By: Dr. G. S. Nadiger*, Dr. H. L. VijayKumar**, Prof. Y. Vrashabhendrappa**,
S. N. Ramesh** and Aravind Kamthane*

*Textiles Committee, Ministry of Textiles, Govt. of India, Mumbai
**Bapuji Institute of Engineering and Technology, Davangere.

1.0 Introduction

India is the second largest producer of Mulberry and Non - Mulberry Silks, next to China. It is the only country, which produces golden yellow Muga Silk in the world. Among the Wild Silks, the Eri Silk accounts to 78.4(%) and its contribution to the total raw silk production in the country is 7.3(%) next only to Mulberry Silks. Eri culture is mainly practiced in North Eastern regions of India. The states of Assam, Nagaland, Maghalaya and Manipur account nearly 98(%) of Eri Silk produced in the country as �Endi�. The area of bordering Assam and Meghalya is considered to be the home for Eri Silkworm. It is also cultured in the states of Bihar, Orissa, West Bengal and Andhra Pradesh on a smaller scale. It is observed that there is vast scope for development of Eri culture on a large scale not only in traditional states but also in non-traditional states like Andhra Pradesh, Gujarat, Rajasthan, Punjab, Karnataka and Uttar Pradesh.

Eri Silk possesses excellent thermal properties and offers tremendous blending possibilities with other natural fibres like other Silks, Wool, Cotton, Jute and Synthetic fibers. The entire Cocoon production in Eri sector is available for Spinning only due to open nature of Cocoons. Development of new products and diversification in the use of available material of Eri Silk offers a lot of opportunities for innovations.

2.0 Eri fibre and its potentialities

Eri Cocoons are open mouthed; they cannot be reeled into raw filament yarn, but are spun like Cotton. Eri Silk has certain excellent textile properties, which are unique in many respects such as fineness, density, and cross sectional shape, surface properties etc. Eri Silk is finer than Muga and Tasar Silk and even softer than Mulberry Silk. Although Eri Silk possesses positive features, imparting proper twist is required to maintain dimensional stability to the fabric especially for garments.

Major portion of the Eri Cocoons are used on traditional devices like Takali (Hand Spindle) and Spinning wheels by pulling the fibre, imparting twist to it simultaneously to form the yarn. The coarse yarn so produced is normally used for production of traditional materials mainly for domestic use. The survival of handloom Silk industry with special reference to Eri silk depends primarily on the diversification of end products to meet the National as well as International demands.

Manipulating at various stages viz., Yarn, Fabric and Garment development can bring about diversification in the Eri products. Introduction of quality Silk with proper twist gives uniform texture for production of fabric. Eri Silk is the softest and warmest amongst all the Silks and has immense potential for commercial exploitation by making finest quality Blankets, Sweaters and Suiting materials. Besides, there is a good scope for Eri Silk to be used with other fibres to develop good blended materials.

3.0 Current status of processing of Eri Silk

The Eri Cocoons are open-mouthed and do not contain continuous filament form and hence are not reelable. They form a good raw material for spinning like Tasar; the cocoons vary in colour, size and softness. The soft cocoons are better for mechanical spinning and the bigger cocoons for hand spinning. The cleaning of cocoons becomes necessary in order to remove non-fibrous materials (Pupae and Moulted Skin), which get entangled with Silk fibre and for easy movement of the machinery used for spinning. So, cleaning of cocoons is pre-requisite for spinning [(Jolley) et al 1979 and Sarkar, 1980].


9.4 Tensile properties

9.4a Silk / Eri Polyester


From the results (Table 17), it can be seen that there is no major change in warp way tensile strength of all the fabrics of Silk / Erisilk + Polyester which may be due to presence of pure Silk in warp way. Weft way tensile strength is least in Mulberry Silk (100%) compared to Mulberry Silk / Erisilk + Polyester. This is because in former, fine denier Silk is used. In case of Mulberry Silk / Erisilk + Polyester, the weft way tensile strength increased as the polyester content increased. This may be due to stronger Polyester fibres in the weft yarn.

9.4b Cotton/Eri Polyester

The tensile strength of Cotton (100%) in warp way is more when compared to Cotton - Erisilk + Polyester. It may pointed out that the count of weft yarn in cotton (100%) is coarser than that of Erisilk/ polyester. In case of Cotton / Erisilk + Polyester, the warp way tensile strength is found to be slightly higher in case of fabric which contained more (%) of polyester. Weft way tensile strength of Cotton / Erisilk + Polyester is more when Erisilk (%) is less. It is also found that weft way tensile strength with Cotton weft is almost similar to Erisilk/ Polyester weft, which may be due to the double and coarser Cotton yarn used.

9.5 Bending Properties

9.5a Flexural rigidity


It can be seen from The Table 17 that warp way flexural rigidity of Mulberry Silk / Erisilk+Polyester is similar and there is slight decrease in flexural rigidity of fabric when the polyester content in the weft increased. Flexural rigidity in weft way is found to decrease when the Eri Silk content increased. This may be due to the fact that Eri Silk fibres are stiffer than Polyester fibres. It is also found that flexural rigidity of (100%) Mulberry silk is less when compared to Mulberry Silk / Erisilk + Polyester, which is due to very fine Silk yarn used for both warp and weft.

9.5b Cotton/Erisilk + Polyester

There is no significant difference in warp way flexural rigidity for all the fabrics. A slight decrease in flexural rigidity is found with the fabrics that have weft with more Polyester content. Weft way Flexural rigidity is more in (100%) Cotton, when compared to Cotton / Erisilk + Polyester because of stiffer Cotton fibres. As Polyester percentage increased, the flexural rigidity decreased, as Polyester fibres are more flexible when compared to Eri Silk.


It can be seen from the Table 15 and Fig 7 that as the Eri Silk percentage increased the tenacity and percentage strain decreased. This may be due to the fact that Eri Silk fibres being weaker and have low elongation percentage at break than Polyester fibres. It can also be seen that the CV (%) of both tenacity and elongation increased as Eri Silk content increased. This is again due to the fact that Eri Silk fibres are natural fibres and length and fineness variation is high.

9.3 FABRIC PROPERTIES


9.6 Fabric shrinkage

Table 18 gives the shrinkage of fabric samples having different composition. Shrinkage (%) of (100%) Cotton and (100%) Mulberry Silk is more than the rest of the fabrics. In warp way, there is marginal difference in the shrinkage (%). As the Polyester content in the weft yarns increased, the shrinkage of fabrics in weft way decreased.

9.7 Crease recovery

From the Table 19, it can be seen that (100%) Cotton and (100%) Mulberry Silk showed minimum crease recovery angle in both warp and weft direction. Warp recovery angle slightly increased when Eri Silk / Polyester is used as weft in both types of fabrics. Weft crease recovery angle increased as Polyester content in the weft increased.

9.8 Drape coefficient

Drape coefficient data (Table19) gives that (100%) Cotton fabrics have least drapability and (100%) Mulberry Silk and Silk / Erisilk + Polyester have better drapability. When Eri silk + Polyester is used as weft in place of Cotton, the drapability increased and the drapability is better for the fabric having more Polyester content.

10.0 CONCLUSION/OBSERVATION

Based on the studies, the following conclusion/observations are made.The Eri Silk / Polyester blend up to 40:60 ratio can be effectively spun on Existing Ambar Charka located in Khadi Institutions in and around Davangere. The above Charkas are used to spin 20s and 30s Nm cotton and Polyester / Cotton yarns. As the Eri Silk percentage increased, the tenacity of the yarn reduced. As the Eri Silk percentage increased, the moisture regain (%) in the yarn also increased which in turn improved comfort property of the fabrics.As the Polyester content reduced, there is a small reduction in the tensile strength of the fabric in weft direction.Warp way flexural rigidity of Mulberry Silk / Erisilk + Polyester is almost same and there is slight decrease in the Flexural Rigidity of fabric as the Polyester content in the weft increased.


As the Polyester content in the weft yarns increased, the shrinkage of fabrics in weft way decreased.The Crease recovery angle of Eri Silk / Polyester fabrics is better than the control samples of 100(%) Cotton and 100(%) Silk fabrics. As the percentage of Polyester increased the crease recovery angle also increased.Drapability of 100(%) Silk fabric is better and the 100(%) Cotton fabric exhibits poor drapability. Eri silk and Polyester blended yarn showed an improvement in drapability when it is woven with Cotton yarn. The increased in the Polyester content in the yarn lead to better draping quality when compared to Eri Silk. Blending of Eri Silk with Polyester improved the mechanical properties and also comforts properties of the fabrics. The 40:60 Eri Silk / Polyester blend ratio appear to give optimum properties both at yarns and fabrics.

Acknowledgement

We are very thankful to Khadi and Village Industries Commission (KVIC), Mumbai for sponsoring this project.

References

Bankim Kumar Mishra (2003), Design Development and Product diversification, Indian Silk 41, pp. 47- 48

Beera Saratchandra (2003), A Thought for development of Eri Culture in India, Indian Silk, Volume 41, pp. 25 � 28.

Y.Debaraj, B.K. Singh, P.K. Das and N. Suryanarayana (2003) Payam: An Evergreen Host Plant of Eri Silkworm, Indian Silk, Volume 42, pp. 5 � 6.

Ghosh.S.S, Sengupta.D, Hukkeri.S.M, Sreenivasa and Thangavelu.K (2000) �Lessons on Tropical Tasar� pp.52-94.

J.V. Krishna Rao, (2003) Initiatives, Experiences and Strategies, Indian Silk, Volume 42, pp. 14 � 17.

P. Jayaprakash, B.V.S. Rao, K.Venkateshwar Rao, J.V. Krishna Rao and B.R.R.Pd. Sinha (2003), Reintroduction of Eri Culture in Andhara Pradesh Hopes Galore, Indian Silk,Volume.41, pp.19 � 20.

Kariyappa, .Umesha and T.H.Somashekar(2003)CSTRI motorized-cum-pedal operated spinning machine, Volume.42, pp. 37 � 40.

M.N. Ramesh and Mukund V.Kirsur (2003), Creativity Sells, Indian Silk, Volume.41, pp. 43 � 45.
Rangam Rajkhawa (2000), Structure Property Co-relation of non-mulberry and mulberry silk fibres, International journal of wild silks moth and silk. Volume.5, pp. 287 � 298.

N.Suryanarayana, P.K. Das, A.K. Sahu, M.C. Sarmah and J.D. Phukan (2003), Recent Advances in Eri Culture, Indian Silk, Volume.41, pp. 5 � 12.

T.H. Somashekar (2003), Recent Advances in Eri Silk Spinning,
Weaving and future prospects,Indian Silk, Volume. 41, pp. 49 � 52.

B.Sannappa, M. Jayaramaiah, R. Govindan and K.P. Chinnaswamy
(2002), Advances in Eri Culture, pp. 1 � 9 and 108 to 110.

Waste Silk Spinning by Hollins Rayner

Silk Production, Processing and Marketing by Mahesh M.Nanavaty.
Hand Book of Silk Technology by Tammanna N.Sonwalkar.


About the author:

Dr. HL Vijaya kumar completed his Ph.D from Anna University, Chennai . His area of interest is Knitting in particularly Silk & their blends. He has published more than 20 papers in national & international Journals. Undertaken many projects with National & International funding agencies & Industries. He has traveled widely to understand the Sector. He worked with State & central Govt. agencies for the development of textile sector. Organised more than 15 national & state level seminars & symposia�s . Worked in many University bodies as chairman to frame the curriculum for textile & fashion courses. At present guiding 5 students for their doctoral degree. 23 years worked in Engg. Institute as lecturer, Asst Professor, professor & Head of textile department. At present working as principal at Army Institute of Fashion & design , Bangalore. The students projects guided by him bagged many national & state awards. Because of his contribution to the overall growth of the textile industry in India, Indian society for Technical education New Delhi , presented the UP govt. National award during the year 2005.

Address: Army Institute of Fashion & Design, ITI, B Area Sheds, Dooravani Nagar
Old Madras Road, Bangalore 560016, Karnataka, INDIA

Mobile: 09448372421 , Phone: 080- 25617309,25617559
Email: hlvijaykumar@hotmail.com


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The cocoons used for spinning are stifled to preserve them for longer period without deterioration. Stifling is a process by which the pupae inside the cocoons are suffocated in order to avoid the emergence of moth so that the continuity of filament in the cocoon is maintained. It can be achieved by steaming or hot air drying methods. Stifling is usually done by exposing the cocoons to sun for 1-2 days.

There are two methods of Degumming of Eri Cocoons; they are traditional method and improved method. In traditional method (Jolly et al and Sarkar) method, ash obtained from Banana leaves, Wheat stock, Paddy straw, Mung / pieces of green Papaya is commonly used instead of Soda / Potash to degum the cocoons. In this method, the cocoons loosely tied in Cotton cloth and boiled in 10% Sodium Carbonate (Na2Co3 ) solution for 45-60 minutes. The individual cocoons then stretched or opened in plain water into their sheets. 3 or 4 such sheets are joined to make a cake �which is boiled and used for spinning�.

In Improved method, cleaned Eri Cocoons are loosely tied in porous cloth and the bundle is immersed in an alkaline bath of 20% Soap and 2% Soda. The liquor ratio is 1:6. Then the cocoons boiled for 1 hour and then washed and reboiled in fresh water for 30 minutes. The degummed cocoons thoroughly washed in fresh water and squeezed for drying. Rangam Rajkhowa (2000) reported that the Eri Cocoons were degummed in 5(%)Sodium Carbonate and 1(%) non- ionic wetting agent for 3 hours duration at 950 C with a material to liquor ratio (MLR) 1:20. The typical Degumming procedure (recipe) is as given in the table 1

The Cocoons are tied in a piece of perforated cotton cloth along with light weight stone and dipped into the vessel containing the bath having liquor of above recipe and are boiled for one hour. Subsequently the tied cocoons are taken out, thoroughly washed without disturbing the material and finally squeezed by hand. After the above Degumming treatment, the material is again boiled with plain water for half an hour to remove the alkaline content. Then, the material is removed from the boiling water, squeezed by hand and dried under shade.

CSTRI has evolved a de-gumming recipe for Eri Cocoons with a two stage treatment, the first stage treats the material with 0.5 g / litre of Hydrosulphite when the fibre material is bleached and the second stage treats the material with 0.3 g per litre of Sodium Carbonate and 3 g / litre of Soap to de-gum the material. The liquor ratio is 1:40 and duration is one hour. Further, the degummed material is boiled in plain water at boiling temperature for one hour. Then the material is dried and conditioned before taking up mechanical processing.
A traditional Spinning device consists of a spindle with a disc base. The spinner holds the cocoon �cake� in the left hand, drafts and then feeds the strand with the right hand to the spindle. The spindle is occasionally rotated by the right hand to impart twist. After certain length of yarn is spun, the spinning is discontinued to wind the yarn onto the spindle and the production is very low.

The N.R. Das spinning wheel is pedal driven and has a flyer system. A large pedal wheel drives the top step wheel, which in turn drives double flanged bobbin. The spindle and flyer are mounted horizontally on a wooden platform with an automatic traverse motion. Continuous rotation of the bobbin gives the yarn uniform twist and simultaneously ensures uniform distribution of the yarn coils as they are wound on the bobbin. Both drafting and feeding of the fibre can easily be controlled. It gives production of about 80 Grams per day.

Chowdhury Spinning Wheel works on the principle of ring and traveller. This machine produces uniformly twisted yarn and production is about 80-100 g per day with a count of 10 to 15s. KVIC has designed and developed Ambar charka for spinning of cotton. This device is adopted for Eri Silk. This Charka yarn is finer and more uniform than the above three appliances. The production on this machine is 450 to 500 gram per day with account of 10 to 30s.

CSTRI motor cum pedal operated spinning machine is a simple model and it can be operated by pedal as well as motor. It runs with 1/8th HP single-phase motor and gives better quality yarn when compared to other spinning devices. This machine is able to produce 150 to 200 gram of yarn per day with a count of 15 to 50s. The yarn produced on this machine is uniform and bulky and the yarn can be used for the manufacture of shirting, ladies dress materials, furnishings, carpet and upholstery.

Spun Silk yarn manufacture involves de-gumming of Silk followed by mechanical processing. Spun Silks in mills are employing either the Japanese or Italian technology. Adopting both the technologies, a range of counts of Eri Silk Spun yarn from 2/20S to 2/120S are produced in a limited way. Further 2S and 7S have also been spun from the wastes generated during the spinning on the noil yarn spinning machinery. It is reported that Eri Silk fibre has performed satisfactorily on both the systems of Spun Silk yarn manufacture and the quality of yarn is reported to be good.

4.0 Materials

Eri Cocoons were procured from Govt. Cocoon market Hyderabad. Around 2000kg of stifled Eri Cocoons was purchased through Central Silk Board, Govt. of India, and Hyderabad. The Table 2and 3 give the Cocoon and Eri Silk fibre properties.

The low temperature Polyester dyeable fibres manufactured by Reliance Industries limited were procured from Textile mill Coimbatore. The Table 5 gives fibre properties of polyester fibre used for the studies.

5.0 Methods

The flow chart (Fig.1) shows the processes employed to prepare Eri fibre from the Eri Cocoons. To improve the shell life of the Eri Cocoons, the Cocoons were stifled using hot air drying. Before taking the Cocoons for Degumming, the dead Pupa was removed by cutting the Cocoons.

Fig 1: Flow Chart

Mechanism used to extract Eri fibres from Eri Cocoons

Raw material

Degumming of Eri Cocoons

The Table 6 gives the recipe used for de-gumming of Eri Cocoons. Before spinning, the Cocoons must be degummed to ensure removal of the gum, which facilitates easy spinning. The de-gumming procedure is as follows. The Cocoons are tied in an open meshed polyester bolting cloth. Then Cocoons were dipped into the vessel containing the above recipe and Cocoons were boiled for one hour. Cocoons were taken out and thoroughly washed without disturbing the material and finally squeezed by hand. After the chemical treatment, the material is again boiled in plain water for 30 minute to remove the alkaline content in the material. Then, the material is removed from the boiling water and then squeezed and dried under shed.

The degummed and dried material was opened in the blow room. In cutting process, the sheet form of material was cut into three parts with the help of scissors. The cut sheet was passed through the cutting machine and it was cut into small pieces of 6 inches in length.

Eri Silk and Polyester blended yarn/ Fabric development

The flow chart (fig.2) shows the process followed in the development of Erisilk + Polyester blended yarn. Sandwich blending technique was followed to blend Eri Silk with Polyester. The following blend proportions were taken till roving to produce the yarn of Eri Silk / Polyester 10/90, 20/80, 30/70, 40/60, 50/50, 60/40, 30/70, 80/20&90/10. After blending the material was sprayed with 2gpl Antistatic agent and the material were conditioned for 24 hrs.

In order to assess the blend composition of Eri silk and polyester, blends were prepared with the above combination and moisture regain was estimated by adopting IS Standards. Table 10 gives the data on moisture regain v/s blend composition. Likewise Fig 3 shows the relationship between moisture regain and blend composition. The relationship is linear in nature. Using the calibration graph, it is possible to estimate the blend composition of any unknown blend of Eri silk and polyester.

6.0 Theoretical prediction to achieve optimum blend percentage

Eri Silk and Polyester was blended to achieve maximum advantages of the fibres and allow to over come the limitations of the inherent characteristics of the fibres. The fig.4 shows the minimum blend percentage of Eri Silk to be taken in the blend to achieve good comfort and mechanical properties. As per the theoretical prediction using the tenacity and elongation properties of both the fibres, it is estimated that 40(%) Eri Silk and 60(%) Polyester will give optimum performance in the yarn.

All tests were carried out at 25o C + 2o C and relative humidity 65% + 2 (%). Minimum of 10 readings were taken for each test, average and Coefficient of Variation (CV) Percentage were determined.

7.0 Yarn Preparation

Roving thus prepared was used to make samples of hand spun yarn on NMC.
These hand spun yarns were used for characterization and preparation of handloom fabrics.

8.0 Fabric development

The following combinations of fabrics were developed on hand loom.

9.0 RESULTS AND DISCUSSION

The results of various properties of the yarns and fabrics developed using Eri Silk and Polyester material are given below.

9.1 Roving

It is very clear from the table 12 and Fig 5 that as Eri Silk percentage increased in the roving, the U (%) also increased.



9.2 Yarns Characteristics

The Table 13 gives the data on yarn spun on Ambar Charka up to 40/60 Eri Silk/Polyester blends. As the Eri Silk percentage (beyond 40(%) Eri silk) increased, the spinning of yarn on Ambar Charka was found to be unsatisfactory because of limitations of the Ambar Charkas available in Khadi Institution in and around Davangere. The existing Ambar Charka has the following limitations to spin yarn of more than 40(%) Eri Silk.

� Drafting force (Low)

� Roller pressures (Low)

� Draft change pinion

� Twist (Low) and High Variation