Utilisation of unbleached kenaf fibers for the preparation of magnetic paper

https://doi.org/10.1016/j.indcrop.2008.03.012Get rights and content

Abstract

Unbleached kenaf fibers were selected for the manufacture of magnetic paper using chemical coprecipitation method. This method involved precipitation and loading of nano-sized ferrite particles into the lumen of the kenaf fibers. While the degree of loading depended on both the degree of agitation and temperature of the coprecipitation, the thermal stability of the produced magnetic paper depended mainly on the temperature. The magnetic particles deposited on the fiber surface had detrimental effects on the strength of the produced paper. The coercivity value of the magnetic paper depended on the type of ferrite produced from the coprecipitation.

Introduction

Natural fibers, such as jute, banana, hemp, sisal, flax, kenaf, and cotton, are abundantly available in nature. Kenaf (Hibiscus cannabinus) is a member of the family Malvaceae. It is a potential fiber crop due to its very fast growth (around 3–4 m within 4–5 months). The stalk of kenaf consists of bast and core fibers. Both fibers possess different properties suitable for various applications including the manufacture of burlap, carpet padding, packing material, oil-absorbent mats, etc. Kenaf has been also considered as a fiber source for pulp and paper industries due to its appropriate physical strength properties (Fuwape, 1993, Saikia et al., 1997). In addition, kenaf can provide strong fibers for re-enforcement of high performance composites (Satyanarayana et al., 1990, Nishino et al., 2003, Aziz et al., 2005, Bullions et al., 2006) with special thermal properties (Liu et al., 2007).

Kenaf fibers possess large lumen that may be incorporated with magnetic materials suitable for making paper for information storage, electromagnetic shielding, multiply printing papers, etc. In addition, the kenaf fibers are able to form good fiber–fiber bonding and the loss of paper strength due to the filler is affordable. There are two methods that can be used to produce magnetic fibers: lumen loading and in situ synthesis. Green et al. (1982) loaded the titanium dioxide pigment into the fiber lumens and washed the external surface of the loaded fibers to produce well-bonded papers. This method has been adopted for producing magnetic fibers with Fe3O4 or γ-Fe2O3 pigment (Marchessault et al., 1992, Rioux et al., 1992, Zakaria et al., 2005). Magnetic fibers can also be prepared using in situ synthesis of ferrite in the presence of fibers. Marchessault et al. (1992) and Carrazana-Garcia et al. (1997) found that this method could produce iron oxide nanoparticles by oxidation of ferrous hydroxide in fiber suspension. However, this method produced some non-magnetic iron oxy-hydroxides which would detrimentally affect the magnetic properties of the paper. Recently, many studies have confirmed that magnetic particles with stronger magnetisation could be produced without oxygen (Wooding et al., 1988, Kim et al., 2001, Pardoe et al., 2001, Chatterjee et al., 2003, Wang et al., 2004, Giri et al., 2005).

In this study we select kenaf as the source of fibers to produce magnetic paper using a coprecipitation method with the presence of ferrous and ferric compounds. The use of cobalt compound for the coprecipitation will be also tried. The effects of temperature and degree of mixing on the magnetic particle size, degree of crystallinity, thermal stability, magnetic and physical properties of the resultant paper will be the main parts of this study.

Section snippets

Materials

Unbleached kenaf pulp was prepared by cooking with 14% active alkali, 25% sulphidity, at 170 °C for 3 h (including 90 min to raise the temperature to maximum). The pulp yield was 40.4% (Kappa number ∼45). Ferrous chloride tetrahydrate (FeCl2·4H2O), ferric chloride (FeCl3), cobalt chloride hexahydrate (CoCl2·6H2O) and sodium hydroxide (NaOH) were purchased from Merck Co. Polyethylenimine (PEI) with a mass-average molecular weight of 750,000 was acquired from Aldrich Chemical Co. All chemicals were

Fiber loading

During the coprecipitation process, magnetic nanoparticles were formed. Under vigorous stirring, a large proportion of these particles diffused into the lumen due to the existence of a concentration gradient from the outside to the inside of the fibers (Petlicki and van de Ven, 1994). The loading of the magnetic papers, which were produced at different temperatures and stirring speeds are plotted in Fig. 1, Fig. 2. The results revealed that at room temperature the degree of loading increased up

Conclusions

Unbeaten kenaf fibers could be used to produce paper with good magnetic properties. The method involved the precipitation of nano-sized ferrite (Fe3O4 and CoFe2O4) particles with the presence of fibers. The degree of loading of the fibers increased with temperature and stirring speed. The magnetic properties of the papers increased with the degree of loading. The coercivity of the magnetic papers made with CoFe2O4 was higher than with Fe3O4. The thermal stability of the magnetic paper depended

Acknowledgements

This research work was financially supported by the SAGA (STGL-009-2006) and IRPA (09-02-02-10055 EAR) grants. The authors acknowledge the Universiti Kebangsaan Malaysia (UKM) and the Forest Research Institute Malaysia (FRIM) for facilities provided.

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