Thermal characterization and thermal degradation of poly(norbornene-2,3-dicarboxylic acid dialkyl esters) synthesized by vinyl addition polymerization

The thermal properties and degradation behaviors of poly(norbornene-2,3-dicarboxylic acid dialkyl esters) (PNB-dialkyl esters) (alkyl = Me (PNB-Me), Et (PNB-Et), Pr (PNB-Pr), and Bu (PNB-Bu)) were investigated by thermogravimetric analysis (TGA) in dynamic conditions and by infrared (IR) spectroscopy. The PNB-dialkyl esters show good thermal stability up to 350 °C, and the thermal stability decreases in the order Me > Et > Pr > Bu with the increase in size of side chain. The effect of side-chain size on the thermal degradation behaviors of PNB-dialkyl esters is evidenced by one-step thermal degradation profile for PNB-Me while two-step thermal degradation profile for PNB-Et, PNB-Pr, and PNB-Bu. Transformation is deduced to undergo β-hydrogen elimination and formation of anhydride group in the first stage of thermal degradation reaction according to TGA and IR results for PNB-Et, PNB-Pr, and PNB-Bu. The apparent activation energy and thermal degradation model of PNB-dialkyl esters are estimated by means of Ozawa-Flynn-wall method and Phadnis-Deshpande method, respectively.     

The effect of (natural) polyols on the initial colour of heavy metal- and zinc-free poly(vinyl chloride)

The propensity of (natural) polyols dispersed in heavy metal- and zinc-free PVC sheets to improve the initial colour, e.g. the colour during the first minutes of exposure to high processing temperatures (short-term stability), has been investigated. It is shown using W(Lab) values that the initial colour improves upon addition of polyols containing primary hydroxyl groups. The polyols act as HCl scavengers, presumably via an acid-catalysed S_N2 substitution of the primary hydroxyl groups by chloride ions. In contrast, polyols with only secondary or tertiary hydroxyl groups accelerate the thermal degradation of PVC. Notwithstanding, the efficacy of the (natural) polyols containing primary hydroxyl groups will be reduced if the polyol is susceptible to competitive acid-catalysed intramolecular cyclodehydration reactions under the processing conditions. This is substantiated by a comparison of the behaviour of mannitol and 3,4-di-O-methyl-d-mannitol. The methylated derivative, which is less prone to undergo intramolecular cyclodehydration, improves the initial colour of heavy metal- and zinc-free PVC sheets more significantly than mannitol itself.     

以钛氧有机物为前驱物制备具有高光催化活性的纳米二氧化钛晶体

 纳米二氧化钛的制备方法及前驱物的差别影响其光催化活性．将20ml钛酸丁酯及30ml乙酐在密闭容器中与50ml环己烷混合，在70～85℃反应30min，生成微细的非晶钛氧有机物；经FT－IR和TGA分析，该物质被确认为计量式是TiOOOCCH3）2和TiO（OC4H9）（OOCCH3）的混合体．该钛氧有机物前驱物经焙烧后得到具有高光催化活性的纳米二氧化钛晶体．表征结果表明，钛氧有机物在焙烧过程中，其表面的吸附物及键合有机基团在400℃以前发生脱附和氧化分解；在389～405℃间形成锐钛矿型晶体，在600℃出现金红石晶型；600℃焙烧3h所得样品的比表面积为86m2／g，其二次粒子呈200～300nm条形体，孔隙大于20nm；单分散粒子为球形单晶，粒径为22nm；表面物理吸附水量为1．21％，加热至800℃时失重1．48％，粉体稳定纯净．光催化实验结果表明，以钛氧有机物为前驱物制备的纳米二氧化钛晶体具有高的光催化活性，光降解丁基罗丹明溶液的反应速率常数约为溶胶－凝胶法制备的催化剂样品的4倍．表面氧空缺和一定量的表面羟基可能是粉体具有高光催化活性的重要因素．     

聚烯烃（聚乙烯）低温热氧化与降解

综述了近年来聚烯烃特别是聚乙烯的低温热氧化机理，动力学以及氧化降解研究现状及发展，指出现今低温热氧化与降解研究意义。     

Some Reactions of 5-(3 or 4-Pyridyl)-1,3,4-Oxadiazoles with Amines and Hydrazines

2-Amino-and 2-hydrazino-5-(3 or 4-pyridyl)-1, 3, 4-oxadiazoles [II_i-k] have been prepared by racting 2-chloro derivatives with the corresponding amines or hydrazines, the 2-hydrazino (II_i-k) compounds that obtained were heated with carbon disulphide and alcoholic potassium hydroxide where 5-(3 or 4-pyridyl)-1,3,4-oxadiazolo (2,3-C)-1,2,4-triazole 5-thione (III_a-c) were obtained, the given structures were biologically screened.     

Degradation of ²-O-4 lignin model and related compounds by the ascomyceteChrysonilia sitophila (TFB 27441 strain)

Growth of the ascomyceteChrysonilia sitophila during degradation of lignin model dimers and monomers was compared to a glucose control. An inhibition of growth by Cα-carbonyl monomers and stimulation by β-O-4 lignin model and vanillyl alcohol were observed. A comparison of the degradation by this ascomycete with the basidiomycetePhanerochaete chrysosoporium showed similarities in relation to the type of degradation caused.     

3-氨基-二氢噻吩-2-酮类Schiff碱的合成和生物活性研究

通过3-氨基-二氢噻吩-2-酮(DL-高半胱氨酸硫内酯)盐酸盐与取代苯甲醛反应, 得到3-氨基-二氢噻吩-2-酮类Schiff碱. 合成了9个化合物, 其中7个为首次报道的新Schiff碱类化合物. 化合物结构经IR, ¹H NMR和元素分析证实, 并对这些化合物进行了室内毒力测试, 结果表明此类化合物具有很好的杀菌、抑菌活性.     

A two-dimensional infrared correlation spectroscopic study on the thermal degradation of poly(2-hydroxyethyl acrylate)-co-methyl methacrylate/SiO2 nanohybrids

Two-dimensional infrared (2D IR) correlation spectroscopy was applied to study the structural changes occurring in the decomposition of PHEA-co-MMA/SiO₂. Complicated absorption spectral changes were observed in the heating process. 2D IR analysis indicates that during heating, covalent bonds, (Si-O-C), between the polymer and the inorganic moiety were formed, which was the main factor in the improvement in thermal properties of the hybrids such as the decomposition temperatures (T_d). The thermal stability of the hybrids was also studied by solid-state ²⁹Si MAS NMR spectroscopy and TGA tests. Their results complemented each other well.     

Degradative analysis of aquatic fulvic acid: CuO oxidation versus pyrolysis after tetramethylammonium hydroxide treatments in air and helium atmospheres

The structural composition of Nordic aquatic reference fulvic acid was investigated using chemical and thermal degradation methods: alkaline CuO oxidation and analytical pyrolysis after tetramethylammonium hydroxide (TMAH) pretreatment. Off-line procedures of the TMAH treatments were carried out under both air and helium atmospheres, with the aim of clarifying the effect of oxygen. Irrespective of the fact that the chemical and thermal degradation methods gave qualitatively quite similar basic products (mainly phenols and phenolic acids together with aromatic and aliphatic carboxylic acids), they also revealed their unique selectivity and efficiency for releasing different kinds of structural constituents. The results verify the formation of additional carboxyl functionality in the CuO oxidation. However, some similar oxidative reactions also appeared to take place during the pretreatment procedures of strongly basic TMAH, especially under an air atmosphere. The use of inert and protective atmosphere during the TMAH pretreatment is therefore recommended for producing more relevant structural information about the complex composition of humic substances.     

Solar Photocatalytic Degradation of 4‐Chlorophenol in Kaolinite Catalysts

This research applies semiconductor photocatalysts, which are formed by metal ion exchange on the surface of kaolinite catalyst with cations, to the study of photocatalytic degradation of 4‐chlorophenol. The analysis results of catalyst properties shows that, after sintering at 400 °C, kaolinite catalyst has a particle size of between 10–100 nm indicating the nano level of synthesized catalysts. Under the same condition, kaolinite‐Ag/Zn catalyst works better in degradation efficiency than single kaolinite‐Ag and kaolinite‐Zn catalysts. Kaolinite‐Zn catalyst declines in degradation efficacy after 150 minutes and performs poorer than the other three types of kaolinite catalysts. In the experiments of different amounts of catalysts, when the concentration exceeds 0.1 wt%, utilization of light energy and degradation efficiency will be reduced due to shielding effect. When at different pH values, the higher the pH value, the more OH‐will be released and that is beneficial for reaction with substances and the increase of reaction rate. Finally multivariate analysis proves that there is one determining factor that influences the photocatalytic degradation of 4‐chlorophenol in kaolinite catalysts, named as “the factor with intermediates competition degree,” the one affecting the 4‐CP degradation at different weight percentages that is referred to as the “shielding effect factor.”