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沃特世公司推出了一种新型的聚合物色谱分析技术,能够更加快速地获取更准确的聚合物分子量信息。该系统将明显提高聚合物峰的分辨率,尤其是在分析低分子量聚合物和低聚物时,其速度比传统凝胶渗透色谱(GPD)要快20倍。 相似文献
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多年的观察和研究初步证实,自然界有机人合物可能存在的合理分子式在种类和数量上是有限和可知的,对分子量1000以下的式范围了符合实际的界定方法和计算式。据此已经人工书写或计算机打印出分子量16-800、只C、H、O、N分子式203470个,初步估算分子量到1000时共有分子式474000个。若以分子量为横坐标,分子式中的碳原子数为纵坐标作图,除个别外,这些分子式均分布在坐系的一个三角形区域内,因而称 相似文献
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质谱能快速而准确地给出被测样品分子量的绝对值。普通质谱不能用于高分子聚合物分析的主要原因是高分子的不挥发性利不稳定性,采用软离子化技术可在一定技术程度上克服上述困难。 相似文献
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熔融指数仪性能比较与检修 总被引:1,自引:0,他引:1
熔体流动速率可以表征热塑性聚合物熔体流动的性能,通过测量可以了解聚合物的分子量及其分布、交联程度和加工性能,测量熔体流动速率的仪器称为熔融指数仪。熔融指数仪在塑料行业中使用普遍、作用重要的一种分析仪器,本中心现有熔融指数仪5个品牌,本文概述从建厂初期直至目前,各个时期陆续添置的指数仪的概况、结构、性能比较,在使用过程中出现的显示、实测和设定值之间不一致情况时的温度校正方法,出现故障时的维修和平时的保养。 相似文献
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本文对奥地利EBEWE公司及国内8家药厂生产的脑活素类注射液的肽色谱图及分子量分布进行分析比较。结果表明,该产品的分子量都低于1万,其组成及分布情况各不相同。由此反映出各厂家工艺的不同,建议有关部门应组织统一的考究并制订出相应的质量标准。 相似文献
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The oxidation behaviour of synthetic oils has been extensively studied during recent decades, and there is general agreement on both the mechanism and products of the oxidative degradation of oils. However, the other phenomenon of oil ageing, polymerization has been little studied. These polymers are responsible for the increase of viscosity, production of sludge and the formation of deposits. In the investigation reported here, oligomers have been isolated and studied at an early ageing stage. The dependence of viscosity on the degree of polymerization is demonstrated. A polymerization mechanism and a monomer for polyolester oils are proposed and discussed. 相似文献
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电喷雾电离质谱在糖甙化合物中的应用 总被引:3,自引:0,他引:3
本文利用电喷雾电离质谱技术测定了十六个带有1—5个不同糖基的甾体皂苷和三萜皂甙化合物的分子量。根据这些化合物的糖基类型和碎片特点对该类化合物的结构提供了证据。同时对麦仙翁种子中的活性天然物之一—麦仙翁甙甲用ESIMS证据证实了它的结构 相似文献
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纳米锌填充超高分子量聚乙烯复合材料微动摩擦磨损性能 总被引:1,自引:0,他引:1
利用热压烧结法制备不同含量纳米锌填充超高分子量聚乙烯(UHMWPE)复合材料,采用微动摩擦磨损试验机研究干摩擦条件下纳米锌含量对复合材料微动摩擦磨损性能的影响。利用场发射扫描电子显微对复合材料断面进行分析,采用扫描电子显微镜对材料磨损表面及钢球进行表征,探讨复合材料的磨损机制。研究结果表明:随着纳米Zn含量的增加,复合材料的摩擦因数和磨损率均表现为先降低后升高;当纳米Zn质量分数为1%时复合材料具有最低的摩擦因数和磨损率,且对偶钢球表面形成连续的转移膜;复合材料的磨损机制主要为黏着磨损和磨粒磨损。添加锌纳米颗粒,可以提高UHMWPE复合材料的微动摩擦磨损性能,当纳米锌质量分数为1%时,复合材料具有最低的摩擦因数和最优的耐磨损性能。 相似文献
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人工髋关节超高分子量聚乙烯(UHMWPE)关节面磨损仍是影响置换关节远期寿命的主要因素,其仿真建模是对关节模拟机磨损测试手段的重要补充,也是实现置换关节临床前性能评估的有效方法。由多向运动产生的交叉剪切效应是影响UHMWPE磨损的主要原因之一,也是仿真建模的关键。现有理论方法将磨损深度确定为滑动距离的函数,并将90°交叉剪切运动条件下的磨损作为度量基准计算不同角度下的交叉剪切效应,但尚未考虑接触应力变量对磨损深度的影响。针对以上问题,提出了在垂直交叉剪切运动条件下将磨损深度表示为摩擦功函数的方法。该方法利用UHMWPE摩擦因数与接触压力的定量关系计算摩擦因数并确定摩擦功,解决了UHMWPE磨损交叉剪切效应中滑动距离与接触应力的耦合问题。基于磨损仿真新模型研究了36 mm直径的交联UHMWPE髋关节,并与已有ProSim模拟机试验结果进行了验证。结果显示该仿真模型可准确计算体积磨损和线性磨损等磨损量以及髋关节载荷方向改变对磨损的影响。磨损新模型为进一步仿真模拟奠定了有效基础。 相似文献
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The dynamic shear properties of molecularly-thin films of unfunctionalized and end-functionalized (telechelic) Fomblin-Z perfluoropolyalkylether
(PFPAE) melts with number-average molecular weight M
n≈ 3000−4000 g,mol-1 have been studied at shear rates of 10-2−105 s-1 at normal pressures of 1 and 3 MPa. The shear responses are compared to measurements on end-functionalized polymers of the
same chemical composition but lower molecular weight, M
n≈ 2000 g,mol-1. The predominantly elastic response and high shear moduli of the confined film of unfunctionalized polymer, Fomblin Z03,
suggest that it forms a structure likely to solidify already at low pressure. Its lubricating properties are less favorable
than the ones found for hydroxyl- (DOL) and piperonyl-terminated Fomblin-Z (AM2001, AM3001), where associated molecules form
a structure less prone to solidification under confinement. The thickness of the compressed films of the end-functionalized
polymers increased more strongly with molecular weight than as M
n
0.5
. The shear moduli were found to be larger, the higher the molecular weight, indicating slower relaxations. At a normal pressure
of 3 MPa, these films solidified and displayed stick–slip as seen already at 1 MPa in the Z03 film. The limiting shear stress
of the unfunctionalized Z03, σ > 3 MPa, exceeded by an order of magnitude the limiting shear stress of all of the end-functionalized
polymers. The limiting shear stress of the hydroxyl-terminated polymer was larger than that of the piperonyl-terminated polymer.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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The evaporation rate at ambient pressure as a function of molecular weight has been measured for two functionalized perfluoropolyether
lubricants, Zdol and Zdol‐TX, using thermogravimetric analysis (TGA). The temperature dependence of the evaporation rate is
well characterized by a zero‐order Arrhenius expression, allowing determination of the molecular weight dependence of the
pre‐exponentials and activation energies. These Arrhenius parameters can then be used to extrapolate the evaporation rate
back to temperatures where it is too small to be directly measured. The extrapolated evaporation rates at 200°C are combined
with Raoult's law to predict the vapor phase molecular weight distribution of Zdol over a polydisperse liquid phase, which
is shown to be in reasonable agreement with the measured vapor phase distribution. The evaporation rate of Fomblin Z fluids
is also shown to be strongly dependent on the functional endgroup for a given molecular weight.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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研究了大气中低分子量醇类化合物的气相色谱测定方法,进行了线性范围,精密度和准确度实验,结果表明:该方法具有简便快捷,准确灵敏的特点,适合于大气污染事故应急监测。 相似文献