Viscose is commonly used with Spandex in the majority of knit fabric applications. Requirements such as wearing fit and comfort are closely associated with the use of Spandex. However, the relationship between Spandex consumption and knit fabric properties has not been extensively studied. Knitters typically rely on their experience to adjust machine parameters to achieve the desired characteristics in the fabric. This paper aims to investigate the relationship between Spandex consumption and fabric weight, fabric width, and the elastic behavior of the knit fabric.

The wear fit and comfort of knitwear are often ensured by the Elastane content in the fabric. Nowadays, there is a significant demand for lightweight Viscose/Spandex fabrics in knitwear, taking into consideration the wearer's comfort and cost benefits. Spandex is typically combined with other yarns like Viscose, Modal, Cotton, etc. Blending Spandex with the ground yarn is referred to as 'Plating.' In the plating process, both yarns are fed to the knitting needles simultaneously, and they form one loop with one yarn covering the other.

In the figure below, Spandex is plated with Viscose yarn, where A represents Viscose, and B represents Spandex. The fabric pattern after plating Spandex is shown in Figure 2. It's important that the Spandex always enters the knitting hook first, followed by the Viscose yarn.

The proportion of Spandex yarn is a crucial parameter in Viscose/Spandex knitted fabric. Fabric GSM (Grams per Square Meter), width, dimensional stability, and elastic recovery are significantly influenced by the Spandex consumption. Yet, the authentic relationship between Spandex consumption and fabric properties is not well-known. Knitters typically make machine adjustments to achieve the required Spandex percentage.

The aim of this study was to investigate the effect of Elastane consumption on three primary fabric parameters: GSM, width, and dimensional stability of Viscose plain single jersey knitted fabrics.

Methodology


We have produced 3 different types of Viscose/Spandex knitted fabrics by varying the spandex percentage in each of the fabrics. Mentioned below are the Single jerseys knitting m/c specifications used for the experiment,


M/cMake - Mayer & Cie Cylinder Dia- 30"

Gauge-24 No. of Feeders - 96

 

Materials Used -


Spandex yarn feed was varied by different spandex feeder speed. The feeder speed can be varied through changing the diameter of the Spandex pulley. We have taken four different feed levels i.e. 3.8, 3.6, 3.5 & 3.2. These are the loop lengths of the Spandex yarn in the fabric. Positive Memminger IRO feeders were used for the study.


All the testing was done after 24 hrs conditioning of the samples under the standard atmospheric conditions of 27 1 degrees temperature and 65 2 % relative humidity. The samples were slit open & allowed to relax in the flat form for 24 hrs. Total five readings for fabric weight and width were taken from different places of the fabric.


Blend analysis for the fabric is done by dissolving the spandex portion of the fabric in Dimethylformamide. The blend evaluation is done by dissolving the spandex & drying the fabric at 105 degrees in oven. AATCC 20A standard test method followed for the same.


Results & Discussion


We have taken four different readings for Spandex feed for this study. Results for the same are as mentioned in the table below.


Effect of Spandex Feed on GSM


As evident from 240 the graphical representation, grey GSM is inversely proportional to the spandex feed. As we reduce the spandex feed, tension in the spandex makes the loops closer and thereby increasing the stitch density which ultimately results in the increase in the weight of the fabric.

 


Effect of Spandex Feed on Fabric Width


As evident from the graphical representation, grey Width is directly proportional to the spandex feed. At higher Spandex feed, Spandex goes for knitting in a relaxed state causing the wales & coarses to be in relaxed state increasing the width of the fabric.


Effect of Spandex Feed on Spandex%


Spandex percentage in the fabric goes on reducing as we reduce the Spandex feed as shown in the above graph. As we increase the feed the amount of Spandex present in the fabric increases.

 

Effect of Spandex Feed on Stretch% on fabric

As evident from the graph Spandex feed is inversely proportional to the stretch percentage of the fabric.


As we increase the feed of Spandex filament, it will go in to the fabric in relaxed form which results in higher Spandex percentage finally resulting in higher stretch percentage.


Conclusion


From the above study it can be concluded that the Spandex feed directly affects the Spandex percentage, Fabric weight, fabric width, Stitch density & stretch percentage of a Viscose Spandex blended knit fabric. According to the application area, we can vary the spandex percentage in the fabric by varying the spandex feed at knitting.

Acknowledgement: The Authors want to acknowledge the Birla Cellulose management for providing the opportunity to carry out the study at TRADC (Textile Research and Application Development Centre).


This article was originally published in the Textile Review magazine, May, 2013 issue, published by Saket Projects Limited, Ahmedabad.


About the Author:


Ganesh Jadhav and Dayal Mahara are associated with the Textile Research & Application Development Centre Birla Cellulose at Kosamba R.S., Dist. Bharuch.