Christian Hansmann

This study investigates the reaction to fire of 9-layer birch plywood bonded with three industrially relevant adhesive systems: urea formaldehyde (UF), melamine urea formaldehyde (MUF), and phenol formaldehyde (PF). Panels were prepared under standardized conditions and evaluated at multiple scales—ranging from fuel property characterisation and thermogravimetric analysis to bench-scale cone calorimetry and ignition testing in the single flame test (SFT). A self-constructed Mini-SBI test (downscaled single burning item test) was developed to capture intermediate-scale reaction to fire with a focus on the orientation of the surface veneer layer. Results reveal that UF-bonded plywood, particularly with lengthwise-oriented surface veneers, exhibited the most critical fire response, including increased susceptibility to ignition during extended localized flame exposure and fire growth promoted by adhesive-controlled veneer separation. PF-bonded samples showed greater thermal stability and higher char formation. MUF-bonded samples exhibited comparatively favourable ignition behaviour, while smoke-production differences among the adhesive systems were not statistically significant. Differences in thermal degradation and flammability highlight the influence of adhesive chemistry and veneer orientation on the reaction to fire of the material. The Mini-SBI setup differentiated between material variants and demonstrated its potential as a material-efficient intermediate-scale method for comparative fire testing during product development. This work highlights the need for adhesive-specific consideration in fire safety assessments of engineered wood products.

The branches of deciduous trees are optimised by nature to allow continuous adaptation and response to changing environmental conditions. As a result, the morphology and internal structure of the wood branches are often more variable than in the stem. Quantitatively, branches and stem tops represent 20–50% of the volume of the above-ground biomass of deciduous trees, which is currently under-utilized and mainly burned. To enable a higher-value application as a safe construction material, a comprehensive technological profile of branch wood is a prerequisite. Therefore, we performed single-blow impact pendulum tests in tangential wood direction on branch and stem wood samples of beech, oak, and poplar to investigate their relationship with wood density, macrostructural properties, fibre properties, and microfibril orientation of selected samples. Our results showed that the significant differences in mean impact bending strength between branch and stem for all species could not be explained by wood density. However, branch and stem wood with higher toughness are generally associated with longer fibres. Overall, branches showed higher MFA (microfibril angle) and lower fibre length compared to stems. We found that higher toughness in selected beech samples was associated with higher density and lower MFA. While oak also had a lower MFA, poplar had a higher MFA in high-toughness samples. Our empirical results provide insights into the species-specific structure-property relationships of hardwood branches, improving the understanding of their properties and variability, and potentially informing their use in structural applications.

Reversed-phase chromatography is based on a polar mobile phase and an apolar stationary phase. This separation mode is regularly used in planar (thin-layer) chromatography, and the necessary plates are commercially available. We investigated the preparation of hydrophobic plates for thin-layer chromatography by chemical vapor sorption of methyltrimethoxysilane directly onto a normal-phase plate. For this, a commercial normal-phase plate is simply exposed to the vapors of the reagent in a closed vessel. The obtained plates were characterized by infrared spectroscopy and dynamic water vapor sorption, which reported an extensive conversion of free hydroxyl groups by the reagent. The obtained plates were hydrophobic with a water contact angle close to 135°. The extent of hydrophobization precluded the use of pure water as an eluent while mixtures with organic solvents were perfectly adequate. The plates’ chromatographic performance was compared with that of C18 and paraffin-coated plates. For this, a set of parabens was separated with mixtures of acetone and water. The height of a theoretical plate was similar for the hydrophobized and the C18 plates (50–90 µm) and larger for the paraffin-coated ones. In contrast to the C18 plate, the hydrophobized and the paraffin-coated plates showed some selectivity for the analyte pair n-butylparaben and iso-butylparaben, which indicates a separation mechanism with the potential for regioselectivity.