Study of the thermal decomposition of flame-retarded unsaturated polyester resins by thermogravimetric analysis and Py-GC/MS

The thermal degradation behaviours of flame-retarded unsaturated polyester resin formulations containing ammonium polyphosphate (APP), Cloisite 25A nanoclay and zinc based smoke suppressants have been studied using thermogravimetric analysis (TGA) combined with infrared analysis of the evolved gases (EGA) and pyrolysis/gas chromatography-mass spectrometry (GC/MS). In TGA-EGA experiments, the mass loss as a function of temperature has been correlated with the evolution of carbon monoxide (CO) and carbon dioxide (CO₂) and oxygen (O₂) consumption as measured by an oxygen analyser. The effect of APP, Cloisite 25A and the smoke suppressants on the evolution of CO and CO₂ has been examined. The decomposition behaviour of flame-retarded polyester resins under isothermal pyrolytic conditions was investigated and the evolved gaseous products were collected and qualitatively and semi-quantitatively analysed via GC/MS. The addition of APP does not yield many new gaseous products relative to the unmodified polyester resin neither does the presence of zinc borate (ZB) and zinc stannate (ZS) together with APP. Possible chemical interactions are discussed in an attempt to explain the observed results.     

Polyhedral oligomeric silsesquioxane (POSS) reinforced-unsaturated polyester hybrid nanocomposites: Thermal,thermomechanical and morphological properties

Unsaturated polyester (UP)-POSS hybrid nanocomposites have been developed successfully through the reaction between maleimide groups Octa (maleimido phenyl) silsesquioxane (OMPS) and olefinic reactive sites (maleimide and styrenic units) present in the unsaturated polyester resin system through free radical polymerization using benzoyl peroxide (BP) as the initiator. The hybrid molecular structure of nanocomposites resulted was evaluated by FT-IR spectroscopy. The data obtained from XRD, SEM and TEM analysis ascertain the presence of homogeneous morphology and nanoscale dispersion of OMPS into the polyester hybrid nanocomposites. Data resulted from thermal (DSC and TGA) and thermo-mechanical (DMA) studies indicated that the incorporation of octamaleimide functionalized POSS into unsaturated polyester systems appreciably improved the thermal properties of the hybrid nanocomposites according to their percentage concentration.     

Exploring the activities of vanadium,niobium, and tantalum PNP pincer complexes in the hydrogenation of phenyl-substituted CN,CN, CC,CC, and CO functional groups

The structures and stability of the designed PNP pincer amido M(NO)₂(PNP) and amino ^HM(NO)₂(PN^HP) complexes [M = V, Nb, and Ta, PNP = N(CH₂CH₂P(isopropyl)₂)₂, PN^HP = HN(CH₂CH₂P(isopropyl)₂)₂] and their hydrogenation mechanisms for phenyl-substituted unsaturated functional groups have been explored at the B3PW91 level of density functional theory. Under H₂ environment, these conjugated complexes can form equilibrium and fulfill the criteria of metal–ligand cooperated bifunctional hydrogenation catalysts. For the hydrogenation of Ph-CN, Ph-CHNH, Ph-CHNH-Ph, Ph-CHNCH₂Ph, Ph-CCH, Ph-CHCH₂, Ph-CHO, and Ph-COCH₃, the reaction prefers either a two-step or one-step mechanism for the hydridic MH and protonic NH transfer. These results clearly show that the V, Nb, and Ta complexes are promising catalysts for the hydrogenation reactions, and these provide experimental challenges.     

Manipulating the enone moiety of levoglucosenone: 1,3-Transposition reactions including ones leading to isolevoglucosenone

The manipulation of the enone moiety associated with the biomass-derived, homochiral and now abundant compound levoglucosenone (1) is described. While the trichloroacetimidates derived from the allylic alcohols 3 and 4 failed to engage in Overman-type rearrangements, certain ester derivatives reacted in the presence of Pd[0]-catalysts to give regio-isomeric mixtures of β,γ-unsaturated malonates or ketones, the structures of which were confirmed by single-crystal X-ray analyses. In other sequences involving 1,3-transposition reactions, an operationally simple means for converting compound 1 into isolevoglucosenone (2) is described.

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Seepage underneath barrages with downstream subsidiary weirs

A subsidiary weir with a sloping middle apron may be constructed downstream from each of the existing barrages on the River Nile in Egypt to secure its stability against the increase in effective heads. The problem is mathematically solved by a conformal mapping technique. Formulas are obtained to calculate the uplift pressures acting on the existing barrage and the subsidiary weir. Also formulas are derived to calculate the exit gradients along the intermediate filter and the downstream bed. We calculate the seepage characteristics for a wide range of boundary conditions, plot the results in the form of curves, and analyze them.     

Investigation of the carrier saturation in facilitated transport of unsaturated hydrocarbons

Single-component facilitated transports of ethylbenzene, styrene, cyclohexene and 1-hexene were carried out using the feed concentrations ranging from 0.5 M to pure. Equilibrium constants of the Ag⁺-solute complex formation, determined by distribution method, were 0.7, 2.2, 32.0, 129.1 M⁻¹, respectively. Carrier saturation was not found with the membrane incorporated with 2.67 M Ag⁺-ion. As the carrier concentration was reduced to 0.51 M, increase in the feed concentration beyond 4.5 M had very little effect on ethylbenzene flux, suggesting the onset of carrier saturation. Styrene and cyclohexene underwent the carrier saturation when the carrier loading was 0.25 M, while a complete saturation was not observed with 1-hexene. Extraction of solute from the membranes revealed that less than 50% of Ag⁺-ions were occupied when the carrier saturation occurred. It was also found that the ability of solute to use available Ag⁺-ions in the membrane was dependent on the equilibrium constant.     

Condensations of γ-Acetylacetonephosphonium Ylide (1-(Triphenylphosphoranylidene) pentane-2,4-dione) with Carbonyl Compounds

Summary. 2,4-Dioxopentyltriphenylphosphonium bromide reacted with aqueous sodium hydrogencarbonate in dichloromethane to give, in almost quantitative yield, 1-(triphenylphosphoranylidene) pentane-2,4-dione. Dianion Wittig- and Michael Wittig condensations of the last mentioned phosphonium ylide with carbonyl compounds gave unsaturated 2,4-diketones which were almost totally enolised in deutero chloroform as 4-hydroxy-2-oxo-3,5-dienes (24–70% yields). These products closely resembled the type of compounds derived from similar condensations with alkyl 3-oxo-4-(triphenylphosphoranylidene)butanoate. Present address: Boron Molecular Pty. Ltd., P.O. Box 756, Noble Park, Victoria, Australia 3174 E-mail: cmoorhoff@boronmolecular.com Received August 27, 2002; accepted September 3, 2002     

不饱和聚酯/环氧树脂嵌段共聚树脂的光固化研究

光固化涂料以其节省能源、减少空气污染、固化速度快、适用于自动化流水线涂布等特点而引起涂料行业的关注 .随着世界范围内对环境保护的日益重视和绿色科技的蓬勃发展 ,光固化技术因其能有效地控制空气污染 ,特别是可以大大减少挥发性有机物的排放而越来越受到青睐[1] .不饱和聚酯树脂 (ＵＰＲ)型的光固化树脂是发展最早和销售量最大的光固化树脂 .它是由二元羧酸与多羟基醇共缩合的缩聚物与活性单体的混合产物 ,二元羧酸中含有部分不饱和成分 .主要用于光敏树脂印刷版、光敏油墨、光敏涂料及印刷电路版的光致抗蚀膜等 .但是感光不饱和聚酯…     

天然差分方法在地下水渗流问题中的应用

在地下水渗流问题中,对不规则网格剖分后的结点控制元进行水量均衡分析,得到与伽辽金有限元法结果形式相同,但性质更优且自动满足质量守恒条件的稳定的计算格式.并可以简便的解决非线性的潜水问题.最后对泰斯问题进行了计算比较.     

Preparation of Some Novel,Highly Unstable Chain Conjugated 2H‐Pyran‐5‐carboxylates

Aldol condensations of conjugated unsaturated β‐ketoesters and unsaturated aldehydes gave chain conjugated 2H‐pyran‐5‐carboxylates.