Iranian polymer journal
Volume:16 Issue: 11, 2007

Velocity profiles are helpful for the confident design of mixing tanks in the transition region. In this article, velocity profiles for helical ribbon impeller have been studied using laser Doppler anemometry for viscoelastic liquids with rheological properties typical of those found in polymer processes. Local tangential and radial velocities were measured at radial positions on a horizontal plane passing through the middle of the helical ribbon impeller. New correlation is suggested for dimensionless local tangential velocity profiles in the transition region, i.e. 70

Abstract View Paper Original: English

Aseries of new polyhydrazides were obtained by direct polycondensation of 4,4''- diphenyl sulphone dicarboxylic acid with dihydrazides in ionic liquids (ILs) as a new class of solvents which have interesting properties such as nonvolatility, high ionic concentration, good thermal stability and non-flammability. Direct polycondensation is successfully proceeded in ILs and triphenyl phosphite (condensing agent), without any additional components, such as LiCl and pyridine. Therefore IL can act as both solvent and catalyst. In this investigation high molecular weight polyhydrazides have been synthesized and their properties such as solubility, and thermal stability were studied. The resulting hydrazide containing polymers exhibited inherent viscosities in 0.26-0.73 dL/g range. All polymers were soluble in polar solvents such as N-methyl pyrrolidone and dimethyl sulphoxide. The polyhydrazides had glass-transition temperatures (Tg) between 165-210ºC. They could be thermally converted into the corresponding poly(1,3,4-oxadiazole)s approximately in the region of 210-330ºC, as evidenced by the TGA thermograms.

The rheological behaviour of plastisols used in coated fabrics was studied by using a computer controlled concentric cylinder viscometer over the temperature range of 20-70ºC. The results indicated that these pastes behave as Newtonian to pseudo-plastic fluids over the temperature range studied and the flow behaviour can be adequately described by the power-law model. The changes in the flow behaviour index (n) with temperature were statistically negligible (P<0.05). Both consistency index (k) and apparent viscosity (η) decreased with increase in temperature. The effect of temperature on the viscosity of the paste was modelled using the Arrhenius model. The activation energy for the temperature range of 20-42ºC, varied between 3.90 and 4.64 kJ.mol-1. Increase in the temperature of the paste had influence on Newtonian behaviour of the paste.

Solubility of carbon dioxide in poly(vinyl acetate) (PVAc) at temperatures (313.15- 373.15K) and pressures up to 17.5 MPa, poly(2,6-dimethyl-1,4-phenylene ether) (PPO) at temperatures (373.15-473.15K) and pressures up to 20 MPa, polypropylene (PP) and high-density polyethylene (HDPE) at temperatures (433.2- 473.2 K) and pressures up to 17 MPa, poly(butylene succinate) (PBS) and poly(butylene succinate-co-adipate) (PBSA) at temperatures (323.15-453.15 K) and pressures up to 20 MPa and polystyrene (PS) from (373.15-473.15 K) and pressures up to 20 MPa are modelled by artificial neural network (ANN) technique. Different types of neural networks have been employed and it is found that the designed ANN, multi-layers perceptron (MLP) architecture, with one hidden layer can be better trained than other types of neural networks. Suitable activation functions for output layer are linear and for hidden layers are sigmoid. The best ANN model derived, a 2-5-1 architecture, has an average relative deviation (ARD) of 0.721 for the test set of PPO(H), 1.319 for PPO(L), 0.599 for PS, 0.583 for PVAc, 1.535 for PP, 0.635 for PBS, 0.503 for PBSA and 1.490 for HDPE. The results obtained in this work indicate that ANN is an effective method for prediction of solubility of carbon dioxide in polymers and have better speed and simplicity compared with the classical methods.

The synthesis and radical polymerization of methacrylamide having Gabapentin (GBP) moieties were examined. The monomer was prepared by reaction of methyl-1-aminomethyl-1-cyclohexane acetic acid salt with methacryloyl chloride in presence of triethylamine in moderate yields. Radical polymerizations of the monomer were carried out in presence of AIBN (3 mol%) in DMF in moderate yield. The thermal behaviour of the polymers was investigated by thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) to determine the thermal degradation pattern and glass transition temperature (Tg). The resulting polymer showed a thermal stability up to ~ 400ºC. We found the molecular weight of the polymer to be 4340 g/mol (Mw/Mn=1.33) and poly[N-[(1-1-methoxyformoyl-1''-methyl) cyclohexylmethyl] methacrylamide] (poly[MFCHM]) were soluble in common solvents.

Polypropylene (PP)/organophilic montmorillonite (OMMT) nanocomposites with three different morphologies have been identified as intercalated, partial intercalated and partial-exfoliated nanocomposites, respectively; which were prepared by controlling the processing conditions. The XRD analysis of nanocomposites determines the interlayer space inside OMMT in them; and the submicroscopic structure of three nanocomposites was observed by transmission electron microscopy (TEM) to distinguish the morphology of the nanocomposites. Furthermore, the melt fluidity, mechanical properties, melting and crystallization behaviour and thermal stability of nanocomposites were measured and analyzed. The melt flow rate (MFR) of partial- exfoliated nanocomposites decreased most; they had the most uniformly dispersed OMMT particles and the highest reinforcement of mechanical properties. The intercalated nanocomposites displayed the highest impact strength. The partial intercalated nanocomposites with good performance had the advantage of simple processing. The results showed that the dispersion morphology of OMMT in PP matrix determines the properties of nanocomposites, which means that the nanocomposites with different structures of OMMT dispersion would have specific properties. It is an achievement to develop polymer/OMMT nanocomposites with different performance capabilities by controlling the processing conditions.

Micron-sized super-paramagnetic polyglycidyl methacrylate (PGMA) particles with imidazole groups were prepared by a process involving: (1) magnetic Fe3O4, obtained by chemical coprecipitation of iron (II) and iron (III) salts in ammonium hydroxide in presence of oleic acid, (2) magnetic micron-sized PGMA based latex particles, prepared by dispersion polymerization of polyglycidyl methacrylate in toluene and ethanol in presence of nano Fe3O4, and (3) functional groups of imidazole, introduced by chemical modification of the PGMA particles with imidazole. The resultant magnetic PGMA particles with imidazole groups were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscope (TEM), vibrating sample magnetometry, and elemental analysis. The existence of imidazole groups and its structure were confirmed by FTIR. The average diameter of magnetic chelating resin was 5.3 μm and the coreshell structure was confirmed by TEM. The chelating resin retained super-paramagnetism. The static adsorptions of Hg2+, Cd2+, Cu2+, Pb2+, Zn2+, Mg2+, and Co2+ were investigated and the adsorption capacities were calculated. The resin can absorb Cd2+ and Hg2+ and show effective adsorption of Cu2+. The highest capacity value of Cu2+ was obtained to be 3.606 mmol/g.

The ultrasonic degradation of polyethylene oxide (PEO) solutions was carried outin water at 20, 25, 30, 35 and 40ºC to investigate the effect of temperature and solution concentration on the rate of degradation. Kinetics of degradation was studied by viscometry. The obtained limiting molecular weights indicate that under the conditions of increased temperature and solution concentration the degradation rate of PEO solutions decreases. The obtained limiting molecular weights were correlated in terms of concentration and temperature. The calculated rate constants also indicate that degradation rate of PEO solutions decreases as the temperature and solution concentration are increased. The calculated rate constants were correlated in terms of concentration, temperature, and molecular weight of polymer. This degradation behaviour was interpreted in terms of vapour pressure of water, viscosity, and concentration of polymer solutions. With increasing temperature, the vapour pressure of solvent increases and as this vapour enters inside the growing cavitation bubbles there is areduction in collapsing shock due to the developed cushioning effect. As a result, the rate of degradation decreases. As the solution concentration increases, the viscosity increases, leading to reduced cavitation efficiency and therefore the rate of degradation decreases.