Conclusion
The Young’s modulus of raw treated coir fiber increased with increase in span length, while the tensile strength and strain to failure of the same decreased with increase in span length.
The surface of raw coir fiber was a bit rough and porous; while the surface of double stage chemical treated coir fiber was found compact and smoother.
Chemical treatment improves the tensile properties of coir fiber.
Double stage chemical treatment showed better properties compared to the single stage chemical treatment.
During single stage treatment basic CrSO4 reacts with fiber cellulose, so a thin layer formed on fiber surface which make it smooth and compact.
In double stage treatment after 3 hours treatment with basic CrSO4 again NaHCO3 is added and another reaction takes place during 2 hours shaking.
Here two chemical agents basic (CrSO4 again NaHCO3) react with the fiber cellulose,
so that a thick and smoother layer is formed on fiber surface.
Clearly it can say that both treatments improve the surface morphology but the double stage treatment provides the better then single stage treatment.
However, both treatments improve the chemical bonding of coir fiber which results good mechanical properties then the raw fiber.
In these two treatments the shaking time is very important to improve the reaction rate. Shaking provides the full reaction of fiber with chemical reagent and cleans the fiber surface.