有机小分子在半晶体聚乙烯中的溶解度

通过测定压力的方法研究了乙烯、正己烷和异戊烷在三种不同结晶度聚乙烯中的溶解度,分析了结晶度、小分子物性以及温度对该过程的影响。得到温度60℃~90℃,乙烯0~2 M Pa,正己烷19 kPa~100 kPa,异戊烷80 kPa~300 kPa范围内三者各自在聚乙烯样品中的溶解度数据。结果表明,乙烯溶解度呈线性,符合H enry定律;正己烷和异戊烷的溶解度呈非线性。聚乙烯结晶度20%~72%范围内,有机小分子在聚乙烯中的溶解度随结晶度的增加而减小。溶解度随压力增加和温度的减小而增加。     

真空下碳化制备各向异性沥青

高溶解度、低熔点的各向异性中间相沥青是石油沥青在真空条件下、430℃时,碳化5小时而制备的。完全发育的各向异性中间相沥青在喹啉中的溶解度为55wt％,熔点为270℃。该溶解度比用同样的原料在回流和气吹条件下制得的中间相沥青的溶解度高的多。真空下完     

基于溶解度参数分析方法的IPN密封材料研究

目的基于耐溶剂性原则选择硝酸异丙酯的密封材料。方法通过溶解度参数的计算验证丁腈橡胶(NBR)与IPN会产生溶胀效应。根据聚合物的耐溶剂性原则,选择三元乙丙橡胶(EPDM)和聚四氟乙烯(PTFE)代替丁腈橡胶,而后比较各材料与IPN的溶解度参数差值。结果 IPN在NBR的可溶球体范围内,两者的三维溶解度参数十分接近;IPN,EPDM与PTFE的一维溶解度参数分别为8.6,7.7,5.14,EPDM与IPN的溶解度参数较为接近;PTFE与IPN的溶解度参数相差较大。结论 EPDM与PTFE均比NBR更适合密封IPN,其中EPDM最适合密封IPN。     

两维制墨方法在包装印刷中的应用

正长期以来,在包装印刷油墨制造和包装印刷过程中加加减减的"技术堆砌法"和通常在油墨配方设计上采用的"特性粘度法"(称取一定期量的聚合物溶解于具有不同溶解度参数的溶剂中,在一定温度下测定其特性粘度,所得的最大特性粘度体系,即可确定为聚合物的溶解度参数等于该体系的溶解度参数值)和"平衡溶胀法"(在一定的温度下将交联的高分子聚合物放于具有不同溶解度参数的溶剂中进行溶胀,当达到平衡后,测定其溶剂体系的溶解度参数即为该高聚物的溶解度参数),     

热力学计算在高氮奥氏体不锈钢研究中的应用

采用Thermo-Calc软件,计算了碳、铬、锰、镍元素和压力因素对22Cr高氮奥氏体不锈钢氮溶解度、凝固过程中相转变以及析出相的影响,并对设计的新型高氮奥氏体不锈钢组织及析出相进行了研究。结果表明:铬元素主要增加液态钢的氮溶解度,增加0.1%(质量分数)的碳即能显著增大奥氏体不锈钢在高温凝固时的最小氮溶解度。锰元素既增加液态钢中的饱和氮溶解度,又增加凝固初期的最小氮溶解度。适当的锰含量能扩大并稳定奥氏体相区,避免"铁素体阱"的出现。少量的镍含量既增加奥氏体不锈钢高温凝固时的最小氮溶解度,缩小高温δ铁素体存在的温度区间,也能使钢在室温下有完全的奥氏体组织。加压冶炼能有效促进氮溶解度。新型高氮奥氏体不锈钢的析出相主要为Cr23C6,Cr2N。采用热力学计算工具可以对高氮奥氏体不锈钢的冶炼、组织控制、热处理和热加工提供科学的指导。     

高浓度CO2在MEA溶液中平衡溶解度的实验研究

采用气液搅拌平衡装置,通过酸碱滴定和皂泡流量计测定了高浓度CO2在不同MEA溶液中的平衡溶解度。利用正交实验设计方法,考察了温度、CO2分压力、MEA质量浓度等因素对CO2平衡溶解度的影响。结果表明,在实验参数选定范围内,影响MEA中CO2平衡溶解度的因素主次顺序为：CO2分压力〉MEA质量浓度〉温度;MEA溶液中CO2的平衡溶解度随压力的增大而增大,随MEA质量浓度的增大而减小,随温度的增大而减小。     

钨丝电热原子吸收法测定温度对碳酸镉溶解度的影响

运用钨丝电热原子吸收光谱仪测定难溶盐碳酸镉在不同温度下的溶解度,在5～40℃时碳酸镉的溶解度随温度升高而减小,在5～30C时,其溶液中镉含量对应超过国家食品卫生限量标准的3.10～1.25倍,且20C时碳酸镉溶解度浓度为4.125×105g/100mL,方法的线性相关系数为0.9991.因此,使用碳酸镉时,应重视其溶解度随温度降低而增大带来的危害.     

道路石油沥青溶解度试验技术研究

研究道路石油沥青溶解度试验仪器及装置、试验原理、试验方法、试验步骤、结果计算、误差要求等。指出JTJ052-2000《公路工程沥青及沥青混合料试验规程》规定的T0607-1993"沥青溶解度试验"存在的问题,建议修改。     

环氧树脂对炭纤维的浸润性能分析

采用动态接触角表征环氧树脂对炭纤维的浸润性能,分析了温度、上浆剂、溶解度参数以及相互作用参数等因素对浸润性能的影响.结果表明,升高温度、使用上浆剂、提高两相间的相互作用参数均可减小树脂与纤维之间的接触角,改善浸润性能,而溶解度参数对树脂浸润纤维的影响不大.     

溶媒回收技术应用

溶媒结晶是指原料药最后的纯化步骤是通过溶解度的差异,或者由于混合溶剂中的溶剂比例改变带来的极性差异引起的溶解度变化,先将原料药制成溶液,再调节以上性质使之析出(比如说先将原料药溶于水,再向其中加入有机溶剂,使得药物溶解度变小而析出,这样的纯化手段称之为溶媒结晶。本文针对母液进行回收套用,提高母液的回收率等方面进行研究。     

(S)-Nitroxycarnitine nitrate production from (S)-carnitine by using acetic anhydride/nitric acid/acetic acid mixtures: safety assessment

The present work aims at assessing both thermodynamic and kinetic parameters of the esterification process of the (S)-carnitine, using calorimetric techniques. The use of the system acetic anhydride/nitric acid/acetic acid as esterifying agent and the explosive behaviour of nitric esters lead to safety considerations that have been investigated by hypothesizing some common process deviations. In particular, it has been investigated in adiabatic conditions both the batch addition of acetic anhydride and the effect of an initial temperature higher than those required by the process.     

Influences of organic ligands on the microstructure and properties of sol-gel antimony-doped tin oxide thin films

The antimony-doped tin oxide (ATO) thin films were prepared by sol-gel dip-coating process from SnCl2 2H2O and SbCl3 in alcoholic solutions. The influences of organic ligands, including acetic acids (HAc), acetic acids with monoethanolamine (in brief HAc + MEA), and acetic acids with acetylacetone (in brief HAc + AcAc), on the the microstructure and electrical properties of the thin films have been investigated. The thermal behavior of the ATO gels powders and the microstructures of the thin films have been characterized by using thermogravimetric (TG), differential scanning calorimetric (DSC), Fourier transform infra-red spectral (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) analysis. The electrical resistivity of the thin films was detected by four-probe instrument measurement. The thin films with HAc + MEA as coordination ligands had a good crystal quality and showed a preferred orientation along (101) plane when heated at 450 degrees C. As a consequence, it exhibited the best electrical performance. An electrical resistivity of about 6.3 x 10(-3) omega cm could be achieved for the films with 500 nm thickness.     

Conformational comparisons between phenoxyacetic acid derivatives in adducts and those in the free form. Part 2

Nine molecular co-crystals containing 2,3-, 2,5-, 2,6- and (3,5-dichlorophenoxy)acetic acid have been prepared and studied using single-crystal X-ray diffraction techniques. The free acid structure of (2,3-dichlorophenoxy)acetic acid is also reported. The bases used to prepare the adducts were 2-aminopyrimidine, 2-amino-2-thiazoline, 2-amino-5-chlorobenzoxazole and 4,4’-dipyridine. The conformations of the phenoxyacetic acid molecules were found in all but one case to be either synclinal (twisted) or antiperiplanar (planar). The one exception was a molecule of (2,6-dichlorophenoxy)acetic acid whose conformation was assigned as anticlinal. General comments are given about the conformational aspects of these and previously reported adducts of phenoxyacetic acid derivatives and how they compare to their free acid structures.     

The role of glass composition in the behaviour of glass acetic acid and glass lactic acid cements

Cements have recently been described, made from glass ionomer glass reacted with acetic and lactic acid instead of polymeric carboxylic acid. From their behaviour a theory relating to a possible secondary setting mechanism of glass ionomer has been adduced. However, only one glass (G338) was used throughout. In this study a much simpler glass ionomer glass (MP4) was compared with G338. This produced very different results. With acetic acid G338 formed cement which became resistant to water over a period of hours, as previously reported, MP4 formed cement which was never stable to water. With lactic acid G338 behaved similarly to G338 with acetic acid, again as reported, but MP4 produced a cement which was completely resistant to water at early exposure and unusually became slightly less resistant if exposure was delayed for 6 h or more. These findings indicate that the theories relating to secondary setting in glass ionomer maturation may need revision.     

Kinetics of Mild Steel Corrosion in Aqueous Acetic Acid Solutions

The kinetics of mild steel corrosion in aqueous acetic acid solution has been investigated by weight loss and polarization techniques at 25,35 and 45℃.The weight loss of mild steel at room temperature (25℃) has been found to be quite significant,indicating poor corrosion resistance in acetic acid.The maximum corrosion rate has been observed in 25% acetic acid solution at all three experimental temperatures.The decrease in corrosion rate after attaining a maximum value has been attributed to the deposition of corrosion product on the surface.Anodic polarization curves exhibit active behaviour at each concentration and temperature with a shift towards higher current density region and increased corrosion rates at higher temperatures.The cathodic polarization curves are almost identical irrespective either of the concentration of acetic acid or temperature.The results obtained by both the techniques are in good agreement,while the surface studies support the conclusions drawn from the weight loss method.     

2-噻吩乙酸的HPLC分析测定

建立了一种2-噻吩乙酸的反相高效液相色谱-紫外检测法.研究了流动相的组成、流速及色谱柱温度等因素对测定的影响.采用色谱柱为VARIAN C18(250 mm×4.6 mm,5μm)反相色谱柱,流动相为甲醇-水(V∶V=70∶30),流速1.0 mL/min,柱温为室温,紫外检测波长235 nm,在6 min内可完成分析.该方法的回收率为98.4%~99.8%,RSD<1%.其优点为2-噻吩乙酸与其同分异构体3-噻吩乙酸得到较好的分离,明显不重叠,且操作简单、快速和准确可靠,用于2-噻吩乙酸产品的纯度测定,结果令人满意.     

Synthesis of copper sulphide nanoparticles in carboxylic acids as solvent

A novel method for the preparation of CuS nanoparticles based on the fast nucleation of the sulphide has been developed. The particles have been synthesized by reaction of thioacetic acid with water and copper carboxylates (acetate, propionate) in the corresponding carboxylic acid (acetic, propionic) as a solvent. The use of carboxylic acids presents several advantages: (i) the hydrolysis of the C-S bond is favoured thus producing a fast CuS supersaturation and a high nucleation rate; (ii) the mobility of the precursor molecules is limited so that nucleation events are favoured with respect to particle growth; (iii) the low dielectric constant of the medium stabilises the nanoparticles dispersion by reducing the critical coagulation concentration. The prepared nanoparticles were investigated by UV-Vis spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy and dynamic light scattering. The nanoparticle suspensions are clear and characterized by a blue-shifted adsorption edge with respect to bulk CuS. Light scattering measurements performed on acetic acid suspensions evidence the formation of monodispersed nanoparticles with an average diameter of about 5 nm.     

中国和欧盟酸性食品模拟物对食品接触材料迁移量的差异性分析

目的 对中国和欧盟分别规定的不同酸性食品模拟物进行差异分析,并对2种不同酸性食品模拟物的迁移试验结果差异进行考察。方法 选取4类典型的酸性食品(共123种)进行pH测试,分别以3%(质量分数)的乙酸和4%(体积分数)的乙酸为食品模拟物对食品接触材料及制品进行迁移试验,并测试样品的总迁移量、甲醛迁移量、三聚氰胺迁移量、双酚A迁移量和重金属(锑)迁移量,比较样品在2种不同酸性食品模拟物中的迁移量差异。结果 pH测试结果表明,中国生产的4类酸性食品的pH范围为2.3~5.1,国外生产的4类酸性食品的pH范围为2.49~4.88,pH<5对4类酸性食品的pH覆盖率均大于或等于pH<4.5。迁移结果表明,在大多数情况下,食品接触材料在4%(体积分数)的乙酸中的迁移量,无论是总迁移量还是特定迁移量都大于或等于在3%(质量分数)的乙酸中的迁移量,食品接触材料在3%(质量分数)的乙酸中的迁移量高于在体积分数4%的乙酸的情况极少。结论 根据研究结果,中国采用pH<5定义酸性食品符合中国人的餐饮习惯,酸性食品覆盖性更广,更具合理性。迁移量测试结果表明,4%(体积分数)的乙酸是比3%(质量分数)的乙酸更为严苛的食品模拟物,因此对于国外出口中国的食品接触材料,即使已经按照欧盟标准采用3%(质量分数)的乙酸进行了迁移量测试,在进口到国内时还应用4%(体积分数)的乙酸按照中国相关标准再次进行迁移量测试,以满足中国标准的相关要求。     

A Phase Study of the System: Oxalic Acid/Acetic Acid/Water; Its Significance in Oxalic Acid Crystal Growth

The presence of limited amounts of water appears to improve the quality of anhydrous oxalic acid single crystals grown from acetic acid solutions. Water concentrations in the saturated solutions which allow crystallization of the anhydrous acid have been determined from the phase study of this ternary system. Near 50 °C the anhydrous acid crystallizes from solutions containing up to 5.2 weight percent water, while the dihydrate appears when water is in excess of this amount.The phase diagram shows a minimum content of oxalic acid in solution at a solvent composition near 83 percent acetic acid, 17 percent water. The solubility increases with increased acetic acid to the isothermal invariant point, found experimentally at a measured temperature of 50.21 °C to have the composition 20.94 percent oxalic acid, 73.89 percent acetic acid, 5.17 percent water. Decreasing solubility occurs at higher acetic acid concentrations. The maximum water content which allows crystallization of anhydrous acid increases with increasing crystallization temperature. The solubility of oxalic acid in acetic acid/water mixtures at 40° and 50 °C is reported.     

Enhanced sensitivity to and classification of volatile carboxylic acids using arrays of linear poly(ethylenimine)-carbon black composite vapor detectors

Vapor detectors formed from composites of conductors and insulating organic polymers have been tailored to produce increased sensitivity toward specific classes of analyte vapors. Upon exposure to acetic acid at 1% of its vapor pressure, detectors consisting of linear poly(ethylenimine) (1-PEI)-carbon black composites showed an approximately 10(3) increase in signal/noise relative to the performance of typical insulating organic polymer-carbon black composite vapor detectors. Compositional diversity in an array of such vapor detectors was obtained by varying the degree of plasticization of the 1-PEI films. The resulting vapor detector array produced sensitive detection of, and robust discrimination between, various volatile organic acids and relatively little response from nonacidic organic vapors or from water vapor. Measurements of the mass uptake, thickness change, and electrical conductivity of such composites indicate that swelling of the polymer film, and thus its normalized resistance response, is beyond that expected by mass uptake alone upon exposure to acetic acid vapor. This additional thickness increase is attributed to charge-induced polymer swelling occurring from polymer-analyte interactions. Electrical percolation also plays a significant role in producing the large increase in normalized resistance response of these composites upon exposure to acetic acid vapor.