Binderless Coir Composites

Binderless Coir Composites

Coir Pith and Short Fibre are conventionally used with limited or no value addition, thereby limiting the value realization. With the objective of developing value-added products from Coir pith and for improving the market as well as realization of the by-products of the de-fibering units.

Finding new applications for relatively low value materials can greatly contribute to providing additional benefits for low-income commodity producers. The use of coir as the base material for higher value-added board material is one of the projects that requires attention. Coconut fibre, or coir, is a low-value by-product of coconut production and it is regarded in most coconut producing countries as waste material. Only in a few countries’ coir is processed into commercially traded products.

Coconut husk is abundantly available in Kerala as a cheap residue of coconut production, from which the coir fibre, used for the production of woven carpets, ropes, brushes and matting are extracted. Fibre extraction is presently carried using fibre extraction machines. The coconut husk comprises 30% by weight coir fibre and 70% pith. Both fibre and pith are extremely high in lignin and phenolic content. The lignin present in the coir fibre and pith act as a thermosetting binder resin. Using the intrinsic resin properties of lignin, high quality particle boards can be made by the compression moulding process without the addition of chemicals and binders. The largely unutilized biomass resource can be transferred into a valuable feedstock for the production of wood substitute products. 

In this section, the idea of using coir pith for binder less coir boards and the process involved in building the boards is essentially explained.

The Wageningen University initiated this research in the early 2000’s to use coconut coir as a base material for higher value-added products. The by-product of the research project led to creating binderless coir boards.

 

Production Process

The figure below shows the production process for the binder-less board.

After the coconut has been dehusked, the husk is passed through the defibering machine. The husk yields, long fiber, short fibre, and coir pith. The short fibre and the coir pith is dried to a moisture content below 12 %. An optimal mix of the short fibre and coir pith is laid evenly onto the mold and compressed at high pressure and temperature.

 

Properties of the Board

The obtained boards show very good mechanical properties (strength of 50 MPa and stiffness of 5 GPa) comparable to those of commercial Medium Density Fibre (MDF) Boards and by far surpassing those of particle board (strength of 15 MPa and stiffness of 3 GPa). 

The thickness swelling and water absorption of the coconut husk board is lower than for MDF. After immersion in water, the coconut husk binder-less boards show mechanical properties that surpass those of MDF by a factor of two. The density of the coconut husk boards (1.3 – 1.4 g/ cm3), however, is higher than for commercial MDF and particleboard (0.8 and 0.7 g/ cm3 respectively).

The performance of the binder-less boards produced in this way opens many possibilities for the development of cheap and strong building materials. In principle 3D molded products can be produced as well, which may lead to marketable products such as beams, laminates, cups, trays and pallets or plant pots. 

Products of varying shapes or molded parts with lower densities can be produced with proportional lower mechanical properties. Fine tuning of the processing conditions would therefore be required for each end use.

 

Market for the product

Panelboard products have served a wide market as major raw materials for household and industrial projects. This includes construction, manufacturing of furniture and fixtures, tables and chairs, coffins / caskets or funeral boxes, packaging materials, and other household accessories etc. Due to fast depleting forest resources across the world, there is a scarcity of raw materials supply. To address this supply gap, the panelboard manufacturers have started to import logs and other wood products such as lumber, plywood, and veneer from other countries. 

This is also an opportunity for other natural materials like coconut husk to fill the gap in the market through products like the binderless coir board. It has superior mechanical properties which surpass those of existing particle boards and medium density fiberboards (MDF).

The key industries that the binder-less coir boards can tackle are: 

  • Construction Industry: Both the public and the private sector can use coir based boards across their projects – construction of houses and building, bridges, government offices and hospitals, water sewerage systems, airports and seaports, and many others. 
  • Packaging industry: The coir-based boards can be used for containers/ crates for export of products. In this case, the binder-less coir board with its firmness, stiffness, density and thickness can match the quality of packaging materials required by the exporters. It is also naturally resistant to termites.
  • Furniture Industry: Coir-based product can be a substitute for panelboard product used as a major raw material in the production of home and office furniture. Home furniture includes cabinets, kitchen and appliance tables, chairs and many others. On the other hand, office furniture includes modular office sets, office tables and chairs, computer tables, etc.
  • Transportation: The boards can be used as base panels for trains, busses and so on. 

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