共查询到20条相似文献,搜索用时 843 毫秒
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以蔗渣木聚糖为主要原料,没食子酸为酯化剂,在丙酮溶剂中合成蔗渣木聚糖没食子酸酯。然后在交联剂N,N′-亚甲基双丙烯酰胺和引发剂过硫酸铵作用下,引发抗坏血酸(LME)、丙烯酸(AA)、丙烯酰胺(AM)与蔗渣木聚糖没食子酸酯发生接枝共聚反应,合成了蔗渣木聚糖没食子酸酯-g-LME/AA/AM复合功能性衍生物。考察了接枝共聚反应时间、反应温度、引发剂浓度、蔗渣木聚糖没食子酸酯与混合单体质量比对接枝率(G)、接枝效率(GE)的影响。确定了适宜的接枝共聚反应条件:反应时间5h,反应温度45℃,引发剂浓度0.008mol/L,m(蔗渣木聚糖没食子酸酯)∶m(混合单体)=1∶2。在该反应条件下,G可达31.02%,GE可达76%。采用傅里叶红外光谱仪、扫描电子显微镜、X射线衍射仪对蔗渣木聚糖和产物的结构进行了表征。 相似文献
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以蔗渣木聚糖(BX)为主要原料,过硫酸铵为引发剂,N′,N-亚甲基双丙烯酰胺(MBAM)为交联剂,在水溶液中与丙烯酰胺(AM)、甲基丙烯酸甲酯(MMA)接枝共聚,合成了AM/MMA-BX交联型接枝共聚物。考察了BX与混合单体(AM-MMA)质量比、单体配比、引发剂浓度、反应温度、反应时间、反应体系溶剂用量、交联剂MBAM用量等对单体转化率(C)、接枝率(G)和接枝效率(GE)的影响。实验确定的较佳反应条件为:m(BX)∶m(AM-MMA)=1∶1,单体配比n(AM)∶n(MMA)=2∶1,引发剂浓度0.043mol·L-1,反应温度55℃,反应时间8.0h,m(BX)∶V(溶剂)=3∶25(g/mL),m(BX)∶m(MBAM)=3∶0.07。采用IR,SEM,XRD对蔗渣木聚糖和接枝共聚物的结构进行了表征。IR在1668cm-1、1737cm-1处出现特征峰;SEM显示颗粒表面结构比改性前光滑,没有粗糙和较大的沟壑;XRD说明分子排列的规整性提高,结晶度增加,结晶区域变大。 相似文献
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《化工新型材料》2015,(3)
以玉米淀粉为原料,过硫酸铵和亚硫酸氢钠作为引发剂,丙烯酰胺(AM)和对乙烯基苄基三丁基氯化鳞(VBTBPC)为单体,在水相体系中制备了季磷盐型阳离子淀粉接枝共聚物。研究了丙烯酰胺浓度、单体配比对反应接枝率(G)、接枝效率(E)、产率(Y)的影响,并对接枝共聚物的阳离子度(CD)和单体的反应效率(RE)做了探讨。采用红外光谱、X射线衍射(XRD)和扫描电子显微镜(SEM)对接枝共聚物结构、结晶性和表面形貌分别进行了分析。结果表明,VBTBPC和AM接枝到了淀粉大分子上,其结晶性比淀粉的结晶性弱。保持单体总质量不变,当n_(AM):n_(VBTBPC)的值等于1.5时,接枝共聚物的接枝率和阳离子度达到最大值,分别为98%和0.21。 相似文献
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以机械活化淀粉为基材,丙烯酰胺(AM)、丙烯酸(AA)为单体,采用反相乳液法合成了接枝共聚物;考察了各因素对接枝共聚反应的影响.实验结果表明,在实验考察范围内的适宜反应条件为引发剂浓度7.30 mmo/L、丙烯酸中和度80%、m(AM):m(从)=0.67、V(油):V(水)=1.2:1、反应温度50℃、m(单体):m... 相似文献
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淀粉/BA-VAc接枝共聚物的合成及应用研究 总被引:19,自引:0,他引:19
以过硫酸铵为引发剂,研究了玉米淀粉与丙烯酸丁酯和醋酸乙烯酯接枝共聚合反应的规律。实验结果表明,单体浓度0.97mol/L,引发剂浓度9.1×10-3mol/L,反应温度68℃,反应3h时,反应体系的接枝率较高。通过红外光谱和X射线粉末衍射对接枝共聚物进行了结构分析。笔者以该接枝共聚物为基料,采用计算机辅助法设计出最优工艺配方,在国内首次研制生产出性能优异的功能性粘接材料 相似文献
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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. 相似文献
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Liebert A Wabnitz H Grosenick D Möller M Macdonald R Rinneberg H 《Applied optics》2003,42(28):5785-5792
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. 相似文献
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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. 相似文献
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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。 相似文献
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M. M. Gadenin 《Inorganic Materials》2013,49(15):1352-1356
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. 相似文献
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V. T. Kornienko 《Strength of Materials》1991,23(7):760-765
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. 相似文献
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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. 相似文献
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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)。 相似文献