M. R. Mahmoudi

Instrumentation for the measurement of fabric air permeability at higher pressure levels

The construction and evaluation of a novel instrument for measuring air permeability characteristics of fabrics at differential pressure levels up to 3 bar is described. Fabrics requiring such testing have reduced porosity, leading to low air permeability, and as a result, the use of standard air permeability testers is impractical. A pressure-related measuring technique is therefore employed in the new instrument, which also enables air permeability characteristics to be measured over a range of pressure levels. The instrument is also equipped for the measurement of distension of the test specimens, so that any variation of fabric air permeability with pressure can be investigated. It was demonstrated that the technique can still be applied, in conjunction with a low pressure transducer, for the measurement of fabrics having normal levels of air permeability.

Fibre Dynamics in a Revolving-flats Card: An Assessment of Changes in the State of Fibre Mass during the Early Stages of the Carding Process

A study is made of the changes in the state of fibre mass fed to the taker-in and transferred to the cylinder during the operation of a revolving-flats card. On the basis of the results of experimental work, an estimate is made of the actual draft at the taker-in/cylinder transfer region. The results confirm that extensive opening to the point of single fibres takes place at the taker-in stage but that there are still many tuftlets present in the fibre mass transferred to the cylinder. Image analysis of high-speed video photographs show that these tuftlets were elongated and orientated by a small draft at the taker-in/cylinder transfer region. It is found that each rear fixed fiat contributes to the breakdown of tuftlets, reducing the number of tuftlets fed to the cylinder by about 60%. The method developed for this study can he used to assess the effect of the taker-in and the rear fixed flats on the degree of fibre-mass opening.

Improving the Bulk of Worsted Yarns. Part I: A Basic Bulking Method

A basic method for increasing the bulk of worsted yarns is described, in which air jet false-twisters are employed. A technique for measuring yarn diameter is introduced and the results of the bulking treatment are assessed.

Aerodynamics and Fibre Transfer at the Cylinder–Doffer Interface

Abstract High-speed photography and image processing were used to study the aerodynamics in the cylinder–doffer transfer region. Smoke tracers were utilised to delineate aerodynamic patterns under the cylinder–doffer set point and the images were analysed as an indication of the pressure and velocity changes of the air flow in the region. High-speed photographic observations of fibre motion in the region were also studied in order to determine the effects of the air flow on fibre transfer. The results showed that due to local air pressure differences, air turbulence is generated under the cylinder–doffer set point, which may affect fibre configuration during the transfer. From the results an explanation is proposed for the occurrence of turbulent flow under the cylinder–doffer set point, and ideas previously reported by other researchers about the fibre transfer mechanism are further developed.

Effect of the Licker-in on Fibre Tuft Assembly

Abstract This paper investigates (i) the effect of fibre type and lap weight on the resiliency of the blowroom scutcher lap, (ii) the effect of licker-in action on the lap, (iii) the shear force, strength and drawing length of the licker-in tuft.

The Use of Air-jet Technology to Produce Self-twist Yarn: Part I: Preliminary Study

In the study reported in this paper, the possibility of using air-jet technology to produce a self-twist yarn was investigated. The method adopted used four jets in tandem, i.e. two Z and two S twisters, in which a high-pressure current of air was tangentially supplied to the inner surface of the yarn passage to create a vortex by which a strand of fibre was twisted.

Novel method for treatment of hollow fiber membranes using hypochlorite

A novel hypochlorite treatment method that enhances hydraulic permeability of hollow fiber membranes used in ultra-filtration was successfully devised and tested. Dope containing polysulfone/poly vinyl pyrrolidon (PVP-K90)/N-methyl-2-pyrrolidone (NMP) in mass ratio of 15:5:80, respectively, were used to produce hollow fibers via dry-jet wet spinning process. NMP in 1:1 ratio and distilled water were used as bore fluid. Hollow fiber membrane samples were post-treated using the novel, 95°C water and traditional hypochlorite treatments. State of membranes before and after post-treatment were morphologically compared using SEM microphotographs of fiber cross-section in conjuncton with image proceesing techniques. It was observed that in general both the novel and the traditional methods results in elimination of PVP swelling alone with alteration of pore size and pore distribution. This was confirmed by an increase in water flux of the hollow fibers that were subjected to these two post-treatment methods. Atomic force microscopy analysis vividly pointed to an intense increase in the roughness of the inner and outer surfaces of the membranes. This was attributed to the effect of post-treatment methods. It was found that in general post-treatments involving hypochlorite, increases the surface roughness of the membranes. However, increase in rate of the roughness of inner surface of traditionally hypochlorite treated hollow fiber membrane was found to be much higher than those subjected to the novel treatment method. It was established that the developed novel hypochlorite treatment method can be successfully used for production of high permeable hollow fiber membranes which have vast potential in therapeutic applications.

The Use of Air-jet Technology to Produce Self-twist Yarn: Part II: The Application of Tandem Jet Twisters

Part I of (his series described the principle of using air-jet technology in a tandem arrangement to produce self-twist yarn. This paper deals with the application of tandem jets to replace the self-twisting roller with computer-controlled switching.

The Effect of Fixed Flats on Yarn Quality

An investigation is reported in which the effect of fixed flats fitted to a cotton card on fibre orientation, revolving-flat load, and strip was studied. A modified Krylov method was used to assess the effects of production speed and of fixed flats on the cylinder load, the fibre-transfer coefficient, and the fibre orientation. Two fibre types, cotton and polyester fibre, were used. The use of fixed flats was found to be beneficial in reducing sliver nep content. However, the rear fixed flats were found to have no effect on the yarns Uster-evenness value, whereas the use of front fixed flats was found to reduce thin and thick places significantly.

Improving the Bulk of Worsted Yarns. Part II: Simultaneous Bulking and Spinning or Winding

Part I [1] described a basic bulking method. This paper deals with the question of incorporating the technique in a conventional ring spinning process.