聚氯乙烯中空纤维膜的研制

以聚氯乙烯（PVC）为原料，N－甲基－2吡咯烷酮（NMP）作溶剂，研究PVC／NMP体系的粘度与溶解温度和PVC含量的关系，定性分析了纺丝细流中的溶剂扩散与中空纤维膜结构之间的关系，同时，通过纺丝动力学原理，讨论了纺丝工艺参数对膜性能的影响，文中描述的聚氯乙烯中空纤维膜的最大透水率为80mL/(cm^2.h)，截留率85％－95％（截留牛血青蛋白分子量为67000）。     

用正交设计研究PVDF印VC／PMMA共混中空纤维膜

制备了PVDF（聚偏氟乙烯）／PVC（聚氯乙烯）／PMMA（聚甲基丙烯酸甲酯）三元共混中空纤维膜，讨论了影响膜性能的主要因素．正交实验结果表明：在PVDF／PVC／PMMA体系中，聚合物总浓度是影响膜的水通量的主要因素；PVDF浓度对膜强度影响最大；PMMA对膜的亲水性有较大的贡献．得到优化的制膜条件为：铸膜液中PVDF：PVC：PMMA=7：1．2：1．8（质量比），聚合物溶质的总质量分数为17％；添加剂吐温-80的质量分数为6％．     

二氧化硅填充聚氯乙烯杂化膜研究

在聚氯乙烯(PVC)纺丝液中适度加入二氧化硅(SiO2)无机粒子,以溶液相转化法制得PVG-SiO2杂化纤维膜.观察纤维膜的形貌,分析讨论SiO2含量和喷丝头拉伸比,对于产生界面微孔的作用及其与膜结构和性能的关系.结果表明,适量SiO2的加入,既可提高PVC纺丝液的稳定性,又使纤维膜产生界面微孔;在喷丝头拉伸比为2:1,SiO2含量为45%时,纤维膜中可产生较为明显的界面微孔结构,从而有效地提高其通透性.     

用正交设计研究PVDF/PVC/PMMA共混中空纤维膜

制备了PVDF(聚偏氟乙烯)/PVC(聚氯乙烯)/PMMA(聚甲基丙烯酸甲酯)三元共混中空纤维膜,讨论了影响膜性能的主要因素.正交实验结果表明:在PVDF/PVC/PMMA体系中,聚合物总浓度是影响膜的水通量的主要因素;PVDF浓度对膜强度影响最大;PMMA对膜的亲水性有较大的贡献.得到优化的制膜条件为:铸膜液中PVDF∶PVC∶PMMA=7∶1.2∶1.8(质量比),聚合物溶质的总质量分数为17%;添加剂吐温-80的质量分数为6%.     

PASS溶液性质对静电纺丝可纺性及纤维形貌的影响

选取苯酚和四氯乙烷的混合物作溶剂,采用不同分子量的聚芳硫醚砜(PASS)树脂配制不同浓度的溶液,考察了溶液动态流变性能、表面张力、导电率对静电纺丝可纺性以及纤维形貌的影响。结果发现溶液的可纺性有实数黏度依赖性,纤维直径受溶液黏度的影响最大。     

表面活性剂吐温-80用量对硬质闭孔型三聚氰胺泡沫的影响

以三聚氰胺、甲醛为原料合成可发性密胺树脂并制备出表面活性剂(吐温-80)含量不同的泡沫样品。通过树脂表面张力测试,发现随着吐温-80含量增加,树脂表面张力呈现先减小后不变的趋势。通过对SEM、力学测试的对比分析,研究了吐温-80含量对泡沫的微观结构及压缩性能的影响。结果显示,当吐温-80含量9%时,随着其含量的增加,泡孔直径逐渐减小,尺寸分布更加均匀,泡壁膜撕破程度增加,但吐温-80含量达到9%后,泡孔直径反而增大,均匀度下降。同时研究发现泡沫的压缩性能受到泡沫微观结构的影响,在吐温-80用量为5%时,泡沫的压缩强度和弹性模量分别达到最大值。泡沫的吸声性能受到泡沫结构的影响,随着闭孔率减小,吸声性能提高。     

PVC改性的各向同性沥青基碳纤维的研究

以各向同性沥青为原料,添加质量分数0.2%~1.0%不同型号的PVC,考察了不同型号、不同质量分数的PVC对沥青的软化点、可纺性和纺丝温度的影响。结果表明:添加PVC提高了沥青的软化点和纺丝温度,降低了沥青可纺性。将不加PVC的沥青和添加PVC的沥青分别经熔融纺丝、不熔化及碳化处理得到沥青基碳纤维,对比了不添加PVC沥青纤维(CF)和添加PVC改性沥青纤维(PCF)两种碳纤维的拉伸强度,用热重分析TG和红外光谱IR分析了不熔化过程。结果显示与CF相比,PCF在较低的不熔化温度和较短的恒温时间内就能够达到较佳不熔化效果,这表明PVC对缩短沥青纤维的不熔化时间有明显的作用。     

电纺制备基于棉纤维素的多组分聚合物纤维

通过在棉纤维素溶液中加入聚偏氟乙烯(PVDF)与聚乙烯醇(PVA)改善纤维素纺丝液的可纺性,针对纤维素电纺难的问题提供一种解决方法。在使用PVA与PVDF促进纤维素纺丝液可纺性持续提升的过程中,成功得到了形貌良好、表面光滑的超细纤维。随着PVA的引入,多组分超细纤维膜的亲水性也得到了明显提高,电纺膜的接触角从139.3°降低至93.9°。     

复合模板剂下制得介孔TiO2光催化活性的研究

以吐温-80（Tween-80）和司班-80（Span-80）为复合模板剂，采用溶胶-凝胶（sol-gel）工艺制得介孔TiO2。通过对甲基橙溶液进行光催化降解试验表明：模板剂的种类与用量、光照距离和甲基橙溶液的原始浓度等因素对所制得介孔TiO2试样的光催化活性产生明显的影响。实验结果证明，本研究所得介孔TiO2材料具有较高的光催化活性，500℃下煅烧5h制备的样品在2．5h内可使浓度为0．02g／L的甲基橙溶液降解率达到94．7％，明显高于市售纳米TiO2粉体的降解率78．1％；通过X-ray衍射分析获知所制TiO2为锐钛矿型。     

分散剂对淀粉接枝P(AA/AM)反相悬浮聚合的影响

以玉米淀粉、水溶性单体丙烯酸(AA)和丙烯酰胺(AM)为原料,环己烷为连续相,N,N′-亚甲基双丙烯酰胺(MBA)为交联剂,过硫酸钾(KPS)作为引发剂,采用反相悬浮聚合法合成淀粉接枝P(AA/AM)高吸水性树脂微球。考察了分散剂种类和用量对聚合体系及树脂吸液性能和平均粒径的影响,研究表明,在淀粉接枝P(AA/AM)反相悬浮聚合体系中,单一分散剂司班80的分散效果最好,且选用复合分散剂的分散效果优于选用单一分散剂,当反应体系分散剂为司班65/司班80复配时,体系的分散性最优。分散剂用量对吸盐水倍率的影响趋势与吸去离子水大致一样,且分散剂用量为6%时都达到最大,有助于吸液速率的提高,随着体系中司班65/司班80分散剂用量的增加,树脂平均粒径趋于变小。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。