负载型二亚胺镍催化剂制备支化聚乙烯的结构与性能

负载型二亚胺镍催化剂制备支化聚乙烯的结构与性能;二亚胺镍配合物; 负载催化剂; 支化聚乙烯     

高强聚乙烯纤维的冷等离子体改进

高强聚乙烯纤维的冷等离子体改进金士九，倪亦斌，张佐光（中国科学院化学研究所北京１０００８０）（北京航空航天大学北京）关键词　高强聚乙烯纤维，等离子体，表面改性，界面性能由高强聚乙烯纤维制成的复合材料抗高速撞击（抗弹）性能远远优于芳纶纤维，广泛用作各种...     

PE膜中层状双羟基复合氢氧化物的红外吸收性能

水滑石;聚乙烯薄膜;PE膜中层状双羟基复合氢氧化物的红外吸收性能     

聚乙烯光引发交联及其工业应用研究的新进展

结合作者近年来在聚乙烯光引发交联及其工业应用研究的系统工作,评述了该领域国内外的研究进展和取得的主要突破性成果,简要介绍了聚乙烯本体光交联的强化引发体系、光交联机理、交联点微结构和晶体形态结构及其性能特征,介绍了光交联聚乙烯电缆新技术和未来的应用前景.     

表面处理剂在氢氧化镁阻燃聚乙烯体系中的应用

探讨了几种常用的表面处理剂对氢气体镁－聚乙烯阻燃体系的力学性能及燃烧性能的影响。实验结果表明,在聚乙烯中添加100phr氢氧化镁后其力学性能已经严重劣化。通过添加适量的表面处理剂可以大大改善体系的新裂伸长率,但是通过会使其拉伸强度有所下降,阻燃性能有所降低。     

线性低密度聚乙烯和聚苯乙烯共混物的原位增容及其形态、结构和性能

反应挤出;线性低密度聚乙烯和聚苯乙烯共混物的原位增容及其形态、结构和性能     

超高分子量聚乙烯的研发及应用

超高分子量聚乙烯(UHMWPE)是一种性能卓越的工程塑料,同众多的聚合材料相比,具有其它工程塑料所无法比拟的耐冲击性、耐磨损性、耐化学药品性、耐低温性、耐应力开裂性、抗粘附能力,优良的电绝缘性、自润滑性及安全卫生等性能,可以代替碳钢、不锈钢、青铜等材料广泛地应用于体育、纺织、采矿、化工、包装、建筑、机械、电气、医疗等领域。本文综述了国内超高分子量聚乙烯生产现状、需求、产品加工和应用情况,并对其以后的发展前景进行了预测。     

国家自然科学基金资助课题

 本文叙述了在聚乙烯-马来酸酐熔融接枝反应过程中,伴随着聚乙烯分子之间的交联反应,少量的己内酰胺添加剂可以有效地阻止交联反应的发生,改善体系的流变性能,而不明显地降低它的接枝率。这种马来酸酐化聚乙烯作为界面相容剂可使尼龙6-聚乙烯共混物的简支梁抗冲击强度比没有界面相容剂的共混物增加近4倍。     

超高相对分子质量聚乙烯纤维

超高相对分子质量聚乙烯是一种重要的高性能纤维 ,本文介绍了该纤维的制备、结构、性能以及应用等方面的研究情况。     

添加群青的蓝光聚乙烯多功能薄膜的研究

通过对添加群青、远红外线阻隔剂的聚乙烯薄膜和普通聚乙烯薄膜的物理机械性能以及透光率、雾度、紫外线透过率、远红外线透过率等光学性能的对比，论述了群青蓝光多功能聚乙烯水稻育秧薄膜的优异性能，并对其在水稻育苗中的实际应用进行了评述。     

Catalytic oxidative degradation of polyethylene crystals

Linear polyethylene crystals have been degraded with oxygen in the presence of a catalyst composed of cobaltous and bromide ions at temperatures between 60 and 130°. The number of carbonyl groups introduced into polyethylene increases as the oxidation temperature is raised. Infra-red spectroscopy and molecular weight evidence suggests that ketone groups are formed by a non-chain scission reaction, whereas aldehyde and carboxylic acid groups result from chain scission reactions. Molecular weight distributions of the degradation products show that reactions occur selectively in the amorphous regions at the crystal surfaces, when oxidations are performed below 110°. At higher temperatures, the chains are degraded randomly. The carbonyl groups introduced into polyethylene were oxidized to carboxylic acid groups with concentrated (～ 70 per cent) nitric acid. The results demonstrate that this two-stage process yields a polydisperse long-chain linear paraffin with carboxylic acid end-groups, when the catalytic oxidations are performed between 115 and 130°.     

Biodegradable network elastomeric polyesters from multifunctional aliphatic carboxylic acids and poly(epsilon-caprolactone) diols

Biodegradable elastomeric network polyesters were prepared from multifunctional aliphatic carboxylic acids such as tricarballylic acid (Yt) or meso-1,2,3,4-butanetetracarboxylic acid (Xb) and poly(epsilon-caprolactone) (PCL) diols with molecular weights of 530, 1,250 and 2,000 g.mol-1. Prepolymers prepared by a melt polycondensation were cast from DMF solution and postpolymerized at 280 degrees C for various periods of times to form a network. The resultant films were transparent, flexible and insoluble in organic solvents. The network polyesters obtained were characterized by IR absorption spectra, WAXS, density measurement, DSC, and tensile test. YtPCL1250, and XbPCL1250 network polyester films showed good elastomeric properties with high ultimate elongation (540-590%), and low Young's modulus (2.5-3.3 MPa). The enzymatic degradation was estimated by the weight loss of network films in a buffer solution with Rhizopus delemar lipase at 37 degrees C. The degree and rate of degradation were significantly affected by the molecular weight of PCL diol, chemical structures of multifunctional aliphatic carboxylic acids and the morphology of network films. The changes in the solid states of network films during the degradation were also estimated by the results of DSC and WAXS. [see text]     

Preparation and chain extension of C100dicarboxylic acid

The selective degradation of polyethylene crystals with fuming nitric acid has been used to prepare a C₁₀₀ chain with terminal functional groups. After treating this product with concentrated sulphuric acid, it is shown by average molecular weight, titration and infra-red spectroscopy measurements that each molecule contains two carboxylic acid groups. This C₁₀₀ dicarboxylic acid is chain extended with several low molecular weight difunctional coupling agents. Block copolymers of this acid and poly(propylene glycol) have been prepared.     

Studies on the photo-oxidative degradation of LDPE films in the presence of oxidised polyethylene

This paper reports the results of photo-oxidative degradation studies of LDPE in the presence of varying amounts of oxidised polyethylene (OPE), which was prepared by heating LDPE films containing 0.1% cobalt stearate in oxygen atmosphere at 100 °C. OPE, with a CI of 12 was used as an additive for LDPE. Varying amounts of OPE (0.5-5%) were blended with polyethylene in an extruder and films of 70 μm thickness were prepared by film blowing process. The physico-chemical properties of the films were evaluated and these were found to be proportional to the amount of OPE. The films thus obtained were subjected to UV-B exposure at 30 °C for extended time periods. The chemical and physical changes induced by UV exposure were followed by monitoring the changes in mechanical properties (tensile strength and elongation at break), carbonyl index (CI), morphology, molecular weight, MFI and DSC crystallinity. Incorporation of OPE was found to be effective in initiating the photo-degradation of LDPE in relatively short span of time and the degradation was found to be proportional to the amount of OPE in the formulation.     

Effect of cobalt carboxylates on the photo-oxidative degradation of low-density polyethylene. Part-I

The effect of three cobalt carboxylates of increasing chain length, namely cobalt laurate, cobalt palmitate and cobalt stearate on the photo-oxidative degradation of low-density polyethylene (LDPE) films has been investigated. LDPE films containing cobalt carboxylates were irradiated with UV-B light at 30 °C for extended time periods. FTIR spectroscopy, mechanical testing, morphological studies, molecular weight, density and MFI measurements were performed to monitor the degradation behaviour. The results of these studies were analysed to explain the structural and chemical modifications taking place in the polyethylene matrix due to UV-B exposure. FTIR studies indicate that the degradation is dominated by formation of carbonyl and vinyl species. The studies on mechanical properties reveal that samples containing cobalt carboxylates, become mechanically fragile after UV exposure for 400 h, while neat LDPE exhibits insignificant changes during this period. The degradation was found to increase proportionally with increasing chain length and follows the order CoSt₃ > CoPal₃ > CoLau₃. Migration studies were performed on food simulant systems to investigate the applicability of these films for food packaging.     

XPS study of carboxylic acid layers on oxidized metals with reference to particulate materials

Low‐molecular‐weight organic additives such as stearic acid are commonly used as surface additives in powder injection moulding (PIM). It is therefore important to know how the additives interact with the surface of the powder used. In this study, such interactions are studied by means of controlled adsorption of carboxylic acids on the oxides of interest. The oxides are prepared by oxidation of flat samples of Fe, Cr, Mn and Si. Surface chemical characterization is done by means of XPS, the main approach on flat samples being a comparison of angle‐resolved analysis and the use of the Tougaard nanostructure analysis technique. Taking advantage of this comparison, the Tougaard method is then applied in the evaluation of XPS analyses of stainless‐steel powder with adsorbed stearic acid. In addition, time‐of‐flight SIMS analysis is used to verify the adsorption of stearic acid on the powder surface. It is shown that Tougaard nanostructure analysis can be used for determining the thickness of an organic layer on particulate material. The layer thickness of adsorbed stearic acid was estimated to be ～20 Å, corresponding to monolayer adsorption. Time‐of‐flight SIMS analysis verified the adsorption of stearic acid on the powder surface. From the XPS analysis of flat samples it was determined that the use of the metal/oxide universal cross‐section in Tougaard nanostructure analysis best described the increased background due to adsorption of carboxylic acids, and that information about molecular orientation could be gained. Copyright © 2003 John Wiley & Sons, Ltd.     

高性能光催化降解聚乙烯薄膜的研究

利用酸性蓝BGA染料敏化的纳米TiO2作为光催化剂, 与低密度聚乙烯(LDPE)树脂复合制备了具有可见光催化降解性能的复合塑料薄膜. 采用SEM、FTIR、VHX-100数码显微镜和高温凝胶渗透色谱(HTGPC)等分析技术系统地研究了该塑料薄膜在紫外光和太阳光照射下的降解性能. 探讨了塑料薄膜在光辐照前后的力学性能、质量和分子量变化规律. 研究结果表明, 该薄膜在经紫外线照射5 d后质量损失达到17.6％, 数均分子量由21800降低为5900; 经太阳光照射48 d后质量损失达到12.5％, 分子量降为8100. 辐照后薄膜拉伸强度和断裂伸长率显著降低, 羰基含量升高.     

Evaluation of the rate of abiotic degradation of biodegradable polyethylene in various environments

The rate of abiotic degradation of polyethylene (PE) films containing a manganese pro-degradant has been studied in various environments at 60 and 70 °C. The degradation was monitored from the change in molecular weight and the elongation at break after exposure to dry and humid air. It was observed that moisture had a strong accelerating effect on the rate of thermo-oxidation of PE films. However, despite the humidity level in the compost environment being similar to that in humid air, the rate of degradation in compost was much slower. It is proposed that ammonia and/or hydrogen peroxide generated by microorganisms in the compost can be responsible for the deactivating effect, as aqueous solutions of these compounds significantly retard the rate of degradation.     

Static SIMS studies of carboxylic acids on gold and aluminium–magnesium alloy surfaces

Static secondary ion mass spectrometry was used to study the surface reactions and lateral distributions of fatty carboxylic acid molecules on sputter‐deposited gold and aluminium surfaces, as well as commercial aluminium–magnesium alloy surfaces, cleaned using UV/ozone. Films were prepared by spin coating dilute solutions of stearic acid and lauric acid onto the above surfaces. These carboxylic acids were shown to react with the oxide formed on the aluminium and aluminum–magnesium alloy substrates to produce a deprotonated acid anion, stabilized by the formation of a magnesium soap on the aluminium–magnesium alloy surface. Secondary ion imaging of stearic acid films revealed the formation of C‐type crystals. Copyright © 2003 John Wiley & Sons, Ltd.     

四硫富瓦烯衍生物/硬脂酸LB膜的表征

研究了四（苄硫基）四硫富瓦烯／硬脂酸（TBT－TTF／SA）（1：1）LB膜、二（亚乙二硫基）四硫富瓦烯／硬脂酸（BEDT－TTF／SA）（1：1）LB膜和四（十六烷硫基）四硫富瓦烯／硬脂酸（THT－TTF／SA）（1：1）LB膜的结构．从X射线衍射结果得到了LB膜的层间距离．X射线衍射图显示了TBT－TTF／SALB膜和BEDT－TTF／SALB膜的层间结构由硬脂酸控制．从偏振红外结果计算出硬脂酸和四硫富瓦烯衍生物在LB膜中的取向角．根据分子取向角确定了LB膜的层间结构．用分子长度和分子取向角得到的层间距离与从X射线衍射得到的层间距离相吻合．