The tensile strength was measured on fibre
collectives by a Stelometer (Spinlab, Knoxville, Tennessee,
USA) according to ISO 3060. The oriented fibre collective
was clamped over 15 mm width in Pressley clamps using a
spacer of 3.2 mm. The clamps were covered with leather for
testing the cotton fibres and with PVC foil (150 lm for the
top part, 300 lm for the bottom part) for testing the kenaf
fibres. Ten collectives of cotton fibres and 20 collectives of
kenaf fibres were tested to obtain a representative set of
results. The strength of fibre collectives in cN/tex can be
calculated from the mass of the tested collective in kilogram
divided by the mass-related fineness of the tested collective
in tex. The mass of the collective was measured with an
accuracy of 0.01 mg.