Texturising Defects, Causes, Effects, Remedies and Prevention through Quality Management

 Texturising Defects, Causes, Effects, Remedies and Prevention through Quality Management

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91. Texturising Defects, Causes, Effects, Remedies and Prevention through Quality Management

Số trang: 200 trang

Ngôn ngữ: English

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Texturising is a very important process in filament yarns to give texture similar to spun natural fibres. This book covers different methods of texturising, normal defects in texturised yarns, their causes, effects, remedies and Prevention through implementation of Quality Management systems. The book is a blend of an academician and an industry personnel with their vast knowledge of the subject in the field, experience of association with the industry.

The authors have covered all the aspects starting from the origin of the texturising technology of yarn modification, type of machinery, process, process control, testing and quality control, and management information systems. The authors have covered the most important aspects in the problems and remedies in the texturising industry.

The book is a good guide for the students studying Man Made Fibres/Textiles in which texturising is an important subject.

Table of Contents

• Preface
• Foreword
• Introduction
• Abbreviations and Explanations of Terms Used
• Brief introduction to Texturising
• Process Variables and Defects
• Normal Defects and Their Causes
• Towards Defect-Free Product and Services to Customer
• Testing of Texturised Yarns
• Appendix
• References
• List of Figures
• About the Authors
• Index

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Introduction

Synthetic filaments were developed mainly to replace costly and scare natural

fibres. They have the advantage of uniformity, possibility of engineering the

fibre by controlling the denier and bulk, developing the tenacity and elasticity

by modifying the structure and so on. Different synthetic filaments were

developed in last one century. Rayon was the first man-made filament fibre,

developed in the 1890s. Nylon was first produced in the late 1930s and soon

followed by the polyesters and polyacrylics. Polyolefins and polyurethanes

were produced during the 1950s. Today, almost all the manufactured fibres

can be used in filament form in filament yarns. Acrylic and modacrylic

are exceptions – they are typically used in staple form. Filament yarns are

composed of one or many continuous filaments. Filament yarns are assembled

with or without twist.

Polyester occupies a distinct position among the textiles in terms of its

versatility and widespread usage in apparel and industrial applications. But

flat filament polyester is uncomfortable for apparel use as it lacks the comfort

properties like that of staple yarn from natural origin. So to introduce the

comfort and aesthetics in flat filament synthetic yarn, ‘texturising’ is the most

widely used technique in the industry.

The yarns available can be grouped as follows:

• Flat continuous filament yarns can be monofilament, which contain

only one single continuous filament, or multifilament yarns with a

number of filaments of fine deniers combined to form one continuous

strand of filaments varying in range from fine to coarse counts.

• Flat multifilament yarns create a very smooth fabric surface. Round

cross-sectional shaped fibres are typically used in filament yarns,

producing very compact and smooth yarns. End uses for these yarns

include seat belts, tire cord and tire cord fabrics. Apparel fabrics

needing closely packed yarns for reduced air and water vapor

permeability also use flat multifilament yarns. This type of filament

yarn has elongation, depending on the fibre type that is used.

• Monofilament yarns are not normally used for apparels as they are

not comfortable, but there are some exceptions of end uses as a dress

material. They are used mainly for technical purposes. Fishing line is

a good example of a monofilament yarn.


• Texturised continuous filament yarns have the filaments modified in

some way to give bulk and/or specific stretch properties. Texturised

filament yarns have a noticeably greater volume than conventional

filament yarns of similar filament count and linear density. The yarns

have a relatively low elastic stretch, but can be developed specifically

to impart stretch. The yarn is sufficiently stable to withstand wet

finishing. The apparent volume of the yarn is achieved through

physical, chemical or heat treatments, or a combination of these.

• Spun yarns are formed using short or non-continuous fibres. The yarn


is held together by twisting the fibres to produce necessary fibre-to-

fibre cohesion and adequate yarn strength.


• Short staple spun yarns utilise fibres less than 64 mm in staple length.

Normally, yarns spun from short staple are more hairy, irregular and

need higher twist.

• Long staple spun yarns utilise fibres from 64 mm (2.5 inches) up to

460 mm (18 inches) in length. However, the most common range of

staple length is 64 mm (2.5 inches) to 152 mm (6 inches).

Filament yarns can be classified as flat or texturised. Flat filament yarns

have all their filaments aligned parallel to the yarn axis. The texturised yarns

have individual filaments lying in a curled, twisted, snarled, looped or crimped

configuration. The most common methods of texturising are false-twist, air jet

and stuffer box. These methods will be discussed later in the module.

Texturising techniques were initially relevant to artificial fibres to

diminish characteristics such as glassiness, slipperiness and the chance of

pilling (configuration of little fibre tangles on a fabric shell). They make

yarns more opaque while improving look and touch and boost warmness

and absorbency. It is by the formation of folds, loops, coils or crinkles in

filaments. Such alterations in the physical shape of a fibre have an effect on

the behaviour and hand of textiles made from them.

Among different types of texturising techniques, ‘false-twist texturising’

is the most popular in texturising industry. It is basically a thermomechanical

deformation process which changes the characteristics of filament yarn to

generate bulk and warmth. Another popular method is air texturising, which

uses air jet to get entanglement and also bulk to impart spun yarn effect.

During texturising process, incidentally lots of defects occur. The help

of students were taken to study different functional defects in false-twist

texturised yarns generated in actual mill working conditions. A systematic

and analytical approach was followed to track the causes of the defects. The

xii Texturising


causes ranged from feed material characteristics, various mechanical defects,

machine parts, process parameters and so on. At the end, practically achievable

remedial measures were also suggested to obtain fault-free consistent end

product. The findings were further validated by referring to various researches

and are presented as a part of this book in Chapter 4.

The term ‘texture’ is derived from the Latin word ‘Texere’ and it describes

those attributes of an object that can be recognised by the human site (visual

characteristics) or touch (tactile characteristics). In textile fabrics, warmth,

opacity, flexibility, good wearing properties coupled with a characteristic

appearance and easy maintenance are the main texture properties desired.

All these desirable properties are inherently provided with yarn spun from

staple fibres, whereas flat synthetic filament yarns lack the human appreciation

though they possess some superior properties, namely, high strength and

good elasticity. The primary object of a flat filament yarn conversion process

is to initiate the desirable properties of normal spun yarn. One method of

achieving this is to cut the continuous filaments into staple and then process

them into yarn using conventional or non-conventional spinning systems. But

this process is time-consuming and involves a number of processes which are

costly. On the other hand, continuous filaments can be converted into yarns by

different methods at lower cost in a single process called ‘texturising’.

The texturised yarns are those yarns that have been processed to introduce

double crimps, coils, loops or any other fine distortions along the length of the

filament. Thus, by texturising, the filament yarns attain soft and ‘natural like’

feel and increased warmth and comfort properties.

The fabrics containing texturised yarns have increased bulk, opacity,

moisture absorbency and improved thermal insulation properties with warmer

handle. Some texturised yarns also confer extensible or ‘stretch’ properties on

fabric made from them.

Texturising being a relatively new technology compared with traditional

spinning and twisting of natural staple fibres, much literature is not available

to educate the new comers on the possible defects, their causes, the effects

and the suggested remedial actions. Hence, an attempt is made to compile the

defects and their causes, so as to educate the students and new comers in the

field.

In the foregoing pages, the defects observed in the most popular and most

commercially exploited ‘draw texturised yarn’ are detailed with definition,

causes, effects and remedies. Wherever possible the photographs of the

defects are given.


Introduction xiii


Attending and correcting a defect is one aspect of working to satisfy the

customers, whereas it is also needed to assure the quality by following suitable

systems by committed employees. The next chapter, therefore, explains

the system to be implemented to ensure defect-free yarns, which include

the concepts of Quality Management System, Work Quality Management

and Total Quality Management followed by a chapter on testing methods

normally followed for the texturised yarns. The importance of educating the

people on the spot on the customer requirements and also on the technical

aspects following good practices of housekeeping maintenance and safety

management is also discussed.

In the end, standard testing methods as specified by standard laboratories

are given as appendixes.