Kenaf fiber diameter

Jute and kenaf fibers develop in the phloem, or bast, region of the stem of the plants, and they appear as wedge-shaped bundles of cells intermingled with parenchyma cells and other soft tissues (Figure 7.1) in the transverse sections of the stem. In the growing part of the stem, a circumferential layer of primary fibers develops from the protophloem, but, as vertical growth ceases in the lower parts, secondary phloem fibers develop as a result of cambial activity. In mature plants, which reach a height of 2.5-3.5 m and a basal diameter of about 25 mm, the secondary fiber accounts for about 90% of the total fiber bundles. 

Generally, some varieties of kenaf can be found in Malaysia. These types may differ in terms of color of stem, shape of the leaf, color of the flower and seed, as well as its suitability in different environmental conditions. Kenaf sp. V36 is a kenaf variety that is widely planted in Malaysia. It is formd to be the most applicable type of kenaf for commercial use [24]. H ng et al. have examined nine varieties of kenaf including the V36 type, especially in terms of their anatomical appearance as well as cell morphology [32]. They have found that all kenaf varieties have slight differences in their length, fiber and lumen diameter. The mean values of fiber length, fiber diameter and fiber cell wall thickness of V36-type kenaf are shown in Table 22.4. Recent data reported by Nayeri et al. [33] are comparable to those published by H ng et al. [32]. 

The best tensile characteristics were achieved by lyocell fibers with 0.33 tex with a tensile strength of 555 N/mm, followed by lyocell 0.13 tex with 519 N/mm, lyocell 0.67 tex with 442 N/mm and lyocell 1.5 tex with 332 N/mm. The highest tensile strength was measured for the kenaf fiber bundles with a tensile strength of 653 N/ mm. Due to the bigger fiber diameter and the probabihty of more defects in the cross-section the tensile strength decreases in trend with an increasing fiber diameter for the lyocell fibers (Vetrotex, 1995). 

Urena and Abutilon. These are less important vegetable fibers of a jute-like nature. Urena lobata (Cadillo) of the mallow family (Malvaceae) is a perennial that grows in Zaire and Brazil to a height of 4—5 m with stems 10—18 mm in diameter. Because of a lignified base, the stems are cut 20 cm above the ground. The plants are defoflated in the field and retted similarly to jute and kenaf. The retted material is stripped and washed and, in some cases. 

Figure 3.3 shows a schematic illustration of an apparatus for grinding. The aqueous suspension of breached kenaf bark fibers is introduced into the upper part of the apparatus, then the suspension is sheared between a pair of circular stones (of diameter 145 mm), one of which is rotated at high speed (1500 rpm). After grinding, the suspension, which has a cream-like texture, is poured out from the apparatus. 

---