壳聚糖接枝丙烯酸高吸水性树脂的制备及性能研究

以壳聚糖(CTS)和丙烯酸(AA)为原料进行接枝共聚,制得高吸水性树脂.通过单因素及正交试验考察AA∶CTS比值、引发剂用量及交联剂用量对树脂吸水性能的影响,确定最佳合成条件.利用红外光谱对产品结构进行表征.结果表明,当AA∶CTS为10∶1,引发剂用量为单体质量的3.5％,交联剂用量为单体质量的0.35％,所制得的树脂吸水率最高,其吸蒸馏水率可达964 g/g,吸盐水率可达58g/g.     

机械活化淀粉接枝丙烯酸高吸水树脂的制备与性能研究

以机械活化木薯淀粉、丙烯酸为主要原料,过硫酸铵为引发剂,采用反相乳液聚合法制备了机械活化淀粉接枝丙烯酸高吸水树脂,考察了引发剂用量、交联剂用量、丙烯酸(AA)中和度和单体淀粉质量比等因素对吸液性能的影响。结果表明:制备机械活化淀粉接枝丙烯酸高吸水树脂的最适宜工艺条件为引发剂用量为0.6%,交联剂用量为0.12%,丙烯酸中和度为80%,单体淀粉质量比为10∶1。在此条件下,树脂吸去离子水倍率为930.67g/g,吸生理盐水倍率为90.57g/g。对产物进行红外分析的结果表明活化木薯淀粉与丙烯酸发生了接枝共聚反应。     

淀粉接枝系高吸水吸油树脂的合成

对淀粉与丙烯酸等接枝共聚制备高吸水吸油树脂进行了初步的研究,采用乳液聚合的方法,以硝酸铈铵为引发剂,以丙烯酰胺、甲基丙烯酸甲酯为单体,研究了单体配比,引发剂用量,淀粉与单体比,交联剂用量等对淀粉改性制备高吸水吸油树脂性能的影响因素.     

微波辐射合成耐盐性羟乙基纤维素高吸水性树脂

以羟乙基纤维素为原料,丙烯酰胺和马来酸酐为接枝单体,N,N'-亚甲基双丙烯酰胺为交联剂,过硫酸胺为引发剂,采用微波辐射技术合成一种新型耐盐型羟乙基纤维素-丙烯酰胺-马来酸酐接枝共聚高吸水性树脂,探讨了微波辐射功率、混合单体AM/MAA比例、羟乙基纤维素浓度、交联剂以及引发剂用量对树脂吸盐水能力的影响.最佳合成条件为:微波辐射功率为400W且间歇加热12min、AM/MAA摩尔比为0.45,羟乙基纤维素浓度为3.0%、交联剂用量为2.0%、引发剂用量为0.15%,制得的高吸水性树脂最大吸盐水率达167g·g-1.     

玉米淀粉接枝丙烯酸制备高吸水性树脂

用硝酸铈铵作引发剂,通过水溶液聚合法制得了玉米淀粉接枝丙烯酸高吸水性树脂。研究了交联剂及引发剂用量、中和度、反应温度以及反应时间等对吸水率的影响。得到的最佳反应条件为:交联剂和引发剂与丙烯酸的摩尔比分别为0.95×10-5和4.8×1-0 3,中和度71%,反应温度45℃,反应时间2 h。制得的高吸水树脂在室温下30 m in每克吸蒸馏水和自来水分别约为其自身质量的1000和200倍。     

聚(丙烯酸-co-丙烯酰胺)/高岭土复合高吸水性树脂的制备

采用N,N'-亚甲基双丙烯酰胺作交联剂,过硫酸铵作引发剂,通过水溶液聚合法制得了聚(丙烯酸-co-丙烯酰胺)/高岭土复合高吸水性树脂.研究了高岭土的添加量、丙烯酰胺用量、中和度、引发剂用量以及交联剂用量等对吸水率的影响.得到的最佳反应条件为:中和度为70%,丙烯酰胺、高岭土、引发剂和交联剂量分别为丙烯酸单体质量24%、18%、0.96%和0.09%.制得的高吸水性树脂在室温下30min每克吸蒸馏水和自来水分别约为其自身质量的890倍和290g倍.     

玉米秸秆基高吸水性树脂的合成及其性能的研究

采用水溶液聚合法将丙烯酰氧乙基三甲基化铵(DAC)、丙烯酰胺(AM)、丙烯酸(AA)3种单体接枝到纤维素骨架中合成玉米秸秆基两性高吸水性树脂。研究单体用量、秸秆用量、交联剂用量、引发剂用量、反应温度、反应时间和中和度对高吸水性树脂吸液率的影响。通过扫描电镜图、红外光谱图对其形貌进行表征。实验结果表明,在秸秆、AA、AM、DAC的质量分别为1、5、1和0.5g,引发剂用量占单体比率为1.2%,交联剂用量占单体总量比率为0.1%,中和度为75%,反应时间为3h,反应温度为60℃的合成条件下,制备的高吸水性树脂(SAR)吸液率达最大,其吸水率为235.9g/g,0.9%NaCl溶液的吸收率为31.3g/g。     

海藻接枝丙烯酸高吸水性树脂的制备及性能研究

采用海藻为原料与丙烯酸接枝共聚制备了高吸水性树脂。通过红外光谱(FT-IR)分析了产物的结构。考查了丙烯酸中和度、丙烯酸用量、引发剂和交联剂的用量以及反应温度等各因素对产物吸水率的影响。结果表明,所得树脂的吸水率可达618g/g,吸盐水率(0.9%的NaCl水溶液)达到120g/g,其吸水速率适中,热稳定性和在室温下的保水性均较好,是一种新的环保型高吸水性树脂。FT-IR初步表明了丙烯酸与海藻的接枝聚合作用。     

高岭土复合聚(丙烯酸-co-丙烯酰胺)高吸水树脂的制备及性能研究

采用水溶液聚合法制备高岭土复合聚(丙烯酸-co-丙烯酰胺)高吸水树脂,用红外光谱对树脂的结构进行表征。在将聚合反应与树脂的干燥同时进行的基础上探讨了交联剂用量、引发剂用量、单体配比、丙烯酸中和度、高岭土添加量等条件对树脂吸液性能的影响。结果表明:当丙烯酸中和度75%、单体配比3.5:1、高岭土添加量15%、交联剂用量0.02%、引发剂用量0.8%时,树脂的吸液性能整体最好,吸水倍率达698g·g-1、吸盐水倍率110g·g-1。红外光谱结果表明,丙烯酸、丙烯酰胺单体与高岭土的-OH发生了接枝共聚反应。     

耐盐性淀粉接枝丙烯酸类高吸水性树脂的制备及表征

以N,N′-亚甲基双丙烯酰胺(MBA)为交联剂,过硫酸钾(KPS)为引发剂,采用水溶液聚合法制备了淀粉接枝丙烯酸(AA)和丙烯酰胺(AM)单体的高吸水性树脂。探讨了引发剂用量、交联剂用量、原料配比、丙烯酸中和度、反应条件等对吸水率的影响。最佳条件下,制得对蒸馏水的吸水率为802.6g/g,对0.9%NaCl溶液吸水率为153.7g/g的高吸水率树脂。用FT-TR对产物进行了表征。结果显示:制备出了高吸水性树脂。该树脂充分利用淀粉的经济性和可降解性等特性,具有环保、吸水率高、耐盐性好等优点。     

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.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

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.     

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 anisotropy of properties on the basis of studies of texture of coarse-grained ingots of thermoelectric materials

An analysis of anisotropy of the properties of a Bi₂Se_0.3Te_2.7 solid solution was carried out using construction of demonstrative surfaces for thermoelectric effectiveness and thermal expansion coefficients. It is shown that the texture is an important factor forming anisotropy of properties and technological fitness of ingots for manufacturing modules. Anisotropy of properties based on the studies of the ingot textures obtained using the float-zone method and Bridgman method (growing thermoelectric plates in a flat cavity) was studied.     

Numerical study of methods of linearization of the output characteristics of radio-frequency sensors of the level of dielectric media

Different constructions of the sensing elements of radio-frequency level sensors based on sections of long lines are numerically investigated by means of the Matlab program for the purpose of minimizing the measurement error caused by the nonlinearity of the output characteristic. It is shown that the nonlinearity is lowest for U-shaped designs. The nonlinearity factor KN may be regulated by varying the capacitance of a correcting capacitor connected to the input of the sensing element and (or) the length of one of the sections of the long line. In selecting an optimal capacitance of the correcting capacitor KN ≤ 0.15% for control media with dielectric permittivity in the range 2.2–30.     

Possibilities of Decreasing the Errors of Determination of the Height of the Pole of a Sessile Drop of Melt

We analyze the possibilities of decreasing the errors of measuring the height of the pole of a sessile drop of melt above its equator by determining the position of the equator according to the midpoints of vertical chords of the image of the drop. The optimal distance between these chords and the edge of the image of the drop is chosen within 10–20% of the radius of the equator. The proposed method guarantees the same level of errors of evaluation of the height of the pole and the radius of the equator, which enables one to substantially increase the accuracy of evaluation of the capillary constant and the surface energy of the melt according to the geometric parameters of the sessile drop.     

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.