The technology of treating the cellulosics with a resin system to impart the necessary cross linking in order to improve the wrinkle recovery properties was one of the major breakthrough of the textile science in the early 20th century. However, the necessary modification in the technology has now come into place where 100% cotton garments are sewn and then resinated to produce a garment with all the natural comfort factors intact along with the desirable degree of WR characteristics.

The garment industry in the Indian subcontinent is poised to witness major surge of WR production facilities in the near future. The methods of producing garments WR involves a series of labour intensive operations along with product specific regulation of various parameters. This note has been compiled with an objective to address to the various issues pertaining to the production of WR garments.

In many cases the WR processing involves compromises. When cotton or other cellulose based fibers are resinated, the fibers become more rigid and a noticeable strength loss occurs. The key to all WR processing is understanding the above property and developing product and process with this in mind.

Before going to the processing, it is necessary to judge what WR performance does the market requires as it is impractical to assume perfect performance. A reasonable performance goal, say 3 to 3.5 minimum on smoothness and crease would be a good starting point. Second question that arises is the fabric strength of the garments. For 8-oz. men's pant, a minimum tensile accepted is 22 kg and anything less allows for a weak product prone to bust at the seams.

While determining the ultimate goal the following relationship has to be always kept in mind.

WR performance µ % resin o.w.b µ fabric degradation.

The main goals of WR finishing are to meet these following requirements.

Crease retention

A subjective measure used to evaluate the afterwash recovery of creases pressed in after curing. Uses a scale from 1 to 5, 5 being the best rating.

Smoothness

A subjective measure used to evaluate the after wash fabric smoothness compared to after press smoothness. Uses a scale from 1 to 5, 5 being the best rating.

Tensile

An objective test used for measuring the warp and fill breaking strengths. The before and after tensiles are an effeciency indicator of the entire finishing process. The garment industry considers a minimum 22 kgs, for trousers, as consumer acceptable.

Tear

An objective test used for measuring the tearing, or shear resistance of a finished fabric. The before and after tear strengths indicate the efficiency of the entire finishing process. The garment industry considers a minimum of 1.5 kg in case of trousers acceptable for the consumers.

Garment pH

Garment pH is used to measure the amount of alkali or acid residuals remaining on the fabric after finishing the pH ranges from 5.5 to 7 are normal for WR products. As many people develop rashes when exposed to pH ranges below 6.0, therefore it is imperative to maintain finished garments above this limit if possible.

Level of formaldehyde

A distinction should be made between low formaldehyde and no formaldehyde. In some instances, no formaldehyde can be construed to mean extremely low formaldehyde release the finished garments. Many resins develop formaldehyde while in the finish baths. While considering formaldehyde levels it has to be ascertained the source whether it is bath or the finished garments.

Flex abrasion

An objective measure used for analysis of the wear expectancy of the finished garment.

SELECTION OF FABRIC FOR GARMENT TO BE PROCESSED

In this section we are dealing with the selection of fabric for garments needs to be WR processed. It is one of the vital factor playing a major role for giving good WR finish.

Compared to non resinated cotton fabrics, resinated fabrics have a number of advantages. These advantages include less wrinkling after washing and tumble drying, shrinkage control, and less fuzzing and distortion of the surface.

For 100% cotton WR products that perform well, considerable attention has to be given to the total engineering including the selection of fiber, the yarn characteristics, the fabric construction, preparation, dyeing, finishing formulations, and procedures. One of the most important considerations for WR 100% cotton is to employ a finish formulation that will yield the desirable balance of physical properties of the fabric. As per the relation: % fabric tensile and tear degradation µ % of crosslinking of cotton with resin µ % performance of wrinkle resistance, the non resinated cotton fabric should have the tensiles and tear which after treating should give a right performance on the base of smoothness and crease retention alongwith the proper performance in the case of adequate wear life of the cotton garments.

Therefore it is necessary to look at applicable fabric and garment physical specifications. Lot many times these fabric specifications are too low to enable the garment processor to resin treat with any chance of meeting garment strength requirements. Table 1 gives the applicable fabric physical specifications for shirtings and Table 2 is a composite for 8 oz. shorts or trousers.

Table 1

Table 2

As the strength of the garment is of major concern in the formation of a WR garments it is important to design fabrics in the required manner. Generally in a conventional 100% cotton fabric are much stronger in the warp direction than the filling, primarily because the fabric is designed with a higher % of warp. However as outlined in the table above we could find that the resin treated garment specs are the same for both warp and filling. By designing the fabrics with a balance between the warp and the filling it is possible to produce a fabric with suitable strength. . For example in case of a 7.5 oz where warp tensile is 56, fill tensile is 26 whereas the warp tear is 3.35 and fill tear is 1.5 the fabric is generally prone to fail in fill tear. To remedy this the product can be modified to 8 oz by increasing the weight of the filling yarn, leaving the warp the same. By increasing the fabric weight to 8 oz with all added weight coming from the filling more balanced fabric is obtained. If 7.5oz weight is to be maintained the warp weight can be decreased and subsequently increasing the filling weight thus producing a more balanced fabric and maintaining the strength both in case of warp and fill. In addition to the filling yarn change, the greige picks/inch can be reduced as the reduction in picks/inch accompanied by an increase in the yarn size to maintain the proper weight produces a more open fabric with better tear strength performance.

There can be many other methods like using stronger cottons, using combed instead of carded cotton, using piled yarns, etc. Many of these methods are not feasible because of economic or production restraints like equipment availability. For a garment manufacturers point it is very important to determine the fabric specification necessary to produce resinated garments with desired strength and smoothness. For the finishing unit of a garment manufacturer it is important to maintain the delicate balance between garment strength requirements and the best obtainable smoothness rating on a particular fabric. The situation for the finishing department becomes more difficult when garment dyeing or other processes such as stone washing proceed the resin treating.

SELECTION OF COMPONENTS

All components used in WR garments should be compatible with the durable press fabrics and process selected. There are products available which are suitable for most of application. Testing of various components in articles before large-scale production is advisable and periodic quality control tests will ensure continued acceptability.

Interlinings

Self-linings are often used, when proper aesthetics can be achieved. Taffetas of polyester however give the best performance garments such as woven shirts, dresses.

Pocketing

The selection of pocketing will depend on the garment end use. Self-pocketing is always satisfactory from a quality standpoint and should be used if cost and aesthetics are suitable. Polyester taffeta or tericot also give good performance in many types of garments, as do fabrics reinforced with nylon or Polyester. While treating with WR process, 100% cotton are generally not recommended because of their poor durability.

Threads and stitching

Proper thread selection is required to obtain a minimum amount of pucker, both initially and after repeated washings. Threads that perform best in a given seam usually possess the following characteristics:

1.Low shrinkage under all pressing, curing and washing conditions.

2.Smallest yarn diameter possible, while still providing adequate strength. For example the polyester threads and the nylon threads are finer and more resistant to abrasion than cotton and thus give stronger and more resistant to abrasion than those of cotton and thus give stronger and smoother seams.

Linings

Generally most of the WR garments require no linings and if linings are required it can of course be made of shell fabric providing the cost and aesthetics permit the same. Otherwise, a 65/35 blend of polyester and cotton is recommended for the same. Conventional rayon or acetates are not recommended in durable press garments.

Other Components

Button fasteners, and decoratives used on an article should be selected to withstand the conditions of WR processing. Zippers are available that meets the needs of all processes; zipper tapes of 100% synthetic fibre or high percentage blends of synthetics with cotton are recommended for satisfactory wear life and good appearance.

After the garments are manufactured, stains and oil spots on durable press articles must be removed before pressing and curing, since high temperature can permanently set some stains, making it impossible to remove after processing. Water and water based cleaners should not be used because they leave rings and remove the WR finish.

FABRICATION PARAMETERS FOR WR GARMENTS

The following procedures before fabrication generally help to improve the quality of WR articles

1. The initial articles and sample articles from each new fabric lot should be evaluated under home laundering condition to determine pattern allowances needed for shrinkage and overall acceptability.

2.Cut fabrics in such a way that seams will be sewn on the bias, rather than in the warp direction.

3. Cut to exactly the same degree of grain (in same direction). Fabrics to be joined with the grain.

4.Cut fabrics in such a way that seams will be sewn in the filling, rather than the warp direction.

5. Avoid top stitching wherever possible.

6. Allow a minimum for easing in the sleeves.

7. Use self-turn back openings instead of plackets and bindings.

8. Usually garments shrink during the curing process, 1 to 2.5% in the warp and 0.5% to 1% in the filling. Allowances for this shrinkage must be made in patterns. Moreover since a shrinkage differential exists between warp and weft, joining of these parts should be avoided to reduce seam puckering.

7. Use selvedge instead of hem in turn backs wherever possible.

8. Press curved seams on curved bucks. Inseam of slacks should have minimum curve to permit flat pressing on a legger-pressing machine.

9. Cut Taffeta interlinings of Dacron on a 25 deg to 45deg bias to minimize edge fraying and to achieve the best appeareance.

10. While stitching use of as few stitches as per inch possible, consistent with good seam quality. For example, use of 12 SPI in lightweight, 10 SPI in medium and heavy weight fabrics. However with fabrics that have very open construction, a few more stitches than are normally required will improve the seam quality: 6 SPI normal, 9 SPI recommended.

11. The use of minimum amount of thread tension possible consistent with the good seam quality. Any tension applied to the thread during stitch formation tends to gather, or pucker, the fabric; the higher the tension more pronounced the pucker.

SELECTION OF CHEMICALS

Identifying and making of the chemical mix is one of the most important processes in the formation of the WR chemicals. The selection of appropriate resin is important with respect to the performance, free formaldehyde, strength retention, and abrasion resistance. For most of the fabrics dimethyloldihydoxyethyleneurea (DMDHEU) is used. The reactant made from dimethylurea and glyoxal (DMUG) is a very interesting chemical since it gives good surface smoothness while maintaining better strength and abrasion resistance than DMDHEU. However, the crease retention with DMUG is not as good as that achieved with DMDHEU. A good compromise of these properties may be achieved by blending DMDHEU and DMUG.

There is much variation of the above products, which include:

1. Regular, unmodified

2. Regular with Buffer

3.Regular with catalyst

4.Regular with buffer and catalyst

5.Low formaldehyde (methylated or glycolated)

6.Low formaldehyde with Buffer

7. Low formaldehyde without catalyst

8. Low formaldehyde with catalyst

These selections offer the finishers a choice as to the best product for the particular application. That application may be determined by fabric style, method of application, or product specification. A combination system where catalyst is premixed gives some simplicity to the formulation. A use of softener is necessary in all combinations.

A number of softener systems are available to provide abrasion resistance while achieving a wide range of handles. The basic choice is still polyethylene because of cost and its handle. A cationic polyethylene has better wash durability and adds some dimension to the hand. By adding silicones even further hand enhancement can be realized. Polyurethanes have also entered the scene for fabric strength enhancement. A right combination mix of these softeners can be made to fit the most of fabric style and construction.

Preparation of garments for finishing

1. The sizing agents, cut and sew lubricants should be completely removed. For this in some cases a desize operation or scour may be required.

2. The fabric should be dyed or bleached before finishing. If dyed, the effect of the WR finish system on dye shade should be tested and the dyeing adjusted if necessary.

3. The fabric should be clean and absorbent. The garment pH should be adjusted to 5.5 to 6.5. Absorbency should be measured so that resin concentration can be adjusted based on the wet pickup.

At times enzyme treatment is recommended for removing the surface fuzz alongwith improving the handfeel.

There are various methods for applying the resin on the garments and can be as

1. Dipping and extraction

2. Metered Addition

Dipping and Extraction

The garment processor should make the decision whether or not to pre rinse the garments. Under known incoming fabric conditions, pre rinsing is not required. If there is any question about the fabric to be finished, pre rinsing of garments with non-alkaline detergent. If bath pH stability is a problem, pre rinsing with 0.25%to 0.50% owg citric acid can cure the source of alkaline contamination.

Garments can be dipped inside out or right side out. Under most of the conditions the garments dipped inside out will show better physicals and overall WR performance.

The garments are saturated in the treating solution and a time of 25 to 30 minutes is recommended for keeping the garments dipped in the solution. The garments are taken out and the resin solution is extracted from the garments till the adsorption is 65 to 70%. This is known as wet pick up of the garments. The 65 to 75% figure can be taken out as (wet weight - dry weight)/ (dry weight)

For example a typical 8 oz trousers would weigh 450 gms. After extraction, if the weight is 750gms. Using the above equation the wet pick up is approximately 66%:

(750-450)/450 = 0.66 converting to % * 100 = 66%

It is advisable not to force and extract through longer times. When setting up a process for the run determine the average extract weights using water as the mix, and then adjust the bath ratio as needed to provide an equivalent % o.w.g.

METERED ADDITION

The primary difference between metered and dipping is in the method of applying the resin mixture. Garment dipping is a procedure where more resin mix is applied than needed and that excess is extracted off. In a metered application a needed amount is applied and there is no extraction. The metered addityion further can be done in two ways either by spray method or by tumbling method.

Any tumbling device can work for spray application. The tumbling machine may have a perforated tub. A working front loading washing machine does a good job.A pump or a spray nozzle is required The volume/weight of mix will need to be applied over a span of 15 to 20 minutes. Resin application will be more evenly distributed the longer the tumbling/application time. The application process should not be speeded up as it may cause unevenness and terrible quality will result.

In a tumble method of metered addition instead of a spray a lined barrel washing machine i.e. a machine where the barrels are without holes. Generally half of the treating solution is poured in then the garments are loaded and the rest of the solution is poured. Then agitate the machine for a span of 15 to 20 minutes.

1. Use water and a load of production garments to establish the proper wet pick up for your particular machine set up. In both spray and tumble applications equilibrium should be reached in approximately 8 to 10 minutes.

2. A typical wet pick up for spray or tumble application on a 8 oz garment is 80-85%. All garments within the load should vary no more than 2% wet pick up. As garment weight goes up more wet pick up will be needed to insure equilibrium of resin. For ex, a 10-oz. denim garment will require a wet pick up of 100 to 105%.

3. If the wet pick up is too low areas around the pockets and fly will remain dry. If the wet pick up is too high the garments will start to drip when taken from. Too high wet pick up will allow the resin mixture to migrate by gravity during unloading and produce garments with both too high and too low resin in the load.

4.The tub rotations per minute (RPM) should allow the garments to drop at the 11 o'clock position. It may turn one way or with reversals. If tub RPM is too high, unequal resin distribution will result, although this can be attributed to low wet pick up.

5. The nozzle should be adjusted to give a fine spray with direction towards the side of the tub. The garments tumbling transfers mix from garment to garment and generally equilibrium is reached within 8 to 15 min of total resin application. The extra tumbling of the garments is always beneficial for getting a right equilibrium thus giving more uniformity. Generally a spray with adjustable nozzle is recommended so that different machines and mounting points can be accommodated with just a turn of the collet.

DRYING OF THE GARMENTS

The drying is one of the very important factors for the manufacturing of the right product. It has been one of the primary problem makers for the formation of a WR garment. It is one of the simplest processes, which is critical for lot of mystery problems. The following measures can be taken for a formation of the right product.

1. On start up plants or processes, maintain dryer outlet temperature at or below 75 deg Celsius. A use of lower temperature can help in being confident that the fabric is not being exposed to excessive heat, thus minimizing the potential for spot curing. Spot curing generally results into the garments with good physicals but low smoothness and crease ratings.

2. It is recommended to maintain the load size at or near to recommended capacity. This ensures even moisture distribution and consistency from load to load.

3. The external humidity (rain, fog, snow), night time, and other conditions effecting the incoming air quality is also one of the reason for some of the potential problems.

Moisture content before going to press is a very important factor for the formation of a right product. Generally a 10 to 14% measured by moisture meter at the thighs and 12 to 16% is recommended if taken by weight measured by load or garment.

These ranges are also indicative of the moisture distribution within the entire load. If the dryer is unable to keep the majority of garments within this range other problems are revealed that must be remedied to insure consistent performance.

An effective cooling with a minimum of a time period of 10 minutes is preferable. Moisture % should be attained during this time. Lengthening of the cool down cycle is a way to salvage lot of problems related to garment moisture inconsistencies.

PRESSING PARAMETERS

The overall goal of pressing is to provide a smooth surface and a sharp crease. These qualities must be imparted and remain with the garment until final curing has taken place. One of the major causes for bad appearance before curing is bad handling. The main things to be considered for the pressing is

1. Press Temperature

2. Steam/Quality of steam

3. Vacuum/Volume/ how much pull measured in inches of mercury.

Press temperature is maintained by using press equipment with high temperature aluminum head. The boiler pressure maintains the temperature. Generally the press temperature is need to be controlled within a range i.e. 140o to 165o c.

The quality of steam furnished to the press effects both the functioning of the press and the quality of the garment. The steam must be dry and free from entrained moisture. It is a very important that no alkali from a raw water source or from the boiler treating compounds is carried over by the steam.

The vacuum is important for setting of the crease. The amount of vacuum pull and where it is placed in the cycle will aid in the cross-linking of fabric in the crease area. It is not necessary to use the post vacuum, provided the vacuum is used during the regular press cycle. Vacuum must be able to pull 6 to 10 inches of mercury while all press equipment is being fully utilized.

A common pressing cycle used for the finishing of garments in WR process is

5 seconds steam

10 seconds high pressure lock down

5 seconds of vacuum to insure dryness of the garments.

With adequate moisture before press the steam cycle can be reduced to 2 seconds or less.

CURING PARAMETERS

Curing is the process of raising temperature to chemically react the resin with the cellulose. In garment finishing, resin curing is accomplished through the use of a batch oven or a continuous oven. Proper curing is required to achieve the maximum WR performance.

A successful set up follows the following rules:

1. Heat distribution should be even from top to bottom and side to side with a variation not more than + 2°c

2.Resin curing measured by nitrogen fixation should be at least 85%.

3.Garments should not be overcured.

4. Tensile variations should be kept to a minimum and should agree with the lab predictions.

If the above rules are followed the curing at 155 deg Celsius for 15 minutes gives a desirable performance.

Beginning oven setups should ideally start with 155 degrees ambient temperatures. Once this temperature is attained time can be lengthened or shortened as per requirement. Regarding the oven temperature there should be a uniform distribution of air throughout thus the temperature in overall variates not more than + 2°C.

Curing time can be adjusted according to the fabric i.e. for a heavy weight fabric the curing time can be increased and for the lightweight garments it can be reduced. Moisture also plays an important role on the curing cycle as garment moisture causes the garment to take longer reaching curing temperature, allowing less surface to be exposed to the targeted time and temperature. The one of the important point is to allow the whole garment (both inside and out) to reach curing temperature and remain there until 85% or greater resin has been cured. Allowing the garment to overcure degrades the cotton due to excessive heat. This degradation is particularly apparent when measuring the flex abrasion. Overcuring can also lead to lower tensile figures for equivalent performance ratings.

The hanging of garments is also a point of consideration in the processing. There are two ways of hanging.

1. One is by cuff using a hanger type, which clamps the cuff of the garment. There is a danger of leaving hanger impression at the cuff when hanging garments with this method.

2. The second method is to hang garments over a bar. There is also a possibility when hanging a garment over a bar that one may not get a good cure in the oven. A hanger or bar mark is expected.

In any case all garments should be hung properly before proceeding to bake the garments. Garments must be hung straight and hung evenly at the cuff.

Special care should be applied when garments are hung over a bar. One cannot allow the legs to fold under on the underside of the bar, which can cause a baked in the pleats. An inspection can be done for all garments prior to entering the oven to insure the proper hanging.

QUALITY CONTROL

A quality control program is essential for success in manufacturing of durable press articles, and for the consistencies in the results the optimum process conditions once established must be frequently verified. A definite way of controlling the Quality is the statistical control.

Statistical Control

Statistics is the only way to maintain control over a production WR operation. With all operations introducing many variables into the processes, the beginning and experienced personnel encounter untold headaches. The mathematical approach to production problems involves two steps: using the mathematical relation already established with meaningful statistics analysis. The inherent variabilities with 100% cotton fabrics pose the greatest problems. Any quality department has to understand the total range of variance to be encountered. For example, fill tensiles on incoming fabric can vary as much as 18 kgs with in the same swatch, let alone a full width or whole cut. This information is readily available with the fabric supplier. The key values to remember are the average and the standard deviations of each performance measure.

CONCLUSION

The true test for any WR product is the consumer. It is strongly advised on any new product to establish performance measures based upon "real world" expectations and "real world" tests by people wearing your products. In many cases the tests and tests measures used in the past will do just fine, however, due to new fabric construction, technology changes, or other unforeseen circumstances new problems arise. Understanding the scope and limitation of WR finishing through every stage of processing, from initial fabric purchase to final; consumer wear ensures a highly successful program from step one.