2.1 Chemical Treatment of Coir Fiber
The Coir fibers were initially collected and cleaned.
For single stage treatment, a solution of 0.5% chromium sulfate with 2/3 drops of HCl was prepared.
An initial pH of 2.5-3 was maintained during reaction this pH became 8-9).
Coir fiber was taken into the prepared solution and shaken for 3 hours.
After 3 hours reaction the fiber is washed properly in distilled water.
For two stages CrSO4 and NaHCO3 treatment, the same procedure was followed with an addition of 0.02% NaHCO3solution.
The solution along with coir fiber was shaken for another 2 hours. Later the fiber was
washed properly with distilled water.
2.2 Tensile Testing
Tensile testing was performed for the span length of 5mm, 15mm, 25mm and 35mm using a tensile testing machine.
The fibers were glued in between two paper frame (fig. 1) to conform a good gripping
and straight direction to the test clamps.
Diameter of single fiber was measured using a scanning electron microscope (SEM).
The paper frame was carefully placed in between the jaws of the load cell.
The load cell and cross-head speed used were 50N and 4mm/min respectively.
Tensile strength was calculated by using equation
1;
σ ═ F max /A (1)
Where σ is tensile strength, F max is maximum force
and A is cross-sectional area.
Cross-sectional area was measured by using
equation 2;
A=π.(d/2)2 (2)
Where d is diameter.
The Young’s modulus was measured from the linear portion of the stress/strain curve and later corrected by using the following analytical equations [1].Correction of tensile properties;
ΔL total = ΔL fiber + ΔL grip (3)
α i = (ΔL total / F) – (L0 /(E0 .Ai) (4)
ΔL total / F = (e*.L0) / (σmax*. Ai) =
(1/ Ei). (L0 / Ai) (5)
E i = σmax*i / e* (6)
ΔL grip / L0 = (α i. Ai. σmax*i) / L0 (7)
2.3 Scanning Electron Microscopy
The surface morphology of raw and treated coir fiber was investigated using a scanning electron microscope. The micrographs are shown and discussed in the following section.