Testing Of Knitted Fabric Washing Knitwear

     

 Strength Properties

The strength properties of apparel have been considered the most obvious indication of the service life of apparel. The strength of a fabric or garment indicates its ability to resist mechanical damage due to stress of normal wear and laundering. The strength properties of apparel can be divided into the following three areas:

è        Fabric strength

è        Seam strength

è        Resistance to yarn slippage

1.      Fabric strength: Fabric strength can be divided into three areas:

è        Resistance to tensile force

è        Resistance to tearing force

è    Resistance to bursting force

Incase of woven fabric resistance to tensile force and resistance to tearing force is measured but in case of knitted fabric resistance to bursting force is measured to assess the fabric strength.

2.      Seam strength: Seam failure of a garment can occur because of either the failure of the sewing thread leaving the fabric intact, or fabric rupture leaving the seam intact, or both breaking at a time. Seam strength is tested in almost the same manner as fabric breaking and bursting strength. The strength of a seam or stitching should be equal to or slightly less than the fabric strength. The elements affecting the strength of seam or stitching are:

è    Stitch type

è    Thread strength

è    Stitches per inch

è    Thread tension

è    Seam type

è    Seam efficiency of the fabric

3.      Resistance to yarn slippage: For oven

Knitted Fabric Strength Testing

Strength of knitted fabric is tested by the bursting tester machine. Bursting tester may be hydraulic type or mechanical type. Here knit fabric strength testing by a hydraulic busting tester is described.

A sample(s) of knit fabric 7″7″ is taken and clamped by a ring over a thin flexible rubber diaphrams “D” which is itself clamped over a circular hole in the upper face of a reservoir may be water or glycerin. The hydraulic pressure is increased by valves or screw driven piston and the diaphram distends, taking with it the sample fabric. At some point the fabric bursts, the pressure being indicated by the gauge

The extensibility of the yarn and the structure of the fabric are factors, which determine the behavior of the test sample.

Discuss On Seam Failure In Knitted Fabric

Knitted fabrics are in general, more extensible than woven fabrics and in some instance very much more extensible; as a result it often happens that when a seam in a knitted fabric is extended along its length, the extension limit of the dewing thread is reached before that of the fabric it self, and the sewing threads that break at one or more points along the seam, the effect is known as “seam cracking”. Once a seam has cracked, even at one point, it is no longer useful, and eventually lead to seam failure.

Thus the behavior of seams under longitudinal in contrast to transverses stress is of much greater importance in knitted structure than woven ones.

Under transverse stress seams in knitted fabric show both types of failures i.e. breaks in which the sewing threads fail but the fabric remains intact and in which the fabric fails but the sewing thread is intact.

In a balance seam an extension of approximately 80% is possible before the seam cracks provided the stitch density is 20 or more. Reduction of stitch density reduces the extensibility, the effect is more pronounced for a cotton thread than for a polyester thread.

If other things being equal, the 2-thread chain stitch seam gives slightly higher extensibility than the 2- thread lockstitch. Polyester thread gives the best result, with an extension of just over 100% at 20 stitches per inch.

Of the four variables, namely stitch density, thread composition, thread denier, and seam structure, Neither thread composition nor the thread denier is important from “seam cracking” point of view. The important variables are stitch density and seam structure, with the sewing thread extensibility playing a minor part.

Fabric strength testing

The reasons of carrying out on tests on fabrics are numerous and some common ones being –

1. To check that the fabric conforms to specifications.
2. To note the effect of changes in structural details.
3. To note the effect of physical and chemical treatment, exposure to weather, laundering etc.
4. To obtain some identification of probable performance in use.
5. To investigate causes of failure and customers complain.
6. To help in design of a fabric for a specific purpose.
7. To study the interaction of fiber, yarn and fabric properties.

Fabric stretch property

There are two categories of stretch fabrics based on degree of stretch ability power or action stretch and comfort stretch. Action stretch provides a fabric with a high degree of extensibility and quick recovery. The stretch factor ranges from 30% to 50% or more. Such stretch fabrics are at best adapted to knitwear, swimwear, athletic clothing and professional sportswear.

Comfort stretch applied to fabrics with less than 30% stretch factor. Such fabrics are used for everyday clothing that needs only a moderate degree of elasticity. This category covers a wide range of end uses in both apparel and the home, as well as in transportation upholstery.

With stretch fabric, comfort is achieved by reducing garment restraint imposed on the body, through increased fabric “give”. No standard exist for the level of stretch required in various garments. However, there are some experimental data available on this subject.

Garments item                                     Stretch                         Direction

Men’s suit Jacket                                30 %                            Horizontal

Men’s shorts                                        30 %                            Horizontal

Men’s shirt (sleeve)                             25 %                            Vertical

Men’s shirt (body)                              25 %                            Horizontal

Women’s shorts                                  35 %                            Horizontal

Women’s slacks                                  35 %                            Horizontal

Skirts                                                   25 %                            Horizontal

Dresses                                                30 %                            Horizontal

From the above-mentioned experimental results they reached the following conclusions –

1. The experiment confirmed the general view that outerwear garments that offer the least resistance to body movements are the most comfortable.
2. Wearer’s preferences for stretch wear established at a 25% to 45% stretch range, depending on the end use.
3. For women’s horizontal stretch slacks, a 35% stretch level effectively satisfies the comfort requirements for this type of garment.

Fabric Pilling Test

Pilling is a fabric- surface fault characterized by little pills of entangled fiber clinging to the cloth surface and giving the garment unsightly appearance. The pills are formed during wear and washing by the entanglement of loose fibers which protrude from the fabric surface. Under the influence of the rubbing action these loose fibers develop into small spherical bundles anchored to the fabric by a few unbroken.

Martindale abrasion tester may be used for the pilling test of any fabric. The normal sample holders are replaced with Lightweight Square holders, which are keyed so that they may have vertical movement but cannot turn on their axes. The samples are given a multi-directional movement and are rubbed against a standard fabric. After certain number of rubs, the samples are examined and the number of pills counted. This may be repeated say in stages of 500 cycles up to 3000 or 5000 and the rate of development of pills noted.

The abrading material may be a 15 oz cotton canvas or the test material itself. The test specimens are mounted on rectangular blocks 1½″2½″ and after a given number of rubs, the numbers of pills are counted.

 

 Color Fastness To Washing

This is of a great importance to the consumer and there are several washing tests, which are applied according to the purpose for which the material is intended.

A specimen is measuring 10 cm4 cm of the material to be tested is cut out. Then the specimen is placed between two pieces of undyed fabric measuring 5 cm4 cm and the three pieces are held together by stitching round the edges leaving 5 cm4 cm exposed. The composition of one of the color less materials enclosing the specimen will be the same as the dyed sample and the other will be as indicated below:

1^st Piece                       2^nd Piece

Cotton                                     Wool

Silk                              Wool

Nylon                          Wool / Viscose

Polyester                     Wool / Cotton

Acrylic                        Wool / Cotton

A solution is made containing 5 g / litter of soap confirming with the following specification.

Free alkali calculated as Na₂CO₃                                0.3% Max.

Free alkali calculated as NaOH                                  0.1% Max

Total fatty matter                                                        85% Max

Titre of mixed fatty acids contained in the soap        30ºC]

To the soap solution 2 g / litter of anhydrous sodium carbonate are added. The composite sample is then treated in a wash wheel at 60ºC2ºC for 30 minutes in sufficient of the above solution to give a liquor ratio of 50:1.

After treatment the composite samples are in every case rinsed twice in cold distilled water and then for 10 minutes in cold running tap water. After squeezing, the stitching is removed on the two long sides and one short side, leaving the dyed specimen and the undyed materials sewn together only along one short side. The pieces are opened out and dried in air at a temperature not above 60ºC.

The change in color of the uncovered portion of the specimen is assessed with gray scale no – 1 and the staining of the undyed materials with gray scale no – 2.

Fabric Shrinkage Test

A sample of test specimen measuring 24″24″ should be taken and marked with different color sewing thread 20″20″. The specimen sample should be laid flat without tension on a smooth flat surface in the standard testing atmosphere (65% R.H. & 68ºF 2ºF) at least for 18 hours. Reference measurement should be taken carefully and accurately.

Then test specimen should be put into the washing machine. Temperature should be adjusted to 38ºC 2ºC. sodium carbonate and neutral wetting agent shall be added in quantities to give a solution containing 0.1% each. The weight of the specimen shall not exceed one half pound per gallop of washing liquor. The washing machine shall be set in motion and kept running without interruption until the washing & rinsing of the specimen are completed.

After running the machine for 15 minutes the washing liquor shall be drained off. After that the specimen shall be washed for 5 (five minutes) three times at 38ºC 1ºC.

Then the specimen shall be taken out form the washing machine, and folded to form a pad having 8 layers and laid against the side of the hydro extractor machine. The hydro extraction should be carried out for 10 minutes to remove excess water from the specimen. Then the specimen should be taken out from the hydro extractor and kept for few minutes to equalize the distribution of remaining water inside the sample.

Then the specimen shall be laid flat without stretching on the pressing table and pressed with heated iron for 30 – 40 seconds and moving the iron without sliding to an adjacent position and repeating this process till the whole area of the specimen becomes dry. After pressing the sample should be reconditioned and measurement should be taken.

Original length – Shrunked length

Fabric shrinkage %                                                                              100

Original length

Industrial Garments Washing

Introduction: In the ready-made garments sector a garment washing is a new technology. After making garments from solid color dyed or pigment printed fabrics, the garments are washed. By garments washing, color and outlook of the garments are modified. As a result new outlook and appearance is produced in the garments, which is mot possible in any other method moreover due to washing, starch materials present in the garments are removed, as a result washed garments could be wear after purchase directly from the store or shop. Some garments shrinks after wash, hence washed garments could be purchased as per required size.

Normally garments washing means cleaning of dirty garments with soap or detergent. But it is not that garments washing. Industrial garment washing is a technology. The technology. The technology, which is used to modify the outlook, appearance, comfort ability & design of the readymade garment made from solid color dyed or pigment printed fabric is called garments washing. In our country garments washing technology started from 1988 and popularity of garments washing is increasing day by day.

Requirements of garments washing: with the change of time, human choice demand, garments design, & fashion is changing very quickly. To meet the demand of users, garments manufacturers are adapting new technology & process. Garment washing is a new technology, which is capable to meet the present requirements. This new technology needs new machines & various types of chemicals. Advantages of garments washing are summarized bellow.

1. Starch present in the new fabrics of the garments are removed, hence feels soft during use.
2. Softness feeling of garments could be increased.
3. Drift and spots present in the garments is removed.
4. Shrinkage occurs in the garments during washing, hence no possibility of further shrinkage.
5. Washed garments could be used directly after purchase.
6. Fading affect is produce in the garments by regular or irregular pattern.
7. Different out look of garments could be produced in the garments by different washing technique.
8. Similar outlook could be produced in the garments by different washing techniques.
9. Initial investment cost to setup a garments washing plant is comparatively low.

Garments washing machine: Industrial garments washing industries needs the following machines for various types of garments washing –

1.      Garments washing machine

2.      Hydro extractor

3.      Garments drying machine

4.      Boiler for steam generation

5.      Sand blasting unit.

Garments washing machine is the main machine where garments washing are done. In our country atmospheric pressure rotary garments washing machine is the most common garments washing machine. Detail description of the garments washing machine is given here.

In this machine, there are two big stainless steel cylinders, one inside the other. The outer cylinder is supported by the machine frame, which is secured tightly in the floor. The outer cylinder is solid stainless steel but the inner cylinder is perforated. Diameter of inner cylinder is about 4 feet and width is about 6 to 8 feet. The inner cylinder is supported by side shaft from two sides. The inner cylinder has two doors with spring loaded lock system to load and unload garments in the washing machine.

The inner cylinder has also 3 bars about six inches high at inside the cylinder, which extends across the whole width. These bars facilitate circulation of liquor & garments during machine running. There are also two slidding doors at the out side cylinder. The inner cylinder rotates at 5 to 35 RPM. Motion is given to the inner cylinder by two big motors from two sides. With the help of a reversal unit, the inner cylinder rotates clock wise & anti-clock wise alternately for all the production time.

There is a panel board in the machine frame, where some controlling of the machine running is monitored. There is a time in the panel board, which can be set for machine running time for each cycle and stops the machine running automatically with alarm sound. There is a temperature controlling indicator and dial in the panel board. Temperature controlling indicator could be pre-set for automatic controlling of liquor temperature. To maintain the liquor ratio, a transparent glass tube is set at the side of the machine with marking of liquor quantity. There is a solid steam pipe running in-between two cylinders at the bottom side, which indirectly heats the liquor. There are two chemicals dosing doors at the middle height of the outer cylinder. Water from overhead tanks is fed in the washing machine by pipeline & gate value. Liquor is drained off by two-pipeline and gate value at the bottom side of the machine.

 

 

Capacity of garments washing machines various from 50 kg to 500 kg, but the 300 kg machine is the most common one.

Garments Washing & Dyeing

Garment dying is a new process, which has been introduced in our country approximately 7 years back. Popularity of garments dyeing specially for casual wear and leisure wear in the western countries are increasing day by day. With the change of season, demand of garments design, fashion, & color is also changed. To meet the quick change of demand popularity of garments dying is also increasing.

In this technique garments is produced from Grey fabric, then the garments are dyed in required color & shade. This technique is practiced only for 100% cotton garments in our country. In the European countries this technique is applied for woolen garments and also for 100% cotton. Garments dyeing, two types of dyes are mainly used.

à    Direct dyes: Poor fastness, cheaper method.

à    Reactive dyes: Fast color, widely used, reasonable cost.

Advantage of garments dying are as follows –

1.      Comparatively lower cost of production for any color.

2.      Less time is required to produce & supply any color of any garments.

3.      No possibility of shade variation within the garments.

4.      Suitable for producing small lots of different colored garments within short time at lower cost.

5.      It is also possible to re-dyes old garments, which may look like new garments.

6.      De-sizing, scouring, bleaching, dyeing and finishing treatments on garments is done in one M/C.

7.      Lower capital investment cost to set-up garments dyeing project.

8.      Garment dyeing is carried out at low liquor ratio, as a result consumption of water & steam is also lower, hence dyeing cost is also lower.

Garments Washing

Garment washing is also a new process and this process is getting popularity day by day. In this process after manufacturing garments for colored or printed fabrics the garments are washed with varieties types of chemical to give special color effect in the garments. This special color effect on garments is not possible in any other method except garments washing method. For example, by using these techniques on Jeans trouser, Jacket & shirts, color of these garments are changed resulting new color effect, fashion & comfort. There are varieties are discussed here.

1. Normal wash: It is the simplest type of garments washing. Washing is carried out with hot water, detergent & some softener. After washing garments are rinsed & tumble dried unit it is 100% dry. Depending on what kind of fabric the garment is made of and how much of a washed look you need our should adjust the temperature and the length of time to wash. This type of washing starch removes present in the fabric, garments become soft & fluffy.
2. Pigment washing (For pigment dyed): The process of pigment wash is similar to normal wash but this pigment wash is done specifically for the garments, which are made from pigment dyed or pigment printed fabric. In washing process the effect of colored pigments are faded resulting a new colored effect. To get the desired faded colored effect on garments; it may be required to alter washing temperature, quantity of detergent used and processing time.
3. Bleach wash (For dyed fabrics): Bleach wash is a process of controlled bleaching action on garments. This type of wash may be carried out on garments made from colored fabrics in case of garments made from colored fabrics; the color of the garments is partially faded by controlled bleach washing process.
4. Stone wash (For woven fabric): This type of washing is common on garments made from jeans fabrics. The idea of washing with porous volcanic stone is to give the garments a strong and rough wash to achieve the pronounced washed effect through abrasion bleach to the wash to make the color fade more seriously such as denim, from navy to light blue. A lot of experience and skill are needed to achieve desired effect.
5. Acid wash (For woven fabric): Acid wash is specifically done on garments made from jeans fabric. The garments are at first designed, rinsed and dried. Then the dried garments are loaded in the garments washing machine but without any water. Porous stone i.e. pumic and the dry garments are rolled by the rotation of rotary garments washing machine. Chemicals within stone, discolors the garments and effect of stone on garments gives brushing action.

Next step is to wash the garments thoroughly in waster. After washing the partly discolored effect is made prominent by using whitening agent. The discolored areas is partly white 7 irregular white pattern effect is produced in the garments which is not possible to produce other than washing technique. Acid wash effect on jeans trouser common all over the world.

6. Enzyme wash: Enzyme wash is a kind of live cell. We use it to wash because we want to clean the projecting hairy from the fabric surface of the garments. It dissolves the hairy fibers and also produces acid wash effect on jeans garments. By this enzyme treatment better & nicer blue & white contrast effects produced on jeans. However, enzyme is rather expensive and therefore enzyme wash is more expensive.
7. Caustic wash (For Pigment Dyed Fabric): Caustic wash is special type of wash, which is dome on the garments made from specially printed fabric. The fabric is printed on Grey state with pigment color & binder. This type of specially printed fabric is used to make the garments. The garments are then washed with caustic &hot water. By this treatment about 30% pigment is washed out together with natural impurities present is the fabric making the printed design or stripe nice & soft. This is the look we call caustic wash.

For caustic wash, the printing must be pigment print with binder and backing treatment to an extent that the color will stay on the fabric only fairly securely to coincide with the caustic wash to be done later.

8. Spray: Irregular fades.