差示扫描量热法测定衣康酸纯度和熔点

文章详细介绍了差示扫描量热法(DSC)测定衣康酸纯度及熔点的基本原理及实验方法,讨论了样品质量和升温速率对衣康酸纯度测试的影响。与传统碘量法相比,DSC法测定之前不需要对杂质鉴别及分离,而且测定过程中不需要基准物质,快速简便,误差较小,所测数据准确可靠。因此差示扫描量热法(DSC)以其优势必将得到广泛的应用。     

N-苯基-β萘胺的提纯及其纯度检测

用重结晶和区域熔融法提纯制备标准物质用N-苯基-β萘胺(防老剂D)。建立了高效液相色谱法(HPLC)和差示扫描量热法(DSC)检测防老剂D纯度的条件。HPLC检测样品纯度为99.24%,相对标准偏差(RSD)为0.14%;DSC检测样品纯度为99.20%,RSD为0.05%。纯度达到国际同类产品水平。     

差示扫描量热分析法测定米力农药物的纯度

运用差示扫描量热(DSC)法,测定了米力农药物的纯度,计算和分析了不同质量的药物试样以及试样在不同升温速率下,其纯度值的差异,并与高效液相色谱法(HPLC)的测定结果进行了比较。结果表明:两种方法结果相差0.03%,基本一致;药物试样精密度测定结果平均值为99.957%,RSD为0.01%;测定不同质量的药物试样,其纯度值最大相差0.077%;不同升温速率下,药物试样的纯度值最大相差0.186%。DSC方法可以用作为测定药品纯度的补充方法。     

防老剂BHT的提纯及其纯度检测

为提高和准确测定防老剂BHT的纯度,采用重结晶和区域熔融法对工业品防老剂BHT进行提纯,并用高效液相色谱仪和差示扫描量热仪对样品进行纯度检测。高效液相色谱法(HPLC)的标准曲线法测得的回收率在100.19%~100.28%之间,相对标准差(RSD)为0.05%;提纯品防老剂BHT的纯度为99.09%,RSD为0.08%。用差示扫描量热法(DSC)测得提纯品纯度为99.16%,RSD为0.14%。纯度达到国际同类产品水平。     

差示扫描量热法测定新戊二醇纯度

介绍了用差示扫描量热仪(DSC)测定新戊二醇纯度的基本原理(熔点降低定律)和实验方法。该方法采用密封式铝坩埚封装样品,升温速率约0.5℃/min,样品量约2~3 mg,N_2流速为20~40 m L/min。从DSC曲线可直接判断样品的纯度高低,应用相关纯度软件,纯度测试拓宽至99.5%(摩尔分数)。该方法简便、快速、准确,可适用于新戊二醇的纯度测定。     

乙烷磺酰胺纯度测定的DSC方法研究

用差示扫描量热法(DSC)研究了乙烷磺酰胺的测定方法，通过实验分析了测定的最佳条件，认为该方法具有操作快捷，样品用量少、准确度高等优点，同时还可得到样品的熔点、熔化热等数据。     

聚丙烯保温材料连续比热容的测定

介绍差示扫描量热法(DSC)测定材料连续比热容的原理和实验过程,用DSC法测定了标准样品苯甲酸及3种聚丙烯保温材料样品在310￣370K的连续比热容。苯甲酸测定结果与文献值之差不大于0.02J/(K.g),3种聚丙烯保温材料样品平行测定结果之差不大于0.03J/(K.g)。     

BOPP主辅料在生产上的应用研究

用差热扫描量热计(DSC)分析仪测定了BOPP主料、辅料的熔点及降温结晶行为,定性分析了辅料的组成,探讨了测试结果在BOPP生产线上的应用。     

基于量热技术的辣椒素纯度分析方法研究

建立了差示扫描量热法测定辣椒素药物纯度的方法。考察了不同升温速率和辣椒素样品质量对测定结果的影响，确定了差示扫描量热法最佳条件为：升温速率2 K·min^-1,辣椒素样品质量为1.5～3.5 mg。该法与高效液相色谱、气相色谱-质谱以及核磁共振氢谱等方法的测定结果进行了比较，结果表明：差示扫描量热法、高效液相色谱法、气相色谱/质谱法和核磁共振氢谱法测定的辣椒素质量分数分别为98.88%、98.88%、98.04%和98.97%,最大偏差为0.93%。讨论了产生偏差的原因。差示扫描量热法操作简单、结果准确，可作为测定辣椒素药物纯度的方法。     

硫代脯氨酸的热化学性质

用纯度为99.999%的量热基准苯甲酸标定了实验室建立的精密转动弹量热计,测定出硫代脯氨酸(tcH)的燃烧能为(-2469.30±1.44)kJ/mol,换算出其标准燃烧焓为(-2469.92±1.44)kJ/mol,计算出硫代脯氨酸的标准生成焓为(-401.33±1.54)kJ/mol。     

Quantification of Phospholipids Classes in Human Milk

Phospholipids are integral constituents of the milk fat globule membranes and they play a central role in infants’ immune and inflammatory responses. A methodology employing liquid chromatography coupled with evaporative light scattering detector has been optimized and validated to quantify the major phospholipids classes in human milk. Phospholipids were extracted using chloroform and methanol and separated on C18 column. Repeatability, intermediate reproducibility, and recovery values were calculated and a large sample set of human milk analyzed. In human milk, phospholipid classes were quantified at concentrations of 0.6 mg/100 g for phosphatidylinositol; 4.2 mg/100 g for phosphatidylethanolamine, 0.4 mg/100 g for phosphatidylserine, 2.8 mg/100 g for phosphatidylcholine, and 4.6 mg/100 g for sphingomyelin. Their relative standard deviation of repeatability and intermediate reproducibility values ranging between 0.8 and 13.4 % and between 2.4 and 25.7 %, respectively. The recovery values ranged between 67 and 112 %. Finally, the validated method was used to quantify phospholipid classes in human milk collected from 50 volunteers 4 weeks postpartum providing absolute content of these lipids in a relatively large cohort. The average content of total phospholipids was 23.8 mg/100 g that corresponds to an estimated mean intake of 140 mg phospholipids/day in a 4-week old infant when exclusively breast-fed.     

The hydration of reactive cement-in-polymer dispersions studied by nuclear magnetic resonance

The behaviour of two novel cement-in-polymer (c/p) dispersions, namely cement-in-poly(vinyl acetate) and cement-in-poly(vinyl alcohol) upon exposure to water at room temperature was investigated by a combination of various NMR methods. The swelling, cracking, and the water ingress were monitored non-destructively using ¹H single point imaging. The hydration of the cement matrix was investigated using ²⁹Si NMR whilst ¹³C CPMAS NMR spectra allowed the quantification of the kinetics of the hydrolysis reaction of poly(vinyl acetate) into poly(vinyl alcohol). The polymer controls the rate of water ingress and swelling which in turn determines the behaviour of the c/p dispersions upon exposure to water. For the cement-in-poly(vinyl alcohol), the rates of water ingress and swelling are much faster than the hydration of the clinker whilst for the cement-in-poly(vinyl acetate) the slow rates of the two processes allow the formation of a cementious matrix which assures the stability of the sample.     

Design and function of novel superplasticizers for more durable high performance concrete (superplast project)

In this article we shall describe our quest and ultimate success in furthering our understanding of the action of superplasticizers on the rheology of cement and concrete. By specifically producing superplasticizers with varied architectures, we have been able to show the important structural features of the macromolecules that lead to a successful superplasticizer or water reducing agent. Both polycarboxylate and lignosulfonate polymers have been investigated. Using both non-reactive model MgO powders, three different types of cement blends, the adsorption behaviour and the effect on the rheological properties of these two important superplasticizer families have been used to further develop a conceptual model for superplasticizer — cement behaviour. This paper will deal mainly with the conceptual model, the materials and methods used to asses the polymer adsorption behaviour and rheological properties of the systems studied. We shall briefly describe the adsorption of the polymers onto the different surfaces and their influence on surface charge and rheology and the influence of the various ionic species found in cement pore solutions that may influence polymer-cement affinity. The key factors are shown to be the effective adsorbed polymer thickness and the induced surface charge which can be influenced by the polymer architecture, the pore solution composition and the initial particle surface charge.     

Interactions between shrinkage reducing admixtures (SRA) and cement paste's pore solution

Shrinkage reducing admixtures (SRA) have been developed to combat shrinkage cracking in concrete elements. While SRA has been shown to have significant benefits in reducing the magnitude of drying and autogenous shrinkage, it has been reported that SRA may cause a negative side effect as it reduces the rate of cement hydration and strength development in concrete. To examine the influence of SRA on cement hydration, this study explores the interactions between SRA and cement paste's pore solution. It is described that SRA is mainly composed of amphiphilic (i.e., surfactant) molecules that when added to an aqueous solution, accumulate at the solution-air interface and can significantly reduce the interfacial tension. However, these surfactants can also self-aggregate in the bulk solution (i.e., micellation) and this may limit the surface tension reduction capacity of SRA. In synthetic pore solutions, SRA is observed to form an oil-water-surfactant emulsion that may or may not be stable. Specifically, at concentrations above a critical threshold, the mixture of SRA and pore fluid is unstable and can separate into two distinct phases (an SRA-rich phase and an SRA-dilute phase). Further, chemical analysis of extracted pore solutions shows that addition of SRA to the mixing water depresses the dissolution of alkalis in the pore fluid. This results in a pore fluid with lower alkalinity which causes a reduction in the rate of cement hydration. This may explain why concrete containing SRA shows a delayed setting and a slower strength development.     

The influence of water removal techniques on the composition and microstructure of hardened cement pastes

The removal of water from hardened cement paste for analysis or to arrest ongoing hydration has been reported to affect the composition of hydrated phases and microstructure. The effect that arresting the hydration of hardened cement paste by replacing the pore water with acetone before drying, and by removing the water by freeze, vacuum and oven drying has on the hardened cement paste has been investigated. Two pastes were studied, a cemented iron hydroxide floc where a high proportion of ordinary Portland cement (OPC) had been replaced by pulverised fuel ash, and a pure hydrated OPC. The results showed that none of the water removal techniques caused any major deterioration in the composition and microstructure of the hardened cement pastes studied, but the pores appeared better preserved after arresting hydration using acetone quenching. Freeze drying appeared to cause more cracking of the microstructure than the other water removal techniques.     

Study of the hydration of CaO powder by gas–solid reaction

Hydration of CaO powders by reaction with water vapor has been studied in isothermal and isobaric conditions. Experimental tests were performed within the temperature range of 70 °C–420 °C and with a water vapor pressure from 5 to 160 hPa by means of a thermogravimetric device. Two powders, exhibiting slight differences in their physical properties, were studied. However, for one of the powders and under some temperature and pressure conditions, the reaction is not complete. The difference of behavior between both CaO powders was interpreted by considering the effect of the morphological properties on the mechanism of growth of Ca(OH)₂.     

2-(2'-咪唑偶氮)萘酚-4-磺酸的合成及其分析性质的研究

合成了新显色剂咪唑偶氮－２－萘酚－４－磺酸（ＩＡＮ－４Ｓ）,研究了试剂的离解常数及其与金属离子的显色反应。     

Influence of bleed water reabsorption on cement paste autogenous deformation

The effects of bleed water reabsorption and subsequent early age expansion on observed autogenous deformation are investigated in this research. Bleeding was induced by varying superplasticizer and shrinkage-reducing admixture dosages and by increasing the water-to-cement ratio. This research revealed that significant early age expansion occurs with increasing chemical admixture dosages and higher water-to-cement ratios, as expected, due to increasing bleeding of those samples. When samples were rotated, negligible early age expansion was observed. Thus, bleed water reabsorption is shown to be the primary mechanism causing initial expansion in sealed autogenous deformation samples. Thermal dilation and ettringite growth appear to have a minimal influence on the observed expansion. Rotating the samples during setting eliminates the potential for bleed water reabsorption and is recommended for all autogenous deformation testing.     

Comparison between surface and bulk hydrophobic treatment against corrosion of galvanized reinforcing steel in concrete

The effectiveness of bulk hydrophobic treatment against corrosion of galvanized steel reinforcement in concrete specimens with w/c = 0.45 and w/c = 0.75 was compared with that of surface treatment, even in the presence of cracks 0.5 and 1 mm wide in the concrete cover. In this case surface hydrophobic treatments were applied both before and after cracking as a preventive and a restorative method against reinforced concrete deterioration, respectively. The obtained results in terms of water absorption, electrochemical measurements, chlorides penetration, and visual observations carried out on reinforced concrete specimens during the exposure to wet–dry cycles in 10% NaCl solution showed that bulk hydrophobization is the most effective treatment in improving the corrosion resistance of galvanized steel reinforcements in concrete also in the presence of cracks. Surface hydrophobization is very effective just in the first few exposure cycles to the aggressive environment and when used as a restorative method which is able to cancel the deleterious effect of cracks only 0.5 mm wide.     

Effect of plasma treatment of polymeric tape carriers on wetting behaviour of aqueous ceramic tape casting slurry

Due to environmental and health aspects, aqueous ceramic slurries are preferred to traditional organic solvent systems in tape casting. An important obstacle associated with the high surface energy of water is poor wetting of aqueous ceramic slurries on polymeric tape carriers. Therefore, we measured the contact angles of an aqueous epoxy-based ceramic slurry on polyethylene terephtalate (PET), polypropylene (PP), polymethyl methacrylate (PMMA), and aluminium-coated polyethylene terephtalate (PET-Al) films and investigated approaches to improving their wetting. We evaluated the effect of plasma treatment of the tape carrier surface on the wetting behaviour and compared it with the effect of adding non-ionic amphiphilic surfactants to the ceramic slurry. The treatment of the tape carrier surface by low-temperature plasma substantially improved the wetting behaviour of aqueous ceramic slurry. The lowest contact angle of 31° was obtained on the PET film. Although the addition of non-ionic surfactants improved both the wetting behaviour of the slurry and the detachment of the polymeric carrier from the ceramic tape even better than the plasma treatment of the carrier surface did, the plasma-treated carriers still present a useful alternative to the surfactants. In the case of the plasma-treated PET carrier the surfactants could be fully eliminated and potential drawbacks related to the use of surfactants could be prevented.