JAHRGANG 55, AUSGABE 2/2014

The acidity of larch heartwood from Europe and from three different locations in Siberia, spruce and pine sapwood (unknown origin) has been explored by cold water-extraction and at the surface using a flat membrane electrode. Larch heartwood from Europe had lower pH-values and less buffering capacity (HCl and NaOH) than larch heartwood from the Siberian locations, with significantly smaller spread of the values between individual boards from Europe. The differences between the three Siberian locations have been overlapping by the spread between individual boards. Measurements of the influence of the processes of change of material close to the surface to the pH-value showed an increase of the pH-values at aged surfaces and a moderate influence of a thermal pre-treatment (exudation of resin) on the pH-value by both measuring methods. The data measured enabled to create a model to estimate the pH-value in the cold water-extract out of the pH-values on the surface for larch heartwood.

Particleboards, MDF and plywood of very low formaldehyde emission were produced with a UF resin of low formaldehyde content (molar ratio U:F = 1: 0.94) and tannin in combination with urea as formaldehyde scavenger. The formaldehyde emission of the boards was partly in the area of the formaldehyde emission of wood particles. With the formaldehyde scavengers (up to 1 % tannin and 1 % urea based on dry wood) the strength and thickness swelling values of the particleboards and MDF remained largely intact.

Procedures and methods for the treatment of biomass for the subsequent production of bioethanol as well as for the analysis of the main components, intermediate and final products of hydrothermal digestion, fermentability and yields of ethanol were established. This built of Institut für Holztechnologie Dresden (IHD) technical and methodological skills permit process developments in the field of production of bio-based liquid fuels (ethanol, butanol), but also of biogas. Specifically, the chemical analytical capabilities to enable response of recurring problems in the field of characterization of lignocellulosics in connection with the chemical modification of wood, characterization of the reaction products of wood or of its components, as well as the interaction with adhesives.

Hydrothermischer Aufschluss von Lignozellulosen

sowie zugehörige Analytik

Es wurden Verfahren und Methoden zur Aufbereitung von Biomassen für die anschließende

Gewinnung von Bioethanol sowie für die Analytik der Hauptkomponenten, Zwischen- und Endprodukte

hydrothermischer Aufschlüsse und der Vergärbarkeit und Ausbeuten an Ethanol etabliert. Diese am

Institut für Holztechnologie Dresden (IHD) aufgebauten technischen und methodischen Fähigkeiten

gestatten Verfahrensentwicklungen im Bereich der Gewinnung biobasierter Flüssigtreibstoffe

(Ethanol, Butanol) aber auch von Biogas. Speziell die chemisch-analytischen Möglichkeiten befähigen

zur Beantwortung wiederkehrender Fragestellungen in den Bereichen der Charakterisierung von

Lignozellulosen im Zusammenhang mit deren Vergütung, der Charakterisierung von Reaktionsprodukten

der chemischen Modifizierung von Holz bzw. von dessen Bestandteilen oder auch der Wechselwirkung

mit Bindemitteln.

The Barkhausen noise map method was used for evaluation of residual stresses distribution in a

circular saw blade. It was also measured the natural frequencies and the vibration modes. Large

fluctuations of the Barkhausen noise signal were recognized for examined saws, which failed in the

beginning of work. The tangential resolution of 11.25° seems to be not sufficient for precise assignment of fluctuations of the Barkhausen noise with deformations of the diameter vibration mode

arms.

The requirements for rigid guards and safety curtains are described in the European standard

EN 848-3 (2010) “Safety of woodworking machines – One side moulding machines with rotating

tools – Part 3: Numerically controlled boring and routing machines“. Regardless of this standard,

accidents were still occurring in the workplace due to the ejection of tool parts out of the machine.

Because of this, the European Commission ordered a revision of the standard, particularly with

regard to the danger of parts being ejected. Formerly guards such as strip curtains had to be able

to withstand a 20 g projectile with a velocity of 70 m/s, whereas according to the new standard, a

projectile mass of 100 g at the same velocity is required to prove their retention capacity. The aim

of these investigations is to develop a machine enclosure that is lighter than conventional sheet

steel housings and has the required retention capacity, according to the standard.

Corrugated cardboard as packaging material is one of the most important and popular packaging materials for the transport of goods. Due to its raw materials corrugated cardboard tends to creep at an increased humidity, which can ultimately lead to loss of strength. The loss of strength of the packaging can result damages to the goods being transported. The creep behaviour and the long-term sustainability of corrugated cardboard can currently only be estimated based on the so-called short-term tests or protracted long-term studies of the packages with the aid of security factors. To enable a reliable, time-saving and space-saving assessment of the creep behaviour of corrugated cardboard, the prototype of a creep rupture test apparatus on ECT-specimens was started up and optimized at Institut für BFSV of Hochschule für Angewandte Wissenschaften Hamburg. To bring the measured creep rates of the specimens in a secure connection with the creep rates of the packages further investigations are necessary.

The natural durability of wood and wood based products against wood-destroying fungi and insects is an important characteristic for any application. There are a lot of standards and technical guidelines available. The standard DIN EN 350 (1994) plays an important role in this field. DIN EN 350-1 (1994) is a guideline for testing methods and classification. DIN EN 350-2 (1994) contains a list of wood species with specifications according to their resistance against wood destroying fungi and insects. At the moment, both parts are under revision and give reason for prolonged expert discussions. The following article summarizes the current state of discussion.