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  Jute/Cotton blends for winter wear

Fabrics constructed with jute-cotton blended yarns are best suited for clothing used for winter wears, provided necessary chemical treatments are given to modify their chemical properties, discloses B Sathish Babu.

Textile technologists have been constantly concentrating on the retrieval of alternative for what had done a lot of hazards to the environment. Fibres produced by synthesis of chemicals posses non-degradability when dissipated from usage though they have been comfort fully used as clothing. There is a profound importance for finding bio-degradable materials that could compete.

Finding a new material with desired properties, it is easier to explore into a deep insight of what is available, the natural fibres. Almost all natural fibres are biologically degradable and possess excellent wearable properties. Researches are being carried out in two phases, one to find high tech materials for advanced applications and the other to enhance the properties of nature gifted materials to common usage.

Wool is the well-known protein fibre utilised for the production of casuals in western countries, which has cold climatic conditions. In Asian countries it is used as the material for sweaters to be used during winter season. The costly prices of wool sweaters are well-known to everyone.

Acrylic is a synthesised fibre, which possesses properties similar to wool and is extensively used for the manufacturing of sweaters in a cost effective manner. This could give a vast production with reduced market costs.

Still usage of acrylic is common because of its easy care. The thermal maintenance of the fibre is also excellent so that it could give warmth of above what had been expected. Acrylic being a man-made polymer fibre it also suffers the same non-biodegradable problem. This would become a serious issue in near future and works to find materials that could replace this are done at a least magnitude.

Natural fibres have been gaining momentum in current industrial situation because of their desirable qualities and abundance in quantity. Also they have to be processed both mechanically and chemically to improve their appearance, feel and other properties which would consume a lot in the end-product price in the market. Methods are to be developed to compete their usage in an economical way with synthetic materials.

Jute has always been a fibre of importance because India has been producing it in an abundant amount in the world next to Bangladesh. Research papers have been published that explores the desirable properties such as high strength, fibre length, tenacity, etc.

Jute also possess a certain degree of thermal retention that can be improved, which makes it suitable for the production of much cost effective winter wears. The main limitation of the fibre that inhibits its usage is its brittleness which yields high haired yarn when spun and also gives harsh feel when worn.

Improvements made in this concern could gain a good gathering in near future and hence bringing the market compatible natural products that would satisfy the expected positive impact on environment. The aim is:

* To produce knitted fabric with the commercially available jute cotton blended yarn.
* To chemically modify the fabric in order to improve its properties and appearance.
* To test the process modified fabric for its crease resistance, drape, bursting strength and thermal conductivity and to interpret the results.
* To sew the garment with the fabric to assess its wear comfort.

Materials & methods
Knitting
The fabric is knitted in single jersey knitting machine with the following particulars:


Chemical processing
In order to modify the surface characteristics of the jute/cotton blended fabric, it is subjected to various treatments with chemicals to improve the feel and hand without affecting other desirable properties. For finding an appropriate concentration of chemicals, four samples have been processed under various conditions of concentrations and treatments. For ease of identification, the samples are designated as follows:


Based on the previous studies made it was reported though woollenisation enables lateral swelling of fibres, a great strength loss occurs due to the excessive removal of pectin that acts as the binder molecules. Hence, it is important to asses the properties and feel of fabrics treated. So, the samples are to be processed in two categories one with woollenisation and the other without that.

Washing

The fabric samples are initially soaked well with detergent in order to remove the contaminations. Raw jute during retting process undergoes biological degradation of binding materials and the residue is in the dispersed form within the molecules of jute. Also it is composed of micro dust particles that inhibit the process in advanced stages. The samples are weighed initially and then wetted before impregnating in the wash bath. The samples are processed with following concentrations of liquors:


Scouring

Scouring is the process of removing the foreign contaminants in the material such as grease, stains etc and is accomplished with Caustic soda in common, for cotton fibres. Jute fibre is very sensitive to caustic soda and major implications such as structural variations, drop in tensile strength are reported. Hence, utilisation of strong alkali is eliminated and mild alkalis such as sodium carbonate, potassium carbonate are utilised for scouring process of jute/cotton blends.

Initially, the fabric samples are weighed in order to assess the Dimensional Stability of the material when subjected for various chemicals. The samples are processed with parameters as mentioned below:

Dehairing
The main limitation of jute and its blended fabrics in the very high magnitude of protruding hairs on its surface, which retards its comfort hand properties and also its usage for apparels. Singeing by means of mechanical methods ought to impart ash particles that affect the appearance of fabric.

The dehairing process is done at three phases with Oxalic acid, sodium hypochlorite and hydrochloric acid. Oxalic acid treatment is reported to be the effective hair removal process and further with other mild treatments enhances the feel.

Hence the samples are subjected for appropriate chemicals for dehairing as reported earlier by researchers. The samples are subjected for consecutive acid treatments for efficient removal of hairs under various parameters.

The fabric treated with oxalic acid is washed with cold water and is subjected for sodium hypochlorite soaking with following parameters.

Woollenisation
It is the process of subjecting jute cotton blended material with strong concentrations of Caustic Soda, inferred with the occurrence of lateral swelling and longitudinal shrinkage, as a result of which the fibre is softened to touch and develops a high degree of crimp. It was reported that the woollenisation effect is enhanced with increase in concentration and decrease in temperature but a pronounced decrease in weight up to 15% and in strength of about 40%. Also the colour of the fibre changes from pale yellow to brown. The optimised concentration that can be used is derived from various articles and the parameters are set.

The degree of Woollenisation increases with decrease in the bath temperature and is efficient under cold conditions. However, the strength loss becomes excessive under these conditions. One sample in each blend is subjected for woollenisation treatment, under specified parameters to assess the quality of woollenised and non-woollenised fabric.

Bio-polishing
Applications of biotechnology in textile processing industry in the form of enzymes is gathering momentum in recent days due to their reliability, specific activation conditions, reusing if effluents and single bath processing methods. Bio-polishing is found more appropriate in improving the surface characteristics to bring out the soft feel and comfortness during wear. Literature comprising Enzymatic Polishing of Jute is limited and is similar to that of cotton and the concentration can be increased for more favorable results as suggested by Resil Chemicals. Thus the parameters are set as follows:

Buffer solution
While processing substrates, maintenance of specified Hydrogen ion concentration and Temperature is of paramount importance because enzymes tend to act on the substrates only under these specified conditions. As mentioned above, the PH should be maintained acidic; An acidic buffer solution is prepared with Acetic acid in a concentration of 1% for usage as liquor with following parameters. The PH is monitored throughout the process with PH paper and acid is further added to maintain the same.

Enzyme denaturing
After 45 minutes of processing the temperature is raised to 65oC and processed for 10 minutes for de-activating the enzyme. The samples are then cold washed and dried.

Dyeing
Similarities in the properties of jute and cotton and their constituent material make it possible to apply the same dye for them. All dyes that are applicable to cotton are also accepted by jute and in this consideration, hot brand reactive dyes are used due to their shade depth and fastness properties.

The samples are dyed with the following recipe in open bath beaker dyeing machine.

Sodium chloride salt is added in two weights after every 20 minutes dyeing for better exhaustion of dye into the fibres. After dyeing the samples are subjected for hot and cold wash and finally dried.

Observations with the samples
It was observed that the feel of the woollenised samples, when dehaired and consecutively singed provides desirable results. Other non-woollenised samples are also good but still the feel and strength based parameters are lesser than that of woollenised one.

Hence for processing the fabric in bulk for garmenting purpose, the woollenised recipe is used and the fabric is subjected for various tests to obtain its technical properties.

Testing
There are four tests to be conducted on the original and processed jute cotton fabric to assess its performance. They are:
* Crease recovery
* Drape
* Bursting strength
* Thermal conductivity

Crease recovery
This test could be done with the disc type equipment called Shirley Crease Recovery tester. The fabric has to be cut for the specified dimensions, to be kept under specified pressure and to be mounted between the clamps. The angle to which the sample recovers is noted. The specified conditions to conduct this test are

* Test room temperature - 27ēC
* Test room RH% - 65%
* No of specimens - 3 ( wale and course wise )
* Specimen dimensions - 2" x 1"

Drape
This test is conducted in equipment called Drapemeter, which consists of two round discs. The large disc to prepare samples and the shorter one to mount the samples. It has a light source from bottom to project the area occupied by the samples. The projected area is marked in a paper of uniform gsm and is weighed. Then the drape coefficient is calculated as follows:

F = (Ws – Wd)/(Wd – WD)
Where,
Ws - Weight of actual projected area
Wd - Weight of specimen
WD - Weight of supporting disc
* Test room temperature - 27ē C
* Test room RH% - 65 %
* No of specimens - 3
* Specimen dimensions - 10" circular

Bursting strength
The bursting strength can be found out by following the procedure mentioned in IS 1966 – 75. The specified test conditions are as follows:

* Test room RH : 65 ą 2 %
* Test room temp : 21 ą 1OC
* No of specimens : 6

Thermal conductivity test
The Thermal Conductivity Coefficient of the jute cotton fabrics are evaluated using two disc tester at the Physics Laboratory, PSG College of Technology.

The fabric is mounted between the two discs and the upper disc is heated with hot water. Thermometers at each disc are noted keenly so that the time for every centigrade fall is obtained with a stop clock. To get the thermal conductivity coefficient the following calculations are made:


Where,
K - Thermal conductivity
M - Mass of the disc (800 gm)
S - Specific heat capacity of the material of the Brass disc ( 370 J/Kg/k)
R - Rate of fall of temperature
H - Thickness of lever disc (1 cm)
D - Thickness of fabric
R - Radius of lower disc (5.5 cm)
A - Area of cross-section of fabric
T1 - Upper disc temperature (OC)
T2 - Lower disc temperature (OC)

Result and discussion
This chapter deals with the results of various tests conducted for the chemically modified jute cotton blended fabrics.

Crease resistance of modified jute cotton blends:
Crease resistance angle for processed fabric in 40/60 and 50/50 blend decreases by 28.39 % and 31.41% respectively than that of original fabric. Decrease in crease resistance improves the creases in fabric that imparts smooth feel.

Drape coefficient of jute-cotton blends
Weight of supporting disc, Wd : 5.67
Weight of specimen, Wd : 2.08

Drape co efficient of 40/60 blend increases by 21.66% compared with original whereas in 50/50 blend it is only 3.1% that of original. This increase enables the fabric to be best suited for apparel sewing.

Bursting strength of jute-cotton blends
Bursting strength of the 40/60 blend decreases by 14.02% with original whereas it gets a pronounced increase by 10.44% in 50/50 blend when compared with the unprocessed original fabric.

Thermal conductivity of jute cotton blends
Thermal conductivity of 40/60 and 50/50 blends decrease by 18.75% and 16.67% respectively when compared the with original. This decrease in the conductivity enhances the thermal retentivity of the jute cotton fabric, which is the prime required factor for winter wears.

Wear study
The subjective wear trial technique is used for the assessment of comfort and hand related properties of the garment constructed wit the modified jute cotton blended fabric.

Eight persons are trained to assess the fabric parameters initially and by conducting a model hand test method, three persons whose results were within the acceptable limits are chosen for the wear study.

The persons were asked to wear the garment for 15 minutes inside a room with controlled temperature of 23.C and were given evaluation sheets to obtain the personal measurements of comfort and other properties.

The subjects were directed to carry their daily activity in the room and for every 5 minutes they are questioned about the parameters and the reports were established.

The results obtained were calculated in figures for interpreting purpose and comparison charts were drafted to know the overall performance of the garment.

Conclusion
Based on the results and discussion, the following conclusions are made:

* Chemically modified fabrics account for approximately 15% of decrease in its thermal conductivity when compared with original fabric. This decrease in conductivity enhances the thermal retention characteristics and makes it quite suitable for winter season.
* Crease resistance angle for processed fabric in 40/60 and 50/50 blend decreases by 28.39% and 31.41% respectively than that of original fabric. Decrease in crease resistance improves the creases in fabric that imparts smooth feel.
* Drape coefficient of 40/60 blend increases by 21.66% compared with original whereas in 50/50 blend it is only 3.1% that of original. This increase enables the fabric to be best suited for apparel sewing.
* Bursting strength of the 40/60 blend decreases by 14.02% with original whereas it gets a pronounced increase by 10.44% in 50/50 blend when compared with the unprocessed original fabric.
* Thermal conductivity of 40/60 and 50/50 blends decreases by 18.75% and 16.67% respectively when compared with the original. This decrease in the conductivity enhances the thermal conductivity of the jute cotton fabric, which is the prime required factor for winter wears.
* The wear study report shows a pronounced decrease in the wear parameters such as comfortness, irritation, rashes and smoothness on increasing time scale and a rapid increase in warmthness.

Thus, through this research the author conclude that fabrics constructed with jute cotton blend yarns are best suited for clothing used for winter wears, provided necessary chemical treatments were given to modify its chemical properties.

Future scope of the project
* Finer yarns can be used for the construction knitted fabrics to impart the good hand to the fabric.
* More advanced chemical modifications like Acetylation, Methylation, etc can be investigated to improve the structural and comfort based properties of the blends.
* Usage of jute blended fabrics for other seasons can also be encouraged and necessary treatments and finishes can be studied.

Acknowledgement
The author expresses his sincere thanks to The Management of PSG College of Technology and Polytechnic College for providing the necessary infrastructural facilitiy for carrying out this research work successfully;

To Frontier Knitters, Tirupur, for providing the raw material and taking much effort in knitting the jute/cotton blended fabric;

To Resil Chemicals (P) Ltd, Tirupur for providing the Enzyme for Bio-polishing;

To SITRA for providing the testing facility to complete the research in time.

References
1. A Cavaco Paula et al: Textile Processing With Enzymes, Woodhead Publishing Limited, Cambridge, 2003
2. Amarjit S Basra: Cotton Fibres: Developmental Biology, Quality Improvement and Textile Processing, Food Products Press, New York, 1999.
3. Robert R Frank: Bast and Other Plant Fibres, Woodhead Publishing Limited, Cambridge, 2005, pp 24 – 92.
4. B P Saville: Physical Testing of Textiles, Woodhead Publishing Limited, Cambridge, 2000.
5. Premamoy Ghosh: Fibre Science and Technology, Tata Mcgraw – Hill Publishing Company Limited, New York, 2004
6. Hassan K Sreenath et al: Enzymatic Polishing Of Jute/Cotton Blended Fabrics, Journal Of Fermentation And Bioengineering, Vol 81, No. 1, 2006, pp 18 – 20.
7. S Amsamani et al: Jute Cotton T-Shirts For Cold Nights, Indian Textile Journal, May 2005, pp 93 – 95.
8. Sankar Roy Maulik: Chemical Modification of Jute: Treatment with Swelling Agents, Asian Textile Journal, July 2001, pp 99 – 105.
9. J Jeyakodi Moses et al: Effect Of Thermal Properties on Textile Fabrics Suitable for Winter Season, Man Made Textiles In India, Nov 2003, pp 31 – 34.
A K Samanta et al: Effect of Selective Pretreatments and Subsequent Mixed Enzyme Treatment on Properties of Jute Cotton Union Fabric, Indian Journal of fibre and Textile Research, Vol 30, December 2005, pp 451 – 467.

Note: For detailed version of this article please refer the print version of The Indian Textile Journal September 2010 issue.

B Sathish Babu
Lecturer, Department of Textile Technology,
PSG Polytechnic College, Peelamedu,
Coimbatore 641 004.

published September , 2010
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