Iranian Polymer Journal / Volume 7 Number 3 (1998) 143147 ISSN: 1026-1265/1998
Graft Copolymerization of Acrylic Acid onto Caesarweed Fibres
by Ceric Ion/Thioacetamide Redox Pair
I.C. Eromosele and A. Kolapo
Department of Chemistry, Federal University of Technology, P.M.B. 2076, Yola, Adamawa State, Nigeria
The graft copolymerization of acrylic acid onto caesarweed fibres initiated by ceric ion/thioacetamide redox pair in aqueous media has been investigated. Ceric ion/thioacetamide redox pair was an effective initiator of the graft reaction in the temperature region of 30-60 °C. However, at 30 °C, the graft yields were generally low but increased with concentrations of ceric ion, acrylic acid and thioacetamide with the highest value of 23% at 0.97 M concentration of acrylic acid. The low graft yields, which are characteristic for acrylic acid, were associated with its solubility in the reaction media. The graft yield showed a linear relationship with acrylic acid concentration suggesting that the latter is non-terminating of the graft reaction. For thioacetamide, an optimum graft yield of 16% was found at its concentration of 18΄10-4 M and thereafter decreased at higher concentrations. This was attributed to a pre-ponderance of termination reactions by thiol radicals at high concentrations of the latter. The temperature dependence of graft yield was investigated in the range 30-60 °C. The graft yield showed positive temperature dependence with calculated activation energy of 6.11 kcalmol-1.
Iranian Polymer Journal / Volume 7 Number 3 (1998) 149156 ISSN: 1026-1265/1998
Elimination Reactions of Secondary and Tertiary Alcohols with
Polystyryl Diphenylphosphine in Tetrachloromethane
A.H. Dabbagh, S.E. Mallakpour, and K. Faghihi
Organic Polymer Chemistry Research Laboratory, College of Chemistry, Isfahan University of Technology,
Isfahan, 84156, I.R. Iran
A cross-linked polystyrene was prepared by suspension copolymerization of styrene with 2% divinylbenzene. This cross-linked polymer was brominated in solution of bromine-tetrachloromethane in presence of ferric chloride catalyst. The cross-linked brominated polystyrene was allowed to react with lithium in tetrahydrofuran under nitrogen atmosphere and subsequently the mixture was reacted with diphenylphosphine chloride to produce the cross-linked polystyryl diphenylphosphine. A gel form of this polymer in tetrachloromethane is used effectively to convert primary alcohols to alkyl halides and secondary and tertiary alcohols to alkenes under very mild conditions. The results of homogeneous reaction of alcohols with triphenylphosphine in tetrachloromethane have been compared with heterogeneous reaction of alcohols with the use of cross-linked polymer. The advantages of this method for the conversion of alcohols to alkyl chloride and alkenes lie in its simplicity, its ability to be carried out under neutral pH, and its facile regeneration of the polymeric reagent. The mechanism of the reactions proceeds via inter-molecular anti-E2 elimination. Polar solvent (acetonitrile) effects the rate of conversion and regioselectivity but not stereoselectivity. Steric hindrance is responsible for the low reactivity but higher selectivity.
Iranian Polymer Journal / Volume 7 Number 3 (1998) 157162 ISSN: 1026-1265/1998
Photosensitive Monomers and Polymers Derived from
E. Rusu1, E. Comanita2, A. Airinei1, and G. Rusu1
(1) Institute of Macromolecular Chemistry P. Poni, Aleea Gr. Ghica Voda nr. 41A, Iasi 6600, Romania
(2) Department of Organic Chemistry, Technical University Gh. Asachi, Iasi 6600, Romania
Compounds with photosensitive cinnamoyl groups were synthesized by reaction of glycidyl cinnamate with monomeric and polymeric carboxylic acid derivatives. These monomers and polymers were characterized by conventional analysis and spectrometry. Upon irradiation in solution the predominant reaction was found to be the trans-cis photoisomerization, while in film the photocrosslinking of cinnamate units occurs.
Iranian Polymer Journal / Volume 7 Number 3 (1998) 163167 ISSN: 1026-1265/1998
Effects of Molecular Weight and Concentration of Itaconic/
Acrylic Acids Copolymer Liquid on Mechanical Properties
of the Formulated Glass Ionomer Dental Cements
M. Keyanpour, R. Salarian, and F. Moztarzadeh
Materials and Energy Research Institute, P.O. Box 14155-4777, Tehran, I.R. Iran
The copolymer of Itaconic/acrylic acids is synthesized via emulsion polymerization, and then it is used as an aqueous solution along with an ion-leachable glass with L (+) tartaric acid for formulation of the glass ionomer cement. It is found that increase in average molecular weight and concentration of the polymeric liquid both linearly increase the compressive and bending strengths. Although, the latter has non-linear effects on the working and setting times as well as on the P/L ratio, it has, however a linear decreasing effect on the solubility of the cements in water. It is found that physical and mechanical properties of the formulated sample fall within the range of some well known commercial samples.
Iranian Polymer Journal / Volume 7 Number 3 (1998) 169175 ISSN: 1026-1265/1998
Gel-casting of Engineering Ceramics
M. Kokabi1, A. Pirooz1, and M. Nekoomanesh Haghighi2
(1) Polymer Engineering Group, Tarbiat Modarres University, P.O. Box: 14155-4838, Tehran, I.R. Iran
(2) Iran Polymer Institute, Tehran, I.R. Iran
Gel-casting is a novel method for moulding ceramic powder based on concepts derived from traditional ceramics and polymer chemistry. In this paper gel-casting of silicon powder is investigated. It is based on the in situ polymerization of acrylamide monomers as the setting mechanism for forming the green body. It has the following features; slurries with high solids loading and low viscosity (1.2 Pa.s at 75% solids), dried green bodies containing less than 4 wt % binder, linear shrinkage of about 2.9%, a density of 142 kg.m-3, a mechanical strength of 32 MPa.s, and also the ability to gel in the presence of O2 and to fabricate complex shaped bodies.
Iranian Polymer Journal / Volume 7 Number 3 (1998) 177184 ISSN: 1026-1265/1998
On the Specific Resistance of Cakes of Latexes
Chemical Engineering Department, Razi University, P.O. Box: 1166, Kermanshah, I.R. Iran
In the ultrafiltration of latex particles, a cake is formed on the membrane surface. This cake consists of latex particles and small size surfactants which are used to stabilize the colloidal latex. The resistance of this cake is high due to filling of the voidage between the latex particles by the surfactant, so the measured specific resistance cannot be considered as the property of the latex beads. A membrane with a pore size large enough to allow the passage of small surfactants can negate the presence of the surfactant on the specific resistance of the latex cake layer. Estimated specific resistances of the latex cake on the surface of the PM30 ultrafilter and the Nuclepore microfilter have been reported and compared. Another important factor is the hydrophobicity of the membrane which can affect the specific resistance of the cake. Hydrophobic GVHP and hydrophilic GVWP microfiltration membranes were used to investigate this phenomenon. Hydrophobic membranes provide a stronger interaction between the membrane surface and latex particles. This interaction is less in the case of hydrophilic membranes due to the chemical treatment of the membrane surface to produce hydrophilicity. However, higher adsorption of the latex particles on the membrane surface causes higher specific resistance of the latex cake.
Iranian Polymer Journal / Volume 7 Number 3 (1998) 185194 ISSN: 1026-1265/1998
Effect of Electrochemical Cell Overcharge on Electrical and
Electrochemical Properties of Polymer Composite Electrodes (II):
Mechanism of Electrode Deterioration
V. Haddadi-Asl1 and M.S. Rabbani2
(1) Department of Polymer Engineering, Amir Kabir University of Technology, P.O. Box: 15875-4413, Tehran, I.R. Iran
(2) Faculty of Science, Tehran University, Tehran, I.R. Iran
Electrical and electrochemical studies show that the carbon-polyolefin composite is a suitable electrode matrix material for the vanadium redox battery. The effect of overcharge on the performance of the vanadium redox cell that employs conductive carbon-polymer composite/graphite felt electrodes is examined. The electrical resistivity of the electrode and the cell resistance show a dramatic increase after overcharge. The effect of overcharge on the electrical resistivity and surface chemistry of the graphite felt are also investigated.
Iranian Polymer Journal / Volume 7 Number 3 (1998) 195203 ISSN: 1026-1265/1998
Modifications to Non-linear Rheological Models
of Viscoelastic Fluids
S. Savarmand1, M.R. Golcar Narenji1, and W.L. Wilkinson2
(1) Faculty of Chemical Engineering, Amir Kabir University of Technology, P.O.Box: 15875-4413, Tehran, I.R. Iran
(2) BNFL, Warrington, U.K.
Four constitutive equations have been used to describe the behaviour of viscoelastic fluids viz., (i) upper convected Maxwell, (ii) Oldroyd 4-constant, (iii) Bogue-White and (iv) Bird-Carreau. These were modified to improve their ability to predict the observed behaviour of viscoelastic fluids in viscometric and oscillatory shear flows. The fluids used during the experimental work are four different concentrations of polyacrylamide (Separan AP 30) solutions, i.e. 0.6, 0.8, 1.0, and 1.2%, in glycerine / water mixtures. The experimental data are obtained under simple shear and small-amplitude oscillatory shear flow conditions. The viscosity data, obtained from steady shear experiments, and the dynamic viscosity and storage modulus obtained from oscillatory shear experiments have been used to determine the model parameters. The performance of the original and modified models have been studied by comparing their predictions of the viscosities, in steady, and the dynamic viscosities, in oscillatory shear flows. The average root mean square has been used as a criterion for the comparison. Finally, the results of the predictions made by the modified models to the first normal stress coefficients are given to see how they can predict a material function other than those used to determine the model parameters. This may justify the application of these modified models in complex flows such as free coating.
Iranian Polymer Journal / Volume 7 Number 3 (1998) 205213 ISSN: 1026-1265/1998
Microbial Damage to Iranian Cotton Fibre (Sahel Variety)
S.H. Amirshahi, M. Morshed, and H.T. Ahangari
Department of Textile Engineering, Isfahan University of Technology, Isfahan 84154, I.R. Iran
Damages resulting by micro-organisms on Iranian cotton (Sahel variety) with 65-70% relative humidity and 25 °C temperature within four months storage period are investigated. A number of tests are currently available to identify and quantify such cottons called cavatomic. These tests include pH and reducing sugar determinations, microscopy techniques, staining methods and determination of physical changes. Some of these tests have been applied to evaluate possible microbial damage to cotton of Gonbad-Ghabous spring crop. The effects of the micro-organisms growth on the whiteness and dye-ability of different samples are also determined. Data and observations totally support the slow growth of the micro-organisms in this variety of cottons.