Characterisation of hardwood fibres used for wood fibre insulation boards (WFIB)

Abstract

Wood fibre insulation boards (WFIB) are typically made from softwood fibres. However, due to the rapid decrease in softwood stands in Germany, the industry will be forced to adapt to the wood market. Therefore, alternative approaches for the substitution of softwood with hardwood will be needed in the fibre industry. The objective of this paper is to address the characterisation of hardwood fibres regarding their availability for the WFIB industry. The physico-mechanical properties of WFIB are significantly determined by the length of the fibres. Longer softwood fibres usually generate higher strength properties and a lower thermal conductivity than shorter hardwood fibres. In this paper, the potential application of hardwood fibres (up to 20,500 μm long) produced in a refiner by thermo-mechanical pulping (TMP) to WFIB production was examined. The scanner-based system FibreShape was used for the automatic optical analysis of the geodesic length distribution of fibres. The analysed hardwood fibres contained significantly more dust and were shorter than respectively produced softwood fibres, limiting their applicability for WFIB production. Thus, two analytical approaches were chosen to receive longer fibres and less dust: (1) blending hardwood fibres with supporting softwood fibres (20%, 50 and 80% proportion of softwood), and (2) mathematical fractionation of hardwood fibres based on the fibre length to remove all particles smaller than 500 μm. It was concluded that the practical fractionation seems to be economically and ecologically challenging and that blending hardwood fibres with at least 50% softwood fibres offers a promising approach, which should be further studied.

Thermoplastic Hybrid Composites with Wood Fibers: Bond Strength of Back-Injected Structures

“…For the same material, measurement deviations between the methods are therefore unavoidable. Currently, there is no standard method for sufficient characterization [ 62 , 63 ]. A more precise analysis of the fiber geometries, as well as the length–diameter ratio (L/D ratio) via optical fiber length measuring systems (FASEP Eco System, FiberShape Cross M) and computed tomography (TomoScope XS Plus), is currently being investigated at the TH Rosenheim.…”

Study on Attenuation Characteristics of Acoustic Emission Signals with Different Frequencies in Wood

“…At the same frequency, the energy attenuation distance of hard wood was smaller than that of soft wood, with the farthest propagation distance of 192.94 mm for hard wood and 207.57 mm for soft wood. This was due to the fact that the AE signal propagated mainly along the fiber direction in wood, and, therefore, in hardwoods with shorter fibers [36], the AE signal energy attenuated more quickly.…”

Herstellung von Holzfaserdämmstoffen auf Laub- und Nadelholzbasis mit dem Fokus auf der Fasercharakterisierung, sowie der Ermittlung der physikalischen, mechanischen und biologischen Eigenschaften

“…While the value for beech boards is only one-third of that reported in this study, the value for spruce boards is one and a half times as high and that for oak is almost the same in both studies. The reason for the different results may be attributed to differences in the process conditions, particularly the disc gap, for fibre production, which influences the length and geometry of the fibres (Imken et al 2021a).…”

“…Veröffentlichung 3: Examination of various hardwood and softwood fibres for the usage in wood fibre insulation boards (WFIB) The defibration conditions from Table 1 are based on findings from a previous study (Imken et al 2021a), while did not indicate it. A previous study using a disc gap of 0.6 mm revealed internal bond strengths of 1.1 kPa for birch and 6.0 kPa for spruce (Imken et al 2021b).…”

“…The proposed bias affected all examination subjects equally and allows the results to be related to each other and to porosity data acquired at similar resolution to be considered reliable. However, as dust particles smaller than 500 µm are more common in hardwood fibres (Imken et al 2021a), the underestimation of porosity might have had a stronger effect on hardwood specimens than on softwood specimens.…”