Abstract
In papermaking, the formation of bonds between single pulp fibers is influenced by the hardness of the fibers in their wet state. In this work, transversal hardness and modulus of pulp fibers have been studied via atomic force microscopy-based nanoindentation in dependence on relative humidity (RH). Additionally, the change in hardness of cellulose and xylan/cellulose model films was also investigated as a function of swelling in the presence of water and calcium chloride (CaCl2) solution. The hardness of pulp fibers is decreasing slowly from 240 MPa at 5% RH to 90 MPa at 80% RH and exhibits a distinct decrease to 2.7 MPa at the fully wet state. The hardness in water is reduced by a factor of almost 100 compared with the dry state; therefore, a form change is easily possible and facilitates the formation of hydrogen bonds on the fiber surfaces. The investigations on the model films reveal that pure cellulose hardens in the CaCl2 solution, compared with distilled water, whereas xylan on cellulose is becoming softer.
Financial support by Mondi and the Federal Ministry of Economy, Family and Youth and the National Foundation for Research, Technology, and Development, Austria, is gratefully acknowledged. We thank Herbert Wormeester and Arzu Colak (University of Twente, Enschede, The Netherlands) for sharing their know-how regarding a controlled humidity setup.
References
Binnig, G., Quate, C., Gerber, C. (1986) Atomic force microscope. Phys. Rev. Lett. 56:930–933.10.1103/PhysRevLett.56.930Search in Google Scholar
Chhabra, N., Spelt, J.K., Yip, C.M., Kortschot, M.T. (2005) An investigation of pulp fibre surfaces by atomic force microscopy. J. Pulp Pap. Sci. 31:52–56.Search in Google Scholar
Clauß, S., Gabriel, J., Karbach, A., Matner, M., Niemz, P. (2011) Influence of the adhesive formulation on the mechanical properties and bonding performance of polyurethane prepolymers. Holzforschung 65:835–844.10.1515/HF.2011.095Search in Google Scholar
Clifford, C.A., Seah, M.P. (2005) Quantification issues in the identification of nanoscale regions of homopolymers using modulus measurement via AFM nanoindentation. Appl. Surf. Sci. 252:1915–1933.Search in Google Scholar
Djak, M., Gilli, E., Kontturi, E., Schennach, R. (2011) Thickness dependence of reflection-absorption infrared spectra of supported thin polymer films. Macromolecules 44:1775–1778.10.1021/ma102905vSearch in Google Scholar
Dunford, J.A., Wild, P.M. (2002) Cyclic transverse compression of single wood-pulp fibres. J. Pulp Pap. Sci. 28:136–141.Search in Google Scholar
Follrich, J., Stöckel, F., Konnerth, J. (2010) Macro- and micromechanical characterization of wood-adhesive bonds exposed to alternating climate conditions. Holzforschung 64:705–711.10.1515/hf.2010.096Search in Google Scholar
Gindl, W., Gupta, H. (2002) Cell-wall hardness and Young’s modulus of melamine-modified spruce wood by nano-indentation. Compos. Part A Appl. S. 33:1141–1145.Search in Google Scholar
Gindl, W., Gupta, H., Schöberl, T., Lichtenegger, H., Fratzl, P. (2004) Mechanical properties of spruce wood cell walls by nanoindentation. Appl. Phys. A Mater. 79:2069–2073.Search in Google Scholar
Gindl, W., Konnerth, J., Schöberl, T. (2006) Nanoindentation of regenerated cellulose fibres. Cellulose 13:1–7.10.1007/s10570-005-9017-0Search in Google Scholar
Gindl, W., Reifferscheid, M., Adusumalli, R.-B., Weber, H., Röder, T., Sixta, H., Schöberl, T. (2008) Anisotropy of the modulus of elasticity in regenerated cellulose fibres related to molecular orientation. Polymer 49:792–799.10.1016/j.polymer.2007.12.016Search in Google Scholar
Grignon, J., Scallan, A.M. (1980) Effect of pH and neutral salts upon the selling of cellulose gels. J. Appl. Polym. Sci. 25:2829–2843.Search in Google Scholar
Hartler, N., Nyren, J. (1970) Transverse compressibility of pulp fibers. Tappi J. 53:820–823.Search in Google Scholar
Hirn, U., Schennach, R., Ganser, C., Magnusson, M., Teichert, C., Östlund, S. (2013) The area of molecular contact in fiber-fiber bonds. In Proc. of the 15th Pulp and Paper Fundamental Research Symposium, Cambridge, September 8–13, 2013, accepted for publication.Search in Google Scholar
Hoeger, I., Rojas, O.J., Efimenko, K., Velev, O., Kelley, S.S. (2011) Ultrathin film coatings of aligned cellulose nanocrystals from a convective-shear assembly system and their surface mechanical properties. Soft Matter 7:1957–1967.10.1039/c0sm01113dSearch in Google Scholar
Hutter, J.L., Bechhoefer, J. (1993) Calibration of atomic-force microscope tips. Rev. Sci. Instrum. 64:1868–1873.10.1063/1.1143970Search in Google Scholar
Jee, A.-Y., Lee, M. (2010) Comparative analysis on the nanoindentation of polymers using atomic force microscopy. Polym. Test. 29:95–99.Search in Google Scholar
Kontturi, E., Thüne, P., Niemantsverdriet, J. (2003) Novel method for preparing cellulose model surfaces by spin coating. Polymer 44:3621–3625.10.1016/S0032-3861(03)00283-0Search in Google Scholar
Kontturi, E., Tammelin, T., Österberg, M. (2006) Cellulose-model films and the fundamental approach. Chem. Soc. Rev. 35:1287–1304.Search in Google Scholar
Korsunsky, A., McGurk, M., Bull, S., Page, T. (1998) On the hardness of coated systems. Surf. Coat. Technol. 99:171–183.Search in Google Scholar
Lee, S.-H., Wang, S., Endo, T., Kim, N.-H. (2009) Visualization of interfacial zones in lyocell fiber-reinforced polypropylene composite by AFM contrast imaging based on phase and thermal conductivity measurements. Holzforschung 63:240–247.10.1515/HF.2009.033Search in Google Scholar
Lehringer, C., Koch, G., Adusumalli, R.-B., Mook, W.M., Richter, K., Militz, H. (2011) Effect of Physisporinus vitreus on wood properties of Norway spruce. Part 1: aspects of delignification and surface hardness. Holzforschung 65:711–719.10.1515/hf.2011.021Search in Google Scholar
Nečas, D., Klapetek, P. (2012) Gwyddion: an open-source software for SPM data analysis. Cent. Eur. J. Phys. 10:181–188.Search in Google Scholar
Nilsson, B., Wagberg, L., Gray, D. (2001) Conformability of wet pulp fibres at small length scales. In Proc. 12th Fundamental Research Symposium, Oxford, pp. 211–224.Search in Google Scholar
Oliver, W., Pharr, G. (1992) Improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments. J. Mater. Res. 7:1564–1583.Search in Google Scholar
Pelegri, A.A., Huang, X. (2008) Nanoindentation on soft film/hard substrate and hard film/soft substrate material systems with finite element analysis. Compos. Sci. Technol. 68:147–155.Search in Google Scholar
Persson, B.N.J., Ganser, C., Schmied, F., Teichert, C., Schennach, R., Gilli, E., Hirn, U. (2013) Adhesion of cellulose fibers in paper. J. Phys. Condens. Matter 25:045002.Search in Google Scholar
Pinto, G., Lorenzo, V. (1998) Correlation between microhardness and optical anisotropies and crystallinity in lamellar regenerated cellulose. Polym. Eng. Sci. 42:593–595.Search in Google Scholar
Scallan, A.M., Grignon, J. (1979) The effect of cations on pulp and paper properties. Svensk Papp. 82:40–47.Search in Google Scholar
Schmied, F.J., Teichert, C., Kappel, L., Hirn, U., Schennach, R. (2012a) Analysis of precipitated lignin on kraft pulp fibers using atomic force microscopy. Cellulose 19:1013–1021.10.1007/s10570-012-9667-7Search in Google Scholar
Schmied, F.J., Teichert, C., Kappel, L., Hirn, U., Schennach, R. (2012b) Joint strength measurements of individual fiber-fiber bonds: an atomic force microscopy based method. Rev. Sci. Instrum. 83:073902.10.1063/1.4731010Search in Google Scholar PubMed
Song, J., Liang, J., Liu, X., Krause, W., Hinestroza, J.P., Rojas, O.J. (2009) Development and characterization of thin polymer films relevant to fiber processing. Thin Solid Films 517: 4348–4354.10.1016/j.tsf.2009.03.015Search in Google Scholar
Swadener, J., Rho, J., Pharr, G. (2001) Effects of anisotropy on elastic moduli measured by nanoindentation in human tibial cortical bone. J. Biomed. Mater. Res. 57:108–112.Search in Google Scholar
Tang, B., Ngan, A.H.W. (2003) Accurate measurement of tip-sample contact size during nanoindentation of viscoelastic materials. J. Mater. Res. 18:1141–1148.Search in Google Scholar
Tranchida, D., Piccarolo, S., Soliman, M. (2006) Nanoscale mechanical characterization of polymers by AFM nanoindentations: critical approach to the elastic characterization. Macromolecules 39:4547–4556.10.1021/ma052727jSearch in Google Scholar
Tze, W.T.Y., Wang, S., Rials, T.G., Pharr, G.M., Kelley, S.S. (2007) Nanoindentation of wood cell walls: continuous stiffness and hardness measurements. Compos. A Appl. Sci. Manuf. 38:945–953.10.1016/j.compositesa.2006.06.018Search in Google Scholar
Villarrubia, J. (1994) Morphological estimation of tip geometry for scanned probe microscopy. Surf. Sci. 321:287–300.Search in Google Scholar
Welch, B. (1947) The generalization of student’s problem when several different population variances are involved. Biometrika 34:28–35.10.2307/2332510Search in Google Scholar
West, B., Hotle, B., Jakes, J., Considine, J., Rowlands, R., Turner, K. (2008) Nanoindentation studies of paper. In: Progress in Paper Physics Seminar. Eds. Kotomaki, K., Koivunen, H. Espoo, pp. 163–166.Search in Google Scholar
Wild, P., Omholt, I., Steinke, D., Schuetze, A. (2005) Experimental characterisation of the behaviour of wet single wood-pulp fibres under transverse compression. J. Pulp Pap. Sci. 31:116–120.Search in Google Scholar
Yu, Y., Tian, G., Wang, H., Fei, B., Wang, G. (2011) Mechanical characterization of single bamboo fibers with nanoindentation and microtensile technique. Holzforschung 65:113–119.10.1515/hf.2011.009Search in Google Scholar
©2014 by Walter de Gruyter Berlin Boston
