Zur Fibrillarstruktur nativer Cellulose

Abstract

Die Mikrofibrillarsturktur von Algencellulose, Bakteriencellulose, Ramie, Baumwollinters und Chemiezellstoff wurde mittels Elektronenmikroskopie und Röntgen‐Weitwinkelstreuung vergleichend untersucht. In Abhängigkeit von der Herkunft der Cellulose werden elektronmikroskopicsch Mikrofibrillen mit unterschiedlichen Merkmalen und Lateralen Abmessungen zwischen 4nm und 95 nm gefunden. Mit Hilfe der Röntgen‐Weitwinkelstreuung wurden laterale Kristallitabmessungen und erstmalig an Cellulose‐I‐Proben (Valonia, Ramie) zusätzlich laterale Gitterstörungen auf der Grundlage einer Fourier‐Reflexprofilanalyse ermittelt. Die mittleren lateralen Abmessungen der Kristallite als Subbaueinheiten der Mikrofibrillen variieren zwichen 4nm für Holzzellstoff und 10 nm für Valonia‐Cellulose, Modell vorstellungen zur Feinstruktur der Mikrofibrillen wurden anhand der Ergebnisse kritisch diskutiert.

Indirect evidence of supramolecular changes within cellulose microfibrils of chemical pulp fibers upon drying

“…According to the fringed fibrillar model (Klemm et al 2005), the crystalline segments are separated in the longitudinal direction by amorphous segments; in other words, the height of CNCs should essentially be similar to the width of a cellulose microfibril. The heights in this study (Table 2) correlate fairly well with the microfibril width determinations from kraft pulp by NMR (Hult et al 2001;Rebuzzi and Evtuguin 2006) or X-ray diffraction (Fink et al 1990). …”

Proposed Nano-Scale Coalescence of Cellulose in Chemical Pulp Fibers During Technical Treatments

“…This model consists of a fibrillar structure, the smallest entity of which is the microfibril (FreyWyssling 1954;Fengel 1970). The diameter of the microfibril is dependent on the origin of the cellulose (Fink et al 1990). For example, the microfibril width for hardwood kraft pulp measured by NMR spectroscopy is 3.9 nm (Wickholm et al 1998).…”

“…This is seen as loss of mechanical properties (Borrega and Kärenlampi 2008), loss of hygroscopicity (Borrega and Kärenlampi 2010), and loss of porosity (Borrega and Kärenlampi 2011). Aggregated microfibril bundles, also referred to as macrofibrils, are found in various cellulosic fibers (Fink et al 1990;Wickholm et al 1998). These are partly due to the tendency of the microfibrils to form bundles already in a living organism and partly due to the drying-induced microfibril coalescence into aggregates.…”

Combining small-angle and intermediate-angle neutron scattering to study the hierarchical structure in microbial cellulose

“…The arrangement of the crystalline cellulose http://dx.doi.org/10.1016/j.eurpolymj.2015.03.012 0014-3057/Ó 2015 Elsevier Ltd. All rights reserved. microfibrils in plants has been studied before by using wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) [23][24][25][26][27][28]. A mean thickness of the fibrillar unit of 25 Å was reported, and the shape of cellulose microfibrils was well approximated by a cylinder with a size distribution.…”