Unit 3 Lecture 16 Topic 1

Question 1

___ and ______ are direct systems of yarn measurement. Larger numbers correspond to ______ yarns.

Answer 1

Tex, denier, larger

Question 2

Length per unit weight:

Answer 2

An indirect system of yarn measurement where smaller numbers correspond to larger yarn. Historically, all yarn numbering systems were indirect and many of these systems are still in common use. This is measured by the number of skeins or hanks of a fixed unit of length required for a fixed unit of weight (usually 1 pound). The fixed length of the skein or hank varies with fibre type.

Question 3

Twist Level:

Answer 3

The number of turns about its axis per unit length. Filament yarns require less twist than staple yarns and finer yarns may require more twist than coarser yarns. Knitting yarns tend to have less twist than yarns for weaving.

Question 4

Twist Level:

Answer 4

The number of turns about its axis per unit length. Filament yarns require less twist than staple yarns and finer yarns may require more twist than coarser yarns. Knitting yarns tend to have less twist than yarns for weaving.

Question 5

High twist levels in yarn:

Answer 5

30 to 40 turns per cm (tpc), or 75 to 100 turns per inch (tpi).

Question 6

Moderate twist levels in yarn:

Answer 6

15-30 tpc or 40-75 tpi.

Question 7

Low twist levels in yarn:

Answer 7

2-3 tpc or 5-8 tpi.

Question 8

Twist levels are most common in ____ yarns.

Answer 8

Spun

Question 9

Spin directions:

Answer 9

Yarns are either spun in a ‘s’ twist or a ‘z’ twist, depending on the angle at which it spins.

Question 10

How is spin direction correlated to plied yarns?

Answer 10

In plied yarns, spin direction of yarn is opposite to direction of plies. For example, a 2-ply yarn is a ssZ (two single S-twist yarns forming a Z-twist plied yarn).

Question 11

How does yarn twist effect tensile strength?

Answer 11

Staple yarns have moderate to high twist, resulting in a higher tensile strength. Filament yarns have a lower twist, but this still increases the tensile strength.

Question 12

How does yarn twist effect abrasion resistance?

Answer 12

Staple yarn abrasion resistance increases as twist is increased.

Question 13

How does yarn twist effect absorbency and water vapour permeability?

Answer 13

Absorbency and water vapour permeability is greater in lower twist yarns.

Question 14

How does yarn twist effect the feeling of fabrics?

Answer 14

Lower twist yarns usually produce softer fabrics.

Question 15

How does yarn twist effect soiling of fabric?

Answer 15

Yarns with high twist are better able to shed soil (smoother surface), but low twist yarns are better able to mask soiling (more irregular surface).

Question 16

How does yarn twist effect lustre?

Answer 16

For staple yarns, lustre increases as twist increases. For filament yarns, luster decreases as twist increases.

Question 17

How does yarn twist effect pilling characteristics?

Answer 17

Pilling can be reduced by increasing the amount of twist in spun yarns.