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  Jute Reinforced Composite Technology

Fabrication of Composites Hybrid composite of glass and jute fibre can be fabricated initially by the hand lay-up technique for making the sheet-moulding compound and subsequently by using a compression-moulding machine. 10-ply hybrid laminates containing 8 inner plies of untreated/silane/titanate/TDI treated jute fibre sandwiched between two outer plies of glass fibre (weight content of jute :25-27%) can be made by the aforesaid process. Curing is done at 80oC under a pressure of approx. 2X105 N/m2 for a period of 90 min.

Jute composites are at present being used commercially in India for applications like automobile interiors. There are also some temporary outdoor applications like low cost housing for defence etc. However, use of jute alone as reinforcing fibre would not be suitable for high strength applications. Combination can be well suited for such applications. Incorporation of glass with jute brings about large increase in mechanical properties of composites.  Phenolic resins is one of the first synthetic resin exploited commercially for fabrication of jute-composite products mainly because of its high heat resistance, low smoke emissions excellent fire retardance properties and compatibility with jute   fibres.  Phenol-formaldehyde based jute composites products have been used  for quite sometimes as wood & ceramic substitutes. 

 Today, where costs & performance have a high impact on economics, phenolic resins have been accepted in many high performance applications in composite materials.  Compression moulding of composites based on  jute-phenolic system has been commonly practised since few decades. 
In this process, jute is impregnated with the phenolic resin by spraying process followed by drying under hot air drier. These pre-impregnated jute layers are arranged together for desired thickness and compression moulded at high pressure of 700-800 kg/m2 and at temperature of around 120-1400 C. A report from the National Institute of Research on Jute and Allied Fibre Technology (NIRJAFT), Calcutta reveals that, usually for moulded jute composites with polyester resin, the resin intake can be maximum upto 40%. Both hot press moulding and hand lay-up technique can be used for its fabrication. In the latter process, the resin take up may go upto 300-400 % on the basis of jute fibre used which is not economical. Also, it is seen that some pre-processing of jute/treatment of fibre is required so that the interface problem could be solved. Generally, when unsaturated  polyester resin is used with glass fibre, the ratio maintained is 2.5:1. Whereas, for resin with jute, the ratio maintained is 3.5-4:1.  However, increase in temperature increases the productivity. Even with unsaturated polyester resin, hot condition impregnation is usually done for higher productivity.

 Pultrusion is a another unique process that converts primary raw materials directly into finished products, continuously and automatically, utilising most of thermoset/thermoplastic resins.  Jute, available in continuous forms such as mat, roving, tapes, yarn etc., is impregnated with resin & passed through hot die to cure the product. The speed of pultrusion ranges from 0.4 mtr. to 1 mtr. per minute depending on the complexity of the products. The loading of jute is anywhere between 50-70%. Pultruded jute composites have good electrical insulation, corrosion & high resistance properties. They find applications in roofing sheets, cable trays, doors & window frames, panelling, sections for wardrobe, partitions, etc.

 The characteristics of natural fibre composite boards are as  follows:
 Attractive natural look as it can be painted, polished  or laminated at will
 Water proof with minimum surface absorption
 Economical 
 Strong and Rigid 
 Environment-friendly
 Can be nailed, screwed and cut sharply