Comfort analysis of structurally modified polyester/PVA yarns produced through DREF spinning system

Excerpt: The structurally modified friction spun yarn fabric by using polyester as a sheath material and PVA is used as a core material.

Abstract

The structurally modified friction spun yarn fabric by using polyester as a sheath material and PVA is used as a core material. The processing of fabric to dissolve the core and making the yarn structure as hollow. Thus a fabric with hollow polyester yarn is produced. The various comfort characteristics of the fabric were tested and the results were compared between before and after dissolving PVA core component fabric. The various comfort characteristics going to test are Air permeability, Thermal conductivity, Wicking, Tensile strength, Moisture management test. All the above mentioned tests were to be carried out as per the standards testing procedures. Due to the variation in yarn structure that is the hollowness of the yarn, the characteristics like Air permeability, Water vapour permeability and resistance to flow of heat are better than the normal fabric. Thus comfort characteristics of the fabric are better than the normal polyester fabric.

Keywords: Comfort, Moisture Management, wetting, Wicking, Polyester, PVA

Introduction

POLYESTER fabrics are known for their high resiliency, resistance to wrinkling, high durability, dimensional stability and resistance to chemical and environmental attack. The primary drawback to polyester fabrics is the materials low moisture absorption which makes the resulting garments less comfortable to wear than cotton. To some extent, this can be overcome by using polyester blends with cotton or other more absorbent fibers. The structurally modified polyester yarn will compensate the drawback of a normal polyester fabric. The air entrapped in the yarn structure will enhance the absorbency of the fabric and it will be actively ventilated and the fabric weight also be reduced, which makes the wearer to feel good [2].

On over all evaluation of the fabric's thermo-physiological comfort properties, the structurally modified yarn fabrics are found to be better than other fabrics. In general, thermal resistance, thermal absorption, wicking and drying properties of all types of structurally modified yarn fabrics increase after repeated laundering, while air permeability, water vapour permeability and water absorbency of structurally modified yarn fabrics mostly decrease. In contrast with fabrics made from yarn produced through DREF spinning only improves fabric water vapour permeability [1].

Materials and methods

In general the structurally modified yarn fabrics were found to be more comfortable when compared to regular woven fabric made of polyester. Structurally modified yarn is produced by using friction spinning (DREF III) system and used to decrease the fiber packing density in the core of the yarn, thus improving the softness and bulkiness. In structurally modified yarn spinning, to analyze the comfort properties for using in summer. This study aims to develop the polyester covered PVA core friction spun yarn using DREFIII spinning system. From this the plain woven fabric is produced to modify the yarn structure by dissolving the PVA component. To study the thermo-physiological comfort characteristics of the clothing.

Six different samples with same core-sheath ratio (30:70) and compared with each other. The six different samples are given below:

Results and discussion

This chapter deals with the results obtained from testing the fabric made out of polyester hollow yarn before and after dissolving the PVA. Totally six samples were taken, tested and the results are discussed in this chapter.

Yarn Count and Strength

The Count and strength is an important parameter; it is measured by using wrap reel and strength tester and expressed in terms of lbs.

The CSP is an important parameter; it is measured by using wrap reel and strength tester and expressed in terms of lbs. From the results tabulated above, it can be clear in high significant changes in the strength of the yarn. The S5 & S6 sample shows strength loss when compared to all the other samples. The samples met a considerable strength loss; this nature is due to the dissolution of the PVA present in the yarn.

Thickness

The fabric was compressed under 2Kgf/cm² loading and the thickness was recorded. There are 5 tests per sample is conducted and the average value of the samples were taken.

From the above chart, the thickness was found to be high after dissolving fabrics except S5 & S6. S5 & S6 have a PVA sliver in sheath and core components. S5 & S6 have high amount of PVA than polyester in yarn structure. During treatment, PVA was dissolved.

  • GSM Test results

The above graph shows the GSM, it can be clear in high significant changes in GSM. The S5 & S6 sample shows GSM when compared to all other samples. The samples met a considerable weight loss; this nature is due to the dissolution of the PVA present in the yarn.

  • EPI& PPI

From the above chart, EPI of the after dissolving from before dissolving is high. It shows fabric shrinks in warp side during treating of PVA. The results of EPI between before and after dissolving PVA shows significant difference.PPI of the before and after dissolving results does not show any major difference. It means than there is no change in weft side.

  • Wickability Test

Wickability of the fabric is depends on the diameter and surface energy of its inside face, the smaller the diameter or the greater the surface energy, the greater the tendency of a liquid to move up the capillary. In textile structures, the spaces between the fibers are effectively from capillaries. Hence, narrower the spaces between these fibers, greater the ability of the textile to wick the moisture. And also the hollow space inside the yarn enhances the wickability. There are 5 tests carried out per sample. From the above table, wicking length was found to be maximum in after dissolving PVA fabric samples. The t test conducted between the samples shows significance difference.

  • Thermal conductivity

The thermal conductivity of fabrics in terms of W/MK was recorded. A higher value of thermal conductivity indicates more rapid movement of heat from the skin to the fabric surface, which will provide a cooler feeling. However, a higher fabric density will have a better thermal conductivity a less space to trap the air inside. Therefore, it has better thermal ventilation.

From the above chart, thermal conductivity is found to be good in before dissolving PVA fabric sample. The after dissolving samples have a low thermal conductivity due to the air entrapped in the yarn structure. Air is the bad conductor of heat, so the conductivity is low. But due to fiber collision in the yarn the air space is very low. Hence it shows a very little difference when compared with before dissolving sample.

  • Air permeability

The air permeability of the samples was studied by TEXTEST air permeability tester. The value was recorded directly in terms of cm3/cm2/Sec.

Air permeability is an important factor in comfort of a fabric as it plays a role in transporting moisture vapour from the skin to the outside atmosphere. The air permeability of a fabric is closely related to the construction characteristics of the yarns and fabrics in which large volumes are occupied by air. There are some factors affect the air permeability of the fabric, e.g. fabric density, fabric structure, thickness, surface characteristics, etc. there are five tests carried out per sample.

From the above chart, air permeability is found to be good in after dissolving PVA fabrics. It was found that the yarn collision due to the dilution of core increases the air space inside the sheath.

  • Moisture management

The following test results are noticed but there is no significant difference between the samples.

  • Wetting time Top (sec)
  • Wetting time Bottom (sec)
  • Top Absorption rate (%/sec)
  • Bottom Absorption rate (%/sec)
  • Top Max wetted radius (mm)
  • Bottom Max wetted radius (mm)
  • Top Spreading speed (mm/sec)
  • Bottom Spreading speed (mm/sec)
  • Accumulative one way transport index (%)

Overall moisture management capacity (OMMC) values of the fabrics are given in graph and the values are compared with the grading table given by the manufacturing company (0-0.2: very poor, 0.2-0.4: poor, 0.4-0.6: good, 0.6-0.8: very good, >0.8: excellent). According to the results, S6can be stated that all the fabrics are in the “good” category in terms of moisture management capacity. The above graph shows the OMMC (Overall Moisture management capacity) value in sample-6 is best, when compare to other samples.

Fabric Strength

The fabric strength is an important parameter; it is measured by using Instron Tensile tester and expressed in terms of kgf. The test has been carried out in warp wise, weft wise and shear side of the both treated and untreated fabrics. From the results tabulated below, it can be clear in warp wise; there are no significant changes in the strength of the fabric. The S6 sample shows only a very minute strength loss when compared to all the other five samples.

In weft wise, all the samples met a considerable strength loss; this nature is due to the dissolution of the PVA present in the fabric.

  • Flexural Rigidity

The above graph shows the flexural rigidity, it can be clear in high significant changes in flexural. The S5 & S6 sample shows flexural rigidity when compared to all other samples. The samples met a considerable loss, this nature is due to the dissolution of the PVA present in the yarn.

  • Bending Modulus

The below graph shows the bending modulus, it can be clear in high significant changes in bending modulus. The S5 & S6 sample shows bending modulus when compared to all other samples. The samples met a considerable loss, this nature is due to the dissolution of the PVA present in the yarn.

Based on the above test results Sample 6 can be concluded that the polyester structurally modified friction spun yarn fabric is better comfortable than normal polyester fabric. This conclusion enhances the idea about further improvement of comfort clothing and gives idea about doing further projects in the areas like assessment of comfort properties in hollow yarn fabric with different core sheath ratios.

Conclusion

The moisture management, air permiability and the wickability of the polyester structurally modified yarn fabric is higher than the normal polyester fabric and other properties like thickness, thermal conductivity, flexural rigidity and GSM of the fabric is lower than the normal polyester fabric. Structurally modified polyester has significant effect on fabric properties.

References

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Author Details

Thambidurai A.1, Arunraj A.2

Department of Textile Technology, Kumaraguru College of Technology, Coimbatore.