Professor and Head, Dept. of Textile Technology

Shri Vaishnav Institute of Technology and Science, Indore

1.                   INTRODUCTION

Excellent comfort properties of weft knits have made their entry into formal wears for men and women. But with the technological advancement in manufacturing of cloths and the awareness of consumers to quality, the expectations in knit goods too have gone high. However, knit goods are known for their high structural sensitiveness to deformation during manufacturing process or at their end use. The research work of the past focused on macro level aspects of quality control while the market demand today is on micro level. The quality criteria in the future would be much different than what is being counted today.

The improvement of knit structure at micro level calls for better understanding of mechanics of loop formation, fluidity of knit structures and their influence on quality of knit fabrics. The quality of hosiery yarn has to be considered with due weightage to these aspects. If they are not addressed, probably satisfying the customer at global level may become difficult.

This article aims at initiating a thought provoking process on above lines for assessing fabric quality as well as that of yarn for manufacturing superior quality fabrics apart from highlighting role of certain yarn properties on knit fabrics. The technological compulsions, not of the knitting machine technology but of the future demand of quality level in the fabric by the customer and also progress in technology in assessing fabric quality leading to reconsideration of machine, material and process parameters at micro level on for superior in yarn quality are explained.

2.                   Quality of Knit Fabrics

At present knit fabric quality is decided by few physical parameters namely GSM, loop dimensions (loop length, wales and courses per unit length), fabric width, dimensional stability and defects in the fabrics. However, aesthetic value of the fabric or the appeal to the customer regarding the fabric, which ultimately accounts for satisfying the customer, is not measured by these parameters. At the same time the comfort properties of the fabric like smoothness and fluidity of loops that influences shear and low stress mechanical properties are also not sufficiently covered by above listed parameters. Further, more than just the stability of the fabric/garment, for which knits are known to be poor, the localized variation in dimension would hamper the appearance and useful life of it. Though objective assessment of these parameters is not possible commercially today, with the introduction of image analysis technique for fabric quality inspection such an assessment may become reality in the future. The customer too may consider subjective assessment of the same by observing the garment under different light sources which enhances the localized variation and get a feel of quality level.

2.1               Parameters of Fabric Quality

The quality of fabrics at micro level could be, loop to loop variation in their dimension (rather than an averaged value) including loop shape (not as a shape factor but as geometrical shape of the loop) and localized variation in loop density (rather than GSM). The important loop dimensions are loop length, loop width (wale spacing) and loop height (course spacing). The uniformity in dimension of loops provides attractive appearance to fabric, as it eliminates blurring effect of irregular dimensions. The fabric would be more elegant, lustrous, smoother, softer and stable. This is like better cover in woven fabric. In woven fabrics those produced on shuttleless machines are better in appeal to eyes than those from auto-looms or plain power looms. In woven fabrics the balance of crimp between warp and weft yarns also plays a vital role on its aesthetic property.