Comparison of EI and metastable atom bombardment ionization for the identification of polyurethane thermal degradation products

Polyurethanes are widely used in the manufacture of commercial products such as foams and paints. During combustion, these polymers can generate isocyanates, which induce adverse health effects. Polymer pyrolysis (Py) hyphenated with mass spectrometry (MS) allows the investigation of polymer thermal degradation over time/temperature. A diphenylmethanediisocyanate (MDI) polyurethane foam was analyzed with electron ionization (EI) and metastable atom bombardment (MAB) ionization at a pyrolysis temperature of 400 °C. The recently introduced MAB ionization source uses discrete energy stored in metastable atoms of gases to ionize the analytes. This characteristic allows modulation of the ionization energy by simply changing the ionization gas. The extensive fragmentation of molecular ions observed using EI 70 eV is not totally eliminated with EI 10 eV. However, only molecular ions are observed with MAB using N₂ as the ionization gas. Temperature gradients were used to separate the products generated during the thermal degradation of a 1,6-hexamethylenediisocyanate (HDI) polyurethane paint. The analysis of mass spectra was facilitated owing to a selective desorption of pyrolysis products. Furthermore, changing the MAB ionization gas allows elucidation of the structure of the pyrolysis products by controlling the extent of their fragmentation. During these experiments, isocyanic acid, methyleneisocyanate, ethyleneisocyanate, propylisocyanate and butylisocyanate were detected.     

1,6-六亚甲基二异氰酸酯自聚产物的结构表征

用IR与NMR表征了用醋酸钾为催化剂时 1,6 六亚甲基二异氰酸酯 (HDI)自聚产物的结构 .结果表明 ,自聚主产物是三聚体异氰脲酸酯 ,主要含有三聚体异氰脲基、异氰酸根 ,同时含有由杂质带来的微量氨基甲酸酯、脲基甲酸酯基、取代脲基、缩二脲基 .一维核磁谱及二维化学位移相关谱分辨出 7种羰基 ,一种NCO基 ,确定了氮上 8种不同取代结构的分子链连接情况 .通过建立理论模型 ,定量地描述了自聚产物的结构 .     

Zn-Co bimetallic supported ZSM-5 catalyst for phosgene-free synthesis of hexamethylene–1,6–diisocyanate by thermal decomposition of hexamethylene–1,6–dicarbamate

A set of mono-and bimetallic(Zn-Co) supported ZSM-5 catalysts was first prepared by PEG-additive method. The physicochemical properties of the catalysts were investigated by FTIR, XPS, XRD, N_2adsorption-desorption measurements, SEM, EDS and NH3-TPD techniques. The physicochemical properties showed that the Zn Co_2O_4 spinel oxide was formed on the ZSM-5 support and provided effectual synergetic effect between Zn and Co species for the bimetallic catalyst. Furthermore, bimetallic supported ZSM-5 catalyst exhibited weak, moderate and strong acidic sites, while the monometallic supported ZSM-5 catalyst showed only weak and moderate or strong acidic sites. Their catalytic performances for thermal decomposition of hexamethylene–1,6–dicarbamate(HDC) to hexamethylene–1,6–diisocyanate(HDI) were then studied. It was found that the bimetallic supported ZSM-5 catalysts,especially Zn-2Co/ZSM-5 catalyst showed excellent catalytic performance due to the good synergetic effect between Co and Zn species, which provided a suitable contribution of acidic sites. HDC conversion of 100% with HDI selectivity of 91.2% and by-products selectivity of 1.3% could be achieved within short reaction time of 2.5 h over Zn-2Co/ZSM-5 catalyst.     

有序介孔硅片粒子表面的修饰及其表征

采用溶胶-凝胶的方法制备了粒径在50~300nm,具有正六边形的介孔二氧化硅片,用1,6-己二异氰酸酯(hexamethylene diisocyanate,HDI)对有序介孔硅片粒子表面进行有机化修饰,使其表面接枝能够参与反应的N=C=O活性基团。用FTIR、热重分析、TEM等分析方法对修饰后的有序介孔硅片粒子进行了表征,以确定HDI接在了有序介孔硅片粒子的表面。     

西佛碱型液晶聚氨酯的合成及表征

亚甲基二异氰酸酯（ＨＤＩ）,甲苯二异氰酸酯（ＴＤＩ）及４,４’－二苯基甲烷二异氰酸酯（ＭＤＩ）进行缩聚,得到晶液聚氨酯ＢＨＢＡＰ－ＨＤＩ,ＢＨＢＡＰ－ＴＤＩ及ＨＢＨＡＰ－ＭＤＩ,其液晶性质用ＤＳＣ,Ｘ－光射线衍射及热台偏光显微镜进行了表征。ＢＨＢＡＰ－ＨＤＩ,ＢＨＢＡＰ－ＴＤＩ分别在２００￣２３１℃,１６７￣２１１℃区域显示液晶行为,而ＢＨＢＡＰ－ＭＤＩ的熔融温度则高于２８０℃。并且利用ＤＳＣ对Ｂ     

Latest advances in zwitterionic structures modified dialysis membranes

End-stage renal diseases are affecting many patients and as a result, demand to receive dialysis service is growing annually. Morbidity and mortality rates are reported to be higher in comparison with healthy humans. The reason is reported to be the hemoincompatiblity of blood purification membranes, which hinders patients’ lives. Activation of different immune systems in the body, in case of blood-membrane interaction, results in several side effects, of which cardiovascular shocks have been mentioned to be a major one. Efforts to solve this issue have resulted in different generations of dialysis membranes. Zwitterionic immobilized membranes are the latest (third) generation, which owns a higher degree of hemocompatiblity with more stability of immobilized structures. This critical review intends to cover recent efforts conducted over the zwitterionization of polymeric membrane surfaces with the goal of improving hemocompatibility. Different aspects of third-generation membranes are discussed for a better understanding of the current gap and gathering the knowledge to further develop the field. Accordingly, this critical survey provides an in-depth understanding of blood purification membranes zwitterionization for paving the way for the optimum enhancement of hemodialysis membrane hemocompatibility.     

Method for determining airborne diisocyanates

A method has been developed for quantitatively determining 3 typical diisocyanates, viz. 2,4-toluylene diisocyanate (2,4-TDI), hexamethylene diisocyanate (HDI) and 4,4-diphenyl-methane diisocyanate (MDI). The technique relies on chemisorption onto a suitable carrier material contained in an absorption tube coated with 1-(2-pyridyl)piperazine (2-PP). Stable urea derivatives with high molar absorptivity are formed, desorbed from the carrier material, separated by means of highpressure liquid chromatography and identified. The limits of detection for a sample volume of 20 1 of air are 0.9g m^–3 for 2,4-TDI and HDI, and 0.6g m^–3 for MDI. The derivatives are stable at 4°C for longer than 30 days. The influence of atmospheric humidity and the interference of dibutylamine on the detection reaction were investigated for 2,4-TDI and HDI. The whole procedure is easy to perform, highly sensitive and very reproducible and is suitable for monitoring concentrations of 2,4-TDI, HDI and MDI.Dedicated to Prof. Dr. W. Fresenius on the occasion of his 75th birthday     

"一带一路"与人文发展的空间依赖性分析

基于2014年"一带一路"沿线61个国家的人文发展指数,利用Moran'I空间自相关统计量检验"一带一路"沿线国家人文发展指数之间的空间自相关性,利用空间误差模型研究了"一带一路"战略对沿线国家的教育、医疗卫生等指数的影响.结果表明:"一带一路"沿线61国人文发展水平之间存在明显的空间自相关性,即空间聚集性和异质性并存;"一带一路"战略的实施必将对沿线国的教育、医疗卫生等发展做出积极贡献.     

NMR研究HDI与水的加成产物N-100结构

用NMR研究了六次甲基二异氰酸酯与水的加成产物N－100的结构．结果表明：N－100中含有脲基、缩二脲基、双缩二脲基、三聚体异氰脲基、异氰酸酯和氨基等基团，是一种以氢原子为交联点、胺和异氰酸酯为端基的具有复杂网络结构的多异氰酸酯．一维核磁谱及二维化学位移相关谱不但分辨出4种羰基，还确定了氮上5种不同取代结构的分子链连接情况．通过建立理论模型，准确地定量描述了N－100的网络结构．     

The synthesis and characterization of new thermoplastic poly(thiourethane‐urethane)s

New thermoplastic segmented poly(thiourethane‐urethane)s (SPTUUs) were prepared by a one‐step melt polymerization from 20 to 80 mol % poly(tetramethylene oxide) of = 1000 or poly(hexamethylene carbonate) diol (PHCD) of = 860 as soft segments, hexamethylene diisocyanate (HDI) and bis[4‐(mercaptomethyl)phenyl]methanone (BMMPM) as a new dithiol chain extender at the NCO/(OH + SH) molar ratio of 1 in the presence of dibutyltin dilaurate as a catalyst. The structures of the SPTUUs were examined by FTIR, X‐ray diffraction analysis, and scanning electron microscopy. The SPTUUs were also characterized by physicochemical, thermal, and tensile properties as well as Shore A/D hardness. The SPTUUs with the PHCD soft segments showed better tensile properties than those with the PTMO soft segments. A nonsegmented polythiourethane based on BMMPM and HDI is also described. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1770–1782, 2008