7.1.5 Spinning of long fibres

The long fibres have the highest quality; they are stronger, finer, less hairy, and more regular than the shorter fibres. The fibre fineness is a result of splitting during scutching (§7.1.1), hackling (§7.1.3) and further pre-processing (§7.1.4). This allows the long fibres to be spun into much finer yarns than the shorter fibres. During spinning, the fibres on a rove bobbin are further refined and twisted around each other, giving the yarn (also called 'thread') its strength.

The long fibres are usually wet spun via the ring-spinning system (Figure 35). The wick ('rove' at the top of the figure) passes through a hot water bath at 60-70 °C, which softens the remaining glue (pectin) between the fibres and allows the fibres to move more freely during the spinning process and therefore position/orient themselves more ideally in the yarn. Subsequently, the fibres pass through the drafting zone where the rove can be refined to the desired yarn fineness, up to 18 times. Finally, the fibres are spun into yarn by a rotating guide ('wire traveller' at the bottom of the figure) which creates a twist in the yarn; each rotation creates one twist in the yarn.

The production speed in ring spinning is limited by the fact that winding the yarn is linked to twisting the yarn. On a ring spinning machine, a twist can be given from about 300 to 700 rotations per minute. Wet spinning of bast fibres is a more cost-intensive technology than spinning short staple fibres using rotor spinning (§7.3.2).

The thickness of a yarn is indicated by the so-called yarn number (§7.1.6). The finest yarns are obtained when the fibres are bleached prior to spinning. Wet spinning produces fine, smooth, regular but fairly hard touch and shiny yarns that are processed into clothing and interior (home) textiles. Wet-spun yarns can be obtained with yarn numbers in the range Nm 26 to 39.

In the process of semi-wet spinning, the yarn passes over a copper dip roller after the drafting zone (Figure below). The roller rotates in a water bath. The water makes the yarn slightly smoother but it retains the character of dry-spun yarn: fluffier, weaker, coarser and no ‘eternal’ lustre.

Typical applications of long fibre yarns are clothing and interior textiles.

[1] Els Janssens, ‘Yarn technology 1: mechanical spinning’ (Dutch), Course 2019-2020. https://issuu.com/communicatie-hogent/docs/garentechnologie_1

[2] Khan et al., Journal of Textile Science and Technology, 2020, 6, 19-39, https://www.scirp.org/pdf/jtst_2019122416553807.pdf