Iranian Journal of Polymer Science and Technology
Year:2002 | Volume:15 | Issue:3 (ISSUE NO.59)|Papers Count:7

Samples of polypropylene bulk continuous filament yams are exposed to the outdoor sunlight in Tehran and xenon radiation in a controlled condition in Xenotest apparatus, free of tension and under tension as well. The results of the measurements of mechanical properties indicate that after exposure to light the tenacity, breaking extension and the work of rupture of the filaments decrease and the imposed tension affects the reduction of the mechanical properties. Due to the exposure of samples to the natural and artificial light, the formation of -OH, -OOH, -CO and -COO groups are confirmed by infrared spectroscopy, iodometric technique and staining with methylene blue. The shrinkage of yams in boiling water does not show any change and the changes in the thermal characteristics determined by differential scanning calorimetry do not show a consistent trend. Prolong exposure to outdoor sunlight degraded the stabilized polypropylene filaments. The effects of tension and light on the degradation processes are explained in terms of the current structural theories.

The main purpose of this study is to investigate inhibition of bacterial deterioration of a type of polyurethane binder by eight species of bacteria: P. aeruginosa, P. putida, N. brevicatena, C. flaviscense, C. pourometabolum, B. divaricatum, M. roseus, M. leutus. The methods used include: (1) Coating the surface of a polymer by antimicrobial chemical agents or non- competitive inhibitors in order to cause a delay in bacterial adhesion or complete inhibition of that process by using solutions of FeCl3, NaOCI and NaHCO3. (2) Promoting of anti-microbial property in polymer by chemical reaction of an anti-microbial agent material in the process of polymer production. In this process FeSO4.7H2O was added to the polymer. In the second method, induction of anti-microbial property to the polymer was investigated by using spectroscopy (ATR-FTIR) and anti-bacterial inducing property in process of polymerization was carried out by experimental bacteria. The inhibitory process of bacterial deterioration in presence of a stabilizing agent was investigated. In this study, to evaluate the process with more satisfactory results, polyurethane was utilized as a sole source of energy and carbon by microbial suspention. In absence of these conditions the production of deteriorating enzymes would be induced and the rate of deterioration would be also increased to a great extent.

In this research, enzymatic hydrolysis of the blend of cotton-polyester woven fabric has been investigated. In the first step the fabric samples were hydrolyzed only by lipase of zero and 0.5 g/L concentrations in different treatment times, and then these samples were treated by cellulase enzymes under proper conditions of biopolishing. In the second part, the samples were at first hydrolyzed by cellulase and then by lipase enzymes. The effects of hydrolysis on the one hand and sequential treatment of cellulase and lipase on the other hand on fabric properties were evaluated by means of measuring the weight loss, moisture absorption, breaking load of warp yams, IR spectrum and dyeing behavior of the samples. The results showed that the rates of cellulolytic and lipolytic hydrolysis were related to the percentage of cotton and polyester fibers present in the fabrics. The moisture absorption of the samples after being treated by lipase an alkaline buffer solution was increased. If the fabric was hydrolyzed first by lipase and then by cellulase, though the alkaline buffer solution would increase the activity of cellulose enzymes, but lipase denaturation would restrict the effects of cellulase on the samples. When cellulolytic hydrolysis is preceded first, the effect of lipase enzymes would increase. Finally, although the dyeing behavior of polyester part does not produce any major changes, but the absorption of direct dye increases.

Manufacture of ceramic micro-and nano-composite membranes requires the following steps such as: preparation of porous ceramic support systems with exact microstructure, suitable pore size and pore size distribution with reasonable physical and mechanical properties. In this work, gel-casting (in aqueous medium) was used to manufacture porous support systems from alumina powder with a particle size distribution in the range of 63-75mm. It was loaded 40% by volume in organic suspensions containing 5% by weight of acrylamide and N;N'-methylene bisacrylamide based on ceramic powder. The thermal treatments of green bodies were carried out in three distinct steps: (i) drying, using our own new novel drying method, i.e. liquid desiccant drying method, (ii) debinding, and (iii) sintering. The results obtained from Archimedes, nitrogen adsorption and bubble point tests show that the final sintered articles have 40% by volume open porosities, in a manner that 95% by volume of pores are narrowly distributed between 0.3-1.16 mm. This means that these porous ceramic supports have a desirable performance. These support systems have a uniform microstructure, good mechanical properties and it can sustain at least a pressure of 4 bars.

In this paper, the static and dynamic analyses of the composite as well as metallic bicycle frames using the finite element software, NISA II has been studied. Using the software, the composite and metallic frames were modeled and loaded according to four static and three transient dynamic loading conditions. With the proper selection of the materials and geometry for both frames and the ply sequences in composite frame as well, the stresses obtained in the frames have shown to be much lower than the allowable stresses. The study of displacement has shown that the composite frame has lower out-of-plane displacement compared to the metallic one, and therefore much less energy is stored in that frame. The analysis of the natural frequencies of modal shapes for both the frames has shown that the composite frame has better stability particularly at higher modal shapes. Using various core materials with different densities, some improved vibrational and dynamic performances are achieved in composite frame. As the core densities were reduced, the natural frequencies in the composite frame increased. Both the composite and metallic frames had adequate strength and stiffness in static and dynamic responses, but the advantage of the composite frame is higher with respect to strength/weight and stiffness/weight as well as the safety factor/weight ratios compared to metallic one. The integrity of the composite frame and also its aerodynamic shape provide better ride and more comfort to the rider.

Elastomers and plastics are intrinsically insulating materials, but by addition of some conductive particles such as conductive carbon black, carbon fibers and metals, they can change to conductive form. Conductivity of these composites is due to formation of the lattices of conductive filler particles in polymer chains. In this report, conductivity of chloroprene rubber filled with carbon black and carbon fibers as a function of temperature and pressure are studied. Electrical conductivity of chloroprene in a function of temperature and pressure are studied. Electrical conductivity of chloroprene in the presence of carbon black' with proper mixing conditions increases to the conductivity level of semiconductors and even in the presence of carbon fibers it increases to the level of a conductor material Meanwhile, the sensitivity of this compound to heat and pressure rises. Thus these composites have found various applications in the manufacture of heat and pressure sensitive sensors.