PRE-TREATMENT(INTRODUCTION)

Lecture# 1-3

Mujahid Mehdi Abro Indus University Karachi.

• As the name suggest word pre-treatment mean, before treatment

• It is a set of processes to prepare fabric for coloration and finishing

INTRODUCTION

• Uniform whiteness• Uniform Absorbency• Removal of seed husks• Good Tegewa (removal of Sizes)• Surface smoothness• Dimensional stability• Environmental friendly and ecological

OBJECTIVES OF PRETREATMENT

Pretreatment is important !!! 70% of problems during dyeing and finishing is caused

by pretreatment.

Why pretreatment?

Mechanical

• Shearing• Mending

Thermo-Mechanical

• Singeing

Chemical

• Desizing• Scouring• Bleaching

PRETERATMENT SCIENCES

Physico-chemical

• Mercerization

SEQUENCES OF WOVEN PRETREATMENT

1 •Mending

2 •Singeing

3 •Desizing

4• Scouring

5• Bleaching

6• Mercerization

SEQUENCES OF KNITTING PRETREATMENT

1 •Mending

2 •Scouring

3 •Bleaching

4• Bio Polishing

GREIGE INSPECTION(A Practical Approach)

Brushing• The purpose of brushing is to remove the short and loose

fibers from the surface of the cloth.

• Brushing is mainly done to fabrics of staple fiber content.

• Brushing before cropping minimize pilling.)

Shearing• Shearing is an operation consists of cutting the loose

strands of fibers from either surface of a fabric with a sharp edged razor or scissors.

MENDING

SINGEING The word “singe” means to burn off. Singeing is a thermo-mechanical process. It burns off protruding fibers from the

surface. Aim of singeing is produce smooth and

fiber free surface

TECHNIQUE OF SINGEING

Technique

Roller Singeing

Plate singeing

DESIZING

o It is a process of removing size material from the yarn.

o Desizing is irrespective of what desizing agent is.

o There are four method of desizing that are used.

METHODS OF DESIZING

Rot steep

Enzymatic desizing

Oxidative desizing

Acid desizing

Removal of water soluble size

Scouring

• It is a process in which impurities like oil,fat, wax and hand dust are remove to produce hydrophilic and clean textile material

Objectives of Scouring To make the fabric highly hydrophilic

Remove impurities like oil, wax, fat etc from the fabric.

To increase the absorbency of fabric or textile material without physical and chemical damage.

To make the fabric suitable for next process like bleaching, dyeing and finishing process.

Objectives of Bleaching

To remove natural color

To remove cotton seed husk

To improve the dye uptake for level shade

BLEACHING

Bleaching

Oxidative Agents Reductive Agents

Most commonly used Bleaching Agents

a) Sodium Hypochlorite (NaOCl)b) Bleaching Powder (CaOCl)c) Hydrogen Peroxide (H2O2)

MERCERIZATION

• Mercerization is a finishing treatment of cotton with a strong caustic alkaline solution in order to improve the luster, hard and other properties.

• It was names after its discoverer, John Mercer.

PURPOSE OF MERCERIZATION

1. To improve the luster.

2. To improve the strength.

3. To improve the dye uptake and moisture regain.

Factors of Mercerizing:

In mercerizing followings are important:

a) Twaddle (Concentration of NaOH)

b) Temperature

c) Tension

d) Time

Recent Development in textile Pretreatment process

1. Pretreatment using plasma

2. Biotechnology