Free radical grafting of glycidyl methacrylate onto polypropylene in a co-rotating twin screw extruder

Free radical grafting of glycidyl methacrylate (GMA) onto molten polypropylene (PP) was studied in a co-rotating twin screw extruder. Grafting yields of GMA obtained under various experimental conditions along the screw length allowed for a good appreciation of the effects of chemical parameters (the presence of styrene and the concentrations of peroxide and monomers) and those of processing parameters (feed rate, screw speed, and specific throughput). Similar to the results obtained in a batch mixer,¹ free radical grafting of GMA carried out in the extruder in the presence or absence of styrene proceeded rapidly, as it was virtually completed half-way down stream of the extruder. Additionally, the presence of styrene as a second monomer increased the GMA grafting yield reatly with reduced PP chain degradation. The ultimate GMA grafting yield increased with increasing concentration of peroxide, 1,3-bis(tert-butylperoxyisopropyl)benzene. This similarity between the batch mixer and the extruder is related to the fact that in both cases it is the concentration of the peroxide and its half lifetime that determine the grafting rate and the ultimate grafting yield. On the othe hand, the GMA grafting yield decreased with increasing screw speed or feed rate. For a particular specific throughput (the ratio of throughput to screw speed), an increase in throughput with a concomitant increase in screw speed brought about a decrease in GMA grafting yield. It was concluded that the GMA grafting yield is affected primarily by the residence time in the zone in which free radicals are not depleted. The effects of screw speed, feed rate, and specific throughput manifest mainly through this local residence time distribution. Specific energy is not a good measure of the performance of the extruder with respect to the free radical rafting of GMA onto PP. © 1995 John Wiley & Sons, Inc.     

Quaternary reactive dyes containing a thioether‐ethylsulphone group. Part 2; Application methods for the dyeing of nylon†

A member of the new series of cationic reactive dyes containing a thioether‐ethylsulphone grouping referred to in Part 1 of this series has been applied to nylon at pH 3–10. The dye is water soluble and shows excellent substantivity for nylon 6.6 when dyed at the boil at pH 8–10. Under alkaline conditions, gradual β‐elimination back to the vinylsulphone dye occurs and covalent bond formation quickly takes place with the fibre; the higher the pH the more rapidly this occurs. Dyeings carried out at pH 10 showed very good brightness and levelling, together with good wash fastness. The light fastness of dyeings at moderate depth was 4–5 on the Blue Wool scale.     

Ethanol electrooxidation on novel carbon supported Pt/SnOx/C catalysts with varied Pt:Sn ratio

Novel carbon supported Pt/SnO_x/C catalysts with Pt:Sn atomic ratios of 5:5, 6:4, 7:3 and 8:2 were prepared by a modified polyol method and characterized with respect to their structural properties (X-ray diffraction (XRD) and transmission electron microscopy (TEM)), chemical composition (XPS), their electrochemical properties (base voltammetry, CO_ad stripping) and their electrocatalytic activity and selectivity for ethanol oxidation (ethanol oxidation reaction (EOR)). The data show that the Pt/SnO_x/C catalysts are composed of Pt and tin oxide nanoparticles with an average Pt particle diameter of about 2 nm. The steady-state activity of the Pt/SnO_x/C catalysts towards the EOR decreases with tin content at room temperature, but increases at 80 °C. On all Pt/SnO_x/C catalysts, acetic acid and acetaldehyde represent dominant products, CO₂ formation contributes 1-3% for both potentiostatic and potentiodynamic reaction conditions. With increasing potential, the acetaldehyde yield decreases and the acetic acid yield increases. The apparent activation energies of the EOR increase with tin content (19-29 kJ mol⁻¹), but are lower than on Pt/C (32 kJ mol⁻¹). The somewhat better performance of the Pt/SnO_x/C catalysts compared to alloyed PtSn_x/C catalysts is attributed to the presence of both sufficiently large Pt ensembles for ethanol dehydrogenation and C-C bond splitting and of tin oxide for OH generation. Fuel cell measurements performed for comparison largely confirm the results obtained in model studies.     

Application of pulse discharge sintering (PDS) technique to rapid synthesis of Ti3SiC2 from Ti/Si/C powders

To synthesize Ti₃SiC₂ samples, pulse discharge sintering (PDS) technique was utilized to sinter elemental powders of Ti/Si/C with stoichiometric and off-stoichiometric ratios in a temperature range of 1200–1500 °C. The results showed that high purity Ti₃SiC₂ could not be obtained from the Ti/Si/C powder with molar ratio of 3:1:2, and Ti₃SiC₂ preferred to form at relatively low sintering temperature for a short time. When 5Ti/2Si/3C and 3Ti/1.5Si/2C powders were sintered for 15 min, the TiC content was respectively decreased to 6.4 and 10 wt.% at 1250–1300 °C. The corresponding relative density of the samples sintered from 5Ti/2Si/3C powder was calculated to be as high as 99% at the temperature above 1300 °C. It is suggested that low-temperature rapid synthesis of Ti₃SiC₂ would be possible through the PDS technique, provided that the composition of the starting powders should be adjusted to be off-stoichiometric ratio from 3:1:2.     

大直径浅圆仓缩尺模型试验研究

大直径浅圆仓在生产过程中,由于仓底的偏心卸料使筒仓仓壁产生不均受力,会给筒仓结构的使用带来安全隐患。通过对浅圆仓缩尺模型试验,模拟筒仓生产过程的卸料状况,并对筒仓仓壁及仓底廊道顶部进行压力测试,将测试结果与理论计算进行对比,从而得出偏心卸料与静载状态的超压系数,为大直径浅圆仓设计提供依据。     

国外聚甲醛生产技术现状与发展

综述了国外主要甲醛生产厂商的工艺技术，树脂生产技术的发展和品种开发情况。     

短纤维-橡胶复合材料在输送带中的应用

介绍了以不连续的聚酯短纤维群为骨架材料，ＮＲ／ＳＢＲ为基质胶的定向短纤维橡胶复合材料（ＯＳＦＲＣ）在输送带中的应用。结果表明，ＯＳＦＲＣ输送带与棉帆布芯输送带相比，使用寿命提高１倍，带体综合物理性能好，在应力作用下不脱层，无受潮霉烂现象，输送平稳且不打滑，适宜在苛刻条件下使用。     

Oxidative coupling of methane over Na+-ZrO2-C1-/Al2O3 catalysts

Oxidative coupling of methane (OCM) was carried out over Na⁺-ZrO₂-Cl /A1[₂O₃ catalysts in a temperature range from 1023 to 1123 K. The catalysts were prepared by impregnating the α- or γ-Al₂O₃ supports with sodium carbonate and/or zirconyl chloride. The OCM activity was examined using the catalysts prepared by three different preparation procedures. The best catalyst was the one prepared by subsequent impregnation of sodium carbonate-preimpregnated γ-Al₂O₃ with a mixed solution of sodium carbonate and zirconyl chloride. It was found that preimpregnated sodium played an important role in reducing the combustion activity of the γ-Al₂O₃. The catalyst with an optimal composition showed the highest C₂ selectivity and yield of 40.8% and 15.1%, respectively. From the X-ray diffraction analysis it was found that tetragonal ZrO₂ was formed and that NaCl existed in the catalysts with relatively high sodium contents.     

Electrodeposition Behaviour of Cadmium Telluride from 1-ethyl-3-methylimidazolium Chloride Tetrafluoroborate Ionic Liquid

Voltammetry at a glassy carbon electrode was used to study the electrochemical deposition of Cd–Te from the Lewis basic 1-ethyl-3-methylimidazolium chloride/tetrafluoroborate air-stable room temperature ionic liquid between 80 °C and 140 °C. Deposition of tellurium alone occurs through a four-electron reduction of Te(iv) to Te which could be further reduced to Te(-ii) at a more negative potential. The Cd–Te electrodeposits could be obtained by the underpotential deposition (UPD) of Cd on the deposited Te. The UPD of Cd on Te was, however, limited by a slow charge transfer rate. Samples of Cd–Te electrodeposits were prepared on tungsten and titanium substrates and characterized by energy dispersive spectroscope (EDS), scanning electron microscope (SEM), and X-ray powder diffraction (XRD). The results showed that an excess amount of Cd(ii) was required in order to prepare CdTe codeposits with a Cd/Te atomic ratio approached 1/1. The deposit composition was independent of the deposition potential within the Cd UPD range. Raising the deposition temperature increased the UPD rate of Cd and promoted the formation polycrystalline CdTe.     

Preparation and characterizations of interpenetrating polymer network hydrogels of poly(ethylene oxide) and poly(methyl methacrylate)

Interpenetrating polymer network (IPN) hydrogels based on poly(ethylene oxide) and poly(methyl methacrylate) were prepared by radical polymerization using 2,2‐dimethyl‐2‐phenylacetophenone and ethylene glycol dimethacrylate as initiators and crosslinkers, respectively. The IPN hydrogels were analyzed for sorption behavior at 25°C and at a relative humidity of 95% using dynamic vapor sorption. The IPN hydrogels exhibited a relatively high equilibrium water content in the range of 13–68%. The state of water in the swollen IPN hydrogels was investigated using differential scanning calorimetry. The free water in the hydrogels increased as the hydrophilic content increased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 258–262, 2003