P. W. Foster

A New Test Method for Studying the Thermo- bonding Behaviour of Synthetic Fibres

A description is given of a fibre–loop test developed to assess the absolute thermal–bonding strength of fibres by tests on short lengths of single filaments by means of new FTMA (flexible thermo–mechanical analyser) equipment. Rapid heating and cooling and short residence times were used ln line with commercial practice. Various grades of polypropylene and copolyester fibres were used. Thermal behaviour, by means of DSC (differential scanning calorimetry), and structural changes, by means of SEM (scanning electron microscopy), were also studied. The new loop test gives a measure of the effectiveness of a bond formed between fibres.

Structure/Property Relationships of Poly(ethylene terephthalate) Continuous-filament Yarn

Two commercial PET yarns, one as-spun and the other highly crystalline and drawn, were annealed at l8°C under various conditions. Mechanical and thermal-response measurements were made under high transient-heating conditions by using a UMIST-built Universal Fibre Tester (UFT). Differential-scanning-calorimetry (DSC) measurements were also made. A middle endotherm was observed on DSC traces for both the PET samples that had been annealed freely (free to shrink). Further thermo-mechanical treatments of these pre-annealed samples were made and thermal, creep, tangent-modulus, and other mechanical properties are recorded. The experimental results show structural instability in the fibre morphology irrespective of the process histories.

Constant-bulk False-twist Texturing. Part I: Principle and Method

Current false-twist texturing processes are all carried out under constant-temperature conditions. White the product is good and commercially acceptable, changes in bulk and hence in dyeability do occur, due, for example, to alterations in yarn properties caused by changes in package build from inside to outside. New work described in this paper shows that, by texturing at constant bulk, substantially improved yarn and fabrics can be obtained. The new process developed at UMIST uses very small heaters (4–8 inches in length) under feedback control. The bulk and dyeability of the textured yarn are monitored on-line. A closed-loop system is used, and texturing conditions are automatically changed to keep the bulk and dyeability of the textured yarn constant. In this new process, the texturing temperature is changed in such a way as to keep the bulk constant. The process is therefore non-isothermal, in contrast to the isothermal, constant-temperature approach of all current false-twist texturing equipment. Th...

Thermobonding Behaviour of Polypropylene and Other Fibres

An investigation is reported in which a new fibre-loop test, developed earlier for a flexible thermomechanical analyser (FTMA), was used with varying conditions of time, temperature, and tension to assess the thermobonding responses of three different grades of polypropylene fibre and one of copolyester fibre. Heating and cooling rates were rapid to correspond with commercial practice, and scanning electron micrographs were taken of the bonded loops. Conditions for optimum bond strength are determined.

False Twisting of a Staple Yarn in a Potential Dyeing Process

A previously developed, environmentally friendly method of continuous dyeing of filament polyester yarn used technology based on the Fibre-M constant bulk texturing system. This paper describes some progress towards modifying aspects of this technology to facilitate processing of staple yarns as a precursor to developing a dyeing process for staple yarn based on the technology. Originally, the high-pressure steam input to the system caused instant breakages in staple yarns. However, by the introduction of a false-twist jet, modest running times have been achieved. The next step is to apply the new technology in an actual dyeing process.

Effects of core-yarn overfeed on texturing performance: comparison between air-jet and steam-jet texturing

The objectives of this research work were to investigate the use of high-pressure steam in order to replace air in the production of spun-like textured yarns and to investigate the optimum level of core-yarn overfeed ratio for steam-jet textured yarn for the application of sewing threads. An existing air-jet texturing machine was modified to supply either air or steam to the texturing nozzle. Using an identical nozzle, both air-jet and steam-jet textured yarns were manufactured. Loop instability and loop density increased and strength and tenacity decreased when the core-yarn overfeed was increased in both air-jet and steam-jet textured yarns. Steam-jet textured yarns have lower loop instability, lower loop density and higher tensile properties than that of the air-jet textured yarns. Sewability results show that for both air-jet and steam-jet textured sewing threads, core-yarn overfeed ratios of 5.5 and 8.3% give better sewability.

Effect of nozzle size on texturing performance: comparison between air-jet and steam-jet texturing

The objectives of this research work were to investigate the use of steam in order to replace air in the production of spun-like textured yarn and to investigate the optimum nozzle size for steam-jet textured yarn for the application of sewing thread. An existing air-jet texturing machine was modified to supply either air or steam to the texturing nozzle. Using four texturing nozzles, both air-jet and steam-jet textured yarns were manufactured. The effect of nozzle size on process and yarn parameters has been studied and compared with air-jet textured yarns. The results show that spun-like textured yarn manufactured using steam has lower loop instability and higher tensile properties than air at comparable fluid pressures. SEM image analysis shows that the entangled structure of the steam-jet textured yarns is similar to air-jet textured yarns. Further, sewability results show that steam-jet textured yarns are suitable to manufacture sewing threads.

Investigation of the use of steam for spun-like textured yarn manufacturing: effect of fluid pressure on yarn properties

The objective of this research work was to investigate the use of steam in order to replace air in the production of air-jet (spun-like) textured yarns. An existing air-jet texturing machine was modified to supply either air or steam to the texturing nozzle. Using standard commercial nozzles, both air-jet and steam-jet textured yarns were manufactured. The effect of fluid pressure on yarn tension, loop instability, loop density, linear density, strength, tenacity and elongation has been studied. The results show that spun-like textured yarn manufactured using steam has lower loop instability, higher liner density, strength, tension and elongation than the one manufactured using air at comparable fluid pressures. SEM image analysis shows that the intermingled structure of the steam-jet textured yarns is comparable to the air-jet textured yarns. Therefore, it can be concluded that steam can be used as an alternative fluid for air in making spun-like textured yarns.

Investigation of the effect of core-yarn wetting on air-jet and steam-jet spun-like texturing performance

The objective of the research work was to investigate the use of steam as an alternative fluid for air in spun-like textured yarn manufacturing and to investigate the effect of wetting on texturing performance. An existing air-jet texturing machine was modified to supply either air or steam to the texturing nozzle. Both air-jet and steam-jet textured yarns were made using the same process parameters with and without core-yarn wetting. The effect of core-yarn wetting on the texturing performance has been studied. Results show that core-yarn wetting is critical for air-jet texturing but do not have considerable impact on steam-jet texturing. Therefore, core-yarn wetting could be eliminated in steam-jet texturing. Further, steam-jet texturing shows its capability in manufacturing spun-like textured yarns with better performance than the air-jet. Therefore, it can be concluded that steam can be used as an alternative fluid for air in making spun-like textured yarns without core-yarn wetting.

Constant Bulk False Twist Texturing

The false twist threadline length has been substantially reduced by the use of very small high intensity heaters using hot fluids as the heat transfer medium. The use of rapid response heaters permits a feed back loop to be introduced. Various methods of on-line bulk measurement are discussed and it is shown theoretically that if a tension barrier is deliberately introduced in the second zone of the false twist threadline that measurement of velocity correlates with yarn bulk. Experimental work has verified this approach and a high speed machine, of low cost that can be used in flexible shift patterns of working is described. Substantial yarn quality improvements flow from the use of feed back control to keep the heat flux to the twisted yarn constant, while permitting the temperature of the heating medium to change.