Abstract
The garments produced from woven fabrics have produced many problems, and experience has shown that existing styles as developed for piece-dyed fabric cannot be just assembled from grey fabric and thrown into the dyeing machine, unless they have been engineered from the original design stage for garment dyeing.
To obtain a high quality final Garment there should be a thorough co-ordination between fabric supplier, accessories supplier, garment manufacturer and garment processor.
Introduction
The recent surge in export of garments has created a challenging opportunity for the garment processing industry because of:
1) Short pipeline necessary for quick response.
2) Reduced losses from dyed fabric waste.
3) No subsequent shrinkage.
4) Reduced inventory.
5) Lower energy, water and labour costs.
6) Ability to produce small batches.
7) Most importantly to produce uniformly dyed garments with no variations in shade of the different parts of the garment, which is a major problem for garment manufacturers using piece dyed fabric because of sort to sort variations.
Structure of the Garment dyeing and finishing sectors
1) Conventional finishers
Traditional finishing plants that have adopted garment dyeing in addition to their conventional production.
2) Laundries/Dry Cleaners
These establishments do garment dyeing as an additional profitable activity, to give a new lease of life to garments with no gurantees offered on the final appearance of fastness.
3) Garment Dyers
Composed of established fully fashioned dyers.
Quality Control in Garment Processing
The garments produced from woven fabrics have produced many problems, and experience has shown that existing styles as developed for piece-dyed fabric cannot be just assembled from grey fabric and thrown into the dyeing machine, unless they have been engineered from the original design stage for garment dyeing. Care should be taken that the grey fabrics dye-up identical in shade and if necessary must be adequately pretreated before dyeing.
The other major areas for control are:
1) Seams, elasticated areas, waist bands, cuffs
2) Shrink behaviour
3) Chafe marks/creases
4) Accessories
5) Sewing thread
6) Foreign substances
7) Interlinings
8) Care labeling depending on the fastness requirement, being the most important of them all.
1) Elasticated areas, waist bands and cuffs, must be fairly slack, and seams should not be too tight or bulky, or poor penetration of dyestuff occurs especially with heavy articles and heavily swelling fibres like cotton.
However the problem can be solved by using suitable dyes and the right process control.
The use of a high application temperature dyes not only ensures that the migration potential is fully realized, it also offers several additional advantages. Higher temperatures means better diffusion, better penetration and better running of the cloth facilitating liquor flow. These benefits assume particular significance in garment dyeing,especially in garments that have multilayered seams of woven fabrics ( pockets, lapels, zips etc) or tight elasticated waists and ribs.
Thus a short period at high temperature i.e. 950C before cooling for fixation with reactive dyes has overcome even the most difficult seam penetration problems.
2) Shrink Behavoiur is important because of excessive shrinkage of the article or uneven shrinkage where knitted and woven fabric are mixed lead to seam -puckering, when it becomes important to prerelax knitted fabric and the pretreated woven fabric must be fully preshrunk by giving the various shrink proofing treatment for high quality fabrics. To rule out the possibility of later complaint it is advisable to carry out a blank dyeing.
3) Chafe marks and creases are a problem particularly for delicate articles due to the mechanical stress in drum dyeing machines which have a negative influence on the final product. Articles which are prone to chafe marks or pilling effects should be turned inside out and dyed with the addition of a non-foaming lubricant while adopting the shortest possible dyeing process. With woven fabrics certain types of weaves are liable to creasing and breaks. One preventive measure from the outset is to avoid overloading the dyeing drum.
4) Accesseories
Care must be taken with the selection of zips and metal accessories, such as buttons and studs. Ferrous metal must be avoided, and good quality components fabricated from nickel or its alloys must be used if breakdown through corrosion in bleaching or reactive dyeing, with its high concentration of electrolyte and alkali, is not to be a problem.
The composition of buttons can be a difficult choice. Those buttons, such as those of casein and cellulose, break up under the dyeing conditions, while polyester buttons donot dye at all and must be used either as a neutral colour, capable of co-ordinating with a range of shades or be purchased ex- stock. Nylon buttons can be coloured in the garment dyeing process but it is difficult procedure to control to obtain consistent results.
Elastomerics,either natural rubber or polyurethane fibres such as Lycra, are used in ribs and both types can give rise to problems. Natural rubber is adversely affected by ceratin metals, and for this reason it is important to use dyestuffs that donot contain copper. Polyurethane fibres are seriously weakened in presence of strong oxidizing agents such as Chlorine, but hydrogen peroxide bleaching can be used with the polyester type of elastomeric fibre. Hence it is very important to specify the correct lycra tape to avoid breakdown in dyeing.
To prevent the major problems due to the metal accessories corrosion protection agents must be used.
An anionic ,organic corrosion inhibitor protects metal accessories such as buttons, zip fastners etc. made of non-ferrous and white metals ( but not Aluminium) from oxidation and tarnishing. It prevents the metal ions from attacking sensitive dyes and, when added in the last rinsing bath, prevents corrosion when wet goods are left lying.
5) Sewing thead is undeniably one of the most vital components to be found in countless articles we use. It is a component taken for granted and the demands on the threads we use are so many that it must satisfy a wide range of needs.
Properties desirable for sewing threads
a) It must be strong and yet fine enough to produce a neat seam and last for the whole life of the product.
b) Considering the modern high speed sewing machines where the speeds of the machines are as high as 6000 stitches /min, the thread is accelerated at over 100miles/hr and hence must be designed to withstand these speeds. An additional lubricant is required to reduce friction between the thread, needle, and thread guides and the fabric and also protect synthetic – fibre threads against needle heating. Therefore before dyeing these lubricants have to be removed, since otherwise it will inhibit dye uptake by the sewing thread.
Selection of Fibre type for the thread
For garment dyeing the thread and the fabric have to be of the same fibre type, however this is suitable mainly for cotton as sewing threads are not produced in all fibre type because of their dyestuff specific nature.
Thread selection and Precautions in stitching
In sewing fabrics made from cotton, in order to obtain equivalent seam strengths, heavier cotton threads must be used. Further it is necessary to keep sewing tensions to a minimum on lockstitch and chain stitch operations, deliberately producing slack stitches, since otherwise pucker will be introduced owing to shrinkage of the thread during subsequent garment dyeing.
All these factors would slow down the production speeds for garments to be post dyed and hence coatings should be carefully adjusted. Whichever thread is selected ultimately it will be a trial and error situation and hence sampling is essential before bulk dyeing.
6) Foreign substances
To reduce value loss it is better to prevent the foreign substances such as stains due to oil, grease, and other lubricating agents used during the course of manufacturing. Further proper handling and good house keeping also would reduce the stains. Other foreign substances could be sizes and resins containing additives such as elastomers and oil repelling agents which would cause poor appearance of the final goods and hence must be taken care of before dyeing.
7) Interlining
The purpose of an interlining ,whether fusible or non-fusible, is to stabilize and add body to the outer fabric with the introduction of post-dyed garments, certain special properties had to be introduced into interlinings to ensure that they performed satisfactorily.
The special properties required are:
a) It must take up dye from the bath to a similar level as that of the outer fabric.
b) The adhesive bonding of the outer fabric to the interlining base must remain intact during and after the dyeing operation.
c) The handle after dyeing should be that required by the customer.
d) There should be no adverse colouration caused by dye absorption in the fusible resin used in the fusible.
The three main components of any fusible which should have the above properties are:
i) base fabric
ii) base fabric finish and
iii) the fusible resin coating
The best choice for the base fabric is cotton as it would not cause problems during dyeing.
The base fabric finish is also important. Resin could be used, however they take up the normal hydroxyl sites needed resin and mechanical shrinkage has to be done to get even dye absorption and prevent the differential shrinkage.
The fusible resins used must be resistant to breakdown during dyeing and hence they should have the following properties:
a) They should be hydrophobic
b) Inert to pH changes
c) Have high melting points
d) Method of coating–Scatter coating is economic but gives poorer results, whereas dot coatings give smoother finish.
e) Rapid cross-linking and no subsequent crosslinking during storage.
The most successful fusible resins are the polyolefins with high crystallinity and melting points.
8) Carelabelling
The garment dyed goods generally have fastness properties inferior to the normal piece dyed goods. The major properties are:
a)Dimensional stability
b)Colour fastness to washing
c)Colour fastness to rubbing
Based on the various physical and colour fastness properties a suitable care label is arrived at, which tells the customer the precautions he should take when cleaning or washing the garment.
The various “care labeling” systems used are:
American
European
British
Canadian
The labels are designed such that they must give specific instructions with respect to the method of washing, bleaching, drying, ironing, suitability for dry cleaning and other relevant parameter.
Except for the American system which is based on written instructions, all other carelabelling systems are based on symbols.The objective is to inform the consumers on the correct care labeling of textiles.
Conclusion
Thus it is seen that Garment Processing and Manufacturing is not without problems. To obtain satisfactory results an absolute teamwork is required between:
gament fabric supplier
accessories supplier
garment manufacturer
garment processor
Taking all the necessary precautions during making and processing of a garment the export earnings can be tremendously increased.
About the author: Master of Science ( Technology)
Textile and Chemicals Technologist, Gold Medalist
15 years experience in Textiles and Chemicals, worked in Indian as well as MNCs. Having vast knowledge of textiles, processing, chemicals, etc.
Currently practicing as Consultant and Colour Matching expert.
Have various publications in Indian as well as International journals.
MS VIJAYA SHANBHAG
MSc(TECH) TEXTILE TECHNOLOGY Gold Medalist
R- 3C,Bhaskar society,naikwadi,Aarey road,Goregaon east
Mumbai-400063.tel: 91-022 -29275327 / M -091-9322821793
Email: vijaya2150@rediffmail.com
http://vijayatextiles.50megs.com
