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High cellulose solubility is an essential to successful production of regenerated cellulose, from which hydrogels can be produced. Additionally, some pretreatment usually facilitates cellulose solubility. Bleached cellulose pulp from kenaf core (BK), consisting of lignin (0.3%), hemicellulose (5.2%) and ash (0%), was treated with an electron beam irradiation (EBI) at 10, 30, 50 and 70 kGy. The BK and irradiated bleached cellulose pulp (IK) were then dissolved in either sodium hydroxide/urea or lithium hydroxide/urea solvents which subsequently crosslinked with epichlorohydrin (ECH) solution to stabilize the formation of regenerated cellulose hydrogels. The amount of α-cellulose component in IK samples decreased as much as 38% and caused the viscosity average molecular weight (Mv) and degree of polymerization of IK samples to be reduced significantly by 84 and 87%, respectively. This resulted in an increase in cellulose solubility (up to 30%) for the IK samples in both solvent systems. However, this treatment resulted in a reduction in the overall cellulose fibre strength. X-ray diffraction of the hydrogels showed a transformation from cellulose I to amorphous cellulose. These hydrogels exhibited a higher degree of swelling, transparency and porosity compared to hydrogels prepared from non-irradiated pulp. [ABSTRACT FROM AUTHOR]

Kenaf core pulp has been successfully autohydrolysed using an autoclave heated in oil bath at various reaction temperature at 100, 120 and 140 °C. Membranes, hydrogels and aerogels were then prepared from autohydrolysed kenaf in urea/alkaline medium by casting on the glass plate, by using epichlorohydrin (ECH) as cross-linker via stirring and freeze-drying method, respectively. The autohydrolysis process reduced the molecular weight of cellulose and enhanced cellulose solubility and viscosity. Structure and properties of the regenerated products were measured with Field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), Ultraviolet–visible (UV–Vis) spectrophotometer and swelling testing. As the autohydrolysis temperature increased, the porosity of cellulose membranes (as seen from the morphology) increased. The autohydrolysis process improved the swelling porperties and transparency of regenerated cellulose hydrogels. This finding is expected to be useful in reducing molecular weight of cellulose in order to produce regenerated bio-based cellulose materials. [ABSTRACT FROM AUTHOR]

Here, a stable derivative of cellulose, called cellulose carbamate (CC), was produced from Kenaf (Hibiscus cannabinus) core pulp (KCP) and urea with the aid of a hydrothermal method. Further investigation was carried out for the amount of nitrogen yielded in CC as different urea concentrations were applied to react with cellulose. The effect of nitrogen concentration of CC on its solubility in a urea-alkaline system was also studied. Regenerated cellulose products (hydrogels and aerogels) were fabricated through the rapid dissolution of CC in a urea-alkaline system. The morphology of the regenerated cellulose products was viewed under Field emission scanning electron microscope (FESEM). The transformation of allomorphs in regenerated cellulose products was examined by X-ray diffraction (XRD). The transparency of regenerated cellulose products was determined by Ultraviolet–visible (UV–Vis) spectrophotometer. The degree of swelling (DS) of regenerated cellulose products was also evaluated. This investigation provides a simple and efficient procedure of CC determination which is useful in producing regenerated CC products. [ABSTRACT FROM AUTHOR]

The hydrothermal pretreatment on kenaf core pulp (KCP) was carried out using an autoclave heated in a oil bath at 140 °C for 0.5/1/3/5 h. The hydrothermal pretreated kenaf (HPK) was dissolved in a LiOH/urea aqueous solution and subsequently used to produce cellulose membrane and hydrogel. The effects of hydrothermal pretreatment time on solubility, viscosity, crystallinity and morphology of the cellulose membrane and hydrogel were investigated. The hydrothermal pretreatment leads to higher cellulose solubility and higher viscosity of the cellulose solution. The formation of cellulose II and crystallinity index of the cellulose membrane and hydrogel were examined by X-ray diffraction (XRD). The pore size of the cellulose membrane and hydrogel displayed an upward trend with respect to the hydrothermal pretreatment period observed under a field emission scanning electron microscope (FESEM). This finding provides an efficient procedure to improve the solubility, viscosity and properties of regenerated cellulose products. [ABSTRACT FROM AUTHOR]

Bleached kenaf core pulps (BKC) were hydrolyzed in H 2 SO 4 (0.5 M) at different time (0 min to 90 min) at room temperature. After the hydrolysis process, the viscosity average molecular weight ( M ŋ ) for BKC sample has reduced from 14.5 × 10 4 to 2.55 × 10 4 . The hydrolyzed BKC was then dissolved in NaOH:urea:water and in LiOH:urea:water mixed solvent at the ratio of 7:12:81 and 4.6:15:80.4, respectively. The increased in hydrolysis time has decreased M ŋ of cellulose leading to easy dissolution process. Higher porosity and transparency with lower crystallinity index (CrI) of regenerated membrane produced can be achieved as the M ŋ reduced. The properties of membrane were observed through FESEM, UV–vis spectrophotometer and XRD. This study has proven that acid hydrolysis has reduced the M ŋ of cellulose, thus, enhanced the properties of regenerated membrane produced with assisted by alkaline/urea system. [ABSTRACT FROM AUTHOR]