Properties and Uses of Plain Knit Structures

Knitting is a method by which thread or yarn may be turned into cloth or other fine crafts by loop forming. Knitted fabric consists of consecutive loops, called stitches. It can be done using machine or by hand. Knitting is two types. One is warp knitting and another is weft knitting. Weft knit structures are four types; plain knit structure, rib knit structures, purl knit structures and interlock knit structure. In this article I will explain about characteristics of plain knit structure.

Plain Knit Structure:
Plain knit structure is the simplest and most basic structure. Which is also called ''single knit''. Plain is a knit structure family, which is produced by the needles of only one set of needle with all the loops intermeshed in the same direction. Although the plain knit family encompasses a great number of structures all produced on a single needle bed, its general characteristics are described as follows:

Properties or Characteristics of Plain Knit Structures:

A. Appearance:
The fabric is unbalanced, because each side of the fabric exhibits a different appearance. Within each side, the loops on all courses and wales are identical. Each side of the fabric is made of a single type of loop i.e. either face or back (reverse). The top and bottom of each loop occurs on the fabric back and the center (legs) of the loop appears on the fabric face. So the face of the fabric is smooth and shows the side limbs of the loops as a series of interlocking “V” s. The reverse is rough and looks like columns of interlacing semicircles.
Technical face of plain knit structure
Fig: Technical face of plain knit structure
Fig: Technical back of plain knit structure
B. Extensibility:
The fabric is stretchable although not always elastic. Usually, the fabric can be stretched much more in the width then in the length. The fabric is extensible in a course wise direction and in a wale wise direction. However, the degree of extensibility is different when pulled top to bottom from when pulled side to side. The course wise extension is approximately twice that of the wale wise extension due to the degree of constraint imposed on each loop by its intermeshing. The loop pulled vertically extends by half its length ½ l, while the loop pulled horizontally extends by its whole length, l. The degree of recovery from stretch is not a property of the construction but depends on the nature of the raw material and yarn construction. It normally has a potential recovery of 40% in width after stretching.

C. Edge curling:
This fabric curls at the edge when the fabric after cut in relax state. Lt has a tendency to curl towards the back at the sides and towards the front at the top and bottom. The difference in construction between the two faces causes stress in the structure so that the fabric tends to curl. The loop arms (face) exert a length wise stress that curls the top and bottom edges of the fabric towards the face. The needle and sinker loops which are on a horizontal plain, pull the sides of the fabric and curl them towards the reverse side of the fabric. Pressing or other heat/water processes are used to minimize or eliminate such curling which is caused by the directionality of the loop formation.

D. Unroving:
The plain knit structure can be easily unravelled from the edge which was knitted last. This selvedge is the top edge when the fabric is held upright, as produced on the knitting machine. In contrast to other knit families, the plain knit construction is symmetric a land can also be unravelled from the edge knitted first. This edge is at the bottom when the fabric is held upright. So the plain fabric can be unroved (unravelled) from either end. Note that this ability is limited to the most basic structures of the plain family when no special loop types are incorporated.

E. Laddering: 
If a stitch is dropped during the knitting or at a later stage, a chain reaction may occur in which the following loops in the same, wale will drop in succession and a “ladder” will form. It is a fault but we consider it as properties. We mending (repair) it by manually with single needle. Since the fabric is symmetrical it might ladder vertically towards the bottom or the top. Lt must be appreciated that the tendency of the structure to curl, unravel and ladder is greater if the fabric is slack. The unraveling and laddering tendencies are also more severe when the fabric is made of smooth yarns.

This structure has the maximum covering power. Plain fabric is the commonest weft knitted fabric and is produced by widely different sorts of knitting machinery in all forms from circular fabric piece goods to fully-fashioned panels. It is the base structure of ladies hosiery, fully-fashioned knitwear and single jersey fabric.

Notation of plain knit structure:
The following figure shows the symbols of one popular method used in many countries around the world. In this system an “x” symbol represents a face loop and an “0” is used to represent a reverse loop. 
Face loop notation
Fig: Face loop notation
Reverse or back loop notation
Fig: Reverse or back loop notation
End uses of plain knit structures:
Plain knit structures are used for basic T-shirt under garments, men's vest, ladies hosiery, fully-fashioned knit wear etc. End use depends on some factors such as material used; yarn types and yarn count/linear density; machine gauge; fabric thickness and weight; types of finishing etc.