Sevgi Ulutan

Separability of ethanol and water mixtures through PTMSP–silica membranes in pervaporation

Abstract Asymmetric poly[1-(trimethylsilyl)-1-propyne] (PTMSP) composite membranes having silica on one side, which were prepared in this study, have been examined for the enrichment of aqueous ethanol solutions using the pervaporation method. FTIR spectrum and SEM pictures have been taken to characterize the membranes. Sorption isotherm measurements were also made to elucidate the impact of silica on PTMSP. While PTMSP considerably swells with ethanol, no swelling has been observed with water. However, the silica-containing membranes have shown a greater degree of swelling in dilute ethanol solutions because of the high affinity of the silica to water. All of the membranes preferentially permeated ethanol, although the permeation rate and the permselectivity altered with the silica content of the membrane and with the amount of ethanol in the feed. A large amount of silica on PTMSP creates an effect like “scaling” and reduces the ethanol uptake of the membrane. The membranes having medium and low silica content exhibited high separability for dilute and medium ethanol concentrations. The pervaporation behavior of all of the membranes conforms with their swelling behavior.

Characterization of Hollow Chemical Garden Fibers from Metal Salts and Water Glass

Hollow fibers formed from water glass and metal salts of IIA(Ca), VIIB(Fe, Co, Ni) and IB(Cu) groups were characterised in this study. Fragile fibres obtained herein broke down into small pieces during isolation and drying. Quantitative information about morphology, chemical composition and surface structure of the fibres were obtained. The diameter and wall thickness of the fibers were around 50 μ and 3 μ. respectively. They had particulate inner and smooth outer surfaces. Fibers had variable composition with metal (II) oxide/SiO2 ratio in the range 0.31 to 1.02. While group VIIB metal (II) fibres were amorphous, group IIA and IB metal (II) fibres were partially crystalline All the fibres had pores both in micro pore and meso pore region. The B.E.T surface area from N2 adsorption data was in the range of 10–249 m3 g−1 and 8–176 m2 g−1 from Langmuir and B.E.T models respectively.

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

Abstract Flexible 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 × 10 −13 m 2 /s values have been determined respectively. The measured permeability of water vapor through membranes 1.6–7.3 × 10 −6 ((cm 2 /s)/(cm 2 cmHg))cm, were much higher than predicted permeabilities 0.85−2.73 × 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.

A recycling assessment of PVC bottles by means of heat impact evaluation on its reprocessing

Poly(vinyl chloride) (PVC) products are very convenient for reclaiming and recycling. Therefore, the heat impact at 160–180°C temperature during the recycling process was investigated in the current study by means of spectroscopic studies, such as infrared and ultraviolet, and of differential scanning calorimetry curves. The bottle samples are slightly and considerably affected at 160 and 180°C heat treatments, respectively, which were determined as the formed decomposition products, color change, loss of volatile components, and peroxide formation in air. However, since this decomposition occurred at 30 min of experimental time, which is about sixfold that of real process times, the reclaimed material found recyclable as is. Judicious recomposition of the powdered reclaimed material making up the lost or consumed component makes possible the use of this material in the production of window sections, profiles, pipes, and even bottles.

A study of adsorption of water vapour on wool under static and dynamic conditions

Adsorption of water vapour on wool provides not only textile comfort, but also convenience in transportation due to increase in its bulk density. The adsorption and desorption isotherms of water vapour for wool were determined by both volumetric technique using a Coulter Omnisorp 100CX instrument and gravimetric method employing a Cahn 2000 electronic microbalance. Adsorption isotherm fitting to B.E.T. model and hysteresis on desorption was observed. The average effective diffusion coefficient of water in wool was found to be 8.4 × 10-14 m2s-1 at 25°C from gravimetric data. The effects of packing height and air velocity on the breakthrough curves were also investigated in the wool packed columns. For pseudo first order model, k values changing between 0.33 × 10-6 − 69 × 10-6 s-1 was obtained for 2.2–6.4 cm s-1 air velocity and 0.05–0.20 m packing height ranges.

Interfacial enhancement of flexible PVC-silica composites by silane coupling agents

Enhancement of a flexible poly(vinyl chloride) (PVC)-silica composite interface was studied by the application of γ-aminopropyltrimethoxysilane on silica. Composites containing silica and silanized silica up to 25.6 phr (per hundred resin) and prepared by sol-gel technology were subjected to water and water vapor attacks similar to that in their daily use. Silane application resulted in diminishing liquid water and water vapor sorption by about 24.0% and 11.9%, respectively. Equilibrium weight gain values of the composites having different amounts of silica correlated well with a peak at 3400 cm-1 in the IR spectra which was attributed to the stretching vibration of the O-H group of water. Liquid water and water vapor diffusivities in composites determined by the evaluation of weight gain against time data were about 0.4 x 10-13 and 0.4 x 10-12 m2 s-1, respectively. Inhibition of dioctyl phthalate (DOP) migration from composites by silane application was also determined as 24% using UV measurements. The m...

WATER VAPOUR ADSORPTION ON ORGANIC AND INORGANIC POLYMERS

Water vapour adsorption on polymers affects their processing behaviour and useful properties. Water vapour adsorption on organic polymers, silk, Nylon 6 fibres in undrawn and permanent set forms, polyester micro fibres, plasticised PVC films with 60 phr dioctylphthalate (DOP) and inorganic polymer sepiolite particles were investigated in this study. The materials were examined using the BET equation. The surface areas of silk, cast Nylon 6 and muss Nylon 6 were determined as 108, 46 and 23 m2 g−1, respectively. Sepiolite did not fit BET equation. Polyester and PVC adsorbed very small amounts of moisture.

Dynamics of water vapor adsorption on humidity-indicating silica gel

Abstract Well-defined CoCl2-containing silica gels were prepared by impregnation of the aqueous solution of the salt to silica hydrogel, drying and aging methods. Silica gels having 392–437 m2 g−1 surface area and 0.21–0.37 cm3 g−1 pore volume and having an average particle size of 3 mm were obtained. Aging in CoCl2 solutions decreased the surface area of silica gels from 540 cm2 g−1 to 392–430 m2 g−1 and pore volume from 0.27 to 0.21–0.23 cm3 g−1 for CoCl2 concentration smaller than 0.28 mol dm−3 in silica gel. Adsorbed water desorbed from the gels absorbing 1917–2555 J g−1 energy as determined by differential scanning calorimetry. The CoCl2-containing gels were successfully used in dynamic column experiments, with linear relation between velocities of inlet air and movement of blue to pink boundary. The colour change also makes the detection of the defects in column filling which causes air channelling.

Flexible Pvc-Silica Composites as An Adsorptive Material for Water Soluble Dyes

Methylene Blue (MB) adsorption studies were performed on flexible Polyvinyl Chloride/Silica composites which were obtained by using plastisol-plastigel technology. Change of MB concentration in aqueous phase as the adsorption process advanced was followed by using visible spectroscopy. The diffusion of MB through the composites exhibited non-Fickian behavior with a diffusivity of 10−11m2s−1. Making use of such PVC-silica composite sheets as column packing, the packing time will be reduced and the surface available for diffusion will be increased.

Production of a Polymeric Composite Material Filled with Halogen-Free Flame Retardant

In the present study a composite material to be used in cable industry, which has LDPE/EVA (low density polyethylene/ethylene-vinyl acetate copolymer) polymer blend and alumina trihydrate (ATH) filler, which is a halogen-free flame retardant (HFFR), has been formulated and characterized in terms of its mechanical, rheological and flame retardant properties comparing with the commercial mixtures. Composite blends having 40% polymer component with various PE/EVA ratio and two PE type and 60% ATH were prepared. As the EVA content of composites increased from 26% to 65% the storage modulus increased by 180-220%, viscosity increases by %61-107. Composites containing 65% EVA exhibit similar properties to the commercial one. Limiting Oxygen Index (LOI) value was found as 30 for composites containing 26 mass% of EVA, it increased to 32-34 when EVA content increased to 65 mass%.