resin finishes on cellulosic fabrics

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RESIN FINISHES ON CELLULOSIC FABRICS Presented by: T. SRIVANI Asst. Prof., DFT Dt: 18.02.09 FABRIC AND GARMENT FINISHING

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Page 1: Resin Finishes on Cellulosic Fabrics

RESIN FINISHES ON CELLULOSIC FABRICS

Presented by:

T. SRIVANIAsst. Prof., DFTDt: 18.02.09

FABRIC AND GARMENT FINISHING

Page 2: Resin Finishes on Cellulosic Fabrics

Cotton is mainly selected for apparel purposes because oftheir durability, ability to withstand the rough laundering treatmentespecially under alkaline conditions, good perspiration absorptioncharacteristics, comfort during wear and ability to take up a wideRange of dye stuffs.

But the main limitation with the cotton fabric is crease formationDuring washing, laundering and in use.

As formation of crease is an undesirable property for apparelThe material has to be made either crease resistant or crease recoverable.

The object of resin finish is to keep the fabric flat and smooth and free from undesirable creases. So the finish is referred as

“Anti crease or Anti crush or Crease Resistant or Crease Recovery finishor Resin finish since resins are used for this finish”.

Page 3: Resin Finishes on Cellulosic Fabrics

Resin finishing was originally developed in the mid 1920s to improve the crease recovery problems associated with cellulosic materials and to give them a recovery similar to that of wool.

It was found that urea and formaldehyde would react with the hydroxyl groups in cellulose to form a bond which gave the product both good recovery from creasing and improved dimensional stability.

Usually Cotton, Linen, Viscose and Cuprammonium rayon are finished with resin.

Page 4: Resin Finishes on Cellulosic Fabrics

Resins are the chemical group applied as wet finishes and used in many of the finishes.

For example, they are the principal chemical ingredients in many crease-resistant, wash and wear and also for durable press finishes and are used primarily on cellulosic and cellulosic-blend fabrics.

There are several types of resins, but most belong to the urea formaldehyde or related groups of organic compounds.

These formaldehyde components have been suspected of being carcinogenic (cancer causing) materials.

Another group of resins, used less ex tensively due to their relatively high cost and limited effectiveness, are the dimethyl urea glyoxalin compounds which are non-formaldehyde producing.

Page 5: Resin Finishes on Cellulosic Fabrics

The cellulose molecules will get cross linked by resin.

The resin plus a catalyst, softener and wetting agent would bepadded on to the fabric at 6-8%, dried at 1200C to a residualMoisture of 8%, cured at 1600C for three minutes, washed to remove any catalyst and un reacted resin and finally heat set to width and dried.

Resin finishing improved the dimensional stability of the fabricto washing. So, a fabric in the untreated state would have a wash shrinkage of 8% would have a wash shrinkage of less than 3% after resin finishing.

The major causes for shrinkage of cotton are relaxation shrinkage and fibre swelling, which in turn swell the yarn.Resins prevent fibre swelling as it renders fibre non absorbent.

Page 6: Resin Finishes on Cellulosic Fabrics

Mechanism of crease formation:

Structure of cellulose chain:

Cotton cellulose chain contains –OHgroups in both amorphous and crystallineregion.

When a cotton fabric is folded and pressedbeing a weak bond of force the Hydrogen bondsformed between the –OH group of adjacentcellulose chain in the crystalline region arebroken and the formation of new hydrogen bondsin the amorphous region causes the formation of creases

Page 7: Resin Finishes on Cellulosic Fabrics

The resins crosslink cellulose chains and they do so in theamorphous regions of the structure where the spacing between fibre molecules is relatively open.

The effect of this is to give a more crystalline character to the fibre,so that if the fibre gets distorted it will have a greater tendency to spring back to its original position.

This pseudo crystalline character due to the resin treatment makes the fabric stiffer.

No one treatment will maximize all fibre properties, it is a case ofprioritizing according to the requirements of end product.

Page 8: Resin Finishes on Cellulosic Fabrics

Resins are colorless and are applied to fabrics in liquid form, then dyed and finally treated at high temperature, causing the resin to react chemically with the cellulosic component of the fabric.

This heat treatment is called curing which requires treatment at temperatures of 300°F to 350°F (145°C to 165°C), for 30 seconds to 2 minutes depending on fabric type and the amount of resin used. Curing can be performed at lower temperatures, but this requires longer exposure time.

Resins are classified as durable (rather than permanent).

Resins have a profound effect on fabrics and cause changes in the hand, drape ability, and physical characteristics of textiles. Although many benefits are achieved through these changes, there are also some shortcomings.

Page 9: Resin Finishes on Cellulosic Fabrics

Resins modify fabrics in the following ways:

They add stiffness to fabrics and are thus used as stiffening agents or to create a firm hand.

They stabilize fabrics in the same shape or configuration as when the resin was cured.

Fabrics cured in a smooth, non-wrinkled condition will return to that shape after being wrinkled in wear, and fabrics cured with creases in garments will retain these creases.

Yarns in fabric are stabilized and resist shrinkage in laundering.

Fabrics become less moisture absorbent and thus dry more rapidly.

They are also less comfortable in warm, humid weather.

Page 10: Resin Finishes on Cellulosic Fabrics

Resins combine chemically with cellulosic fibers (cotton, rayon, etc.) to cause significant reductions in abrasion resistance, breaking strength, and tear strength. This reduction can be as high as 50 percent.

Most resins produce an offensive fish-like or formaldehyde odor in fabric. This odor eventually disappears on exposure to air and/or laundering. Ethylene glycol and similar compounds added to the resin bath have been found to be very effective in eliminating or reducing this odor.

Resins have an affinity for oily soils, creating a soiling problem. Soil-release finishes help to alleviate this problem.

The degree of these changes is dependent on the amount of resin applied (called the resin add-on). Add-on may range from less than 2 percent for certain crease-resistant finishes to 10 percent for some durable press applications.

Page 11: Resin Finishes on Cellulosic Fabrics

Change in shade towards yellow end of the spectrum occurs with all crease resistant finishes

There is a possibility that the formaldehyde liberated at the time of curing resins can get retained by the fabric

Control over the levels of formaldehyde exist, as they are permitted only in Certain garments and not for children’s clothes.

Page 12: Resin Finishes on Cellulosic Fabrics

Types of ResinsResins mainly fall in to two groups

Deposition type of resinsCross linking type of resins

Deposition type of resins: No reaction takes place between the fibre and the resin

They include: Phenol formaldehyde Resins CondensationAlkyd Resins

Ketone ResinsMostly used: Vinyl Resins Polymerisation

Dimethylol urea

Page 13: Resin Finishes on Cellulosic Fabrics

Deposition type of finishes are applied in soluble formon the surface of the cotton fabric using padding mangles with an acid catalyst and dried.

The same finish if cured will become a cross-linking type of resin

Deposition type of resins give stiffness to the fabric and some extent of crease recovery, which is lower than cross-linking type.

Page 14: Resin Finishes on Cellulosic Fabrics

Cross-linking type of resins chemically react with the fibresubstance and cross-link with the fibre molecules

These are much durable and better than deposition type

They are also known as N-Methylol compounds

Though these compounds are referred as resins, only calling themas resin precondensates is correct. The resin precondensates are furtherpolymerised to form resins

Cross-linking type of resins used for crease resistant finishes:

• DMU – Dimethylol Urea• DMEU- Dimethylol Ethylene Urea• DMDHEU- Dimethylol dihydroxy ethylene urea• TMM- Trimethylol melamine

Page 15: Resin Finishes on Cellulosic Fabrics

Problems with resin precondensates containing –NH groups (DMU, TMM)

NH groups are susceptible to hypochlorite solution.When resin treated fabrics are taken for laundering with chlorine based agents, chlorine gets cross-linked with NH groups forming –NCl and results in loss of crease resistance. It is known as Chlorine retention.

The chloramines thus formed will result in yellowing of fabrics

Excessive cross links causes harsh feel besides reducing tear and tensile strength

Page 16: Resin Finishes on Cellulosic Fabrics

Normally cross linking agents (urea formaldehyde)are applied by Pad- Dry- Cure method.

Steps involved in Resin finishing

• Preparation of fabric for better penetration of liquor (Scouring and Bleaching)

• Impregnation of the fabric in the prepared resin solution by two bowl or three bowl padding mangle with an expression of 80% at room temp.

• Drying in stenter with min. tension at 70-80o C

Page 17: Resin Finishes on Cellulosic Fabrics

• Curing at higher temp.of 120-150oC for 2-5 min by using dry heat to polymerise the resin and cross link to the molecular chains.

• Washing and soaping in open width or rope form in a dilute solution of soap and soda ash to remove the unfixed resin and also to neutralise the residual acidity • Softening by rinsing the material in water containing softening agents • Drying on stenter

Page 18: Resin Finishes on Cellulosic Fabrics

Resin Treatment and Curing

Resin treatment and curing of fabric are done by one of two processes Pre curing or Post curing

Pre curing: The most frequently used resin treatment process and involves treating and curing the fabric in the textile finishing plant. The fabric is sold to an apparel manufacturer in a completely finished state

The fabric is set in a flat position and used for itemsthat do not require extensive shaping ex. Blouses, Shirts, Dresses, Bed sheets, Curtains and Draparies.

Almost all pre cured fabrics are blends of cellulosic fibres and polyester as polyester compensates for the abrasion resistance and strength loss, the celluloseundergoes during the resin application

Page 19: Resin Finishes on Cellulosic Fabrics

Pre cured fabrics may sometimes be used for shaped garments ( such as pants with a center crease). The stitched items are then pressed with high temperature pressing equipment called hot-head pressers.

This equipment reaches temperatures that heat set the polyester component of the fabric. The results, although satisfactory are less effective than those resulting from thePost cure method.

Page 20: Resin Finishes on Cellulosic Fabrics

Post Curing: Post curing involves curing the resin on an already sewn and completed garment.

There are two types of post curing processes.

1. The textile finishing plant applies and dries the resin, but does not cure it. (cotton polyester blend)

The fabric is sold to an apparel producer in an uncured but sensitized state. It is sewn into garments and then pressed at low temp. to impart creases in pants, sleeves, pleats and other shaping.

The entire garment is then cured as an individual item of clothing.

post cured durable press garments retain their wrinkle free and crease retentive properties better than the pre cured type.

They may retain these properties through 40-50 launderings.

Page 21: Resin Finishes on Cellulosic Fabrics

2. The process is performed on 100% cotton fabrics.

Apparel products made by this process are usually described as wrinkle-free, wrinkle-resistant, no iron, or simply WR.

The fabrics used, the methods of application and results obtained are different from those of the durable press method described above.

To reduce the resin -induced loss of abrasion resistance and tensile strength of cellulose, specially constructed fabrics and unique finishing treatments are required

The fabric used is of long-staple cotton, tightly twisted yarn and tightly constructed.

Page 22: Resin Finishes on Cellulosic Fabrics

The resin finish consists of following modified post curing process.

1. The completely sewn but untreated garments are first immersed in, or sprayed with a resin solution and then semidried and pressed at warm temperatures while still damp.

2. Curing of the garment follows quickly after pressing in speciallyconstructed conveyor ovens.

This method minimizes deterioration of cellulose because relatively low add-on of resin is required.

The resultant product has a medium-soft hand often enhanced with silicon softeners as compared to the firm hand and somewhat stiffer polyester-cotton post cured garments.

Page 23: Resin Finishes on Cellulosic Fabrics

The wrinkle free/no-iron condition is retained for about 12-15launderings, rather than the 40-50 launderings to be expectedwith the cotton polyester durable press method.

Despite the lowered performance and higher costs (premier grades of cotton fibres and tighter construction of fabric), the wrinkle free types are preferred by many consumers because of the greater comfort and softness provided by the 100% cotton fabric

Most 100% Cotton wrinkle-resistant fabrics are used for casual wear and sports wear such as pants and shorts. The process is also used for men’s dress shirts, skirts, blouses and sleep wear.

Page 24: Resin Finishes on Cellulosic Fabrics

Possible effects of Resin treatment on cotton fabric:

Property Effect on resin treatment

Crease recovery ImprovedWash shrinkage DecreasedStiffness IncreasedAbrasion Resistance LoweredTear strength LoweredHandle HarsherEffect on dyes Tends to yellowEnvironment FormaldehydeBleach Cl retention

Page 25: Resin Finishes on Cellulosic Fabrics

Advantages:

It improves the Crease Resistance and Crease Recovery Property

It reduces the shrinkage of the fabric during laundering

It imparts a smooth and quick drying property

It improves resilience, handle and draping qualities

It improves the weight and dimensional stability

Page 26: Resin Finishes on Cellulosic Fabrics

It increases the strength of Rayons in both wet and dry state

It gives resistance to degradation by light and laundering

It improves the fastness to light and washing of many dyestuffs

It prevents the intermolecular slippage in the fibre core

It becomes partially water proof and rot proof

Page 27: Resin Finishes on Cellulosic Fabrics

Disadvantages:

It decreases the tensile strength and tear strength

It decreases the abrasion resistance

It gives an unpleasant odor

It gives unwanted harsh and stiff feel

It turns the fabric yellow after chlorine bleaching

Incorporation of proper softener and catalyst in the pad bath can reduce the loss in the above mentioned properties of the fabric

Page 28: Resin Finishes on Cellulosic Fabrics

Thank you