Effect of alkali treatment on physical and mechanical properties of Cattail and Kenaf fibres

NaOH treatment is widely used for natural fibre extraction. However, the different treatment conditions produce fibres with other characteristics. The present work aims to study the effect of alkali treatment conditions on Kenaf bast and Cattail stem fibres’ properties. Two conditions at two different levels were selected. They are soaking time (2 and 4 hours) and alkali treatment temperature (80 and 120°C). Untreated Kenaf and Cattail fibres were used as control samples. The NaOH process occurred due to the decline in the fineness of Cattail and Kenaf fibres. SEM micrographs of treated fibres showed a clear surface with rectangular pits for Cattail fibres and dissociation of the technical fibre. Best tensile strength obtained for Kenaf fibres for 80°C and under 4 hours. However, a temperature of 120°C and a duration of 4 hours confirmed the best results in terms of lignin removal, proved by IR spectra. Also, X-ray diffractograms suggested that the crystallinity index increases with the highest conditions. The properties of Kenaf bast fibres are found to be superior to Cattail fibres. Characteristic ranges of Cattail and Kenaf fibres after alkaline treatment can be resumed respectively as the diameter of (205–496) and (66–162 μm), the linear density of (31–48) and (14–22 tex), tenacity of (6–8) and (13–17 cN/tex), elongation of (2.6–3.3) and (3–6.2%), lignin ratio of (20.7–23.7) and (15.13–22.6%), alpha-cellulose of (50.2–55.6) and (53–59%), and crystallinity of (43.9–58.6) and (55.4–66.3%). Findings showed that Kenaf bast fibres are found to be great resistant and thinner than Cattail fibres and compared to other fibres.