Iranian polymer journal
Volume:15 Issue: 4, 2006

Polyamide (PA 66) membranes were prepared with immersion precipitation via phase inversion from mixtures of polyvinylpirrolidone (PVP) and ammonium oxalate (OX) as constant additives and acetic acid, acetone, formamide, and water as variable additives. The formic acid and pure water were employed as solvent and nonsolvent, respectively. The influences of additives on structure and permeation properties of the membranes were analyzed by scanning electron microscopy (SEM) technique and separation expriments using milk as the feed. In general the addition of water and formamide in the casting solution slightly improves the flux without a pronounced effect on the retention of protein. This behaviour is due to instantaneous demixing (for water) and swelling mechanism (for formamide). When acetone was added to the casting solution, flux was lower and rejection was higher in comparison with the addition of water and formamide.This is due to the establishment of hydrogen bonding between acetone and polyamide. The addition of acetic acid results in lower flux and higher retention due to delay demixing.

The hydrodynamics of the flow in stirred-tank reactors, i.e., velocity profiles, stress fields, turbulence characteristics and etc., are essential for the confident design of mixing tanks. fluctuation tangential and radial velocities were measured using a two-component laser doppler anemometry (LDA) system for a typical Rushton turbine impeller. The working fluids had different concentrations of polyacrylamide (PAA) with rheological properties typical of those found in polymer processes. It is shown that the correlations for fluctuating velocities in Newtonian fluids do not apply to the case of viscoelastic liquids. New correlations are given in the lower part of the transition region, i.e., 30 < Re < 2000, for fluctuating tangential and radial velocity components values along the centre line of the impeller tip.

Various phase inversion methods were applied to fabricate oxygen selective membranes out of polymeric materials such as polycarbonate (PC), ethylene vinyl acetate (EVA), and polyvinylchloride (PVC) that were dissolved in solvents like chloroform, tetrahydrofuran (THF), cyclohexanone, and dimethylformamide (DMF). Developed membranes were investigated using their permeability data and scanning electron microscopy (SEM) images. The more concentrated was the solution, the more homogeneous overall structure was obtained with smaller pores and more decreased gas diffusivity. Application of DMF as the solvent was found to be incorporated in the formation of larger porosity in the membranes. Less crystalline and hence more permeable membranes were made using volatile solvents such as THF. In casting 10% PVC solution in THF via the wet phase inversion method, micro-voids developed in the membrane and a non-homogeneous finger-type structure with porous skin was formed. Films with 28% vinyl acetate prepared by thermal phase inversion had a semi porous skin and a dense structure in the sub-layer. Results showed that EVA containing 28% vinyl acetate demonstrated the most appropriate permeability and selectivity for separation of oxygennitrogen gas mixtures.

To examine the effect of different aftertreatments, on dyeing of silk fibres using acidand direct dyes the dyed samples were aftertreated using different commercial systems:such as full backtan, syntan, and syntan/cation processes. When all dyeings were subjected to ISO105C06 wash test, it was found that all three aftertreatments improved wet or wash fastness. However, aftertreatment of the dyeing using backtanning system showed greatest wash fastness improvement toward wash testing. A commercial syntan improved the wash fastness and the sequential application of a cationic compound to the syntanned dyeing caused further improvement in wash fastness. The effect of syntan in reducing dye removal was increased by decreasing the applied pH, which indicats that ion-ion interactions operating between the protonated end groups in the silk fibre and anionic syntan contribute towards syntan-fibre affinity. Also the effect of syntan in reducing dye removal increased with decreasing liquor ratio. Increasing the concentrationof syntan that accompanied a decrease in liquor ratio can be expected to increasethe degree of syntan aggregation in solution. It can be suggested that the aggregation ofthe syntan will occur in solution by virtue of both polar and non-polar forces operatingbetween the large molecular size syntan molecules which in turn can be considered toresult in greater uptake of the tanning agent. However, the aftertreatment with full backtanhad markedly improved the fastness to washing of the six dyes used and showedgreatest wash fastness improvement.

N-Trimellitylimido-S-valine was reacted with thionyl chloride, and N-trimellitylimido- S-valine diacid chloride was obtained in quantitative yield. The reaction of this diacid chloride with p-amino benzoic acid was performed in dry tetrahydrofuran, and bis(p-aminobenzoic acid)-N-trimellitilylimido-S-valine (6) was obtained as a novel optically active aromatic amide-imide diacid monomer in high yield. The direct polycondensation reaction of the monomer amide-imide diacide (6) with bisphenol A, phenol phethalein, hydroquinone, 4,6-dihydroxypirimidine, bis(4-hydroxyphenyl) sulphone, bis(4- hydroxyphenyl) sulphide, biphenyl-2,2’-diol, 1,5-naphtalene diol, 4,6-dihydroxytoluene, and 2,4 dihydroxyacetophenone was carried out, respectively in tosyl chloride (TsCl)/pyridine(Py)/dimethyl formamide (DMF) system. The effect of the amount of dimethyl formamide,aging time, reaction temperature, and reaction time was studied on the reactionyields and polymer viscosities. The resulting novel optically active poly(amide-esterimide)with inherent viscosities ranging 0.36-0.71 dLg-1 were obtained in high yield. All ofthese polymers were fully characterized with FTIR spectroscopy and specific rotationtechniques. Some elemental analysis, thermal properties and 1H NMR of these new optically active poly(amide-ester-imide)s are reported.

Dispersion of carbon nanotubes (CNTs) in polymeric matrix is a key factor on formingCNTs/polymer composits. In this work the raw multi-walled carbon nanotubes (MWNTs) at first were treated with a mixed solution of concentrated sulphuric acid and concentrated nitric acid (named as O-MWNTs); then the O-MWNTs were dispersedwith ultrasonic in phosphoric acid and the products were denoted as U-MWNTs. Poly(pphenylene-2,6-benzoxazole) (PBO) had been synthesized in the presence of O-MWNTsor U-MWNTs in poly(phosphoric acid) using typical PBO polymerization conditions. Raman spectra, scanning electronic microscope and atomic force microscopy techniques were used to analyze the morphology of MWNTs/PBO composites. Topographies showedthe better dispersion of U-MWNTs in the composites.

Aseries of water dispersible polyurethanes containing carboxylate anion as the hydrophilic pendant group were prepared from toluene diisocyanate (TDI), 1,4- butanediol (1,4-BDO), dimethylol propionic acid (DMPA) and different molecular weight of polytetramethylene glycol (PTMG). IR Spectroscopy was used to check the end of polymerization reaction and characterization of polymer.The effect of PTMG molecularweight was studied on the particle size distribution, contact angle, and mechanical andthermal properties of the emulsion-cast films. Average particle size of prepared polyurethane emulsions decreases with increasing the PTMG molecular weight. Tensilestrength and hardness decrease and elongation-at-break and contact angle increase withincrease of the PTMG molecular weight. Thermal property and thermal stability are alsoaffected by variation of PTMG molecular weight. The thermal stability increases withincreasing PTMG molecular weight. Glass transition temperature (Tg) moved toward thelower temperatures by increasing molecular weight of the polyol. Decrease in Tg and tensile properties are interpreted in terms of the decrease in hard segments and the increase in chain flexibility and phase separation in high molecular weight PTMG basedpolyurethanes.

Modified polyacrylamide containing amino functionality was synthesized by transamidation of polyacrylamide with 1,6-diamino hexane. The catalyst was easily characterized by routine analytical methods. It proved to be an efficient and chemoselcetive heterogeneous catalyst for Knoevenagel condensation of aromatic and aliphatic aldehydes with ethyl cyanoacetate, malononitrile, and cyanoacetamide in water and solvent-free system to afford the desired alkenes in good purity and yields. Ketones were almost unreactive. The reactivity of the catalyst increased considerably in protic polar solvents such as water and ethanol. The order of reactivity of methylene compounds was malononitrile> cyano ethylacetate> cyanoacetamide. The results showed that the polymeric catalyst could be regenerated and used many times. The green and mild reaction condition, medium to short reaction time, high to excellent yields, low cost,readily preparation, and easy work up of the reactions are the main advantages of thiscatalyst.

This work reports the effects of solvent properties, solvent system, electrostatic field strength, and inorganic salt addition on electro-spinnability of the as-prepared polystyrene(PS) solutions and morphological appearance and/or size of the resulting fibres. The single solvents were 1,2-dichloroethane (DCE), dimethylformamide (DMF), ethylacetate (EA), and methylethylketone (MEK), while the mixed solvents were DMF/DCE, DMF/EA, and DMF/MEK at a fixed volumetric ratio of 75/25. The PS solution 10% (w/v) in DMF was found to exhibit the highest electro-spinnability, followed by its solutions in DCE, MEK, and EA, respectively. Generally, electrospinning of 10% (w/v) PS solution resulted in the formation of the beaded fibres, while electrospinning of 20 and 30% (w/v) PS solutions only resulted in the formation of smooth fibres. The size of the obtained fibres was found to increase with an increase in both the electrostatic field strength and the concentration of the PS solutions. Interestingly, the presence of DCE, EA, and MEK as the minor solvent (at 25 vol%) in a mixture with DMF reduced the size of the obtained fibres. Finally, incorporation of LiCl and KCl to modify the conductivity of the PS solutions caused the size of the fibres to increase appreciably.