VOLUME 62, ISSUE 2/2021

The authors have evaluated the montan wax-based dispersion of the type DW 55 for the water repellency of wood-based materials for the first time in industrial use. The excellent water-repellent effect shown on the pilot scale at the Institut für Holztechnologie Dresden (IHD) with regard to thickness and edge swelling has been confirmed. Problems during processing due to insufficient shear stability led to the development and establishment of a ROMONTA internal measuring method in order to compare shear stabilities on a laboratory scale and enables us to exclude these effects during product development. As a result, new, shear-stable formulations DW 55-1 to DW 55-3 with high solids content were developed which, with improved properties, show the same highly effective water-repellent effect on laboratory scale. In a follow-up project with the IHD (Scheffel, 2021), this should be demonstrated in comparative tests with dispersions based on natural plant waxes in wood-based materials.

Materialspezifische MC-R-Funktionen wurden für thermisch sowie chemisch modifiziertes Holz (DMDHEU, Acetylierung, Furfurylierung) bestimmt. Grundsätzliche führten die Holzmodifizierungen zu einer Erhöhung der elektrischen Leitfähigkeit. Materialspezifische MC-R-Funktionen sind somit erforderlich, um die Holzfeuchte modifizierten Holzes auf Basis elektrischer Widerstandsmessungen präzise vorherzusagen. Die Anwendung von MC-R-Funktionen unbehandelten Holzes zur MC- schätzung in modifizierten Materialien derselben Holzart führte zu einer systematischen Überschätzung der MCmaterial modifizierten Holzes von bis zu 12,0 %. Wurde MCwood in chemisch modifiziertem Holz betrachtet, lag bei entsprechendem Vorgehen eine Überschätzung von MCwood mit bis zu 14,0 % vor, was zu einer signifikanten Unterschätzung der Gebrauchsdauer modifizierten Holzes führte. Korrekturen der vorliegenden, materialspezifischen MC-R-Funktionen modifizierten Holzes sind denkbar, sofern angepasste Prozessbedingungen (Temperatur, Druckatmosphäre) oder Art und Menge der Modifizierungsreagenzien die elektrische Leitfähigkeit beeinflussen.

The PyroForCE research project investigated the extent to which the fire behaviour of façade timbers can be changed by the creation of a surface pyrolysis layer alone in such a way that the requirements for classification as a flame-retardant building material are permanently fulfilled. For this purpose, a continuously operating wood pyrolysis system was developed with which reproducible pyrolysis surfaces could be produced on test specimens of the wood species oak, larch and spruce. By additional stabilisation with sodium silicate, both the surface abrasion resistance and the fire protection effect can be improved. Façade timbers modified in this way can achieve a classification as a “flame-retardant” building product in the single-burn item test. This means that the goal has been achieved of modifying the fire behaviour of façade timbers only through surface pyrolysis in conjunction with stabilisation using purely mineral sodium silicate in such a way that they can be classified as flame-retardant building materials and thus be used as façade materials in urban contexts and building classes 4 and 5.

The aim of the investigations was to develop a robot application for the precise joining of fasteners by means of adhesive during the joining process in the cabinet press. In cooperation with the company Hüttenhölscher, a changing tool for robots was developed for the inductive bonding of fasteners. The fasteners are joined with repeatable accuracy and cleanliness by using fasteners precoated with hotmelt adhesive. As part of the project work, the technology for providing, heating and processing the fasteners was developed and manufactured. The robot used for this purpose enabled, in addition to the repeatable processing of the fasteners. Homogeneous heating of the adhesive with minimum heating time was defined as the target value in the process. A modified mounting plate from Blum company was used as a fastener. The strength was verified on pot hinges according to DIN EN 15570 (2008). The state of the art and the development of the robotic cell are described in Part 1 of the publication. The second part of the paper presents the results of the tests on the heating behaviour and the suitability of the process.

After investigating the material based influencing factors in the production of flame-retardant MDF in the first part of the publication, the second part focuses on the influence of the dosing point of the fire-retardants (FR). The addition of the FR was tested at five positions during the defibration process. Cone calorimetric analysis were used to identify differences between the dosing point and the thermal decomposition behaviour on FR-modified MDF. The addition of 10 % FR is sufficient to achieve low flammability of the MDF, regardless of the dosing point. In contrast to mUF-glued MDF, heat release was higher with pMDI gluing. On the other hand, the reduction in mechanical-physical properties was greater for mUF-bonded MDF. When pMDI was used and the FR was added before the grinding disks of the refiner or in the blowline, it was possible to produce flame-retardant MDF that met the requirements according to DIN EN 622-5 (2010). This was true for both tested FR, for melamine polyphosphate (MPP) as well as for the mixture of MPP and soluble starch phosphate carbamate (LSPC).