点。 相似文献
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玻璃化相变及其对食品干燥贮藏影响的研究进展 总被引:1,自引:0,他引:1
在玻璃化转变的相关基础理论上,综述了影响玻璃化转变温度的主要因素,指出了玻璃化转变温度作为建立在动力控制过程的非平衡态基础上的物理化学参数,与水分含量和水分活度两重要指标相结合,可以用来解释玻璃化相变对干燥贮藏过程的影响,并对玻璃化相变温度的测定方法进行了总结评价。 相似文献
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利用差示扫描量热仪(DSC),分别对两种聚酯纤维——聚对苯二甲酸乙二酯(PET)和聚对苯二甲酸丙二酯(PTT)的热性能进行了测试,通过研究PET和PTT在不同升温速率下的热焓变化规律确定了升温速率,研究了PET的质量与热焓的线性关系,确定了PET-PTT混纺面料产品中各组分的定量分析方法。 相似文献
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《中国石油和化工标准与质量》2017,(24):51-53
本文依据国家标准GB/T 19466.3-2004,采用差示扫描量热法(DSC)测量尼龙6(PA6)的熔融焓,讨论了测量过程中的不确定度来源并对测量不确定度进行评定,结果表明DSC测定PA6熔融焓的不确定度的结果为50.92J/g,u95=2.06J/g(4.0%)。 相似文献
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采用差示扫描量热法测定了PVC管材的塑化度,考察了样品质量和升温速率对测试结果的影响,并计算了试验的精密度。结果表明:适宜的样品质量为20 mg,升温速率为20℃/min,试验的重复性和再现性均较好。 相似文献
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衡量氟化镓基玻璃稳定性的一种新判据 总被引:1,自引:1,他引:1
提出了改进的玻璃析晶动力学判据k(Tp0),它既能反映特征温度与玻璃抗析晶能力的关系,又不存在受升温速率影响的问题,而且保持了k(Tp)判据物理意义直观明确的优点。制备了x=5,10,15,25的20GaF3·15InF3·20CdF2·15ZnF2·(30-x)PbF2·xSnF2系列氟化镓基玻璃样品,用差示扫描量热法在不同加热速率下对此系列玻璃进行研究。用从改进的JohnsonMehlAvrami方程获得的k(Tp0)判据来估价玻璃的稳定性。结果表明:当x=10时玻璃的抗析晶能力最好,这与玻璃的实际熔制情况相符。 相似文献
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Tsuyoshi Imamura Koichi Saito Shinichi Ishikura Mamoru Nomura 《Polymer International》1993,30(2):203-206
The application of a continuous Couette-Taylor vortex reactor to continuous emulsion polymerization was studied. First, the mixing characteristics of the reactor were examined by the stimulus-response method. It was found that the reactor performance was similar to that of a continuous flow reactor consisting of more than 60 well-stirred tanks in series if the reactor was properly designed and operated near the critical Taylor number. It was also demonstrated by a comparison of the particle size distributions of the latexes produced in a batch reactor and in the continuous Couette-Taylor vortex reactor that the continuous reactor could produce latex particles with fairly narrow size distribution. Furthermore, since no stirrer is involved, this continuous reactor is suited for the purpose of avoiding coagulation of latex particles that are very sensitive to mechanical shear. 相似文献
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Emulsifier‐free emulsion polymerization of styrene was performed in the presence of small amount of methacrylic and itaconic acids as carboxylic acid monomers and potassium persulfate as an initiator at 70°C to prepare monodisperse polymer particles. Diameter of monomer swollen polymer particles (dpswol) was measured by dynamic light scattering for samples taken from the reaction mixture during the Intervals II and III of the emulsion polymerization. Graphically treatment of dpswol versus conversion data allowed us for the first time to directly determine the critical monomer conversion (xc), from which constant monomer concentration in the polymer particles (CMP) during the Interval II was then calculated. xc and CMP were obtained to be 0.379 and 5.68, respectively. CMP value is in good agreement with that obtained by centrifugation method and those reported in the literature for the similar system. Attempts were also made to evaluate the average number of growing chain per particle ( ) during the Interval II of emulsion polymerization of styrene. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
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A new method to determine monomer concentration in the polymer particles of emulsion polymerization systems by dynamic light scattering 下载免费PDF全文
Mahdi Abdollahi 《应用聚合物科学杂志》2018,135(7)
In the published article cited above, by considering corrections made on the eq. (19) which will be discussed in the next section, Figure 6 should be replaced with a following new Figure 1. Hence, and values of 0.379 and 5.68 mol.dm?3, respectively, on pages 1055, 1061, and 1062 should be changed to their accurate values of 0.426 and 5.29 mol.dm?3, respectively. 相似文献
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《Carbon》2014
We demonstrate the rheological percolation of carbon nanotubes (CNTs) in microstructured polymer matrices. Polymer/CNT composites are fabricated from polycarbonates with different molecular weights to diversify the microstructures, which vary with the polymer radius of gyration and entanglements. We propose a model for the dispersion of CNTs in polymer matrices, which explains the electrical and rheological properties. The percolation theory represented by a power–law relation cannot account for the rheological percolation of CNTs in this work. Therefore, we investigate the crossover points to provide a quantitative indication of the rheological percolation threshold of nanofillers in polymer matrices. For the first time, the rheological percolation threshold is determined experimentally with this definition. The effects of molecular weight and shear viscosity of the medium on the percolation of CNTs are demonstrated separately. 相似文献
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Giddappa Nagendrappa S. Subramanya Raj Urs S. Rajalakshmi 《Journal of the American Oil Chemists' Society》1998,75(12):1219-1221
Chloramine T (N-chloro-p-toluenesulfonamide sodium salt) and iodine (2:1, w/w) in carbon tetrachloride and acetic acid (1:1, vol/vol), referred to
as reagent (I) was found to be effective for the determination of Iodine value of edible oils. Reagent (I) reacted quantitatively
with the double bonds of oils of known weight. The reagent left unreacted after 20–25 min was titrated against standard sodium
thiosulfate solution (0.04 M) in presence of potassium iodide (10%, 5 mL). The difference in volume of sodium thiosulfate
solution consumed by reagent (I) without and with oil was a basis to calculate the iodine value of oils used. The iodine values
of different oils were also determined separately following the standard procedure of Wijs, and calculated iodine value was
obtained from the gas chromatographic profile of fatty acids. The iodine value obtained by the new method was in agreement
with the results of the standard methods. The results obtained indicate that the method could be a complementary or an alternative
to the Wijs method. 相似文献
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Giddappa Nagendrappa S. Subramanya Raj Urs S. Rajalakshmi 《Journal of the American Oil Chemists' Society》1998,75(9):1219-1221
Chloramine T (N-chloro-p-toluenesulfonamide sodium salt) and iodine (2:1, w/w) in carbon tetrachloride and acetic acid (1:1, vol/vol), referred to as reagent (I) was found to be effective for the determination of Iodine value of edible oils. Reagent (I) reacted quantitatively with the double bonds of oils of known weight. The reagent left unreacted after 20–25 min was titrated against standard sodium thiosulfate solution (0.04 M) in presence of potassium iodide (10%, 5 mL). The difference in volume of sodium thiosulfate solution consumed by reagent (I) without and with oil was a basis to calculate the iodine value of oils used. The iodine values of different oils were also determined separately following the standard procedure of Wijs, and calculated iodine value was obtained from the gas chromatographic profile of fatty acids. The iodine value obtained by the new method was in agreement with the results of the standard methods. The results obtained indicate that the method could be a complementary or an alternative to the Wijs method. 相似文献