Microscopy and Microanalysis

Biological Applications

Quantitative Electron Microscopy of Cellulose Nanofibril Structures from Eucalyptus and Pinus radiata Kraft Pulp Fibers

Gary Chinga-Carrascoa1 c1, Yingda Yua2 and Ola Diseruda3

a1 Paper and Fiber Research Institute (PFI AS), Høgskoleringen 6b, NO-7491 Trondheim, Norway

a2 Department of Materials Science and Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway

a3 Norwegian Institute for Nature Research (NINA), NO-7485 Trondheim, Norway

Abstract

This work comprises the structural characterization of Eucalyptus and Pinus radiata pulp fibers and their corresponding fibrillated materials, based on quantitative electron microscopy techniques. Compared to hardwood fibers, the softwood fibers have a relatively open structure of the fiber wall outer layers. The fibrillation of the fibers was performed mechanically and chemi-mechanically. In the chemi-mechanical process, the pulp fibers were subjected to a TEMPO-mediated oxidation to facilitate the homogenization. Films were made of the fibrillated materials to evaluate some structural properties. The thicknesses and roughnesses of the films were evaluated with standardized methods and with scanning electron microscopy (SEM), in backscattered electron imaging mode. Field-emission SEM (FE-SEM) and transmission electron microscopy (TEM) were performed to quantify the nanofibril morphology. In this study, we give additional and significant evidences about the suitability of electron microscopy techniques for quantification of nanofibril structures. In addition, we conclude that standard methods are not suitable for estimating the thickness of films having relatively rough surfaces. The results revealed significant differences with respect to the morphology of the fibrillated material. The differences are due to the starting raw material and to the procedure applied for the fibrillation.

(Received January 14 2011)

(Accepted March 20 2011)

(Online publication July 11 2011)

Correspondence:

c1 Corresponding author. E-mail: gary.chinga.carrasco@pfi.no