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Articles by Ramin Khajavi
Total Records ( 4 ) for Ramin Khajavi
  Ramin Khajavi , Seyed Hossein Mossavi Pourgharbi , Amir Kiumarsi and Abosayeed Rashidi
  Gum Tragacanth (GT) is one of the most widely used natural gum across the globe and it is shown that GT from Asteragalus gummifer can be processed into fiber via alkaline treatment. In this study a complementary description of GT fibers is provided and the effects of influencing factors on properties of GT fibers investigated. Spinning Dope (SD) prepared by adding ribbon type GT of Astragalus gummifer species to alkaline solutions and fibers produced by solution spinning method. The effects of some processing factors including: draft ratio, residence time in coagulation bath, GT concentration in SD, ripening time of SD, kind of coagulant agent and the pH of washing bath on some mechanical properties of GT fibers studied. It was concluded that with increasing the coagulant concentration the mechanical properties of fibers improved, but it caused formation of sheet core structure. ZnCl2 as coagulant agent improved mechanical properties and applying glycerol caused more flexibility in GT fibers, even though their tenacity reduced.
  Ramin Khajavi , Morteza Sattari and Ali Ashjaran
  In the presented research, the main aim is to investigate the antibacterial effectiveness of BAC solutions on acrylic fibers used in machinery carpet. An acrylic pile carpet laid in a public place for 30 days and the existence of some microbes were investigated on it. The antimicrobial effect of different BAC solutions for identified microbes was studied in vitro. The acrylic fibers were treated with the same different solutions of BAC as before and the antibacterial effectiveness was assessed by the zone of inhibition method in different times. Two pieces of carpet untreated and treated with BAC solution sewed together and laid for one week in the public place and the amounts of bacterial growth determined by colony count method and the results compared. Finally some mechanical properties of treated acrylic fibers measured after 30 days and compared with untreated one. The results showed the presence of some pathogenic microbes on the laid carpet such as Escherichia coli and Staphylococcus aureus. The inhalation time for treated acrylic fibers improved. The amount of colony growth on treated carpet reduced considerably and besides the mechanical tests results showed no significant deterioration effect of studied properties in comparing with untreated yarn.
  Ramin Khajavi , Bita Novinrad and Amir Kiumarsi
  In the presented research the effects of ultrasonic US on worn out process is under consideration. Samples of two different vats dyed denim fabrics chosen and were worn out with the aid of sodium hydrosulphite and neutral cellulase enzyme individually and together and the effects of ultrasound were investigated in parallel testes. Pictures were taken from samples by microscope and scanning methods and the amounts of brightness, color difference, degree of whiteness and color absorption of treated samples in US and ordinary environments were determined and compared. The back staining effects were also evaluated by the aid of degree of whiteness for samples. All the measured parameters were varied and increased between 50 to 98% for US environment and the back staining effects were declined in the presence of US significantly. It was concluded that the general properties of US wave especially in wet processes makes it applicable in worn out process for improving the efficiency and producing a different view, color change and fluffy look.
  Ramin Khajavi and Rogheih Damerchely
  In this study it was aimed to produce nano fibers of poly vinyl alcohol PVA polymer via electrospinning ES method and to investigate the role of PVA concentration in the spinning dope on diameter, beads and HHS of produced fibers. Spinning dopes with different concentrations of PVA at rang of 5 to 20% (wt/wt on weight of solution) prepared. The requisite voltage for ES (30 kv) was supplied by a DC high voltage power supply and for collecting the fibers a grounded aluminum foil target placed 17 cm below the tip of capillary tube (spinning nozzle). The results showed that spinning dopes with PVA concentration between 8 to 12% (wt/wt) are capable of producing PVA fibers, but those below 8% (wt/wt) concentrations because of low viscosity formed droplets known as electrospray effect. Electrospinning suppressed at spinning dope concentrations above 12% (wt/wt) due to high viscosity of dope. According to the SEM photographs of electrospun PVA fibers it revealed that in higher concentrations produced nanofibers have larger diameter with less beads and HHS in compare with lower concentrations.
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