Rieter Com4®jet for more economy in knitting

A Com4®jet knitted fabric is a synonym for optimal pilling resistance, minimal seam drifting and highest colour fastness.

The largest application area of the Rieter Com4®jet yarn is currently for knitted garments. The yarn quality with very well bonded fibre ends, hairiness characterised by short protruding fibres and high evenness is convincing from Figure 1. Those are yarn quality features that promote a low pilling tendency, a uniform appearance and a soft touch with a knitted fabric.

In an extensive test series, Viscose Com4®jet yarns in five different knitting qualities were produced as shown in Figure 2. The yarn flow properties in the knitting plant and the material behaviour in the finishing process were assessed. The wearing properties of the finished textiles were determined by means of standardised testing methods.

The viscose fibre from South Pacific with a staple length of 38 mm and a fibre fineness of 1.3 dtex was spun to a Rieter Com4®jet yarn with a yarn count of Nm 50 (Ne 30). At a delivery speed of 420 m/min and a total draft of 181 fold, a satisfactory yarn quality was achieved. In the process, the spinning peak U 1.2 at a spinning pressure of 6 bar was applied, as shown in Figure 3.

In industry, benchmarks for air-jet yarns are lacking. Of course, the usual standard yarn tests are also used at Rieter to make assessments. However, technologists repeatedly find that a knitting of the yarn and observation of the yarn structure in the fabric is significantly more informative. Apparently, the numerical values of the yarn evenness and those of the imperfections do not reflect the optical effect in the finished fabric.

Knitted fabric structures

In a European knitting plant, yarns with five different stitch structures were processed. To obtain stretch knits, a 76 dtex f24 Polyester and Polyamide as well as a 33 dtex cladded as shown in Figure 4.

The "single elastic" knitted fabric structures were produced with a knitting machine gauge of E28 with 24 U/min and reached a fabric weight of 220 – 240 g/m2. The two other structures "fine stretch lining" with 30 U/min and "PiquT" with 18 U/min were produced with a gauge of E24, whereby with the fine lining a fabric weight of 280 – 300 g/m¦ and with PiquT 190 – 210 g/m¦ were ascertained. The knitting machines operated at standard speeds and achieved efficiencies of far above 95.

With the processing of the supplied Com4®jet yarns, the extremely low dust and fibre fly formation on the knitting machine was very obvious. For the knitting plant, this means less maintenance due to longer cleaning intervals. The good running behaviour led to a very good product quality.

Raw materials appearance

Already in the raw material, all knitting fabric structures showed a very even appearance. Contrary to knits with comparable ring or compact yarns, the fabric appearance is clearly smoother and more even.

The reason lies in the special character of Com4®jet yarns in comparison to products from other spinning technologies. In the knitting plant, the Com4®jet yarns are convincing by the very well bonded fibre ends, which leads to a reduced dust and fibre fly formation. The special hairiness of the Com4®jet yarns – many short hairs below 3 mm length – creates the fluff on the surface of the knitted fabric that is significantly responsible for the soft fabric touch. The hairs are short enough to prevent any undesirable fibre knots, or pills, from developing.

Results of the fabric test

Various textile technological tests were carried out to enable an optimal assessment of the functional properties in practical use.

• Garment appearance and handling behaviour.
• Shrinking behaviour.
• Penetration resistance.