by Dr. Anita Nishkam, Rama Kant Yadav, N.B. Singh and Lokesh Shukla

Abstract: This endeavor is to study abrasion performance of fabrics, knitted by P/W DRF yarns in co-relation to processing parameters namely fiber length (65, 70 and 75 mm), twist multiplier (2.00, 2.25 and 2.50) and strand spacing (10, 14 and 18 mm). Using box and Behnken’s centrally rotatable design the response surface equations at various levels of variables have been drawn. The contours of each equations are drawn,the maximum abrasion cycle is found 1325 and the minimum is 1150 cycles, optimum abrasion cycles are observed at wool fiber length 70 mm, strand spacing 14 mm and TM 2.25.The optimum performance is found at the zero coded level of processing variables.

1. Introduction

Considerable efforts have been directed towards eliminating two-folding (plying) in the production of weaving / knitting yarn. The ultimate aim being to produce as fine yarn as possible on the spinning frame, which can be woven / knitted without resorting to either two-plying or sizing. In the main, two approaches have been followed, namely Double Roving Feed (DRF) spinning and Compact Spinning.

DRF Yarn is a special spin twisted yarn, which can be produced directly on the ring-spinning machine. In this process, two roving are fed in parallel through the drafting system, separated by two specially developed condensers, and are drafted separately. The twist is introduced as for a normal single yarn by means of ring and traveler. The roving, which are drafted parallel, are combined after passing the front rollers at the exit from the drafting system, with the twist being reproduced in the individual components right up to the nip point. Once past the front roller of the drafting system, the two yarns are combined with the ply twist (previously determined) to give the desired yarn count, producing a two fold yarn with the same direction of twist as for single yarns.2

Weaving yarn is normally two-fold that is, made up of two strands twisted together. Ordinarily the strands must be first spun and then two-folded, allowing a two-fold yarn to be produced in one step from wool top.3

The economic effects are not restricted to the wool spinning stage. Fabric producers are also affected, in three principal ways. First, yarns have slightly different weaving characteristics from conventional yarn, and this increases the cost of weaving by about 1%. Second, because Siro yarns can be produced at significantly lower cost than conventional yarns, part of this cost saving is passed on to fabric producers. The second effect out weighs the first, resulting in a net saving to fabric producers. Third, fabric has distinct quality characteristics.4

The abrasion is general weakening of fabric structure and majority of the tears and splits, which occur many worn in fabric, are a direct consequence of the fabric breakdown.5

The researches on the effect of various fibres have done lot of work and process parameters on yarn structure and yarn characteristics of DRF yarn, but little work has been done on the influence of fabric structure and characteristics. This endeavor “Abrasion of Fabric, Knitted by Polyester Wool Double Roving Yarn in Co-relation to Processing” is a proto-type experimental approach to investigate the role of processing parameters namely fiber length, twist multiplier(TM) and strand spacing in abrasion cycle performance of knitted fabrics .

Authors note: Dr. Anita Nishkam is the Director of the Govt. Central Textile Institute at Kanpur, India. Rama Kant Yadav from New Victoria Mills, N.B. Singh (Worsted Superintendent) from Cawnpore Woolen Mills, Lal Imli Mills, Civil Lines, Kanpur and Lokesh Shukla, Govt. Central Textile Institute, Kanpur.

2. Material and Methods

The Polyester Long Staple (Varying Cut Length) staple length longest (mm) 150, average (mm) 89, shortest (mm) 35, Fineness (denier) 2.50, Bundle Strength (gram/tex) 14.4 blended with merino wool fiber staple length longest (mm) ranging from 160 to 170, average (mm) 65 to 75, shortest (mm) 15, micron (µ) 2.5, Moisture regain (%) 16.3, Bundle Textile strength (gram/tex) 12, Residual Grease (%) 0.5, Alkali Solubility 10.5 in 70: 30 ratio.

The 40S Tex 70:30 P/W yarns samples are produced as per experimental plan in NMM (WS 436) Ring Frame by DRF technique. The yarns are knitted in knitting machine model BlackBurn (U.K.), having 8 (two yarn per feed) feeder, gauze of 10 needles /inch at 22 rpm speed.

It Abrasion Cycles are measured as per ASTM 1375: 69 T method using Martindale Abrasion tester. Sets of specimen are mounted on rectangular blocks of 1.5 X 2.5 inches with abrading material fabric itself.

To study the effect of individual parameters and their interaction, a quadratic equation is developed for abrasion formation in terms of variables.

The experiments are conducted according to a compound centrally rotate-able scheme proposed by Box and Behnken’s6 involving the three variables i.e. fiber length, twist multiplier and strand spacing. The coded and actual values of variables with results evaluated of different samples are given in Table-2.1 on the next page.

3. Result and Discussions

The response surface equation of abrasion performance of fabrics, knitted by P/W DRF yarns is given below:

Y(abrasion) = 1298.33 + 16.88*X3 - 64.79*X2^2 - 27.50*X1*X2 - 47.50*X2*X3

The coefficient of correlation (R2) between the experimental values and the calculated values obtained from the response surface equation was found 0.71. Therefore, the response surface fairly agrees well with the experimental data, and the variables considered in the study have substantial influence on abrasion performance of fabrics, knitted by DRF yarns.

3.1. Effect of Fiber Length

To find out the effect of wool fiber lengths response surface equations at various levels are given in Table-3.1. Contour maps were constructed as given in Fig. 3.1.(a),(b),(c) respectively by these equations.

Fig. 3.1. (a), depicted in contour that as TM value increases from 2.00 to 2.25 and strand spacing 10 to 18 mm a decreasing trend in abrasion cycles is found. At TM value 2.25 and strand spacing 14 mm as the strand spacing increases and TM value decreases to 2.00 a steep decline curve is shown, however, a slight increase in TM shows a rapid rate of increase in abrasion.

The maximum abrasion cycles are noted at TM level 2.50 and minimum abrasion is noted at TM level 2.00. The strand spacing increase shows the decreasing trend in abrasion. The 1300 cycles of abrasion are noted at TM level 2.25 and strand spacing 14 mm.

Fig. 3.1. (b), depicted in contour that as TM decreases and strand spacing increases the abrasion cycles are also reduced. The minimum numbers of abrasion cycles are found at TM level 2.00 and strand spacing 10 mm. The maximum number of abrasion cycles are found at TM level 2.50

The maximum numbers of abrasion cycles i.e. 1300 are reported at between strand spacing 10 to 14 mm and TM between 2.25 to 2.50. The contour lines between the TM below 2.25 are parallel and show an equal impact on abrasion cycles due to increase in strand spacing. The best DRF yarn for knitting fabric for optimum abrasion cycles can spin at TM between 2.25 to 2.50 and strand spacing 14mm

Fig.3.1.(c), depicted in contour that as TM decreases from 2.25 and strand spacing increases the abrasion cycles also decrease. In case of TM decreases from 2.50 to 2.25 comparatively less rate of reduction in abrasion cycles are noted. The maximum abrasion cycles are found at TM level 2.50 and lowest abrasion cycles are noted at TM level 2.00. The trend at TM value 2.25 is noted different as TM increases slight increase in abrasion cycles is noted between strand spacing 14 to 18 mm. However, rapid decline trends is observed between the 14 to 18 mm strand spacing in abrasion cycles.

The optimum abrasion cycles are responded at strand spacing 2.25 TM value and Strand spacing 14 mm for knitted fabric of DRF 70:30 Polyester Wool blended yarns.

3.2. Effect of Twist Multiplier

To find out the effect of TM, response surface equations at various levels are given in Table-3.2. Contour maps were constructed as given in Fig. 3.2.(a),(b),(c) respectively by these equations.

Fig. 3.2. (a), depicted in contour that as all the parallel vertical lines depict that as wool fiber length increases from 65 to 75 mm abrasion cycles also increase at each strands spacing. The lowest value of abrasion cycles is found at lowest wool fiber length

The co-relation between the wool fiber length and strand spacing is not clear. The all lines in contour are perpendicular to the X-axis it shows the individual impact of strand spacing in each wool fiber length. The response of these two variables i.e. Fiber length and strand spacing could not investigate the optimum value for spinning 70:30 P/W yarn suitable for knitting, keeping the optimum abrasion cycles.

Fig.3.2. (b), depicted that as this contour at wool fiber length 75 and strand spacing increases it tends to decrease in abrasion cycles, however, the maximum value of abrasion cycles is noted at wool fiber length 75 mm and the minimum abrasion cycles are found at wool fiber length 65 mm. The maximum numbers of abrasion cycles are found at strand spacing 10 mm and the lowest numbers of abrasion cycles are found at strand spacing 14 mm.

All lines are parallel in nature and in declining trend this shows the equal impact of two variables at each level. The 1300 abrasion cycles are noted at strand spacing 18 mm and fiber length 70 mm it is optimum value of abrasion cycles in this case.

Fig.3.2. (c), depicted that as this contour as, the fiber length increases from 65 to 75 and strand spacing increases from 10 to 18 mm the abrasion cycles decrease. As all lines are parallel it shows same relationship at each strand spacing and wool fiber length.

The maximum abrasion cycles are noted at wool fiber length 75 mm and strand spacing 10 mm. However, the minimum abrasion cycles are noted at wool fiber length 65 mm and the strand spacing 10 mm. These observations concluded that the abrasion cycles of knitted fabric increase as the fiber length increases. Also concludes that as strand spacing increases the abrasion cycles of knitted fabric decrease.

3.3. Effect of Strand Spacing

To find out the effect of strand spacing, response surface equations at various levels are given in Table-3.3. Contour maps were constructed as given in Fig. 3.(a),(b),(c) respectively by these equations.

Fig. 3.3 (a), depicted that as the TM increases from 2.00 to 2.25 and fiber length increases from 65 to 75 the tendency of reduction in abrasion cycles is noted. Also it is noted that as the TM increases at wool fiber length 75 mm a declining trend is observed. The optimum abrasion cycles in knitted fabric are noted 1300 at spinning of wool fiber length 75 mm and 65 mm at TM value 2.25.

Fig.3.3 (b), depicted that as wool fiber length increases from 65 to 75 between the TM values below 2.25, the abrasion cycles also reduced in knitted fabric produced by DRF yarns.After TM value 2.25 as wool fiber length increases from 65 to 70 the abrasion cycles also increases. And wool fiber above 65 mm as TM increases from 2.25 to 2.50 it shows a declining trend.

The maximum abrasion cycles are found 1300 at wool fiber length between 65 to 70 and TM between 2.25 and 2.50.The higher abrasion cycles are noted at wool fiber length 75 mm and TM value between 2.00 to 2.25 and slightly below to TM Value 2.50.

Fig.3.3. (c) depicted in that as the wool fiber length 75 mm shows the maximum abrasion cycles. The trend observed is reducing as the TM value increases, the minimum abrasion cycles are noted at wool fiber length 65 mm. At TM level between 2.00 and 2.25 and wool fiber length 75 as the length decreases to 65, the abrasion cycles decreases but abrasion cycles increased at 2.25. In the range of TM 2.25 and 2.50 the trend observed is decreasing with the increase in TM value. The all lines in this range being parallel it shows the same impact on the DRF yarn knitted fabrics.

The optimum values of abrasion cycles are noted at fiber length 70 mm and TM between 2.25 and 2.00, and wool fiber length between 65 mm to 75 mm at TM level between 2.25 and 2.50 i.e. 1300 cycles

Hearle J. W. S.12 reported constitutive relations for yarns and fabrics. The hierarchy is in the box below:

Therefore, yarn structure has direct effect on the properties of the fabrics.

The process variables selected in proposed investigation are mainly affecting the yarn characteristics. The impacts of fiber length, twist multiplier and strand spacing on knitted fabric is due to the yarn abrasion performance of DRF yarn.

It is revealed that as the fiber length increases in the yarn, the physical and mechanical properties at higher fiber length are better. In ring spinning, the spinning triangle is the yarn formation zone. The individual fibers or groups of fibers are twisted here and consolidated to form the ring spun yarn structure.

On DRF yarn the role of fiber length is miscellaneous due to the spinning angle as it increases from a certain limit the angle remains constant, as the strand spacing is constant. At higher the strand spacing the spinning angle should remain same, however the strand spacing should be more.

S. Bhatnagar and others8 reported that the abrasion resistance improves with spacing. This may be due to the increased amount of strand space available for binding the surface fibers, further the higher packing of fibers.

Ishtiaque et. al.9 attributed to the increased angle of inclination of fibers to the yarn axis caused by greater interlocking of two strands. Owing to the increased angle of fibers inclination, the cross sectional are of the fibers in the yarn section increases leading to higher packing density of fibers in the yarn. The average values of angle of inclination of fibers in siro spun and ring spun yarns are 27-30° and 18-20° respectively. The greater packing density of fiber in the cross section is one of the reasons for higher strength of siro spun yarn.

It is reported that as strand length increases in higher strand spacing the disturbances at convergence point is greater which is responsible for higher false twist generation as strands resulting in more trapping of surface fibers .1.

This phenomena has been observed during yarn production using stroboscope, it was seen that in the convergence point twist are imparted to strands in the opposite direction momentarily and which ultimately merged with the final yarn.

The optimum TM value, the emerging fiber trapped at higher binding force and shows better packing density.

Due to better trapping of surface fibers, abrasion resistance is also higher in wider spaced roves, thus suppress the influences of low hairiness or better fiber trapping 10.

Anurab Chaudhary and co- worker’s11 findings are similar, as in same weaving conditions, the breaking strength, tearing strength, abrasion resistance and crease recovery properties of fabric perform improvement in case of Siro spun than plieds yarn. An increase in the polyester content in the blend significantly enhances the wear life and mechanical properties of woven fabrics.

4. Conclusions

4.1.The abrasion performance of knitted fabric is directly proportional to constituent yarn. 4.2.Overall it is observed that the maximum abrasion cycle is found 1325 and the minimum is 1150 cycles 4.3.The optimum abrasion cycles are observed at wool fiber length 70 mm strand spacing 14 mm and TM value 2.25. 4.4.The trend observed in abrasion up to 70 mm fiber length increases consistently and further decreases. The TM impact shows the increasing trend first than decreasing. Increasing trend is observed as strand spacing increases. However, optimum abrasion cycles are found at 14 mm strands spacing. Comparatively higher abrasion is found at 18 mm to 10 mm strands spacing. 4.5.As the wool fiber length and strand spacing increase the abrasions first increases then decreases. 4.6.As TM and strand spacing increases the abrasion decreases in knitted fabrics P/W DRF yarns.

References

1. Plate DEA, Siro spun: Goodbye to the twofold? Text. Horoz., 2(2), Feb (1982) 34. 2. Leary R.H., Textile Asia, April (1976) 72-76. 3. Henshaw, Worsted Spinning, Textile Progress, (1999) 9-12. 4. Barella A., and Manich, A.M. Proceeding of 34th International Textile Conference, Budapest, Hungary, (1982) 311. 5. Shukla Lokesh, Dixit B.D., Textile Magazine, Vol. 44, No 3, January (2003) 24-27. 6. Box G P E & Behnken D W, Techno metrics, 2 (1960) 455. 7. Dieter Geriche, The Indian Textile Journal, May (1995) 102. 8. Bhatnagar S., The Indian Textile Journal, Vol. 101, No 4, November (1991) 31. 9. Ishtiaque S.M., Sharma I.C., and Sharma S, Structural Mechanism of Siro yarn by microtomy, Indian Journal of Fiber & Textile Research., Vol. 18, Sep (1993) 116-119. 10. Morton WE, The arrangement of fibers in Single yarn, Text. Res. J. 26, (1995) 325. 11. Anurab Chaucshary, Study of DRF Yarn Process Variables, M. Tech. Dissertation, Kanpur University, Kanpur, (2001). 12. Hearle J. W. S. Indian Journal of Fiber & Textile Research,

Architectural Textiles Set to Boom in Build-Up to Beijing Olympics

Architectural textiles will be employed extensively in the Beijing National Stadium, the center piece of the 2008 Summer Olympic Games to be held in Beijing, China, according to the latest issue of Technical Textile Markets, published by Textiles Intelligence.

Approximately 40,000 m2 of single-ply ethylene tetrafluoroethylene (EFTE) sheeting will be employed to protect 40,000 tons of steel from weather damage. The steel will be used to construct a “bird’s nest” structure in the stadium. Furthermore, a 50,000 m2 shield of polytetrafluoroethylene (PTFE)-coated glass fabric will be installed inside the stadium to ensure good acoustics. Textiles have a number of advantages over conventional roofing materials, not least their flexibility in terms of shape, their lightweight properties and the low cost of their manufacture. Fabrics employed in most architectural textiles include woven polyester coated with polyvinyl chloride (PVC), although other synthetics and coatings can be used. PTFE-coated glass fabric is employed for special properties and enhanced durability, while pneumatically pre-tensioned ETFE sheets offer a plethora of striking design possibilities.The use of textiles in architecture first came to prominence at EXPO 67, held in Montreal, Canada, when Germany showcased its ground-breaking tent-shaped National Pavilion and established itself as a pioneer in this form of construction.

Almost 40 years later, the FIFA World Cup, held in Germany in June 2006, illustrated just how far this application of technical textiles has advanced. Many of the stadiums which hosted the World Cup matches are equipped with complex textile roofing and support structures. Since the event in Germany, architects have announced that they will use architectural textiles in Beijing as preparations are made for the forthcoming Summer Olympic Games, which will be held in the city in 2008. The design for the stadium in Beijing was conceived by Swiss architects Herzog & De Meuron. It is these designers who were responsible for one of the most innovative applications of architectural textiles thus far-at the new Allianz Stadium in Munich, Germany. The Allianz Stadium is covered by an outer skin which consists of some 2,874 lozenge-shaped membranes made from ETFE. The stadium, which is home to Munich’s two top division football clubs, employs EFTE sheeting in the covering to enable the entire stadium to change colour, depending on which of the two teams is playing there, in a similar way to a giant LED screen. In fact, each of the 1,058 panels around the outside of the stadium can change colour and be made to either pulsate or glow, creating infinite cascading patterns. The new roof of Berlin’s Olympic Stadium is equally impressive. It consists of two membrane systems each measuring 31,000 m2. Examples of other textile buildings can be found extensively in Germany but also throughout the world-in public buildings and auditoria, open air theatres, railway stations and airports, shopping centres, parks and landscaped spaces, entrances and walkway areas.

Architectural Textiles: World Cup Showcase in 2006 and Beyond” was published in Technical Textile Markets, Issue No 66. For further information, please contact Belinda Carp or Robin Anson at Textiles Intelligence Ltd.

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