Mercerized cellulose biocomposites: a study of influence of mercerization on cellulose supramolecular structure, water retention value and tensile properties
- 991 Downloads
In this study the effect of the mercerization degree on the water retention value (WRV) and tensile properties of compression molded sulphite dissolving pulp was evaluated. The pulp was treated with 9, 10, or 11 % aqueous NaOH solution for 1 h before compression molding. To study the time dependence of mercerization the pulp was treated with 12 wt% aqueous NaOH for 1, 6 or 48 h. The cellulose I and II contents of the biocomposites were determined by solid state cross polarization/magic angle spinning carbon 13 nuclear magnetic resonance (CP/MAS 13C NMR) spectroscopy. By spectral fitting of the C6 and C1 region the cellulose I and II content, respectively, could be determined. Mercerization decreased the total crystallinity (sum of cellulose I and cellulose II content) and it was not possible to convert all cellulose I to cellulose II in the NaOH range investigated. Neither increased the conversion significantly with 12 wt% NaOH at longer treatment times. The slowdown of the cellulose I conversion was suggested as being the result from the formation of cellulose II as a consequence of coalescence of anti-parallel surfaces of neighboring fibrils (Blackwell et al. in Tappi 61:71–72, 1978; Revol and Goring in J Appl Polym Sci 26:1275–1282, 1981; Okano and Sarko in J Appl Polym Sci 30:325–332, 1985). Compression molding of the partially mercerized dissolving pulps yielded biocomposites with tensile properties that could be correlated to the decrease in cellulose I content in the pulps. Mercerization introduces cellulose II and disordered cellulose and lowered the total crystallinity reflected as higher water sensitivity (higher WRV values) and poorer stiffness of the mercerized biocomposites.
KeywordsCP/MAS 13C NMR Compression molding Mercerization Cellulose II Supramolecular structure
This work was supported by Research Institutes of Sweden (Rise). Domsjö Fabriker AB is acknowledged for gift of sulphite pulp.
- Blackwell J, Kolpak FJ, Gardner KH (1978) The structure of cellulose I and II. Tappi 61:71–72Google Scholar
- Fink HP, Walenta E, Philipp B (1999) Investigations of the time dependence of the conversion of cellulose to alkali cellulose by X-ray diffraction. Papier 53:25–31Google Scholar
- McKenzie AW, Higgins HG (1958) The structure and properties of paper. Sven Papperstidn 61:893–901Google Scholar
- Sarko A (1978) What is the crystalline structure of cellulose? Tappi 61:59–61Google Scholar
- Zhou Q, Malm E, Nilsson H, Larsson PE, Iversen T, Berglund LA, Bulone V (2009) Nanostructured biocomposites based on bacterial cellulosic nanofibers compartmentalized by a soft hydroxyethylcellulose matrix coating. Soft Matter 5:1–8Google Scholar