M. S. Joharei - Assistant Professor، Department of textile Engineering Amirkabir University of Technology, Iranian Academic Center for Culture, Education &Research of Amirkabir University Tehran, Iran
S.M. Etrati - Assistant Professor، Department of textile Engineering Amirkabir University of Technology, Iranian Academic Center for Culture, Education &Research of Amirkabir University Tehran, Iran
M. Varsei - Instructor، Department of textile Engineering Amirkabir University of Technology, Iranian Academic Center for Culture, Education &Research of Amirkabir University Tehran, Iran
H. Dabiryan - Instructor، Department of textile Engineering Amirkabir University of Technology, Iranian Academic Center for Culture, Education &Research of Amirkabir University Tehran, Iran

Earlier investigations have demonstrated that air interlacing improves the mechanical properties of Self-Twist (ST) yarns. In following of previous efforts, this paper discusses improving of mechanical properties ofST yarn by using double-nozzle jet.In the present work, at first, a Murata jet was attached to Repco ST yarn machine which the air pressureand distance of double-nozzle jet from twisting rollers were varied. For the experimental work, the distanceof jet from twisting rollers was adjustable from 255 mm to 505 mm. Also, a wide rang of the air pressure hasbeen supplied. The results showed that elongation and tenacity of yarns increase relatively by increasing ofmentioned distance up to 355 mm. Also, the results showed an improvement of tensile properties of yarnwhen the air pressure of first and second nozzle are 1 and 4 bars, respectively.

Self-Twist Yarn, Mechanical Properties, Double-Nozzle Jet, Zero-Twist Parts, Air Pressure