采用DSC快速测试聚乙烯密度的方法研究

密度法是测试聚乙烯密度的常规方法,但密度梯度液的配制相对复杂并且测试观测时间长,降低了分析效率。本文通过采用示差扫描量热仪(DSC)测试一系列密度已知的中低密度聚乙烯的结晶度,发现所测得结晶度跟密度有着良好的线性关系,进一步得出线性方程,为测知聚乙烯样品的密度和结晶度提供了快速分析方法,该方法对高密度聚乙烯同样适用。     

密度天平法测定聚乙烯树脂密度方法的探讨

通过试验考察了密度天平法测试聚乙烯树脂密度的重复性和准确性, 同时对比了密度梯度法测定聚乙烯密度的结果,两种方法测试结果能满足现密度方法要求的准确度和精密度范围,重复测定两结果之差：高密聚乙烯树脂≤0.0005 g/cm3,低密聚乙烯树脂≤0.0003 g/cm3。两种方法可以互替,相互补充,并讨论了影响密度天平法测定因素。     

国能新疆化工有限公司研发出测试聚乙烯密度新方法北大核心

国能新疆化工有限公司研发出利用U型管振荡法测试聚乙烯密度的新方法。采用该方法测试聚乙烯密度能满足GB/T 1033.2—2010要求的准确度和精密度,且测试结果与密度梯度柱法无显著差异;该方法不需要已校准的玻璃浮子,其密度测试范围可以覆盖所有聚乙烯密度;该方法分析步骤简单、准确快速,测定过程影响因素相对较少,可为生产装置及时提供准确可靠的密度测试结果。     

聚乙烯密度测试影响因素的研究

分别对聚乙烯材料密度测试中是否采用熔条、是否水煮以及熔融挤出时采用的载荷对测试结果的影响进行了系统的研究与分析，并指出了不同的试样类型、不同的试样处理方法及不同的测试条件对聚乙烯密度测试结果的影响。     

密度梯度柱法测定聚乙烯树脂密度

采用密度梯度柱法测定聚乙烯树脂的密度,研究影响该方法测定聚乙烯树脂密度准确性的因素.实验结果表明:样品的处理方式、密度梯度柱的使用温度、密度梯度柱的配制效果等因素均可对测试结果造成影响.针对这些影响因素,提出了相应措施,并确定了适用于测定密度范围(0.9530±0.0030)g·cm-3高密度聚乙烯树脂密度梯度柱的配制...     

中国专利

包含茂金属生产的树脂和铬生产的树脂的聚乙烯共混物的制备方法本发明涉及的均质聚乙烯的制备方法包括:a)在茂金属催化剂存在下,在反应器中生产第一聚乙烯树脂,该聚乙烯树脂具有0.942~0.970 g/cm3的密度和0.5~150.0 g/10 min的熔体流动速率(MFR),其中,MFR按照ASTM D 1238—2010在190℃,21.6kg的负荷条件下测试,密度按GB/T 1505—2010测试。b)在铬催化剂存在下,在反应器中单独生产第二聚乙烯树脂。c)将第一聚乙烯树脂和第二聚乙烯树脂物理共混生产均质聚乙烯,该均质聚乙烯至少包含质量分数为25%的第一聚乙烯树脂。     

测试条件对测定管材类聚乙烯树脂等温氧化诱导时间的影响

等温氧化诱导时间是检测聚乙烯燃气管材的一项重要指标。文章以4种管材类聚乙烯树脂为样品,分别分析了测量温度和试样制备方式对管材类聚乙烯树脂等温氧化诱导时间测试结果的影响。根据评价效果和实际测试需要给出了适合管材类聚乙烯树脂等温氧化诱导时间测定的试验条件。对规范塑料产品等温氧化诱导时间的测量工作具有借鉴意义。     

γ射线液位测量中的密度校正

高压聚乙烯装置高压分离器γ射线液位测量中,随机的气相密度使γ射线强度造成大量衰减。本文用最小二乘法原理确定密度校正式中的系数,由常规仪表组成带有密度校正的液位测量控制系统,有效地提高了测量精度。     

气固流化床中声发生机理及在工业装置中的应用

利用声测量技术,结合频谱分析,建立了颗粒碰撞的声波频率模型,可定量描述声波主频随颗粒粒径、弹性模量和密度的变化规律.通过改变流化颗粒的粒径、弹性模量参数和密度,发现声波主频与频率模型计算值之间的最大偏差为8.3%,说明声波主频可以代表颗粒在壁面的碰撞频率.讨论了热态和冷态条件下声波主频之间变化规律,通过对弹性模量参数的校正,声测量技术可以用于预测工业装置中物料的平均粒径变化,并将该模型应用于线性低密度聚乙烯、高密度聚乙烯和双峰聚乙烯工业生产装置中的平均粒径测量,发现与传统的取样筛分方法所得测量结果十分接近.同时,发现当系统产生聚合物颗粒结块时,声波主频将急剧降低,声波频谱的能量分布将明显集中增大,这可作为判断流化床稳定运行的一个判据.     

23MHz核磁测定聚乙烯密度的影响因素

采用聚乙烯标准试样,将用密度梯度柱法测试的密度值与在共振频率为23 MHz的核磁共振波谱仪(简称23 MHz核磁)上测得的核磁共振时域信号建立标准曲线。以此标准曲线为准,在23 MHz核磁上研究了温度、试样量、预热时间、添加剂对聚乙烯密度的影响。结果表明:23 MHz核磁的核磁管恒温温度对聚乙烯密度的影响最大;适宜的试样量为4.0～5.5 g;在干浴恒温器中预热60 min后的密度值基本稳定;粒料测定结果的整体离散程度小于粉料。     

Internal particle size distribution of biofuel pellets

Several methods for disintegration of biofuel pellets were tested and compared for their ability to break up the pellets into the original particles of the raw material. Analyses performed on softwood pellets and straw pellets concluded that wet disintegration in water at ambient temperature is insufficient for a determination of the internal particle size distribution of wood- and straw pellets. When the wet disintegration was performed with water heated to the boiling point and coupled with mechanical disintegration in terms of stirring a more complete disintegration of the pellets was obtained. Based on the results obtained in the initial study a round robin was set up including six European laboratories where the selected method was tested. In the round robin test the method combining heated water and stirring of the slurry was tested on solid biofuel pellets produced of comminute straw, deciduous wood and coniferous wood respectively. With the method a satisfactory disintegration was obtained of all three types of pellets.Further wet disintegration of coniferous pellets was compared to a dry disintegration using a hammer mill. The dry disintegration of the coniferous pellets resulted in smaller particle sizes compared to the wet disintegration using heated water and stirring of the slurry indicating a further disintegration of the original particles in the hammer mill process.Overall the wet disintegration combined with mechanical impact was found to be the most suitable method for disintegration of solid biofuel pellets. Combined with sieving analysis the method gives realistic image of the internal particle size distribution of solid biofuel pellets.     

HPLC法快速测量市售卫生球中萘的含量

萘是一种潜在的致癌物.市售卫生球中萘含量的测定受到关注.多采用气相色谱法测定卫生球中的萘含量.探讨了HPLC法用于测定卫生球中萘的含量的方法.以甲醇为流动相,用纯萘为标准物质,建立了HPLC法测量萘含量的标准曲线,用HPLC法测定了在市场上随机购买的5种樟脑丸中萘的含量.结果表明,萘的含量都较高.     

1-脱氧野尻霉素控释微丸的制备工艺优化及其药动学研究

1-脱氧野尻霉素控释微丸采用挤出滚圆和流化床方法进行制备。首先使用羟丙基甲基纤维素和微晶纤维素等辅料制备分散体、丸芯,再使用羟丙基甲基纳米纤维素邻苯二甲酸酯作为主要包衣材料进行包衣,并装入胶囊。采用SEM观察微丸的微观形态,以及测定其产率、脆碎度、密度、水分含量和粒径分布等物理性质,研究结果显示微丸性质符合中国药典标准规定。在体外释药试验中,溶出介质和放置方式对药物释放无显著影响,释放过程符合Baker-Lonsdale模型。对比研究1-脱氧野尻霉素原料药、分散体微丸和控释微丸在比格犬体内的控释特性,结果表明：与1-脱氧野尻霉素原料药相比,分散体微丸和控释微丸分别使1-脱氧野尻霉素的生物利用度提高了183.37%和243.87%。此外,1-脱氧野尻霉素控释微丸的体内-体外研究的相关性分析可知体外溶出和体内吸收之间呈现良好的线性关系。     

PE固相法氯化反应的研究

采用固相氯化法制备改性CPE,实验结果表明反应温度、氯含量及引发剂用量对CPE的力学性能有很大影响,在PE固相法氯化反应过程中,其HCl的释放速率与PE及Cl2的量有关。     

一种快速测定湿法磷酸固含量的方法

介绍计算法测定湿法磷酸固含量的原理,通过测定磷酸中固相物的真密度、磷酸样品的密度和清磷酸的密度,计算可得出固含量。该测定方法快速、简便,测定结果与国家标准法测定的结果比较无显著性差异,准确度能达到生产控制需要,可用于磷肥生产中磷酸固含量测定。     

Fe-Cr高变催化剂的模压成型和机械强度的动态研究

引　言目前国内绝大多数工业催化剂的成型过程工艺都是由经验决定的 ,往往缺乏催化剂成型基础理论的系统研究 .近年来 ,科学家对于催化剂成型进行了一些有益的研究和探索 .朱洪法[1] 对催化剂成型过程进行了论述 .李永丹[2 ] 研究了铁氧化物催化剂的机械强度和模压成型过程 ,认     

Comparison of flow characteristics for dilute phase pneumatic conveying for two different plastic pellets

A series of dilute phase pneumatic conveying experiments using two different types of plastic pellets has led to the determination and development of distinguishing flow characteristics. Separate experiments on polystyrene and polyolefin pellets captured pressure-drop fluctuations and values at two different measuring points—one at the lower horizontal section of the transporting pipe and another at the upper section and at two different solid-loading ratios for each material.Also, comparison and analysis of the pressure-drop fluctuations and values obtained from the experiments were carried out under the same solid-loading ratio and blower rotational speed for both materials. Basic pressure drop calculations were made to find pressure drop due to pure gas, and that due to the presence of solids using a solid friction factor. In addition, the power spectral density analysis, and the wavelet analysis were conducted for both materials to evaluate the flow characteristics.     

MEASUREMENTS OF EFFECTIVE DIFFUSIVITY IN LARGE-PORE PERMEABLE PELLETS WITH VARIOUS GEOMETRIES USING THE CHROMATOGRAPHIC METHOD

Mathematical models for solid cylinder and hollow cylinder pellets, where intraparticle convection was considered, have been established and solutions in the Laplace domain have been obtained. Consequently, the equivalence between the hollow cylinder and the slab characteristic dimensions was presented for the first-order-reaction/diffusion/convection problem. A modified chromatographic method has been developed to measure the intraparticle diffusivity in solid cylinder pellets. The axial dispersion of the column packed with the hollow cylinder pellets was measured and a correlation for the Peclet number versus Reynolds number has been obtained. Intraparticle convection has been measured with large pore sphere pellets which present a “foam structure” by using the conventional chromatographic method. Intraparticle Peclet numbers and the permeability of this pellet were determined.     

EFFECTIVE DIFFUSIVITIES IN CALCIUM CARBONATE AND CALCIUM OXIDE SOLID PELLETS

Effective diffusivities in calcium carbonate and calcium oxide pellets have been determined by steady state diffusion method. It has been found that the diffusion in the solid pellets is controlled both by molecular and Knudsen mechanisms. The value of the tortuosity factor obtained is approximately 2 for these solid pellets.     

EFFECTIVE DIFFUSIVITIES IN CALCIUM CARBONATE AND CALCIUM OXIDE SOLID PELLETS

Effective diffusivities in calcium carbonate and calcium oxide pellets have been determined by steady state diffusion method. It has been found that the diffusion in the solid pellets is controlled both by molecular and Knudsen mechanisms. The value of the tortuosity factor obtained is approximately 2 for these solid pellets.