FirmoLin Technologies BV

Deurne, Netherlands

FirmoLin Technologies BV

Deurne, Netherlands
SEARCH FILTERS
Time filter
Source Type

The wood moisture sorption (WMS) isotherm is generally considered to contain information on the water-cell wall interaction and the abundance of water sorption sites (SSs) in wood. The Hailwood-Horrobin (HH) model-as an example of the multilayer surface sorption models-is discussed for its suitability to analyze experimental WMS isotherms, to elaborate the fundamental sorption parameters. Based on multiple independent experimental and theoretical arguments, it was concluded that the basics of the surface multilayer-sorption models do not apply to wood. This is clearly illustrated by applying the analysis to the temperature-dependence of WMS isotherms, to the comparison of adsorption vs. desorption isotherms and to the quantification of SSs in wood. A sorption site occupancy (SSO) model is presented as an alternative for the HH model. It provides a comprehensive, thermodynamically consistent and quantitative basis for the analysis of WMS isotherms. The predicted SS densities are realistic and can be used to quantify sorption hysteresis and cell wall relaxation. © 2015 by De Gruyter 2015.


Willems W.,FirmoLin Technologies BV
International Wood Products Journal | Year: 2016

This research analyses the effect of a glassy state of wood polymers, as found in some dense naturally durable wood species and in thermally modified wood (TMW), on their equilibrium moisture content, mechanical and fungal resistance (durability) performance. In the EN350-class I durability range, moisture and fungal durability are argued to become controlled by the physical state of wood polymers rather than their chemical composition. Glassy polymers may assist the dimensional stability and fungal resistance of wood, as characterised by standardised accelerated laboratory tests. However, for long-term mechanical performance and fungal resistance in service, strong cross-links must prevent the natural (aging) relaxation of the glassy state. Physical aging is expected to occur in TMW, as opposed to naturally durable wood species. The current test methodology for dimensional and fungal stability does not take physical aging effects in wood polymers into account. © 2016 IWSc, The Wood Technology Society of the Institute of Materials, Minerals and Mining.


Willems W.,University of Gottingen | Willems W.,FirmoLin Technologies BV | Altgen M.,University of Gottingen | Militz H.,University of Gottingen
International Wood Products Journal | Year: 2015

A large number of different heating technologies has been put into use for industrial scale thermal modification of wood. A useful classification of these processes is by the level of water vapour pressure, which ranges from vacuum to high saturated steam pressures. Only high water vapour pressure systems can maintain a finite moisture content during the heat treatment, but little is known about the water vapour pressure dependence of the thermal modification chemistry and the resulting modified wood properties. It is concluded from our analysis that the thermal wood reaction chemistry at the molecular functional group level is quite independent of the process and wood species. Wood properties that are strongly determined by wood chemical composition, such as the fungal durability and the equilibrium moisture content (EMC), can hence be equally achieved by all processes and for all wood species. This finding cannot be transferred to every other thermally modified wood property. © 2015 IWSc.


Willems W.,FirmoLin Technologies BV
Holzforschung | Year: 2016

The equilibrium moisture content (EMC) of a wood specimen is known to be a function of the (absolute) temperature T and humidity h of the environment. In the present paper, it is directly derived from equilibrium thermodynamics that EMC is more specifically a function of the water chemical potential μ=RT ln h (Polanyi's postulate). It is shown that wood moisture thermodynamics then becomes considerably simplified, allowing the calculation of the energy of wood-water interactions from the data of a single-temperature moisture adsorption. A critical comparative analysis on the theoretically calculated adsorption enthalpy and published data, obtained from isosteric and calorimetric measurements, is given. It is deduced from the theory that all bound moisture is non-freezing and that the heat capacities of bound and free wood moisture are equal. © 2016 Walter de Gruyter GmbH, Berlin/Boston.


Willems W.,University of Gottingen | Willems W.,FirmoLin Technologies BV | Gerardin P.,CNRS Wood Materials Research Laboratory | Militz H.,University of Gottingen
Polymer Degradation and Stability | Year: 2013

It has recently been reported that the oxygen to carbon-ratio (O/C) of thermally modified wood is a reliable indicator for the resistance against attack by Basidiomycete fungi. The present theoretical study is an attempt to clarify causality between the O/C-ratio of thermally modified wood and its fungal resistance, as measured by standardized laboratory test procedures. It is shown that different wood species, with varying degree of thermal modification, reveal a remarkable correlation in elemental composition when plotted in a van Krevelen state diagram, suggesting a common modification chemistry shared by these species. The overall chemical reaction types responsible for the composition changes appear to be mainly dehydration, with some decarboxylation. The latter reaction decreases the mean overall oxidation state of carbon atoms present in thermally modified wood, leading to an inherently improved resistance against oxidation of the material. A known general correlation, between the average oxidation state of organic matter and the Gibbs free energy of the oxidation half-reaction, was found quantitatively consistent with the observed trend in the fungal resistance of thermally modified wood with the O/C-ratio. © 2013 Elsevier Ltd.


Willems W.,FirmoLin Technologies BV | Willems W.,University of Gottingen | Lykidis C.,Institute of Mediterranean Forest Ecosystems and Forest Products Technology | Altgen M.,University of Gottingen | Clauder L.,Eberswalde University Of Applied Sciences
Holzforschung | Year: 2015

Thermally modified wood (TMW) is currently produced commercially by a range of processes across many countries. A prerequisite of the commercial success is an efficient quality control (QC), and methods with this regard are discussed in this review. When direct measurement of the key attribute of the material is not feasible, QC is based on a suitably chosen physical or chemical "marker". A critical evaluation of currently applied markers reveals that most of them only provide data for comparative purposes for a particular species and/or over a narrow process range. Such markers do not allow making an objective judgment of quality, which is independent of process information or reference samples provided by the manufacturer. On the other hand, they can be very useful for monitoring product variability in the TMW factory and wood during the heat treatment. Recommendations for future development are the general validation of (combinations of) known TMW markers for different wood species and processes, resulting in (1) a reliable and fast laboratory QC method for given samples of unknown origin, (2) a simple and fast indicative QC test for end users, and (3) in-line product markers for feedback-controlled production. © 2015 by De Gruyter.


Willems W.,FirmoLin Technologies BV
Wood Science and Technology | Year: 2014

By expressing wood moisture content data as a function of adsorption energy, an interesting scaling capability is obtained, wherefrom the general hydrostatic pressure and temperature dependence of wood moisture content is determined. The scaling law is fully consistent with the thermodynamics of swelling. It can be used to transform room condition sorption isotherms to other temperatures and hydrostatic pressures, provided that the wood matrix is not irreversibly modified. A special procedure is suggested for the case of an irreversibly changing wood matrix, as in thermal modification and thermo-hydro-mechanical treatments. Using the present scaling theory, several fundamental aspects of wood moisture sorption are explained, such as the absence of a significant quantity of strongly bound wood moisture, the internal stress generation by sorption hysteresis in the wood cell wall, and the reason for the reversible disappearance of the sigmoid shape of the sorption isotherm at higher temperature. The results of this research may be useful (a) for transformation of known sorption data to other conditions, notably where in situ moisture measurements are difficult to perform and (b) to quantify the effects of internal stresses in the ultrastructure of the cell wall on moisture content. © 2014 Springer-Verlag Berlin Heidelberg.


Willems W.,FirmoLin Technologies BV
Wood Science and Technology | Year: 2014

A new method of wood moisture sorption analysis is presented using sorption isotherms of a series of mildly heat-treated specimens with varied and known elemental composition. This method allows the determination of the occupancy of accessible sorption sites in wood as a function of relative humidity h, θ(h) ≈ h, found in agreement with the literature data on the non-freezing water occupancy of hydroxyl groups for h < 0.9. Complementary sorption isotherm shape analysis identifies an empirical power law occupancy function, θ(h) = h α, α ≈ 0.73, which is close to the former two determinations in the same humidity range. The validity of widely accepted surface sorption theories for wood with a strongly bound primary layer and loosely bound secondary layers is disproven. To explain the found occupancy function, θ(h) ≈ h, a near-ideal liquid mixture of moisture and polar dynamic microvoids in the cell wall substance is postulated. The power law occupancy function is used to calculate the humidity-dependent number of sorption sites in adsorption/desorption isotherms to show that (1) the number of sorption sites from the adsorption line monotonically increases with increasing humidity - argued to represent the equilibrium number of sorption sites at each humidity, and (2) the number of sorption sites from the desorption line fails to fully return to that of the (equilibrium) adsorption line. Hysteresis is quantitatively explained as the result of non-equilibrium excess sorption sites being occupied according to the occupancy law. The relaxation of non-equilibrium excess sorption sites is satisfactorily modeled by a first-order rate equation. Applying the analysis to study mild thermal modification of moisture sorption isotherms revealed that (1) moisture contents decrease directly linear to the removed amount of sorption sites at all humidity <0.95, and (2) the absolute hysteresis is nearly unaffected as a result of counter-acting effects of the reduced number of sorption sites and reduced amount of relaxation. © 2014 Springer-Verlag Berlin Heidelberg.


Willems W.,University of Gottingen | Willems W.,FirmoLin Technologies BV | Mai C.,University of Gottingen | Militz H.,University of Gottingen
International Wood Products Journal | Year: 2013

Wood compositional changes during thermal modification follow a characteristic trajectory when mapped in a van Krevelen diagram. The trajectories of widely different wood species appear to merge into a single master curve, suggesting a common thermal modification chemistry shared by these wood species. The largest effect of thermal modification on the chemical composition can be explained by dehydration reactions, followed by decarboxylation reactions. A carbon valence electron donor-acceptor model is proposed, which relates the observed compositional changes to changes in polarity and redox character, which in turn are related to the characteristic hydrophobic and fungal resistance effects on wood by thermal modification. © 2013 IWSc, the Wood Technology Society of the Institute of Materials, Minerals and Mining.

Loading FirmoLin Technologies BV collaborators
Loading FirmoLin Technologies BV collaborators