Iranian Journal of Polymer Science and Technology
Year:2000 | Volume:13 | Issue:3 (ISSUE NO.49)|Papers Count:6

Theoretical as well as experimental work are conducted to increase our understanding on the behavior of heat transfer and deformation taking place in film blowing of the extrusion process. The film blowing process was simulated by solving the force balance and energy equations established for the blown film moving in upward direction. Low-density polyethylene was employed for carrying out non-isothermal work and some operational parameters were measured. Four non-linear complex differential equations resulted from the balance and the energy equations were solved numerically, using the fifth-order Runge-Kutta method. In this method, considering the effect of gravity on the elevating film made the calculations more precise and reliable. The good agreement, observed between the simulation and experimental results, is a credit to the applicability of the established model in industrial scale. The established mathematical model predicts the bubble shape, temperature profile and film thickness as a function of the distance along the machine axis.

In this study, in order to increase the impact strength of polyacetal, the polymer was alloyed with thermoplastic elastomer polyurethane (TPU). In this regard, alloys of polyacetal consisted of 5-50% of thermoplastic elastomer polyurethane were prepared and the physical-mechanical, thermal, rheological and morphological properties were investigated. This study indicates that between these prepared alloys, the impact strength and elongation-at-break reach to a maximum level with 15% and 30% of TPU, respectively. Meanwhile, the impact strength, elastic modulus and crystallinity decrease with increasing the amount of TPU. Studying the dynamic-mechanical properties implies that the damping peak would be higher with increasing the amount of TPU. Morphological investigations indicate that the size of particles of TPU dispersed phase will change in the range of 1-10 mm with increasing the amount of TPU.

This research paper is devoted to the application of a unit work method for the scale up of rubber mixing process in banbury type internal mixers. Mooney viscosity and carbon black dispersion factor were selected as the parameters for the determination of the state of mixing. Based on a specific compound formulation, the above mentioned parameters were measured in three mixers with different chamber sizes (60, 300 and 1500 mL). It is shown that by this method the operating points of a bigger size mixer can be accurately obtained from the experimental data obtained 011a small size mixer.

Alkaline hydrolysis of polyester (PET) is applied to improve the polyester fibers properties. Rate of the reaction depends on the treatment temperature, time, alkaline concentration and presence of quaternary ammonium compounds. In this paper polyester fabric, were treated with sodium hydroxide solutions prepared in methanol and ethanol. The weight loss levels obtained were considerably higher than those obtained with an aqueous solution of sodium hydroxide at equivalent parameters of concentration, time and temperature of treatment. A good linear correlation was observed between weight loss and breaking load of treated fibers.

Wear is the major problem of the acrylic artificial teeth. Attempts have been made to reduce the problem by using cross-linking agents and inorganic fillers. In this study difunctional monomers (EGDMA and Bis-GMA) as cross-linking agents were incorporated to the acrylic teeth formulation to improve their wear resistance. The wear of modified samples was compared with that of the controls. The results indicated that the difuntional monomers can significantly decrease the wear of acrylic teeth.

Due to environmental consideration, there is an interest in the application of enzymes of wool instead of usual finishing processes. Protease enzymes can remove the cuticles of wool, reduce felting capacity of fibres and help to produce cashmere like handle. In this paper the effects of protease enzymes on woolen yarn have been reported. The results show that the treatment by enzyme leads to a weight loss and tensile strength reduction. More depletion is achieved by increasing the treatment duration and enzyme concentrations. As a result, the whiteness index and the wettability of treated samples are increased. The electron microscopic images show that the control of treatment condition is very important, because the damages occur to the surfaces as well as the interior of the fibers and as a result the wool quality would be dameged.