Synthesis of Unsaturated Polyester Resin—Effect of Sequence of Addition of Reactants

Abstract

Unsaturated polyesters were synthesized in the laboratory by the condensation of maleic anhydride and phthalic anhydride with propylene glycol. The condensate obtained was mixed with styrene monomer to get an unsaturated polyester resin formulation. The properties of the polyester resin synthesized were found to be affected by the synthesis parameters. In this study, the effect of sequence of addition of reactants on the properties of resin was investigated. Properties such as tensile strength, tensile modulus, elongation at break, toughness, impact strength, surface hardness, abrasion resistance, and water absorption were evaluated after curing the resin. Propylene glycol necessary for esterification of both the anhydride fractions was initially reacted with phthalic anhydride. Later, the esterification was completed by reaction with maleic anhydride. This sequence of addition of reactants was found to give the best mechanical properties among all possible methods of reactant addition. Moreover, it was found that this sequence of addition of reactants gives the shortest reaction time.     

Mechanism of the Initial Stage of Thermal Decomposition of Nitroguanidine

A theoretical and experimental study of the thermal decomposition of nitroguanidine(NQ) has been carried out. Various thermolysis channels were studied by quantum chemistry methods at the CCSD(or DLPNO-CCSD) level using the aug-cc-pVDZ basis set. It is shown that the lowest activation enthalpies(170—180kJ/mol) are characteristic of the reactions of NO₂ abstraction from the initial NQ and the reaction channel with the transfer of oxygen from the nitro group to carbon in the limiting st...     

Effect of Addition of Al and Mg on properties of Periclase-Spinel-Carbon Brick

Periclase-spinel-carbon brick was made from sintered spinel,fused magnesia and flake graphite as principal raw materials,the influence of Mg/Al(w/w) ratio and the addition of Al,Mg in the matrix of periclas-spinel-carbon brikc on the carbonization and thermal expansion coeffi-cient and the weight los of the brick after heating at 1500℃ in a flowing stream of dry N2for 1.5 h have been studied.The results show that to control Mg/Al(w/w) ration and to add both Al and Mg appropriately can obvi-ously improve the properties of the bricks.     

Microstructure of Matrix of High technology Castable

Microstructures of matrixes of a series of high technology castables have been analyzed.In these low cement ,ultra-low cement and non-cement castable matrixes,which were sintered respectively at 1350℃ and 1500℃， silica ulrtafine and α-Al2O3 ultrafine were added ,The results show that the non-cement castable had the best properties at high temerature;adding α-Al2O3 ultrafine was helpful to calcium-feldspar deveoping and growing;and highly purified silica ultrafine stiumulated mullite crystal developing while the common one stimulated its growing.     

Identification of the pathway of α-oxidation of cerebronic acid in peroxisomes

Cerebronic acid (2-hydroxytetracosanoic acid), an α-hydroxy very long-chain fatty acid (VLCFA) and a component of cerebrosides and sulfatides, is unique to nervous tissues. Studies were carried out to identify the pathway and the subcellular site involved in the oxidation of cerebronic acid. The results from these studies revealed that cerebronic acid was catabolized by α-oxidation to CO₂ and tricosanoic acid (23:0). Studies with subcellular fractions indicated that cerebronic acid was α-oxidized in fractions having particulate bound catalase and enzyme systems for the β-oxidation of VLCFA (e.g., lignoceric acid), suggesting peroxisomes as the subcellular organelle responsible for α-oxidation of cerebronic acid. Etomoxir, an inhibitor of mitochondrial fatty acid oxidation, had no effect on cerebronic acid α-oxidation. Further, cerebronic acid oxidation was found to be dependent on the presence of NAD⁺ but not FAD, NADPH, ATP, Mg²⁺, or CoASH. Intraorganellar localization studies indicated that the enzyme system for the α-oxidation of cerebronic acid was associated with the peroxisomal limiting membranes. Studies on cultured fibroblasts from normal subjects and patients with peroxisomal disorders indicated an impairment of α-oxidation of cerebronic acid in cell lines that lack peroxisomes [e.g., Zellweger syndrome (ZS)]. On the other hand, α-oxidation of cerebronic acid was found to be normal in cell lines from X-linked adrenoleukodystrophy, adult Refsum disease, and rhizomelic chondrodysplasia punctata. Our results clearly demonstrate that α-oxidation of α-hydroxy VLCFA (cerebronic acid) is a peroxisomal function and that this oxidation is impaired in ZS. Furthermore, this α-oxidation enzyme system is distinct from the one for the α-oxidation of β-carbon branched-chain fatty acids (e.g., phytanic acid).     

Effect of spatial confinement on the development of β phase of polypropylene

The focus of this study was the effect of spatial confinement on the development of nucleating agent-induced β phase polypropylene (PP) in the dynamically vulcanized thermoplastic elastomers (TPVs) based on dynamically vulcanized PP/ethylene-propylene-diene rubber (EPDM) blend. The melting behaviors, crystalline structures and the morphologies of the blends were studied by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and scanning electron microscopy (SEM). The results indicate that the EPDM phase undergoes a series of changes from the dispersed phase to a continuous one, and again to the dispersed phase with increased content of curing agent, and the PP component always shows itself in a continuous phase. In this process, with the content of the nucleating agent unchanged, the content of β phase PP in the blends initially increases a little and then decreases with increasing PF (Phenolic resin) content. We believe spatial confinement provides a good explanation for the development of β phase PP.     

A Study of Materials of Silicate Production by Means of X-Ray Fluorescent Spectrometers of the “Spektroskan” Series

Refractories and Industrial Ceramics -     

Prediction of Swelling Behavior of AT-Isopropylacrylamide Hydrogels in Aqueous Solution of Sodium Chloride

In this paper, a model is presented to correlate and predict the swelling behavior of hydrogels in aqueous solutions of electrolytes. The model is a combination of VERS-model, "phantom network" theory and "free-volume" contribution. The VERS-model is used to calculate Gibbs excess energy; "phantom network" theory to describe the elastic properties of polymer network, and "free-volume" contribution to account for additional difference in the size of the species. To test the model, a series of N-isopropylacrylamide based hydrogels are synthesized by free radical polymerization in oxygen-free, deionized water at 25℃ under nitrogen atmosphere. Then, the degree of swelling of all investigated gels as well as the partition of the solute between the gel phase and the surrounding coexisting liquid phase are measured in aqueous solution of sodium chloride. The model test demonstrates that the swelling behavior correlated and predicted by the model agrees with the experimental data within the experimental uncert     

Correlation of the Rates of Solvolysis of Two Arenesulfonyl Chlorides and of trans-��-Styrenesulfonyl Chloride �C Precursors in the Development of New Pharmaceuticals

Additional specific rates of solvolysis have been determined, mainly in fluoroalcohol containing solvents, for benzenesulfonyl chloride (1) and p-nitrobenzene-sulfonyl chloride (2). For trans-β-styrenesulfonyl chloride (3), a study has been carried out in 43 pure and binary solvents, covering a wide range of hyroxylic solvent systems. For the specific rates of solvolyses of each of the three substrates, a good correlation was obtained over the full range of solvents when the extended Grunwald-Winstein equation was applied. The sensitivities to changes in solvent nucleophilicity and solvent ionizing power are similar to values determined earlier and an S_N2 process is proposed. For 3, kinetic solvent isotope effects of 1.46 for k_H2O/k_D2O and 1.76 for k_MeOH/k_MeOD were determined. These are also compared to literature values for other sulfonyl chlorides.     

Determination of optical purity of substituted β-lactones

An octakis (3-O-butyryl-2,6-di-O-pentyl)--cyclodextrin capillary gas chromatographic column was used to determine the optical purity of seven different -lactones, having substituents in - or -position, and DL-lactide. The resolving power varied from one lactone to another. The optical purity values determined by GC were in agreement with those obtained from NMR spectroscopy or optical rotation.     

Rheological Behavior of the Matrixes of Bauxite-Based Castables

Rheology of castables is greatly affected and cantrolled by rheological behavior of their matrix,In this work,the rheological properties of bauxite-based castable matrix have been studied.The effecfts of super-fine silica and alumina addition,water/cemenl ratio,dispersants and baurite particle-size on viscosity,shear rate and shear stress of the slurries have been investigated.Based on these results,the range of optinium composition of the matrix with good rheological behavior has been obtained.     

Ion-exchange synthesis of α-modification of nickel hydroxide

An anion-exchange method for synthesizing nickel hydroxide using industrial strongly basic AV-17-8 anionite has been proposed. The influence of conditions (concentration and nature of starting salt, amount of the anionite, process duration, etc.) on the precipitate yield has been established. The product has been investigated by scanning electron microscopy, IR and Raman spectroscopy, X-ray phase analysis, and thermal and chemical analyses. It has been established that the product is a disordered layered modification of nickel hydroxide α-Ni(OH)₂, which contains anions and water molecules in the interlayer spacing. Nickel hydroxide particles are needle crystals (40–80 nm) that form agglomerates 0.3–0.5 μm in size.     

Influence of sulfation and structure of zirconia on catalytic isomerization of n‐hexane

Two series of sulfated zirconia have been prepared by immersing amorphous or crystalline zirconia in an H₂SO₄ solution (0.25–2.5 M). They were compared with a commercial sulfated zirconium hydroxide. Activation temperature was varied between 300 and 725°C. Sulfate density varied so that the mean surface area of an individual sulfate ranged from 0.14 to 0.54 nm². Three limiting sulfate states are evidenced and characterized by TPRMS. Catalysts are tested for isomerization of nhexane at 150°C and 3 MPa. Factors influencing the activity are discussed. The data show that a highly active and selective catalyst for producing hexane isomers requires tetragonal zirconia with a sulfate occupancy of about 0.40 nm². Preparation parameters must therefore be adapted to match these constraints.     

Mechanisms of Phenol Ozonation—Kinetics of Formation of Primary and Secondary Reaction Products

Organic acids are part of assimilable organic carbon (AOC) formed from natural organic matter (NOM) during ozonation for drinking water production. To elucidate the formation of organic acids, phenol as surrogate compound for NOM was ozonated while suppressing reactions of ^·OH radicals by addition of tert-butanol. Batch experiments show benzoquinone (40 and 18%), catechol (33 and 1%), cis,cis-muconic acid (6 and 3%), and hydroquinone (2 and 7%) to be the most abundant primary products at pH 7 and 3, respectively. The tertiary product oxalic acid was obtained in similar yields from phenol ozonation (0.8%) as during ozonation of lake water (1.6%). Together with other low molecular weight organic acids it was formed upon small ozone exposures, as was shown by time-dependent experiments in time ranges of 0.4–23 and 0.07–1.0 seconds for pH 3 and 7.25, respectively.     

Direct measurements of voltage–Current characteristics of single grain boundary of ZnO varistors

In order to comprehend electrical properties of grain boundaries and other microscopic regions of electroceramics, an analytical apparatus based on scanning electron microscope (SEM) was newly developed. The apparatus was composed of SEM in which two micro probes made of Pt–Ir alloy were attached at the sample stage, an outer electric DC power supply and energy dispersion type X-ray analyzer (EDX), so that element analysis of specific area of samples was possible. Direct measurements of voltage–current (V–I) characteristics of single grain boundary of ZnO varistors having small grain size (≤10 μm) were attempted by the apparatus. As a result, nonlinear behavior of V–I characteristics of ZnO varistors was confirmed to take place at one grain boundary and, furthermore, inhomogeneity of the nonlinear V–I characteristics was observed.