Isolation of Cellulose Nanowhiskers from Kenaf Fiber - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 189

removes the amorphous parts of the cellulose, leaving single and well-defined crystals
in a stable colloidal suspension. The rod-like cellulose particles from different sources
have a diameter and length ranging from 5 to 20 nm and 100 nm to several microm-
eters, respectively, after the acid hydrolysis (Candanedo, Roman, and Gray, 2005).
The introduction of sulfate groups along the surface of the crystallites will result in a
negative charge on the surface as the PH is increased. This anionic stabilization via the
attraction/repulsion forces of electrical double layers at the crystallites is probably the
reason for the stability of the colloidal suspension of crystallites (Figure 1) (de Souze
Lima and Brosali, 2004).
Figure 1. Esterification of cellulose chain in hydrolysis process.
The whiskers with high stiffness, surface area, and crystallinity are suitable for ap-
plication in polymeric matrices, acting as reinforcing element (Gardner et al., 2008).
Also, it can be used as a rheology modifier in foods, paints, cosmetics, and pharmaceu-
tical products (Turbak et al., 1983).
The aim of this study was extraction of cellulose from kenaf fiber which is avail-
able in Malaysia and preparation of nanocellulose whiskers from extracted cellulose in
controlled hydrolysis condition. Chemical composition, size of particles, morphology,
crystallinity, and thermal analysis of cellulose whiskers were investigated.
materials aNd methods
materials
The materials used for the study includes raw kenaf bast ( Hibiscus cannabinus ) fibers
were supplied by KFI Sdn. Bnd. (M). Sodium chlorites, sodium hydroxide, sulfuric
acid, glacial acetic acid used were purchased from SYSTERM (M) Bhd.
Preparation of Cellulose Fibers
Kenaf fibers were cut into small pieces before treated with a 4 wt% NaOH solution at
130°C, under mechanical stirring, followed by washing with adequate distilled water
to remove all alkali soluble components. A subsequent bleaching treatment was carried