Devrim Balköse

Effects of mixed metal stearates on thermal stability of rigid PVC

Abstract As 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.

Synergism of Ca/Zn soaps in poly(vinyl chloride) thermal stability

Abstract Synergism of calcium and zinc soaps on thermal stabilization of poly(vinyl chloride) (PVC) was studied using solvent casted films of PVC having commercial zinc and calcium soaps in different proportions. The metal soaps were characterized by X-ray diffraction and X-ray emission techniques. The films that were heated at 80°C for 4 h for the removal of the last traces of solvent methyl ethyl ketone were tested for thermal stability by heating at 160°C for 30 min. Heated films were characterized by infrared and ultraviolet–visible spectroscopy, differential scanning calorimetry and thermal gravimetric analysis (TGA) methods. The migration of Zn2+, Ca2+ and H+ cations to water at 80°C was also studied. While UV spectroscopic analysis and ion migration indicated synergism on PVC heat stability for 4:1 Ca to Zn soaps ratio, this was not confirmed by TGA.

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.

Effect of preparation pH on pore structure of silica gels

Surface 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.

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.

DEVELOPMENT OF SYNERGISTIC HEAT STABILIZERS FOR PVC FROM ZINC BORATE-ZINC PHOSPHATE

The importance of flame-retardant and smoke-suppressed poly(vinyl chloride) (PVC) compositions is increasing gradually in the polymer industry since PVC releases smoke and toxic gases (hydrogen chloride, HCl) during heating at temperatures above 140°C with the result of dehydrochlorination reaction. In this study, the synergistic effects of zinc borate (ZB)-zinc phosphate (ZP) on the thermal stability of PVC were investigated using thermal techniques. The induction and stability time values of PVC plastigels were obtained at 140° and 160°C. The results revealed that PVC plastigels having only ZP and ZB retarded dehydrochlorination of PVC compared with the unstabilized sample. However, the plastigels with both ZB and ZP had a superior synergistic effect on char formation of PVC. Since the induction periods of the samples having both ZB and ZP were higher than those of the unstabilized samples having only ZB or only ZP, the synergistic effect was observed.

NATURAL ZEOLITES IN AIR DRYING

ABSTRACT The local clinoptilolite from Bigadis region in Turkiye, was used for air drying in packed column. The effective diffusion coefficient of water in natural zeolite was found as 5×10−10 m2 s−1 from isothermal uptake measurements. Effects of packing height and airvelocity on breakthrough curves were studied.

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

Abstract Cobalt (II) salts dispersed on different substrates have functions as humidity indicating desiccants and catalysts. CoCl 2 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. CoCl 2 containing silica gels changed colour from blue to pink upon moisture adsorption due to presence of the CoCl 2 , Co 2 SiO 4 and Na 2 CoSiO 4 .

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...