Iranian Journal of Polymer Science and Technology
Year:2006 | Volume:18 | Issue:5 (ISSUE NO. 79)|Papers Count:11

Synthetic polyelectrolyte are used in water and wastewater treatment systems as coagulant and filtration aids. Most of these polymers do not have a short term biodegrable property and some of them cause cancer and genetic mutation in human. In this study, the performance of different natural polyelectrolytes, as replacement materials for synthetic polyelectrolytes, in water treatment and effective parameters on their performance were evaluated. As a result, a suitable operational condition for water treatment was determined. The experimental results showed that biopolymers such as chitosan, sodium alginate and starch can be used as coagulating aid in water treatment system for reduction of turbidity. In comparison with starch and sodium alginate, chitosan has better performance for reduction of turbidity and besides, its operational range is wider. Also, the coagulated particles were bigger and stronger than those resulting from starch and sodium alginate. Therefore, using chitosan is more effective in settling and clarification operations of water treatment.

Application of conductive polymers to textile fibers is considered. For this purpose, the yarns made from cotton, polyester, acrylic and polyamide fibers were coated with polyaniline and polypyrrole as conductive polymers. The effect of coating condition such as oxidizing agent to monomer mole ratio, monomer to fiber weight ratio and doping condition of coating fibers were examined. Electrical resistance and some physical properties of the yarns were measured. The results of measurements indicated that coating with polypyrrole were more effective in the reduction of the yarns, electrical resistance comparing with that of polyaniline coating. The electrical resistance of polypyrrole coated yarns before doping was more stable than those coated with polyaniline and doped polypyrrole. Coating with these two conductive polymers did not change the strength and breaking elongation of the yarns, considerably. The results of the experiments are discussed with reference to the literature source.

The effect of ethylene vinyl acetate (EVA) on the mechanical properties of glass mat thermoplastic (GMT) composites has been investigated. For this purpose, polypropylene matrix and glass mat have been modified with EVA using different approaches. Fourier transform infrared spectroscopy (FTIR) technique is employed to analyze the chemical interactions at the matrix-fibre interface. Tensile and Izod impact test results confirm the enhanced properties of modified samples. Scanning electron microscopy (SEM) studies of fractured surfaces reveal the improved interfacial adhesion characteristics of modified composites compared to the original unmodified samples.

The activated polyethylene glycol with molecular mass of 5 kDa was covalently attached to human red blood cells. Taguchi design of experiments was used to study the effect of process variables on coating the cells. The inhibition of agglutination by a blood-type specific antiserum (anti-B) was employed to evaluate the effect of polymer coating. The remaining single cells after incubation with anti-B sera were counted using a simple method. The morphology of red blood cells was determined by scanning electron microscopy (SEM). Statistical analysis of experimental design together with SEM results showed that the optimum pH and temperature were: 8.6 and 12°C, respectively. But optimum polymer concentration could not be determine and in this study, an amount of 5mg/mL was found to be a suitable concentration.

Blends of HDPE/EVA and LDPEIEVA were prepared by melt blending. The morphology and dynamic viscoelastic properties of the blends were analyzed using scanning electron microscopy (SEM) and an oscillatory rheometer, respectively. The results of morphology observations reveal a two-phase morphology which means that two polymers are immiscible in the whole composition range studied. The droplets of minor phase are smaller in the LDPE/EVA than HDPE/EVA system which is attributed to higher structural similarity as well as lower viscosity ratio in the former blend. The Palierne model was also applied in order to analyze the rheological data and to estimate the interfacial tension. The results confirm the morphological observations.

Residual stresses are formed in composite materials due to mismatch of the coefficient of thermal expansion (CTE) of the components. In polymer matrix composites, reinforced with glass fiber, the CTE of polymer is usually much higher than that of glass fiber. The CTE mismatch of two phases in composite causes the formation of residual stress at the fiber-matrix interface that in turn results in premature fiber-matrix debonding. In this work, the mismatch of fiber and matrix has been compensated through fiber pre-tensioning during the curing of the epoxy resin. It is shown that application of 4 MPa tension is able to remove residual shear stress remained at the fiber-matrix interface of the composites.