Effect of Preparation Ph on Properties of Silica-Gel

WOS: A1990DW9820000

Effects of aqueous solutions of copper ammine and nickel ammine on wool

[No abstract available

Thermal degradation of poly(vinyl chloride) plastigels

WOS: 000071808800006An emulsion, poly(vinyl chloride) (PVC), was analyzed for its components and was used in the preparation of flexible PVC plates utilizing sol-gel processing technology. PVC contained an ether-soluble fraction having carboxylic acid carbonyl groups, a tetrahydrofurane (THF)-insoluble fraction having -COO- groups, and 0.15% aluminum. PVC was mixed with dioctyl phthalate (DOP) in a 0.3-0.8 DOP/PVC weight ratio and heated at 180 degrees C for gelation. The yellowness index (YI) and tensile strength of the plastigels were increased with both heating time and DOP concentration. Infrared (IR) spectroscopy showed that the thermal oxidation and volatilization of DOP occurred simultaneously with dehydrochlorination of PVC upon heating of the plastigels. Agglomeration of PVC particles on mixing with DOP at low DOP levels caused longer gelation times than expected. (C) 1998 John Wiley & Sons, Inc

Diffusivity, solubility and permeability of water vapor in flexible PVC/silica composite membranes

WOS: A1996UR18100011Flexible PVC/silica composite membranes having a porous structure have been produced using plastisol-plastigel technology. Equilibrium and rate studies related to water vapor adsorption on membranes have been studied using a Cahn 2000, gravimetric adsorption system. For the solubility and diffusivity of water vapor in membranes 4.23-7.74 cm(3)/(cm(3) cmHg) and 2.0-3.5 x 10(-13) m(2)/s values have been determined respectively. The measured permeability of water vapor through membranes 1.6-7.3 x 10(-6) ((cm(2)/s)/(cm(2) cmHg))cm, were much higher than predicted permeabilities 0.85-2.73 x 10(-8) ((cm(2)/s)/(cm(2) cmHg))cm. from solubility diffusion data, indicated the membranes had a porous structure. The membranes are suggested as a leather substitute since the permeability through membranes is comparable to that of leather and is at least 100 times higher than that of plasticized PVC film obtained by conventional processing techniques

Characterization and Dehydration Behavior of a Natural, Ammonium Hydroxide, and Thermally Treated Zeolitic Tuff

WOS: 000289262600008Aqueous NH4OH-treated and subsequently calcined forms of local natural zeolitic tuff were characterized by different techniques including scanning electron microscopy (SEM), X-ray powder diffraction, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), volumetric N2 adsorption at -196 degrees C, thermogravimetry (TG), differential scanning calorimetry (DSC), and transmittance infrared spectroscopy. The dehydration behavior of the samples was investigated using an in situ temperature-programmed diffuse reflectance Fourier transform infrared spectroscopy (TP-DRIFTS) method under vacuum. The DRIFTS spectra recorded yielded information about the effect of the NH4OH treatment and subsequent calcination on the dehydration behavior of the natural zeolite. Changes in the infrared bands corresponding to vibrations of the O-H and N-H bonds upon in situ heating under vacuum were analyzed.State Planning Organization [98K122130]This study was financially supported by the State Planning Organization (project number: 98K122130). The authors thank Dr. A. Allahverdiev for his contribution to experimental work

Effects of mixed metal stearates on thermal stability of rigid PVC

WOS: 000081020300015As a representative commercial heat stabilizer, Al 4180 was characterized by spectroscopic and thermal analysis techniques and used in thermal stabilization of rigid PVC. Al 4180 was a mixture of stearates of Al(III), Zn(II), Pb(II) and Ca(II) and metal hydroxides such as Al(OH)(3). Observed acceleration of dehydrochlorination of PVC was explained by the inefficient mixing of the stabilizer with PVC and formation of dehydrochlorination catalyst, ZnCl2 and AlCl3 on heating the films. (C) 1999 Elsevier Science Ltd. All rights reserved

A study of cobaltous chloride dispersion on the surface of the silica gel

WOS: 000080821900012Cobalt (II) salts dispersed on different substrates have functions as humidity indicating desiccants and catalysts. CoCl2, containing silica gel granules of 3 mm size for packed column applications were prepared by impregnation of the aqueous solution of the salt to silica hydro gel at pH near 2, drying and ageing methods. X-ray diffraction and electron microprobe studies indicated cobalt element was both dispersed in particulate form and as sub-monolayer. IR spectra indicated presence of Si-OH groups in all of the silica gels. CoCl2, containing silica gels changed colour from blue to pink upon moisture adsorption due to presence of the CoCl2, Co2SiO4 and Na2CoSiO4. (C) 1999 Elsevier Science B.V. All rights reserved

Effect of Preparation Ph on Pore Structure of Silica-Gels

WOS: A1993LR67700011Surface characterization of silica gels prepared at different gelation pH from water glass and sulphuric acid were made by argon adsorption at 77 K using continuous volumetric method. While microporous silica gels prepared in the pH range of 1-3 had BET surface areas of 504-571 m2 g-1, total pore volumes of 0.26-0.31 cm3 g-1 and micropore volumes of 0.16-0.23 cm3 g-1, mesoporous silica gels prepared in the pH range of 3.36-0.65 had BET surface areas of 374-530 m2 g-1 and pore volumes of 0.61-0.79 cm3 g-1