Iranian Journal of Polymer Science and Technology
Year:2007 | Volume:19 | Issue:6 (ISSUE NO. 86)|Papers Count:8

In this study the improvement in wash fastness of direct cotton dyes on wool and nylon 6 fibers by after-treatment with natural and synthetic tanning agents are examined. For measuring exhaustion, desorption and wash fastness a spectrophotometer was used. After-treatment of the dyeing using full back tan improved wash fastness on nylon and wool to the greater extent than that of synthetic tanning agents.

In the current work, using Monte Carlo simulation method, different properties of linear binary copolymers, especially the microstructure or copolymer chains, with respect to copolymerization system parameters were investigated. For this reason, a-proper and new model for initiation reaction was proposed by regarding the drawbacks found in the models previously presented and the simulation was performed based on this model. The results obtained from the simulation showed that copolymer chains inherited a maximum alteration in a certain feed composition in all binary copolymerization systems. Moreover, employing such a condition in a real copolymerization reaction makes it possible to produce special copolymers with favorite and tailor-made properties. In addition, the number and weight distributions of homogeneous sequences were depicted for each monomer, which enables us to virtualize the microstructure of the copolymer chains. Obtaining such results through experimental methods is either impossible or very expensive, which in turn limits their applications.

The hole drilling method has been used for determination of residual stresses in various materials. The released strains measured by the hole drilling method are converted to residual stresses using calibration factors. There is a standard for hole drilling method for isotropic materials. Also for orthotropic materials, there are various methods for converting the released strains to residual stresses. In these methods the numbers of calibration factors vary from two to nine (a three by three matrix). In this research, using an exact solution method, calibration factors for orthotropic plates are determined. For this purpose, by assuming a plane stress condition, the stresses and strains around the area under a rosette strain gauge mounted to an orthotropic plate are calculated. Making a hole in the centre of the rosette strain gauge changes the distribution of the stress and strain forces. Using the closed form solution proposed in this research the released strains and the calibration factors are calculated, and the residual stresses are evaluated. Using the proposed method, calibration factors for any orthotropic material with any level of orthotropy are calculated.These factors are independent of loading levels and depend on material properties of orthotropic materials and ratio of the rosette diameter to the hole diameter. The material properties and the ratio of the rosette diameter to the hole diameter are considered in the equations, therefore there is no need for presenting the results in tabular form or any interpolations. The results for an orthotropic unidirectional ply made of carbon/epoxy are obtained. Also the calibration factors for three different dunidirectional composites are calculated. The data from the proposed closed form solution are compared with the 'simulated hole drilling method which has been proposed by authors earlier. A good agreement between the results shows the reliability of the closed form solution presented in this study.

Due to the growing applications of polypropylene in different industries, optimizations of its processing conditions and engineering properties have become important issues for research technologists and manufacturers. The incorporation of nucleating agent is suggested as a proper approach to economize the process and enhance the physical and mechanical properties of products. In this study the effects of nucleating agent on two homo- and co-polypropylene are investigated: Sodium benzoate and bis (p-methyldibenzylidene sorbitol) are used as nucleating agents.Differential scanning calorimetry (DSC), X-ray scattering and polarized light microscopy (PLM) are used to determine the crystallization temperature, crystallinity and study of spherulitic microstructure, respectively. Effects of nucleating agent on mechanical properties including yield stress, E-modulus and impact strength are investigated.The results of this study reveal an increase in crystallization temperature by introduction of nucleatirig agent.However, the addition of sorbitol derivative in pp increased the crystallization peak temperature by over 20°C. It is shown that incorporation of both nucleating agents increases crystallinity, yield stress and E-modulus. The impact strength however goes through a maximum by increasing the nucleating agent content.

In this research, polysulphone (PSf) hollow fiber membranes were fabricated by wet/dry phase inversion method for the first time in Iran and the effects of air gap and solvent type on the structure of prepared membranes were investigated.To investigate the solvent type effect, NMP and DMF solvents were used to prepare polymeric solution for spinning.The characterization of hollow fiber membranes was conducted by SEM method. The asymmetric and integrally skinned hollow fiber membranes were spun from PSf/NMP solution and exhibited finger-like pores whereas, hollow fibers spun from PSf/DMF solution showed sponge-like structure. The difference between power solubility of solvents and the solvent/ non-solvent interactions of DMF/water and NMP/water causes the structural differences between the membranes. The difference between solvent activities described via Hansen's solubility parameter. It is concluded that by increasing the air gap, porosity and outer fiber diameter were diminished and denser outer skin layers were formed.

Corona discharge method is utilized in atmospheric pressure and air for improvement of polymer surfaces and textiles.Stone and enzyme washing of denim require large amounts of chemicals with heavy costs. Corona treatment is a useful method for wet processing of textiles that can reduce costs and environmental problems. In this research work a cellulosic film was dyed with indigo dye and then the un-dyed and dyed films were exposed to corona discharge at different levels of powers and number of passages. Colorimetric parameters (L*, a*, b*) and contact angle were determined and surface morphology was studied by scanning electron microscopy and FTIR spectroscopy. The results show that corona treatment can increase L* parameter and decrease contact angle.

Rubber process analyzer (RPA) is a condition-controlled shear cone-and-cone rheometer specifically designed for raw elastomers and rubber compounds. The viscoelastic and cure properties of styrene butadiene rubber (SBR) compounds filled with different loadings and types of carbon black were investigated using RPA, via the strain sweep and cure experiments. At higher level and surface area of carbon black, the linear viscoelastic region disappeared and the strain dependence of G' became more pronounced. Curing tests results expressed that the compounds containing the higher loading and fine particle size of carbon black showed greater cure torque values, higher vulcanization rates and the lower curing times. Ds" (drop in maximum of viscous torque) was reduced with increasing the content of carbon black and its specific surface area, and hence its elasticity.

A comparison is made between the effects of chemical coagulants and natural polymers on sewage sludge dewatering. In this study, six coagulants including four chemical coagulants and three natural polymers were examined and the time to filtration (TTF) and the water content of sludge cake were measured. In this study the best coagulant doses for minimum TIF under optimum pH was determined. The obtained results indicated that ferric sulfate was the best chemical coagulant for activated sludge by increasing 77.5% of the dewatering rate. However, for digested sludge, ferric chloride was more effective than others chemicals. An amount of 1250 ppm of this coagulant at pH=5 produced 80% increase in rate of dewatering. Among all natural polymers, the maximum rate of sludge dewatering efficiency of 61% for digested sludge was achieved when 10ppm of chitosan was used. In this case the amount of water content of sludge was 13% less than blank sample.