# Torsional Properties of Textile Fiber and Textile Materials # Torsional Properties of Textile Fiber and Textile Materials

In this article, garment merchandising will provide Torsional Properties of Textile Fiber and Textile Materials. It is the property of fiber or material when a Torsional force is applied on it. Here Torsional force is a twisty force that is applied on the two split ends of the material in two reverse directions. The behaviors which are revealed by a textile material when it is exposed to a torsional force is known as torsional property. Torsional properties are as below.

1. Torsional rigidity
2. Breaking twist
3. Shear modulus

## 1)  Torsional rigidity:

Torsional rigidity is the resistance of a textile fibre in contradiction of twisting. It may also be define as the torque applied to insert unit twist per unit length of fibre. The unit of torsional rigidity is N-mm2, N-m2 etc.

Scientifically, Rt = ηЕT2/ρ

Where, η = Shape factor

Е = Specific shear modulus (in N/tex)

T = Linear density (in tex)

ρ = Density (in gram/cm3)

### Specific torsional rigidity:

The specific torsional rigidity is the torsional rigidity of a textile fibre of unit linear density. Specific torsional rigidity is generally stated as N-mm2/tex, N-m2/tex etc.

Scientifically, Specific torsional rigidity = ηЕ (1)2 = ηЕ

ρ           ρ

Where, η = Shape factor

Е = Specific shear modulus (in N/tex)

T = Linear density (in tex)

ρ = Density (in gram/cm3)

### Specific torsional rigidity of different fibres:

 Fibre Specific torsional rigidity (mN-mm2/tex) Cotton 0.16 Wool 0.12 Silk 0.16 Viscose 0.085 Nylon-6.6 0.06 Polyester 0.067

## 2)  Breaking twist:

Breaking twist is the twist for which a textile fibre will break. The Breaking twist may  also be define as the number of turns or twists required to break a fibre. The Breaking twist depends upon the diameter of fibre and is inversely proportional to the diameter.

So, Breaking twist, Tb ∞1/d [d = fibre diameter]

### Breaking twist angle:

The angle through which the external layers of fibres are sheared at breaking is known as breaking twist angle.  Breaking twist angle is generally stated as α.

Scientifically, Breaking twist angle, α = tan-1 (∏ d Tb)

Where, d = Fibre diameter & Tb = Breaking twist per unit length of fibre

### Breaking twist angle of different fibres:

 Fibre Breaking twist angle (α) Fibre Breaking twist angle (α) Wool 400 Silk 390 Polyester 330 Glass 40 Cotton 350 Viscose 330

## 3) Shear modulus:

Shear modulus may be defined as the ratio between shear stress and shear strain.

So, Shear modulus = Shear stress/ Shear strain

Shear strain is generally measured in radian. Shear modulus of a fibre is expressed as kN/mm2. For example, shear modulus of wool is 1.3 kN/mm2.

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