Iranian Polymer Journal
Year:2002 | Volume:11 | Issue:6|Papers Count:8

The effect of two important parameters of film blowing process i.e. take-up ratio and blow-up ratio, on the overall orientation of low density blown films have been investigated using birefringence measurements. Furthermore, by combining X-ray diffraction pole figure analysis and birefringence, the White and Spruiell biaxial orientation functions have been determined for afformentioned sample. Within the range of processing condition studied, increasing take-up ratio, increases orientation in both machine and transverse direction. Upon increasing blow-up ratio, orientation in the transverse direction increases and the overall orientation state approaches to equal biaxial one. Characterization of the crystalline regions by pole figure analysis reveals that a and b crystallographic axes preferentially orientate in the film plane and the direction normal to it, respectively. The amorphous regions do not have any preferential orientation.

A number of new poly (ether-ketone) s and poly (ether-ketone-sulfone) s are synthesized by polycondensation of (a) benzofuro [2-3-b] benzofuran-2, 9-dicarbonyl chloride (I), (b) equimolar mixture of I and 4,4’-[sulfonylbis (p-phenyleneoxy)] dibenzoyl chloride (II), and (c) 2,7-biphenylene dicarbonyl chloride (III) with 2,6-diphenoxy benzonitrile and a number of diaryl ethers through indirect polycondensation in the presence of aluminum chloride as catalyst. Molecular structures were confirmed by FTIR spectroscopy and elemental analysis data. Because of the presence of nitride groups along the polymer chain, the polymers were cross-linked. Thermal Properties before and after cross-linking were investigated by TGA and DSC methods.

The rheological behaviour of poly(ethylene glycol) solutions (PEG) with different concentrations was evaluated using concentric cylinder rheometer. The shear rate-shear stress data emphasizes the emergence of the hysteresis loop but in the opposite concept of thixotropic fluids. The rheogram included the results of shear stress and apparent viscosity were obtained by applying the various step changing increments to the shear rate to reach appropriate value, followed by a stress decay at a steady shear rate after each upward step changes. Then, low shear rate was used by different decreasing levels, which showed reduction in the value shear stress. The steady shear was applied after each downward trend and showed a noticeable increment shear stress with time. The results of shear stress confirmed the anti-thixotropic behaviour of different solutions of PEG under all conditions. Increasing concentration of PEG fluids enhances the anti-thixotropic behaviour of the solutions.

The ability of low cost flocculating material, Plantago psyllium mucilage (Psy), for removal of suspended (SS) solid from sewage and tannery has been successfully investigated. Jar test method has been used for flocculation studies. The effects of polymer dose, pH and contact time on per cent removal of solid wastes are reported. Increase in solid wastes removal was observed with increasing polymer dose upto a certain level, beyond which further increase in dosage shows a decreasing trend in solid removal. The maximum solid removal (94.69 %) was seen only after 1 hour and the suitable pH range was acidic to neutral in case of sewage treatment whereas the time required for maximum solid removal (87.03 %) was1 hour and suitable pH range was neutral to alkaline in case of tannery effluent treatment. X-ray analysis of pure P.psyllium mucilage and flocs got after treatment shows the interaction between the suspended solid with the mucilage.

Electrooxidation of β-naphthylamine (β-NA) in different aqueous acid media was investigated. The formation of a film adhered to the electrode surface was observed as a principal product and for which a polymer structure through C-N coupling is proposed. A standard three-electrode electrochemical cell was used for voltammetric experiments. In this system, glassy carbon rod, platinum wire, and KCl/saturated Ag/AgCl were used respectively as the working, counter and the reference electrodes. From the analysis of the voltammetric and spectroscopic experiments some aspects of the mechanism of electrooxidation of β-NA leading to the formation of the film was proposed. The effects of various physical and electrochemical parameters such as type of supporting electrolyte, temperature of the cell, pH, concentration of the monomer, scan rate and the number of scan cycles were studied. The electrochemical behavior of the film was reported as a function of these parameters. A quasireversible behaviour was observed from cyclic voltammograms obtained in different acid solutions. The film behaved as a thin-layer cell when it was obtained at low scan rates and dilute solutions of the monomer.

This paper concerns molecular weight control of a batch polymerization reactor where suspension polymerization of methyl methacrylate(MMA) takes place. For this purpose, a cascade control structure with two control loops has been selected. The slave loop is used for temperature control using on-line temperature measurements, and the master loop controls the average molecular weights based on its estimated values. Two different control algorithms namely proportional-integral(PI) controller and globally linearizing controller (GLC) have been used for temperature control. An estimator, which has the structure of an extended Kalman filter (EKF), is used for estimating monomer conversion and average molecular weights of polymer using reactor temperature measurements. The performance of proposed control algorithm is evaluated through simulation and experimental studies. The results indicate that a constant average molecular weight can not be achieved in case of strong gel effect. However, the polydispersity of product will be lower in comparison to isothermal operation. It is also shown that in case of model mismatch, the performance of cascade control is superior compared to the case where only reactor temperature is controlled based on desired temperature trajectory obtained through cascade strategy.

High performance carbon fibre/epoxy composites, which are increasingly used for structural applications are susceptible to delamination. In response to this problem, the mode I interlaminar fracture toughness of unidirectional carbon/epoxy laminates has been studied under tensile loading by using a double cantilever beam (DCB) specimen. The fracture energy is deduced from the data according to the area and the compliance methods. The morphology was explained through thermal analysis using DMA and fractography from scanning electron microscopy (SEM). Results showed improvement in high temperature moulding compound (HTM) system with 180°C cure in terms of interlaminar fracture toughness. There is also an improvement in MTM and LTM systems. SEM micrographs revealed their excellent delamination resistance as good crack stoppers with the evidence of strong fibre/matrix interface. For MTM systems GIc values dropped after post curing. This reduction was significant for MTM49-3 but not so much in the case of MTM49-7 laminate. On the other hand, the GIc for LTM45-1 did not seem to be affected by post curing at elevated temperature.

N-Trimellitylimido-S-valine 3 was prepared from the reaction of trimellitic anhydride 1 with (S)-(+)-valine (2-Amino-3-methylbutyric acid) 2 in acetic acid solution at refluxing temperature. The direct polycondensation reaction of the monomer imide-diacid 3 with 1,4-phenylenediamine 4a, diaminodiphenylmethane 4b, 4,4"-diaminodiphenylsulphone 4c, diaminodiphenylether 4d, 1,5-naphthalendiamine 4e, 2,4-diaminotoluene 4f and 1,3-phenylenediamine 4g, was carried out in a medium consisting of triphenyl phosphite, N-methyl-2-pyrolidone (NMP), pyridine, and calcium chloride. The polycondensation was performed under two different conditions. In one method the reaction mixture was stirred at room temperature in NMP solution and then it was heated at 60°C, 90°C, and finally at 130°C for different periods of time and the other method the reaction mixture was refluxed only for 1 min in the same solvent. The resulting poly(aimde-imide)s PAIs having inherent viscosities 0.15-0.73 dL/g were obtained in high yield. All of the above compounds were fully characterized by IR, elemental analyses, and specific rotation. Some structural characterization and physical properties of this new optically active PAIs are reported.