session 13 ic2011 bonigut
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Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
Properties of thermally modified oriented strandboards (OSB)
Juergen Bonigut, Dr. Detlef KrugInstitute of Wood Technology Dresden, Dresden, Germany
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
Outline
1. Current situation2. Research goals3. Material and method4. Selected results5. Summary
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
Current situation - TMT
Thermal modification of solid wood is at the centre of R & DDegree of modification depends on the parameters
temperature
ambient pressure
oxygen content
duration of modification
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
Advantages
reduced moisture uptake
increased biological durability
improved dimensional stability by reducing swelling and shrinking
Disadvantages
decreased density
reduced physical properties
increased brittleness
forming of cracks, halos (softwoods)
Current situation - TMT
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
Current situation - PF WBM
Phenol formaldehyde resin bonded wood-based materials:
industry: storage of PF-bonded wbm in a (hot-) stack
during hot-stacking further and complete adhesive curing takes place due to high temperatures of panels right after hot-press
results in enhanced mechanical strength properties and improved hygroscopic properties
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
OSB production
logs / solid wood stranding strands resination forming hot-pressingOSB panels
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
logs / solid wood stranding strands resination forming hot-pressingOSB panels
Treatment types
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
logs / solid wood stranding strands resination forming hot-pressingOSB panels
Treatment types
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
logs / solid wood stranding strands resination hot-pressingOSB panels
Treatment types
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
Goals
Thermal post-treatment of PF-bonded oriented strandboards (OSB)
reduction of equilibrium moisture content (EMC),
reduction of thickness swelling,
improvement of internal bond strength (IB) after 2 h boiling,
reduction of creep behaviour.
Exploratory investigations with MUF-bonded SWP and PF-bonded MDF showed promising results
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
Material
PF-bonded industrial OSB
type: OSB/3 (acc. to EN 300)
density: 620 kg/m3 (38.7 lbs/cu.ft),
thickness: 16 mm (0.63 in.),
adhesive content: 7 % PF (solids/oven-dry wood)
content hydrophobing agent: 1.5 % paraffin (solids/oven-dry wood)
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
Thermal post-treatment
Post-treatment of OSB took place according to Mühlböck- procedure in a partner company‘s treatment chamber
Heating up and cooling down of the chamber: 3 min/KMaximum temperatures:
160 °C (320 F)
170 °C (338 F)
180 °C (356 F)
Holding time: 4 h
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
In analogy to thermally modified solid wood (TMT), OSB showed darker colouration over whole cross-section
Thermal post-treatment
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
Testing of properties
Short-term properties
IB (dry & 2 h boiling) (EN 300, EN 319),
MOR & MOE (EN 310),
TS (EN 317),
WA,
EMC (EN 323).
Long-term property
creep behaviour testing climate: 20 °C (68 F) / 85 % humidity
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
IB
Requirements for load-bearing boards for use in humid conditions (type OSB/3) according to EN 300: 0.32 MPa and 0.13 Mpa, respectively
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
MOR & MOE (main axis)
Requirements for load-bearing boards for use in humid conditions (type OSB/3) according to EN 300 (main axis): 20 MPa (MOR) and 3,500 MPA (MOE), respect.
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
TS
Requirements for load-bearing boards for use in humid conditions (type OSB/3) according to EN 300: max. 15 % after 24 h immersion in water
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
WA
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
EMC
Climate: 20 °C (68 F) / 65 % humidity
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
Creep behaviour
Creep factor describes relation between time-dependent increase of deflection under load and elastic initial deflection
Tested in accordance with ENV 1156
Wood-based panels – Determination of duration of load and creep factors
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
Creep behaviour
Creep behaviour is dependent on:
duration
stress level
climate
Duration of testing: 105 days
Stress level: 25 % of Fmax
Test climate: 20 °C (68 F) / 85 % humidity
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
Creep behaviour
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
Summary
Influence of thermal post-treatment on PF-bonded OSB
Property strongly positive
slightly positive
hardly / minor
slightly negative
strongly negative
IB (dry & after 2h boiling)
X
MOR & MOE X TS & WA (2 h & 24 h) X
EMC X creep behaviour X
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
Summary
Conclusion: by thermally post-treating PF-bonded OSB very positive effects could be shown, i. e. improvemements of most physical properties
Research into thermal post-treatment of wbm will be continued
Bonigut, KrugForest Products Society 65th International Convention Portland, OR, June 2011
www.ihd-dresden.debonigut@ihd-dresden.de
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