VOLUME 47, ISSUE 4/2006

Finger jointing is a widely used technology to increase recovery rates and to improve technical properties of timber based materials. EN2RO (ENDURO) is a finger joint cutter head with which it is possible to reduce finger-jointing cost significantly. Performance-enhancing aMT (AMT) is implanted into the cutting edge which increases edge life multiple times in comparison with conventional tooling. aMT also changes the wear morphology of the cutting edge which leads to high process stability. This technology also enables, when technically allowed, the possibility to run shorter joints. The inserts of the cutter head can be turned over effectively giving double the edge life of one insert. The clamping mechanism always reposts the knives at the exact same cutting circle, even after regrinding. Tool set up time as well as regrinding times are significantly shorter compared with the currently used technology.

The agricultural by-products such as grain straw, hemp and flax shives as well as Miscanthus were milled with an extruder or the combinations extruder/extruder or extruder/refiner (dry). The pre-treatment of the raw materials and the adjusted machine parameters were varied and the fibres quality was evaluated. Using the best fibres different materials (MDF, HDF, insulating materials and cement fibreboards) were produced and tested. The process with the combination extruder/extruder or extruder/refiner is very suitable for the milling of grain straw to produce materials which fulfil EN- standards for boards. The extruder-fibres made from grain straw and their products are similar to the TMP-ones. For other investigated raw materials is better to choose the TMP- process because of fibre and product quality.

Part 1 of this work deals with measurements of variations in specific pressure and mat thickness during the continuous hot-pressing process of MDF and further on with the determination of their impact on the board properties. For these reasons two new sensors were developed to detect variations of specific pressure and mat thickness caused both by the pressing program and the frame construction of a continuous hot-press. Furthermore these variations were recorded in gas pressure readings using the PressMAN®, a transportable device with integrated data logger for mat temperature and gas pressure measurements, which was connected to the sensors during the industrial trials. The variations in mat thickness and specific pressure were verified in industrial scale. The effect of these variations on the internal bond strength of MDF was determined in lab trials.

Medium density fibreboards (MDF), prepared from thermo- mechanical (TMP) and chemo-thermo-mechanical (CTMP) pulps using phenol formaldehyde (PF), melamine urea phenol formaldehyde (MUPF) and tannin formaldehyde (TF) resins as well as adhesives based on 4,4-diphenylmethandiisocyanat (PMDI) as binders and both the blow-line and blender technique as gluing method, were tested as to creep behaviour and dimensional stability. The results reveal: TMP-boards bonded with MUPF-resin (14 %) have much lower creep factors than those bonded with PF-resin (8 %). The creep factor of boards bonded with PMDI (6 %) and TF-resin (14 %) lies between. Furthermore, using the blow-line technique leads to boards with much higher creep resistance, lower creep factors than those prepared from fibres glued by the blender process. Evidence has also been adduced that the dimensional stability of MDF prepared by using PF-resin is much lower than those made by using MUPF-resin or PMDI adhesive.

The influence of starch and moisture on the extrudability and properties of wood polypropylene composites was inves- tigated. The results clearly showed the positive effect of starch on the extrudability and on the properties of WPC profiles. At equal polymer contents the bending strength and the modulus of elasticity as well as the impact strength are significantly higher in profiles containing starch. Even water sorption was lowered by adding starch. In contrast to the positive effects of starch on the properties of WPC, extrusion with materials containing higher moisture con- tents is still a challenge in the wood extrusion technology.

At nine wood species from Rwanda the equilibrium mois- ture content was determinated at 20 °C and 35, 50, 65, 80 and 95 % relative humidity. Using the experimentally determined average values the selected parameter of the Hailwood Horrobin Model such as fibre saturation point, mono- and polymolecular sorptions as well as inaccessibility of the sorbent to sorbat were computed. The fibre saturation point lies for all examined wood species within the range of 31 to 39 % relatively high.

The decay of wood and wood based materials by mould fungi in new or renovated buildings is - unfortunately - still an ongoing theme for experts like wood preservers or biologists. But also at both wooden interiors of churches and sacral assets this problem is current. In several churches of Saxonia where mould decay occurred, complex investigations on mould decay have been carried out. Different materials, typically used by restorers, and fungicides have been tested on their usability under worse conditions and on their effectiveness against mould, respectively. As a result, causes of the mould decay were investigated, and recommendations for its prevention and control were given.