Iranian Journal of Polymer Science and Technology
Year:2002 | Volume:15 | Issue:2 (ISSUE NO.58)|Papers Count:6

The effects of natural polymers and chemical coagulants on the removal of COD and suspended solids (SS) from cheese whey were investigated. The experiments were accomplished in the following two stages: First, optimum pH for the coagulation process was selected. Then the suitable coagulant dose in obtaining the highest COD&SS removal rate was determined.From the results of this study it was observed that natural polymer and chemical coagulant resulted in good SS precipitate. These coagulants resulted in removal of about 22% of COD and more that 90% of SS. But the natural polymer was used in lower dose as compared to chemical coagulant and the sludge volume produced by natural polymer was lower as well. Chitosan and sodium-alginates as natural polymers produced sludge by these coagulant that could be used as animal food.

A prototype wet-spinning unit was constructed and separate batches of polyamide 6 filaments were produced in coagulating baths of aqueous solution of formic acid and aqueous solution of sulfates. The filaments were examined by a polarizing microscope and their mechanical and dye-ability properties were measured. It was found that the rate of coagulation controls the structure and morphology of the filaments.optical microscopy showed that the filaments were originally porous, but drawing them in a chamber of saturated steam reduced the porosity and increased their molecular orientation. The presence of sulfates in the coagulation bath increased the stability of the spinning process and the draw-ability of the newly formed filaments. Desirable property of higher strength together with porous structure in the filaments produced in coagulation bath containing sulfates is remarkable, which may be of importance in manufacturing of special filters.

In this study, kinetics of cross-linking reaction (byperoxide method) in LDPE was investigated by differential scanning calorimetry (DSC) internal mixing and rheometry.Isothermal experiments were carried out in internal mixer and rheometer (160, 180 and 200°C) and non - isothermal experiments were carried out by DSC.It was found that the cross-linking reaction of LDPE followed first order reaction kinetics and concentration of cross-linking agent (di-cumylperoxide, DCP) and temperature did not have any effect on the order of reaction. Overall reaction rate constant (K), activation energy and Ln k0 were obtained from three methods. Activation energy was almost independent of DCP concentration. Because of higher mechanical stress in internal mixer, the rate of curing was faster than other methods.

Bitumen modifiers are materials which are admixtured with bitumen or added during hot-mix preparation to improve the performance of modified bitumen and the corresponding asphaltic concrete. polymers are the most important bitumen modifiers. Crumb rubber powder has been extensively used in bitumen modification. Some advantages of the addition of crumb rubber modifier (CRM) into bitumen are: decreases in traffic noises and the volume of environmentally polluting materials. This paper reports on the net effect of different polymers, CRM and H.V.S. oil on bitumen properties. Incorporation of polyethylene along with CRM improve elasticity and deformation recovery of bitumen at high temperatures and reduces its brittleness at low temperatures. This results in improvements in bitumen's performance grade. H.V.S. Oil acts as a compatibilizer in PE-bitumen system and lowers Frass breaking point.

Blend of PP/PET is an immiscible composition because of the difference between solubility coefficient and lack of attraction between polar/non-polar polymers. For inducing required miscibility in the blend, various compatibilizers are used. In this research, PP-g-MA is being employed. This copolymer is produced from the chemical reaction and grafting between maleic anhydride (MA), dicumyl peroxide (DCP) and polypropylene (PP) The effect of adding DCP concentration (at constant MA) increases the grafting efficiency on PP and on the other hand, enhancing MA concentration (at constant DCP) decreases grafting efficiency. The results indicate that PP-g-MA makes PET fibrillar to become smaller and it also makes the phases to become closer. It is found however that using this compatibilizer, specially in large amount, decreases the mechanical properties of the blend.

In order to produce a green ceramic part with a desirable microstructure and higher density, attaining a stabilized suspension with the maximum ceramic loading level with suitable viscosity to flow and casting is of great importance.In this work, the stability of aqueous α-Al2O3 suspensions in presence of Na+ and NH4+ salts of poly (methacrylic acid) (PMAA) polyelectrolyte was studied and the effects of various parameters such as the amount of polyelectrolytes present, ceramic loading level, the amount of accelerator in gel casting system, i.e. TEMED (N,N,N',N'-tetramethyl ethylene diamine) and the ultrasonic shaking time on the stability were investigated. The optimum amounts of PMAA (for both salts) required to achieve higher stability and lower viscosity for suspensions were determined (0.3mL/ 100 g of dry powder) The results show that increasing the amount of ceramic loading level increases merely the viscosity of suspension in low shear rates. The critical amount of TEMED added to the suspension including polyelectrolyte is 0.4 mL/100 g of dry powder. Above this level, pH and viscosity of suspension increase rapidly. The ultrasonic shaking time has also a limiting level above which the viscosity of suspension rises with a constant slope, i.e. 1.42 mpa, versus time. These valuable results enabled us to prepare a suspension of 53% by volume (more than 80% by weight) of alumina suitable for gel- casting. The effect of polyelectrolyte on the green body density increment and homogenization of the structure was shown by SEM photographs and comparison were made with the suspensions having no polyelectrolyte.