Page 56 - FDMAsia SepOct 2025

54 MATERIALS SEP/OCT 2025 FDM ASIA | www.fdmasia.com

www.freepik.com separated using a sieve shaker and used for SE and SA
A particle fraction ranging from 0.5 to two mm was then

board manufacturing.
Isolated and extracted birch (Betula pendula) outer bark

with a moisture content (MC) of 4–5 wt.% and fraction of 1
< d ≤ 2 mm.
The feedstock was prepared by milling in an SM 100
cutting mill, fractionating by sieving using an AS 200 Basic
vibratory sieve shaker, and extracted in ethanol (96%).
Before SE treatment, crushed raw materials were moistened
by water to achieve MC of 50 percent for WS and 60 percent for
GA and SW. The materials were then pretreated separately using
The novelty of the study is characterised by the fact that a custom-built SE device equipped with a 0.5 L batch reactor.

there was not found in the literature, including our previous SE pretreatment conditions, temperature 220 deg C and
works, the development of biobased particleboards for residence time of 2 min (severity factor logR0 = 3.83), for
application in external façade using these two approaches. WS and GA chips were selected based on previous studies.
This article investigates the influence of technological The SE reactor’s volume was filled by the prepared raw
aspects of board production, focusing on locally available material, and the saturated steam was injected within 3–5 s
lignocellulosic biomass (LCB), like wheat straw, hardwood to reach the pressure of 23 bar and maintained for 110 s.
(grey alder), and softwood (a mix of spruce and pine), board The steam pressure was then elevated to 30 bar for the

type (SE-treated and SA-bonded), and conventional vs. mould last 10 s, after which the reactor was opened immediately,
hot-pressing on the obtained board properties. and a rapid decompression resulted in a steam explosion,
In general, the study has shown the advantage of wood providing the pretreated material to a receiver.
species vs. wheat straw and confirmed both used technologies The selection of SE conditions for SW species was based
are suitable for high-density board production using conventional on the previous work and approved during this study as 230
hot-pressing. deg C–90 s. The SE-pretreated LCB was centrifuged to separate
For the board production, three locally available LCB raw the liquid fraction based on the literature recommendations.
materials of wood and non-wood species were used in the The residual solid fraction was mechanically processed
study: wheat straw (WS, Triticum aestivum), grey alder (GA, through a system of two rotating cylinders coupled with

Alnus incana), and softwood (SW) that was a mix of spruce stainless steel wires, and then oven-dried at a temperature
(Picea abies) and pine (Pinus sylvestris) wood (50/50 wt.%). of 60 deg C to MC of 2% ± 0.2%.
Each species was chopped according to the treatment The SA binder was obtained from extracted birch outer
described below. bark (1–2 mm) by hydrolytic depolymerisation, which was
For the production of SE boards, the raw materials were carried out in a 100 L stainless steel reactor equipped with an
initially crushed using a knife mill equipped with a 10 mm oil heating jacket, reflux condenser, and a mechanical stirrer.
sieve. To produce SA-bonded boards, raw materials were A water solution of four wt.% KOH was used for

subsequently processed using a cutting mill fitted with a depolymerisation, and the bark was suspended at a bark-to-
two mm sieve. liquid mass ratio of 1:10. The depolymerisation was carried