酸解氧化对双醛淀粉性能的影响

以玉米淀粉为原料,盐酸为酸解剂,高碘酸钠为氧化剂,采用一步酸解氧化法合成双醛淀粉,经傅里叶变换红外光谱仪表征证明成功制得了双醛淀粉。研究了反应温度、反应时间、盐酸浓度和淀粉乳浓度对双醛淀粉醛基含量的影响,并利用X射线衍射仪和热重分析仪进行了表征。结果表明,双醛淀粉的醛基含量随着反应温度的升高和反应时间的延长而增大,55℃和4h后,酸解氧化趋于稳定。盐酸浓度和淀粉乳浓度过高会导致双醛淀粉的醛基含量下降,分别以0.6mol/L和8%为宜。X射线衍射仪分析表明,随着盐酸浓度的增加,双醛淀粉的结晶度升高;热重分析仪分析表明,结晶度高的双醛淀粉热分解残余量也更多,而热分解初始温度随着盐酸浓度增加而降低。     

基于响应曲面法优化酸解氧化制备高醛基含量的双醛淀粉的工艺条件

本工作采用响应曲面法优化了一步酸解氧化制备双醛淀粉的工艺,以玉米淀粉为原料、盐酸(HCl)为酸解剂、高碘酸钠(NaIO_4)为氧化剂,设置HCl浓度、淀粉乳浓度、反应温度和反应时间为变量。傅里叶变换红外光谱(FT-IR)和X射线光电子能谱(XPS)分析证明本实验成功制得了双醛淀粉。采用旋转黏度计、扫描电子显微镜(SEM)、X射线衍射仪(XRD)和热重分析仪(TGA)对双醛淀粉的糊化性能、颗粒形貌、结晶结构和热性能进行了表征。结果表明,对醛基含量的影响大小依次为反应温度反应时间淀粉乳浓度 HCl浓度。最佳制备工艺为:HCl浓度为1. 2mol/L,淀粉乳浓度为7%,反应温度为49℃,反应时间为4 h。在该条件下制得的双醛淀粉的醛基含量为85. 17%,与理论最大值86. 26%接近,说明优化结果可信。酸解氧化后,双醛淀粉的糊化黏度降至30 mPa·s,可显著提高反应活性和可操作性。SEM分析显示,双醛淀粉颗粒中间凹陷,呈现出环状结构。XRD分析表明,淀粉的结晶结构发生破坏,重结晶使结晶度增大至36. 05%。TGA分析表明,双醛淀粉受热分解起始温度降低,但分解残余率提高,说明其热塑性和热稳定性有所提高。     

微细化处理玉米淀粉对糊化温度及粘度的影响

目的对比、分析不同研磨介质条件下研磨所得玉米淀粉糊化温度和峰值粘度的变化。方法采用行星式球磨机对玉米淀粉进行微细化处理,分别以无介质、蒸馏水和无水乙醇等为研磨介质对淀粉进行研磨,用淀粉粘度测定仪测定研磨所得淀粉的糊化温度及峰值粘度。结果研磨所得玉米淀粉糊化温度和峰值粘度均随研磨时间的延长而下降。研磨介质对玉米淀粉糊化温度的影响为蒸馏水无水乙醇未添加介质;研磨介质对玉米淀粉峰值粘度的影响为蒸馏水无水乙醇未添加介质。结论球磨能够降低玉米淀粉的糊化温度和峰值粘度,研磨介质为蒸馏水时淀粉性质变化最大。     

纸包装材料用淀粉/丙烯酰胺接枝共聚物制备工艺的研究

以过硫酸铵为引发剂,研究了纸包装材料用淀粉/丙烯酰胺接枝共聚物制备工艺,对引发剂浓度、反应温度、单体浓度、反应时间、糊化温度等反应条件进行了考察。结果表明,制备的最佳工艺条件为:糊化温度80℃,单体浓度0.7mol/L,引发剂浓度2.19mmoL/L,反应温度60℃,反应时间3h,单体和引发剂分两次投加。     

淀粉类高吸水性树脂基水晶花泥的制备及性能研究

以可溶性淀粉、丙烯酸为原料,硫代硫酸钠、过硫酸钾为引发剂,N,N′-亚甲基双丙烯酰胺为交联剂,氢氧化钠溶液为中和剂,采用自由基聚合法制备淀粉类高吸水性树脂。采用单因素控制变量法探讨反应温度、丙烯酸中和度、淀粉乳浓度、单体用量、糊化时间和糊化温度对产物吸水倍率的影响。结果表明:淀粉类高吸水性树脂材料水晶花泥制备的最佳工艺条件为:反应温度55℃,pH=6.5,淀粉乳浓度12%,单体淀粉质量比2∶1,糊化时间30min,糊化温度80℃。在室温下吸水放置17h,材料的最大吸水率41.2220g/g。     

聚乳酸接枝淀粉的原位溶液合成及表征

以L-乳酸为接枝单体,辛酸亚锡为催化剂,采用原位溶液接枝工艺,在同一个反应体系中逐次完成淀粉糊化、丙交酯的生成及淀粉的聚乳酸接枝反应,制备了聚乳酸接枝淀粉,工艺简单、易于控制。研究了反应温度、L-乳酸与玉米淀粉质量比、反应时间和催化剂用量等对产物接枝率的影响,采用FTIR,1H-NMR和SEM对接枝产物进行了表征。结果表明:原位溶液合成产物为聚乳酸接枝淀粉;其最佳工艺条件的反应温度为95℃,L-乳酸与玉米淀粉质量比为3∶1,催化剂为乳酸用量的1%(质量分数),反应时间11 h,聚乳酸接枝率可达到14.81%,淀粉颗粒表面聚乳酸包覆均匀。     

反应温度和时间对干法制备马来酸酐酯化淀粉性能的影响

采用干法制备马来酸酐酯化淀粉,研究了反应温度和时间对酯化淀粉性能的影响。采用红外光谱(FT-IR)证明了马来酸酐成功酯化到淀粉上。利用化学滴定法、X射线衍射(XRD)、差示扫描量热法(DSC)和热重分析(TGA)对酯化淀粉的取代度、结晶结构、糊化温度和热稳定性进行了分析。结果表明,随着反应温度升高和时间延长,取代度逐渐增大。酯化反应一定程度上破坏了淀粉的结晶结构,随反应温度升高和反应时间延长,结晶度逐渐降低。糊化温度和热稳定性跟酯化淀粉的结晶度密切相关,结晶度降低,糊化温度和热稳定性都逐渐降低。     

聚乳酸接枝淀粉原位固相聚合工艺优化研究

为减少淀粉分子链中的亲水羟基,从而提高其与聚乳酸(PLA)树脂的界面相容性,以玉米淀粉为原料,乳酸为接枝单体,辛酸亚锡为催化剂,通过原位固相聚合法制备得到具有一定疏水性能的聚乳酸接枝淀粉(PLA-g-淀粉)。采用正交试验法研究了单体比例、反应温度和反应时间对PLA-g-淀粉接枝率的影响,通过直观分析和显著性分析优化了原位固相聚合工艺,并对疏水性、分子量及分布、糊化粘度进行了分析。结果表明,PLA-g-淀粉制备的最优工艺条件为单体比例25%、反应温度100℃和反应时间为2 h,在此工艺条件下制得PLA-g-淀粉的接枝率为20.78%。经过原位固相接枝改性后,淀粉的疏水性能得到显著改善,数均分子量(M_n)、重均分子量(M_w)、z均分子量(M_z)和分布指数(DI)都不同程度增大,糊化粘度也相应得到增大。     

离子液体中淀粉颗粒接枝醋酸乙烯酯的研究

以离子液体1-乙烯基-3-甲基咪唑氯盐([AMIM]Cl)为溶剂,以过硫酸铵为引发剂,制备了木薯淀粉接枝醋酸乙烯酯共聚物.研究了引发剂浓度、醋酸乙烯酯单体与淀粉的配比、反应温度以及反应时间等因素对淀粉接枝醋酸乙烯酯共聚参数的影响,并对淀粉接枝产物进行了红外光谱、XRD、SEM分析.结果表明,在[AMIM]Cl中淀粉接枝...     

紫外光引发淀粉接枝丙烯腈的研究(Ⅰ)

设计了一套光化学反应实验装置，实现了紫外光引发玉米淀粉与丙烯腈的接枝反应。考查了玉米淀粉糊化、预引发、反应温度、光照强度、搅拌速度等因素对该光引发接枝体系接枝百分率、接枝效率、单体转化率等的影响。得到了紫外光引发玉米淀粉接枝反应的一些规律。     

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.     

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.     

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.     

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)。