Stefan Veigel

University of Natural Resources and Life Sciences Vienna | boku · Department of Material Sciences and Process Engineering

Regarding mechanics, wood is one of the most efficient materials available. Due to its unique combination of composite and cellular microstructure, it exhibits superb specific mechanical properties which exceed many man-made materials. However, concerning absolute mechanical properties, wood is often inferior to metals and novel engineered composit...

Cellulose (rayon) filaments were exposed to various concentrations of hydrochloric acid under aqueous and non-aqueous conditions in order to study differences in degradation. Two sources of polymeric diphenylmethane diisocyanate (pMDI) were used as non-aqueous media. As a consequence of the production process, pMDI was found to contain residual hyd...

Nanoporous silica gels feature extremely large specific surface areas and high porosities and are ideal candidates for adsorption-related processes, although they are commonly rather fragile. To overcome this obstacle, we developed a novel, completely solvent-free process to prepare mechanically robust CNF-reinforced silica nanocomposites via the i...

In recent times, a clear trend towards the use of biobased materials can be seen in many areas. Apart from beneficial ecological properties, high strength and stiffness at low weight are desirable in structural applications, a combination typically offered by cellulose-based materials. As an adaption to mechanical stresses acting on the living orga...

The present study investigated the effect of selected structural parameters on the mechanical performance of regenerated cellulose composites. The experimental setup comprised continuous viscose (rayon) yarns embedded in a matrix of epoxy resin. Mechanical and microscopic characterizations involved comparing the following: yarns consisting of untwi...

Nowadays materials for soft electronics are in high demand; among the different forms of conducting materials, conducting gels have become promising candidates. They provide both the electrical conductivity and mechanical flexibility which are prerequisites for such applications. Herein, one-step facile preparation of polypyrrole–nanofibrillated ce...

In the development of structural composites based on regenerated cellulose filaments, the physical and chemical interactions at the fibre-matrix interphase need to be fully understood. In the present study, continuous yarns and filaments of viscose (rayon) were treated with either polymeric diphenylmethane diisocyanate (pMDI) or a pMDI-based harden...

Fine fibre fractions in wood pulp may contribute to advantageous paper properties, but in some instances their removal from pulp may be beneficial to the production process of certain paper grades. In order to study the suitability of fine fibre fractions for the production of nanocellulose as an alternative use option, sulfite pulp was fractionate...

This study investigates the use of papermaking fines as a reinforcement fibre for fully bio-based highly densified paperboards. Paperboards were prepared in a wet process followed by subsequent densification, aiming to exploit the self-bonding capabilities of cellulosic fibres without addition of synthetic binders. The cohesion of paper-based mater...

Here we present a general concept of wet surface esterification of cellulose using acyl imidazoles, which enables direct acetylation of never-dried cellulose fibres in aqueous conditions. We hope that due...

Aminoplastic particleboard adhesives are reactive, inexpensive and well established in industry. Even so, potential adhesive savings are of interest due to a number of reasons. Therefore, fibrillar cellulosic additives derived from sugar beet pulp and from wood pulp were examined with regard to beneficial effects on adhesive performance. Particlebo...

Golf tees with a plastic head and wooden shaft were prepared by back injection moulding of a beech wood (Fagus sylvatica) shaft with different polymers (i.e. ionomer, polypropylene, and polyamide). In order to facilitate adhesion between the polymer melt and the wood surface, the wooden shafts were pre-treated with different primer substances, incl...

The mechanical reinforcement of porous materials made of microfibrillated cellulose by in situ polymerisation of furfuryl alcohol prior to freeze-drying from aqueous slurry was studied. Besides a slight improvement in the modulus of elasticity measured in compression testing, no beneficial effects of furfuryl alcohol addition on porous materials pr...

2,3-Dialdehyde cellulose (DAC) of a high degree of oxidation (92% relative to AGU units) prepared by oxidation of microcrystalline cellulose with sodium periodate (48 °C, 19 hours) is soluble in hot water. Solution casting, slow air drying, hot pressing and reinforcement by cellulose nanocrystals afforded films (~100 µm thickness) that feature intr...

Urea formaldehyde (UF) resins are important for wood industry due to their attractive properties at reasonable price. Particulate fillers added to UF are of interest with regard to improving the functionality of UF and also in terms of reduced UF consumption. To study their potential as filler, solid UF microspheres were synthesized and characteris...

Microfibrillated cellulose (MFC) is a fascinating material with an obvious potential for composite reinforcement due to its excellent mechanics together with high specific surface area. However, in order to use this potential, commercially viable solutions to important technological challenges have to be found. Notably, the distinct hydrophilicity...

Due to their bio-based character, oil-based coatings become more and more prevalent in wood surface finishing. These coatings impart appealing optical and haptic properties to the wood surface, but lack sufficient protection against water and mechanical influences. The present study reports a simple green route to improve the performance of linseed...

The self-adhesive potential of nanocellulose from aqueous cellulosic suspensions is of interest with regard to a potential replacement of synthetic adhesives. In order to evaluate the performance of microfibrillated cellulose from different (ligno-)cellulosic raw materials for this purpose, softwood and hardwood powder were fibrillated and compared...

Coatings fulfill an important function in providing functionality and service life to wood surfaces. In the present study, the potential of nanocellulosic fillers toward improving waterborne wood coating mechanics is evaluated using free-standing coating films. At 2% filler content, significant improvements in static and dynamic mechanical properti...

In order to produce dry and hydrophobic microfibrillated cellulose (MFC) in a simple procedure, its modification with alkyl ketene dimer (AKD) was performed. For this purpose, MFC was solvent-exchanged to ethyl acetate and mixed with AKD dissolved in the same solvent. Curing at 130 °C for 20 h under the catalysis of 1-methylimidazole yielded a dry...

Several studies demonstrate that the addition of microfibrillated cellulose (MFC) to urea-formaldehyde (UF) wood adhesive improves the mechanical bond strength of wood particle board. In order to elucidate potential underlying mechanisms, the distribution of unmodified UF as well as MFC-modified UF (UF-MFC) in particle board was studied by means of...

Cellulose-reinforced polycaprolactone (PCL) nanocomposite films were produced by casting from organic solvent. Microfibrillated cellulose derived from bleached pulp (MFC) and from pulp with high residual lignin content, termed microfibrillated lignocellulose (MFLC) were used as filler without any kind of chemical surface modification. Visual inspec...

Commercial kraft lignin was thermostabilised by heating up to 250 °C at a rate of 0.01 °C min−1 in ambient atmosphere. Subsequent carbonisation at 2000 °C in argon atmosphere yielded carbon microparticles containing ordered graphitic domains. Micromechanical characterisation by nanoindentation yielded average values of 1.39 GPa for hardness and 8.2...

Microfibrillated lignocellulose (MFLC) was produced from wood subjected to partial lignin extraction using an ethanol/water mixture. After homogenization, the average fibril diameter of MFLC was in the same range as conventional microfibrillated cellulose (MFC). Although MFLC exhibited higher wettability with water compared to MFC, AFM adhesion for...

In the present study, microfibrillated cellulose (MFC) and nanocrystalline cellulose (NCC) were applied as additives for a waterborne acrylate/polyurethane-based wood coating in order to improve the mechanical resistance of coated wood surfaces. Coating mixtures containing up to 5 wt% nanocellulose were prepared by high-shear mixing and applied to...

The feasibility of the isolation of microfibrillated cellulose (MFC) from the fibrous residue of the production of biogas from Miscanthus straw was investigated. Studying two variants of continuous anaerobic fermentation carried out at mesophilic and thermophilic conditions, respectively, MFC was obtained after extensive extraction of non-cellulosi...

Spruce wood specimens were surface-silylated according to three different protocols in order to progressively reduce hydrophilicity and, consequently, adhesion to urea-formaldehyde (UF) glue. Compared to the untreated reference, the macroscopic adhesive strength was drastically reduced in silylated specimens. Specimens treated with the most effecti...

Adhesives on the basis of urea-formaldehyde (UF) and melamine-urea-formaldehyde (MUF) are extensively used in the production of wood-based panels. In the present study, the attempt was made to improve the mechanical board properties by reinforcing these adhesives with cellulose nanofibers (CNFs). The latter were produced from dissolving grade beech...

Thin sheets of nanopaper were prepared from cellulose nanofibrils (CNF) obtained by means of high-pressure homogenisation of dissolving-grade beech pulp. Untreated pulp and pulp pre-treated by TEMPO-mediated surface oxidation were used, which resulted in significant differences in structure and mechanical performance of the nanopaper specimens. Ove...

Cellulose nanofibrils were prepared by mechanical fibrillation of never-dried beech pulp and bacterial cellulose. To facilitate the separation of individual fibrils, one part of the wood pulp was surface-carboxylated by a catalytic oxidation using (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) as a catalyst. After fibrillation by a high pressure h...

The effect of different machining processes on surface roughness and on adhesive tensile strength of end-grain-bonded spruce wood specimens was studied. Surfaces that had been cut with two different circular saws containing 48 and 96 teeth were compared with those that had been further processed by smoothing with a microtome, machine planing, or sa...

A wood composite material comprises a wood veneer (3) having a thickness of 0.2-1.5 mm, where the wood veneer is bonded with a tear-resistant film (1) by using an adhesive (2). The tear-resistant film includes cellulose or cellulose fibers with a thickness of 0.01-0.4 mm. Independent claims are also included for: (1) production of wood composite ma...

In this study, lap shear strength as well as specific fracture energy of bonded specimens from spruce wood were determined in order to verify whether the calculation of adhesive fracture energy is a suitable tool for the mechanical characterization of different adhesive systems, especially in comparison to the commonly used lap joint test method ac...

This paper provides an overview of recent progress made in the area of cellulose nanofibre-based nanocomposites. An introduction into the methods used to isolate cellulose nanofibres (nanowhiskers, nanofibrils) is given, with details of their structure. Following this, the article is split into sections dealing with processing and characterisation...

Testing of adhesive bond strength by means of the lap joint test (European Standards EN 302) delivers no clear differentiation of the adhesives because of the high percentage of wood failure. However, individual adhesives show considerable differences in their stiffness and mechanical properties. Using optical methods i.e. speckle interferometry th...

End-grain surfaces of spruce wood specimens that were planed with a microtome knife were chemically modified by treatment with bleaching reagents, namely sodium hypochlorite and peracetic acid, and the effect of the surface modification on bond strength of end-grain joints was studied. The chemically treated samples were compared with sawn surfaces...