VOLUME 62, ISSUE 1/2021

The implementation of wood as a structural lightweight material in new high-performance applications requires a piece-by-piece characterization of the raw materials. In particular, veneers as base material are attracting much attention due to their excellent properties as well as good processability. For this purpose, the non-destructive characterization of birch veneers ((0.5 - 1.5) mm ± 0.05 mm) was investigated. The methods used included determination of sound wave transmission time, determination of three-dimensional fibre orientation by wide-angle X-ray scattering, determination of tensile strength and strength prediction based on failure criteria established for fibre-reinforced composites. Strength estimation based on three-dimensional fibre orientation yielded satisfactory results for the investigated failure criteria based on Kollmann (R = 0.88), Tsai-Hill (R = 0.87) and Hoffmann (R = 0.86). The properties characterized can be directly incorporated into numerical models and support the digital development of wood-based lightweight materials.

Many industrially produced floor coverings are subject to electrostatic charging when walked on. To counteract this, floor coverings are made conductive or antistatic either by adding antistatic agents during production or by a subsequent coating, depending on the type of covering. However, many additives used commercially as antistatic agents are characterized by various disadvantages, which can also have a negative impact on the durability of the antistatic effect or the usability of the floor covering. Against this background, the industry is supporting the development of transparent coating formulations for floors that are characterized by a permanent antistatic effect. Following on from this, the paper traces the development of a novel coating based on reduced graphene oxide that is suitable for the antistatic coating of floor coverings.

Commercially available insulation materials from various product groups were examined with regard to microbiological parameters. From the visual inspection and the quantitative microbial count using the suspension method, a background concentration of 105 CFU/g was confirmed for moulds and 106 CFU/g for bacteria. Thus, the limit values generally specified for building materials can also be applied to Nawaro insulation materials and defined as normal values of the background concentration in order to clearly identify an infestation in service that leads to significantly higher values. The suspension method was further developed for use with this group of building materials. When determining mould resistance in the laboratory, both standard and practical climatic conditions were realised using a new evaluation scheme and taking into account longer testing times.

At the Institut für Holztechnologie Dresden (IHD) investigations were carried out within a joint project to optimise the production of insulating materials from renewable raw materials. For this purpose, possibilities of changing the fibre qualities produced during the defibration process were investigated, the orientation of the fibres within the panel level was changed and the use of wheat straw fibre was tested. The fibre orientation within the insulation panel has the most significant influence on the thermal conductivity. It is estimated that the customary arrangement of the fibres, usually parallel to the panel level, already exploits this potential very well. A further influence could be demonstrated with regard to the degree of fibre disintegration. Here, a reduction of the refining gap in the refiner led to an improvement in the thermal insulation properties of insulation materials made from these fibres.

The article presents the fire performance, the mechanical-physical properties of thermo-mechanical pulp (TMP) treated with P-N containing fire-retardants (FR), and MDF made out of it. Three P-N containing FR with different P-N ratios were used. The FRs were added to the fibres with two different loadings (10 % and 20 % dry salt on dry wood). In addition to the FR, three adhesive types were tested (mUF, PF, pMDI). The TMP modified with FR were characterised chemically (pH value, buffer capacity, C-N-P content) and thermo-gravimetrically (TGA). The fire properties of the MDF were analysed by cone calorimetry. All three FR lead to a significant reduction in heat release in both the fibres and the MDF, regardless of the P-N content. The FR content exerts the greatest influence on the fire properties. In the case of the three adhesives, the reduction in the mechanical properties is only satisfactorily counteracted by pMDI.