核磁共振对高聚物短链支化的研究

高聚物主链上支化的类型和数量是决定低密度聚乙烯(高压聚乙烯)和高密度聚乙烯(低压聚乙烯)物理性能差异的主要原因。短链支化影响聚合物的形态和半结晶聚合物的固态性质,而长链支化对溶液的粘度和熔体流变行为产生深远的影响。长链支化是由于分子间链转移反应产生,短链支化是分子内链转移反应引起的。在这类聚合物的结构测定中,除了分子量和分子量分布之外,支化度是一个重要的结构参数。     

茂金属聚乙烯(MPE)/线性低密度聚乙烯(LLDPE)共混熔体的流变学

研究了不同比例共混的茂金属聚乙烯 (MPE)和线性低密度聚乙烯 (LLDPE)熔体的流变学行为 ,讨论了共混物组成、剪切速率和剪切应力以及温度对熔体流变曲线、熔体粘度的影响 ,为MPE的共混改性提供了理论依据。结果表明 :随着LLDPE含量的增加 ,共混熔体的粘度降低 ,转变应力和非牛顿指数减小 ,粘流活化能升高 ,MPE的流动性和加工性能得到改善。     

几种聚乙烯毛细管流变性能的研究

采用高压毛细管流变仪研究了聚乙烯(PE)在225℃和250℃下的流变行为.结果表明,PE的粘度随着剪切速率的增加而降低,相同结构PE的粘度随熔体流动速率(MFR)的增加而降低;在同一温度和剪切速率下,当MFR相当时茂金属线性低密度聚乙烯(PE-MLLD)的粘度最大、线性低密度聚乙烯(PE-LLD)次之、低密度聚乙烯(P...     

超高相对分子质量聚乙烯冻胶的流变行为研究

研究了超高相对分子质量聚乙烯(UHMWPE)冻胶的流变特性,以及温度、相对分子质量对冻胶 的lgη_a-lgγ流动曲线、非牛顿指数和结构粘度指数的影响。结果表明:UHMWPE冻胶属于宾汉流体,具 有明显的非牛顿性,结构粘度指数随UHMWPE相对分子质量的增大而增大,随冻胶温度的升高而降低。     

线型低密度聚乙烯流变为的研究

本文利用毛细管流变仪对LLDPE、LDPE和HDPE的流变行为进行了研究,测定了三种聚乙烯的软化温度和流动温度。实验结果表明,LLDPE、LDPE和HDPE均为结晶性聚合物,其熔体为非牛顿假塑性流体,而LLDPE的流动温度、流变行为均与LDPE和HDPE有较大的差别,粘度对剪切速率的敏感性大于粘度对温度的敏感性。     

碳酸钙分散效果对LLDPE/CaCO_3复合材料流变行为的影响

填料分散效果对填充共混物的流变行为产生直接的影响。主要研究碳酸钙(CaCO3)颗粒在线性低密度聚乙烯(LLDPE)中的分散形态对材料稳态流变性能和动态流变性能的影响,通过选择合适的流变模型对稳态黏度曲线进行拟合,结合对热性能的研究对填料分散相形态对流变特性的关系和作用机理进行阐述,目的是通过流变方程中相关参数的变化来描述填料在聚合物基体中不同的分散效果,为建立基于流变测试的填料分散性的评估模型提供理论依据。     

再生胶/低密度聚乙烯热塑性弹性体的流变性能

测定了动态硫化再生胶(RR)/低密度聚乙烯(LDPE)共混物的流变曲线、挤出胀大值和粘度等,讨论了并用比、温度、交联剂用量、返炼次数等因素的影响,评价了共混物的加工性能。结果表明,共混物属假塑性流体,服从指数定律,流动指数n值为0.18—0.42。其表现粘度的绝对值低于按线性共混规则预测的粘度。挤出胀大值较小,可在一般塑料加工设备上进行挤出、模压和注射成型。     

茂金属聚乙烯（mPE）／高压聚乙烯（LDPE）共混熔体的流变学

研究了不同比例共混的茂金属聚乙烯（mPE)和高压聚乙烯（LDPE）熔体的流变行为,讨论了共混物组成、剪切速率和剪切应力以及温度对熔体流变曲线、熔体粘度和膨胀比的影响,mPE的加工提供了理论依据。不同共混比的熔体均为假塑性流体,且熔体假塑性随LDPE含量增大而增强。熔体流动活化能随LDPE组成的增加逐渐增大,粘度对温度的敏感性增强,共混物的非牛顿指数随LDPE的增加而降低,改善了mPE的加工性能。     

助剂对聚乙烯喷涂成型流变性能的影响

分别用硅油、ＥＶＡ、ＬＷＰＥ、钛白粉、超细碳酸钙等助添加到聚乙烯树脂中,研究了助剂对聚乙烯流变性能的影响。结果表明,硅油系列助剂、ＬＷＰＥ的加入能降低聚乙烯熔体的粘度,其中以低分子量的硅油Ｅ最为有铲。而钛白粉、碳酸钙则使聚乙烯熔体的粘度升高。但聚乙烯熔体加入上述几种助剂后,其流变性能符合阿累尼乌斯方程。     

PPS／TLCP共混体系的流变性研究

研究了两种不同粘度热致液晶聚合物(TLCP)与两种熔体流动速率(MFR)相差比较大的聚苯硫醚(PPS)复合体系的流变特性。研究发现,在一定温度下复合体系的流变性与所添加的液晶聚合物的种类以及添加量等因素有关,呈现出较复杂的流变行为。     

佛山市顺德新城区降水中污染物的监测和分析

为掌握佛山市顺德新城区降水中污染物的情况,2015年7月至8月,文章作者分别在雨天进行了降水取样,对降水中的pH、电导率、常见阴离子(F-、Cl~-、NO_3~(2-)、SO_4~(2-))及部分重金属(铅和镉)进行监测分析。选择有相关数据的珠江三角洲和石家庄、厦门等地的降水中污染物的情况进行对比。结果表明,顺德新城区降水中的p H和部分阴离子浓度优于珠江三角洲平均值,酸雨类型属于硫酸和硝酸混合型;其水体洁净程度略差于石家庄;铅和镉的浓度也高于厦门,甚至部分超出了人体能直接接触的安全范围。     

Metabolism of trideuterated iso-lignoceric acid in rats in Vivo and in human fibroblasts in culture

Saturated very long chain fatty acids (fatty acids with greater than 22 carbon atoms; VLCFA) accumulate in peroxisomal disorders, but there is little information on their turnover in patients. To determine the suitability of using stable isotope-labeled VLCFA in patients with these disorders, the metabolism of 22-methyl[23,23,23-²H₃]tricosanoic (iso-lignoceric) acid was studied in rats in vivo and in human skin fibroblasts in culture. The deuterated iso-VLCFA was degraded to the corresponding 16- and 18-carbon iso-fatty acids by rats in vivo and by normal human skin fibroblasts in culture, but there was little or no degradation in peroxisome-deficient (Zellweger’s syndrome) fibroblasts, indicating that its oxidation was peroxisomal. Neither the 14-, 20-, and 22-carbon iso-fatty acids nor the corresponding odd-chain metabolites could be detected. In the rat, the organ containing most of the iso-lignoceric acid, and its breakdown products, was the liver, whereas negligible amounts were detected in the brain, suggesting that little of the fatty acid crossed the blood-brain barrier. Our data indicate that VLCFA labeled with deuterium at the ω-position of the carbon chain are suitable derivatives for the in vivo investigation of patients with defects in peroxisomal β-oxidation because they are metabolized by the same pathways as the corresponding n-VLCFA. Moreover, as iso-VLCFA and their β-oxidation products are readily separated from the corresponding n-fatty acids by normal chromatographic procedures, the turnover of VLCFA can be more precisely measured. A preliminary report of part of this work (Reference 18) was presented at the 5th International Symposium on the Synthesis and Applications of Isotopes and Isotopically Labelled Compounds, Strasbourg, France, June 20–24, 1994.     

高效液相色谱法分析化妆品中微量成分的研究进展

综述了高效液相色谱法在化妆品中防腐剂、防晒剂中紫外线吸收剂以及性激素的检测等几个方面的应用;同时,介绍了分析所用的色谱柱、流动相、使用的检测手段以及样品的提取方法;最后针对目前存在的问题,提出了高效液相色谱用于化妆品中微量成分分析的研究方向和发展前景。     

Denitrification in shallow groundwater in a coastal agricultural area in Japan

In a coastal agricultural area in the central part of Japan (Shizuoka), we found decreasing nitrate concentration with depth in a shallow groundwater, where the depth to water table varied between 0.6 and 1.2 m below ground surface. High nitrate concentrations (5–29 mg N L^–1) were often observed in the upper layer (0–2 m) of the groundwater, but the concentration decreased to less than 1 mg N L^–1 in the deeper layer. Ammonium was scarcely detected, and the concentration of dissolved oxygen was usually low (< 1 mgO₂ L^–1) in the groundwater. Nitrate in the groundwater often had very heavy nitrogen stable isotope ratios (>20{}). There was a negative relationship between nitrogen stable isotope ratio of nitrate and its concentration. When nitrate was injected into the groundwater with acetylene and bromide (a conservative tracer), nitrate concentration decreased to 20% of the initial level within 5 days, accompanied by the increase in nitrite and nitrous oxide concentration and a little change in bromide concentration. These results indicate that microbial denitrification plays a potential role in the decrease of nitrate in shallow groundwater at the study site.     

我国硝酸工业生产技术新进展

系统叙述了我国硝酸工业2000-2007年生产现状及主要技术成果,尤其指出了国产"四合一"机组的成功投运,使我国硝酸国产化装置取得较大的进步,表现在吨酸的铂耗、氨耗和能耗等方面接近国外引进装置水平,同时介绍了国外双加压法硝酸生产技术的进展.我国已成为硝酸生产大国,仍需以先进的技术改造和发展我国硝酸工业,确保我国硝酸工业健康有序地发展,加快从硝酸生产大国向强国迈进的步伐.