Introduction


Resin or wrinkle free finishing is widely usedin the textile industry to impart wrinkle-resistance to cotton fabrics andgarments. Considerable loss in strength and abrasion resistance of the finishedfabrics has been a major concern for the industry. Enhancing dimensionalstability and wrinkle resistance with resin finishing of cotton has constantlybeen correlated with lower abrasion resistance and tear strength. The strengthof the fibre depends on how much the cross-linked chains can still be mutuallydisplaced under tension in order to sufficiently resist the applied load. Therigid cross-links that are formed with the DMDHEU obviously prevent the redistribution of stress by preventing movement within the fibre microstructure. Thecross-linking of cellulose molecules with these relatively rigid cross-linkscauses stiffening of the cellulosic macromolecular network and fibre embitterment,thus dropping the mechanical strength of the treated cotton fabrics. These samemechanisms are responsible for reduced mechanical properties of the fibresurface, thus leading to strength loss. Fibre surface property alteration, suchas through the use of softeners, has been shown to play an important task inminimising strength loss.


Objective


The mixture of inadequate scratch resistance andrelatively severe tensile and tear strength loss has been a major disadvantagefor resin finished 100% cotton fabrics. The objectives of this work are to investigatethe cause and mechanism of loss in abrasion resistance of cross linked cottonfabrics; relationships between the molecular structure of cross-linking agentsand their effect on the mechanical properties of cross-linked textilestructures; and develop a technology for improving the tear strength of resin finishedcotton fabrics by adding special silicones.


Tear and Tensile Resistance


An overwhelming majority of durable press finishing agentsused today are formaldehyde based reagents, such asdimethyloldihydroxyethyleneurea (DMDHEU) and modified DMDHEU, with magnesiumchloride as a catalyst.


The following summarises some of the important aspects so far:


1.    The catalysts used for DMDHEUsystems, such as magnesium chloride, cause degradation of cellulose, thus reducingthe tensile and tear strength of cotton fabric. The magnitude of fabricstrength loss is affected by temperature, time, and concentration of thecatalyst. Fabric strength loss also depends on both the cation and anion of thecatalyst. An activated catalyst system, which includes an organic acid, causesmore severe fabric tensile strength loss.


2.    Tensile strength loss of cottonfabric treated with DMDHEU is due to both the cross-linking of cellulose andthe degradation of cellulose caused by the catalyst. Because a catalyst systemplays such an important role in influencing the strength loss of cotton fabricscross-linked by DMDHEU, the selection of the catalyst system and itsconcentration is crucial for optimising the tensile strength retention of thefinished fabrics.


3.    DMDHEU can be removed from the finishedfabric by using an alkali treatment, as evidenced by the decrease in wrinklerecovery angle with removal. The fabric strength gradually increases as thehydrolysis of the cross-linked fabric progresses, indicating that the fabricstrength loss due to cross-linking the cellulose molecules is reversible andthat it can be restored by removing the cross-links. The remainder of thestrength loss, which has been described as being due to acid-induced de-polymerisation,is permanent and is not reversible upon hydrolysis of the cross-links.


 

 



Experimental


Materials: 100% cotton shirting fabric, GSM of 133 is used for applications.


Application by padding


Liquor pick up: 70%

pH: 4-5

Dry: as usual

Cure: 150C for 3 minutes



Guideline Recipes


1.  Shirting Fabrics

 

     Commercial DMDHEU: 40-60 g/l

           MgCl2: 8-12 g/l


2. Resil Innocelle FSS: 0.5-3%


3. Resil Ultrafab EMS: 0.5-3% + Resil Innocelle FSS: 0.5-3%

4. Resil LFR                   : 40-60 g/l

          MgCl2                       : 8-12 g/l

          Resil Ultrafab EMS     : 10-30 g/l

          Resil Innocelle FSS v  : 10-30 g/l



Effect of Amino Silicone on the Strength Properties of Cotton Shirting Fabric


In order to maintain the desired physical properties of finished fabrics and garments, fabric softeners are frequently used in resin treatment. In a conventional process polyethylene is the most commonly used additive in durable press finish formulations. Low-amino modified polysiloxane gives better strength improvement than polyethylene emulsions.




 



Effect of Combination of Low-amino Modified Silicone and Semi-macro Silicones on the Strength Properties of Cotton Shirting Fabric


Low-amino modified polysiloxane combined with a blend of amino modified polysiloxane and hydroxy terminated polysiloxane show better strength improvement than polyethylene emulsions or amino silicones.




Effects of Amino Modified Polyethylene Based Polymer Silicone Softeners and Semi-macro on the Mechanical Properties of Cotton Shirting Fabric Cross-linked by DMDHEU




Strength loss%

 


CRA




DP RATING



Conclusion


Results indicate enhancement in fabric resiliency and softness as well as decrease in fabric strength. The use of low amino modified polysiloxane combined with a blend of amino modified polysiloxane and hydroxy terminated polysiloxane as an additive minimises strength loss of the cotton fabric with improvement in softness because of treatment with resin and catalyst, without creating negative effects on the wrinkle resistance of the fabric.



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