Browsing by Author "Saake, Bodo"

The biotechnological application of the white rot fungus Physisporinus vitreus named "bioincising" is currently being investigated for permeability improvement of Norway spruce (Picea abies (L.) Karst.) wood. During short-term (<9 weeks) incubation, fungal activity induces degradation of pit membranes and a simultaneous alteration of the tracheid cell wall structure. In Part 1 of this article series, the occurrence of selective delignification and simultaneous degradation was shown by UV-microspectrophotometry (UMSP). Moreover, significant reduction of Brinell hardness was recorded after 7 and 9 weeks incubation. For a better understanding of the chemical alterations in the wood constituents and the corresponding changes of mechanical properties due to fungal activity, we applied microtensile tests on thin strips that were prepared from the surface of incubated Norway spruce wood. Indications for the occurrence of selective delignification and simultaneous degradation were evident. Determination of lignin content and carbohydrate analysis by borate anion exchange chromatography confirmed the results. The present study verifies the findings from Part 1 of this article series and from previously conducted microscopic investigations. Now, the degradation characteristics of P. vitreus are established and the bioincising process can be further optimized with higher reliability.

Wood fibers vary in their properties across species, across trees of the same species, and within single trees. This work takes advantage of wood fibers reinforcing poly(lactic acid) composites that originate from different tissue types of the species Sitka spruce (Picea sitchensis). Fibers were prepared with high temperature thermo-mechanical processing (TMP) from juvenile, mature, and compression wood tissues of Sitka spruce. Composites were made by solution casting with subsequent hot-pressing. Thermal as well as mechanical properties were determined using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and tensile testing. The obtained results showed that the chemical and physical properties of different tissue-type Sitka spruce fibers have significant effects on the thermal and mechanical properties of the Polylactic acid (PLA)/Sitka fiber composites. To increase interfacial compatibility between the hydrophilic fibers and the hydrophobic polymer matrix, the fibers were treated with vinyltrimethoxysilane (VTMO), while PLA was modified with 4,4-methylene diphenyl diisocyanate (MDI). It was found that PLA/Sitka composites treated with VTMO and MDI exhibited improved thermal and mechanical properties, compared to the unmodified control. The work also demonstrates that there is potential to improve biobased composites by utilizing the natural variability of wood fibers. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 2616-2623, 2009