Viscose is used with the Spandex in majority of the knit fabric applications. The requirements like wearing fit and comfort are largely linked with the use of Spandex. However the relation between spandex consumption & knit fabric properties has not been studied much. Knitters generally depend on the experience to adjust m/c parameters to reach the desired characteristics in the fabric. The aim of this paper is to investigate the relation between spandex consumption and fabric weight, fabric width and elastic behavior of the knit fabric.


The wear fit and comfort of knitwear are generally ensured by the Elastane content in the fabric. Nowadays, there is a large requirement of light weight Viscose/Spandex fabrics for the knitwear's considering the wearer's comfort and cost benefits. Spandex is always processed with one or the other yarns like Viscose, Modal, and Cotton etc. Blending Spandex with the ground yarn is called 'Plating'. In plating process, both the yarns are fed to the knitting needle simultaneously and they form one loop with one yarn covering the other.


In the below figure, Spandex is plated with the Viscose yarn where A is the Viscose & B is the Spandex. The fabric pattern after plating Spandex is shown in the Fig. 2. The Spandex should always enter the knitting hook first followed by the Spandex yarn.


Spandex yarn proportion is the most important parameter of a Viscose / Spandex knitted fabric. Fabric GSM, width, dimensional stability & elastic recovery are largely affected by the Spandex consumption. Yet authentic relation between spandex consumption & fabric properties not well known. Knitters generally do the m/c adjustments to achieve the required spandex percentage.


The aim of this study was to study the effect of Elastane consumption on three main fabric parameters viz. GSM, width & 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/c Make - 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.