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USG Technical Paper                      
Improvement of Rot-retardant Properties of Jute and Jute Goods



Improvement of Rot-retardant Properties of Jute and Jute Goods

Natural fibres like jute possess high strength, modulus and moisture uptake and low elongation and elasticity. Because of its high natural strength and robustness, jute has historically and traditionally been used mainly as packaging material e.g. sacking, Hessian/burlap, etc. for agricultural and industrial products. Jute sand bags have been another important area of its traditional use. Food grade jute bags is a newer addition to the traditional packaging materials of jute in view of the growing demand from the consumers/end-users dealing in coffee, cocoa, hazel nuts, shelled nuts etc. While jute hessian /burlap and sacking are primarily used as a packaging material it is also being used in a number of other areas.
  With increasing awareness of environment, biodegradable natural fibres like jute is increasingly being preferred as geo-textile/agro-textile products. Thus jute based geotextiles especially for erosion control, soil consolidation, vegetation growth, civil and road construction, etc. are getting importance day by day. Similarly agro-textiles in the form of nursery sheets, squares, liners, socks, pockets, sleeves etc. are becoming popular and commercially important. 
  Jute is a ligno-cellulosic bast fibre. The basic constituent of jute is cellulose the elements of which form the empirical formula (C6H10O5)n. Both bacteria and fungi can decompose cellulose but are dependant on moisture content.  Resistance of natural fibre like jute to microbial damage may be dependant upon the physical properties (such as, crystalline, chain length, orientation of ultimate cells etc.) and the chemical constituents (such as lignin, hemicelluloses, gummy materials etc.) The higher the lignin content the more resistant the fibre will be to rotting i.e. fungal attack.
   Jute products naturally decompose faster than what is required for some applications like geo-textiles/agro-textiles, sandbags etc. This quick biodegradability of jute based products especially on soil contact and exposure to moisture/water is sometimes disadvantageous.
   Biodegradation is a non-specific process and it can be started in any space which is available to various organisms. Moreover, favorable conditions like heat, light, temperature, moisture, pH value, etc. also have impact on the degradation. This biodegradation seems to occur through free radical mechanisms of jute and jute products.
   Quick biodegradation of jute products is advantageous in case of its disposal after use especially in land filling/land reclamation etc. More so since the degraded jute products have got definite fertilizing effect through increasing soil nutrient and biomass.
   Ordinarily when jute fabric is placed in intimate contact with moist earth or soil, it degrades quite rapidly and degrades completely within 2-3 months. In contrast, a dry sand-bag, filled with dry, clean sand, if maintained in a dry clean state has a life of many months. Since jute naturally decomposes faster than what would be ideally suited in a number of applications the process of biodegradability of jute fabrics/Hessian/burlap etc. needs to be retarded.  The methods protecting jute fabric against micro-biological attack depend on the introduction of a substance into or on the surface of jute fibre/product so that it acts as deterrent or provide toxicity to the micro-organisms and prevents its reproduction and growth. 
  Past investigations have indicated that 0.5 - 2% copper content gives maximum protection against rotting of jute products. The method that is long being used aims at forming a basic carbonate of copper on the jute fibre. 
  The definite protective action of copper-ions impregnated in the fabric has been proved from experimental data and field trials. It has been found that the average life of sand-bags can be increased six fold when treated with copper salts. This increased time/life of serviceability justifies economic pre-treatment of sand-bags/other jute products before use.
   Therefore, to retard the process of decomposition or increase the durability of the jute products these need to be treated with copper compounds like copper sulphate, copper ammonium sulphate, copper ammonium carbonate, copper acetate, copper naphthenate, etc. 
  Since copper compound like copper sulphate is being used for anti-microbial treatment or preservative for vegetables since long, details of copper sulphate as an example is given below.
Copper Sulphate :CuSO4 . 5H20  
Other Name : Blue Vitriol   blue copper  IUPAC  
Name:   Copper Sulphate  
Physical Chemistry:  Mol. Wt. 249.7  (Pentahydrate) 
Form:   Blue Crystals 
V. P:   Non Volatile  
Solubility:  Soluble in water  
Stability:   Slowly efflorescent in Air 
Mode of Action :   Aquatic algicide and foliar fungicide with protective actions:   
 1. In the control of most species of algae in ponds, lakes, potable water, fish hatcheries, rice fields, streams, ditches, swimming pools etc. 
2. Used as a general fungicide when mixed with lime to form Bordeaux mixture.  
3. Used as a wood preservative. 
Environmental fate :  
 Soil / Environment in soil, copper compounds are partly washed down to lower levels, partly bound by soil components and partly oxidatively transformed. 
 For the purpose of this treatment jute fabrics/ Hessian/ burlap is soaked in any of the compounds mentioned above and dried to ensure that 0.75% to 1.5% metallic copper is deposited on the fabric. It is this 0.75% to 1.5% metallic copper content by weight on fabric on dry basis which acts as an antimicrobial agent to protect the fabric from quick biodegradation. This insignificant amount of metallic copper deposition is sufficient to impart rot retardance to the fabric to protect itself without causing any harmful effects to the environment, so far known.  
  A considerable degree of rot resistance is imparted to jute materials by dipping them in a bath of a soluble copper salt such as copper sulphate. There are other copper salts like copper acetate, copper ammonium carbonate, etc. which can be used as well for the same purpose.  
    Copper under these conditions is taken up by jute in appreciable amounts and is fairly resistant to the leaching action of water. Copper, it is suggested, is bound by  chemical/ physical combination with certain reactive groups, present mainly in the non-cellulosic constituents and lignin of jute. In view of the relative cheapness and ease of operations, the treatment appears to offer practical possibility.   
The binding of copper with jute appears to be due to its chemical/physical combination with the fibre material. About 70% of the ash of jute is cationic and these cations appear to be in combination with carboxyl groups which mostly belong to the polyuronic acids. About one eighth of these carboxyl groups appear to be free, three eighths combined with the cations and one half esterified with lignin. It is probable that copper reacts with free and bound carboxyl groups by replacing hydrogen and other cations. A new complex of copper is thus formed.  
  The phenolic hydroxyl groups of tannins and lignin also bind copper. Such chemically bound copper may manifest toxicity against rotting organisms. 
It seems that during the rot proofing treatment of jute with copper sulphate or any other copper compound, a new complex is formed by reaction of copper compound with mainly non-cellulosic constituents and lignin present in jute. The adverse effect of this new complex is not yet known to anybody or documented so far. What is known is that this compound retards rotting of jute during the storage and use thereby ensuring extended life for jute product. This new complex of copper hitherto mentioned on soil contact application will degrade under a different mechanism. So, copper compounds can be used to treat jute for imparting extended life. Further the amount of copper compound used in the treatment of the burlap / hessian is not significant. In the nature, copper exits as copper sulphate, basic copper carbonate, etc. Copper, as a metal, is generally considered harmless.  


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