Kenaf core

CMP produced from kenaf core using alkaline hydrogen peroxide gave a pulp yield of 80%, breaking length of over 4 km, brightness of 60%, and opacity of 92% [74]. 

Chemical components Kenaf whole Kenaf core Kenaf bast... 

Kenaf core High density polyethylene (HDPE)/Soya powder [36]... 

H. Ismail, A.H. Abdullah, and A.A. Bakar, The effects of a silane-based coupling agent on the properties of kenaf core-reinforced high-density polyethylene (HDPE)/soya powder composites. Polym. Plast. Technol. Eng. 49(11), 1095-1100 (2010). 

Ismail H, Abdullah AH, Abu Bakar A. Influence of acetylation on the tensile properties, water absorption, and thermal stability of (high-density polyethylene)/(soya powder)/ (kenaf core) composites. J Vinyl Addit Technol 2011 17 (2) 132-137. 

Figure 11.15 DSC curve of bleached kenaf core fiber and CNC [138].

Screened kenaf Pelleted kenaf core Fines core powder... 

Extensive research has been done on the mechanical separation of the bast from the core on kenaf. The U.S. Department on Agriculture sponsored a research in mechanical retting at the Mississippi State University [10] and with a private firm in Bakersfiled, California [11]. Chopped whole stock was used in a process involving a spiked cylinder and an airline cleaner [12]. Separation efficiencies of 42 to 48% were achieved. It was found that the moisture content was a critical factor in the separation efficiencies and, if controlled, the separation was cleaner and quicker. Fisher [11] used a modified cotton gin and found separation efficiencies of more than 90%. 

The difference between the bast and core fibers in kenaf is shown in Figure 7.4. The bast fibers have thicker walls (see Figure 7.5) as compared to the core fibers. The longitudinal axis of a kenaf bast fiber is shown in Figure 7.6. 

FIGURE 7.4 Cross section of the boundary area between kenaf bast and core. Magnification x 20 (USDA.)... 

In a recent study, Han et al. reported changes in kenaf as a function of the growing season [24]. Their data do not necessarily agree with that of Clark and Wolff. The most critical difference between Han et al. and Clark and Wolff was the difference in fiber lengths. The average length of a bast and core (stick) fiber increased as the plant aged in contrast to that of Clark and Wolff. 

Tests are presently underway to use jute and kenaf sorbents to remove heavy metals, pesticides, and oil from rain water run off in several cities in the United States. Medium-and high-density mats can also be used for oil spill clean up pillows. It has been shown that the core material from kenaf preferentially sorbs oil out of seawater when saturated with water. There are many other potential sorbent applications of agrofiber and core resources such as removal of dyes, trace chemicals in solvents, and in the purification of solvents. 

It is also possible to use core materials as sorbents in cleaning aids such as floor sweep. While this is not a composite, it does represent another way in which jute and kenaf resources can be used as sorbents. 

Kenaf originates mostly from Iraq, Tanzania, Jamaica, South Africa, Cuba and Togo. Kenaf fiber is extracted from bark of the kenaf tree. The fibers extracted both from the bast and the core of the bark (25). Some properties of kenaf fibers are shown in Table 3.3. Kenaf fibers can be used in both thermoplastic and thermoset resins for reinforcement. 

The bast and leaf fibers give mechanical support to the plant s stem and leaf, respectively. Bast consists of a wood core surrounded by stem, and within the stem, there are a numbers of fiber bundles, each containing individual fiber cells or filaments. The bast fibers such as, hemp, flax, jute, kenaf, and ramie are usually grown in warm climates. The leaf fibers, such as sisal, abaca, banana, and henequen, are coarser than bast fibers. The seed-hair fibers, such as cotton, coir, and milkweed, are attached to the plant s seeds [68]. 

There are several different classifications in terms of plant fibers. While the classification of Nishino [59] includes seven groups as bast (soft) fibers (flax, hemp, jute), leaf (hard) fibers (sisal, abaca, pineapple, etc.), stem fibers (bamboo, banana stalk, corn stalk), fruit fibers (coconut), seed fibers (cotton, baobab, kapok), straw fibers (rice, wheat, corn), and others (seaweeds, palm), that of Faruk et al. [3] has six groups bast fibers (jute, flax, hemp), leaf fibers (abaca, sisal and pineapple), seed fibers (coir, cotton and kapok), core fibers (kenaf, hemp and jute), grass and reed fibers (wheat, corn and rice) and all other types (wood and roots). 

Kenaf is an annual plant and a member of the Hibiscus family (Hibiscus cannabinus L. Malvaceae). It has a high growth rate and can reach a height of 3.7-5.S m with a stem diameter of 25-51 mm within 4-5 months in suitable temperature and rainfall conditions [24, 25]. Kenaf, a word of Persian origin, refers to a warm season, short-day and annual herbaceous plant. It is a dicotyledon, which represents three main layers in the stalk an outer cortical (or bast) tissue layer (phloem), an inner woody (called the core) tissue layer (xylem) and thin central pith layer [26]. 

Basically, kenaf has two distinctive stem regions the outer part, or so-called bast, constitutes around 34% of the weight of the stem and the inner, woody core is about 66%. The long bast fibers are usually used to produce paper, protective packaging, and composite boards and are also used in textile industries. On the other hand, the short fibers are used to manufacture products like animal bedding and horticultural mixtures [25]. 

M. Ibrahim, W.R. Wan Daud, W. Rosh, and K.N. Law, Comparative properties of soda pulps from stalk, bast, and core of Malaysian grown kenaf. Bioresources 6(4), 5074-5085 (2011). 

Today s interest in kenaf focuses on it as an alternative source of paper pulp although still on a very limited scale. Ultimately refined bast fibres measure on average 2.6 mm in length and resemble the best softwood fibres while core fibres are only about 0.6 mm long and are similar to hardwood... 

Other uses of core kenaf fibre include also soil-less potting mixes, animal bedding, oil absorbents, packing material, organic filler for plastics, drilling mud binder, grass and flower mats, decorative fibres and insulation as well as animal feed and human food [41]. Bast fibre is also blended with cotton and used in textiles [41]. The bast fibre of kenaf can also be mixed with plastic for injection moulding. 

Before straw is processed and fibres extracted, it has to be retted. In Asia, Africa and Latin America kenaf is still retted in ponds. However, this process is labour intensive and leads to serious contamination of waterways [47,49], therefore, like many other bast fibre yielding crops, kenaf can be dew-retted. The second stage of processing involves a series of decortication machines that break the stem and separate core and bast fibres [50]. 

Four-month old kenaf stems of variety 36 were obtained from the experimental plot of the National Kenaf and Tobacco (NKTB) Company, Malaysia. The harvested kenaf stems were peeled to separate the outer part (bast) from the inner part (core). The bast was then dried in an industrial oven to a moisture content of 9.8%. Acetone was supplied by Mallinckrodt. Sulfuric acid (95%), chloroform, and CAB were purchased from Aldrich, while sodium chlorite and sodium hydroxide were supplied by RND I-Tech Sdn., Malaysia. CAB had a mrniber average molecular weight of 70,000, a density of... 

Figure 3.1 Optical and scanning electron micrographs and chemicai contents of the cross-section of the interface between the bark and the core of a kenaf stem.

Baldwin BS, Graham JW. 2006. Effect of population density and row spacing on dry matter yields and bork core ratio of kenaf (Hibiscus camiabinus L.). Industrial Crops and Prod 23 244-248. 

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