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The porosity and the available surface area of a lignocellulosic fiber can influence the accessibility and reactivity in derivatization and modification reactions because the porous cell-wall network determines the upper size limit for molecules that can penetrate and react with the interior of the wall. To obtain information concerning the accessibility of the porous cell wall of wood fibers, surfactant-templated sol-gel mineralization has been examined. Wood and kraft pulp samples of Norway spruce were impregnated with a silica sol-gel and subsequently heated (calcined) and transformed into structured mesoporous silica. Microscopy studies (environmental scanning electron microscopy, transmission electron microsopy, TEM) on the silica casts showed that the three-dimensional architecture of the wood and pulp fiber cell wall was revealed down to the nanometer level. Image analysis of TEM micrographs of silica fragments from the never-dried pulp revealed complete infiltration of the cell-wall voids and microcavities (mean pore width 4.7 +/- 2 nm) by the sol-gel and the presence of cellulose fibrils with a width of 3.6 +/- 1 nm. Cellulose fibrils of the same width as that shown by image analysis were also identified by nitrogen adsorption measurements of the pore size distribution in the replicas.

A colorimetric bioassay has been developed enabling separation of wood pulp qualities based on the quantity of methyl-esterified galacturonan exposed on fiber surfaces. Thermomechanical pulp (TMP) and chemi-TMP (CTMP) had, respectively, 3.1 and 0.7 microg galacturonan on the surface per mg wood pulp. The presence of galacturonan on the surface of TMP and CTMP was further confirmed by immunogold localization.

Chips of Norway spruce have been impregnated with Na2SO3 and refined at two specific energy consumptions levels at full mill scale. The optical properties of thermomechanical pulps (TMPs) obtained were analyzed in terms of brightness, light scattering, opacity, and autofluorescence by spectral imaging. Even at low sulfite dosage (0.24% sulfite by dry weight) light absorption was reduced, and the brightness was elevated, and a clear dose-response effect was observed. Two-photon spectral imaging (TPSI) showed that sulfonation, impregnation, and refining affect the fluorescence properties differently. Compared to native wood, both processed wood chips and pulp fibers revealed blue-shifted fluorescence maxima, a characteristic of shortened conjugated systems. Two subpopulations of fibers with different optical properties were observed, and the fluorescence of one fiber population was red shifted. [ABSTRACT FROM AUTHOR]

Abstract: The biodegradation of plastics and wood with different susceptibility to fungal attack have in this study been compared in order to show the biodegradability in relation to the properties of plastic and solid wood. Wood blocks of Scots pine and English Oak were treated with biodegradable aliphatic polyester, polycaprolactone, and a non-biodegradable aromatic thermoplastic, polystyrene. The plastics were applied to the wood samples dissolved in an organic solvent and thereafter the treated wood samples were exposed to brown rot decay (Postia placenta) in an agar plate test for 8 weeks. The polycaprolactone treatments did not result in wood protection, whereas polystyrene treatments provided a protection from fungal attack. Both plastics are transparent and after treatment the solid wood blocks retained their natural wood appearance with a somewhat darker shinier surface. Scientific relevance: Usually commercial wood-plastic composites are made using wood derived lignocellulose-fibers melt-blended in a screw extruder with a plastic matrix, and then the resulting material is mainly a plastic (in terms of properties and appearance) which contain some lignocellulose. We have instead used solid wood to which we have added transparent plastics, which preserve the unique and precious esthetic value of natural wood. This study describes the biodegradation of two (a more and a less resistant) wood species in combination with a biodegradable and a non-biodegradable plastic. The purpose was to study any synergetic effect in the biodegradation property between solid wood and plastic since there is a socio-environmental desire to use biodegradable plastics of renewable raw material for e.g. composite material. We show that both the wood and the plastic influence the biodegradation, for example by using an easily degraded European wood specie in combination with a biodegradable plastic (polycarolactone) no protection of the wood is obtained, whereas a relative small amount recalcitrant plastic (polystyrene) can somewhat protect both Scots pine and Oak wood without significantly compromising their appearance. [Copyright &y& Elsevier]