COATINGS FOR THERMOWOOD Fourth International Woodcoatings Congress 25-27 October 2004 The Hague Saila Jämsä
ThermoWood technology The ThermoWood treatment improves woods dimensional stability and durability against decay and gives it a pleasant deep-brown colour ThermoWood is a heat-treatment technology for wood developed and patented by VTT Today the industrial scale of wood heat treatment process, under trade name ThermoWood, has licensed to the members of the Finnish Thermowood Association 10.11.2004 2
Current industrial use Estimated ThermoWood production 30 000 m3 in 2004 Kiln Manufacturers (3) Valutec Ltd Tekmaheat Ltd Stellac Oy Ltd Wood manufacturers (11) Ekosampo Ltd Finnforest Ltd Heinolan Ruskopuu Ltd HJT-Holz Ltd Laukaan Lämpöpuu Ltd Brown Wood Ltd Lunawood Ltd Stellac Wood Mikkeli Ltd Stora EnsoTimber Ltd Suomen Lämpöpuu Ltd UPM-Kymmene Puuteollisus 10.11.2004 3
Wood species/production 2003 39 41 10 6 4 22 000 m3 2002 36 47 8 4 5 25 000 m3 2001 38 39 11 9 3 19 000 m3 0 % 20 % 40 % 60 % 80 % 100 % Pine Spruce Birch Aspen Alder Others Source: Finnish Thermowood Association 10.11.2004 4
Market area 2003 32 61 7 22 000 m3 2002 29 67 4 25 000 m3 2001 42 55 3 0 % 20 % 40 % 60 % 80 % 100 % 19 000 m3 Domestic EU Other Source: Finnish Thermowood Association 10.11.2004 5
Effect of treatment temperature to tangential swelling of pine Swelling(%) 12 11 10 9 8 7 6 5 4 3 2 1 0 Swelling = 0,087*Tmax - 0,00036*Tmax 2 + 3,4 R 2 = 0,93 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 Treatment temperature ( C) 10.11.2004 6
Effect of treatment temperature to tangential swelling of pine Confidence bands have been calculated at a risk level of 0,1 %. Swelling (%) 12 11 10 9 8 7 6 5 4 3 2 1 Swelling = 0,087*Tmax - 0,00036*Tmax 2 + 3,4 R 2 = 0,93 0 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 Treatment temperature ( C) Model Data Control upper CB for mean prediction lower CB for mean prediction upper CB for individual timber lower CB for individual timber 10.11.2004 7
Class ThermoWood standard classes Thermo-S and Thermo-D Properties of softwood (sapwood) Treatment temperature ( C) Tangential swelling (%) Natural durability class Thermo-S 190 6-8 3 Thermo-D 212 5-6 2 Untreated 60-80 8-10 3-4 Source: Finnish Thermowood Association 10.11.2004 8
Recommended end use applications for Thermo-S class heat-treated timber: Thermo-S Softwood - building components - furnishing in dry conditions - fixtures in dry conditions - furniture - garden furniture - sauna benches - door and window components Thermo-S Hardwood - furnishing -fixtures - furniture - flooring - sauna structures - garden furniture - cladding - shutter - fascia boards Source: www.thermowood.fi 10.11.2004 9
Sauna building, Thermo-S pine + sauna protection oil Photo: Finnish Thermowood Association 10.11.2004 10
Recommended end use applications for Thermo-D class heat-treated timber: Thermo-D Softwood - cladding - outer doors - shutters - environmental constructions - sauna and bathroom - furnishing - flooring - garden furniture Thermo-D Hardwood End use applications as in Thermo-S If a darker colour is desired, Thermo-D should be used Source: www.thermowood.fi 10.11.2004 11
Skiing museum Lahti built 1998, photo 1999: Thermo S - D, no coating Photo: Finnish Thermowood Association 10.11.2004 12
Music school, Kauniainen 2002: Thermo S- D, WBstain Photo: Finnish Thermowood Association 10.11.2004 13
Residential garden decking, Espoo: Thermo-D spruce, WB acrylate stain + WB wood oil Photo: Finnish Thermowood Association 10.11.2004 14
Treatment classes 2003 33 59 8 22 000 m3 2002 13 87 0 0 % 20 % 40 % 60 % 80 % 100 % 25 000 m3 Thermo-S Thermo-D Other Source: Finnish Thermowood Association 10.11.2004 15
Heat treated wood needs a protective coating After treatment (pine) After 6 months weathering 10.11.2004 16
Heat treated wood as a substrate for coatings after production wood is dry moisture content is 4-7 % resin bleed from the knots is reduced no problem with the adhesion fats and waxes disappear from the surface 10.11.2004 17
Experimental Pine and spruce panels were treated for 3 hours at 195 o C (class S) and 210 o C (class D) The panels were coated with 10 commercial coatings systems for cladding fence garden furniture door and window The panels were weathered according to EN 927-3 and the exposure time was August 2001 - September 2003 10.11.2004 18
The coating systems and substrates Nr Paint system Intended end-use Material 0 no planed and sawn pine and spruce pressure impregnated (CCA) pine 1 pigmented SB tall-oil stain cladding, fence, garden furniture planed and sawn pine and spruce 2 pigmented SB tall-oil for cladding, fence, garden furniture planed and sawn pine and spruce surface impregnation 3 SB alkyd undercoat /WB cladding, fence planed and sawn pine and spruce dispersion paint 4 SB alkyd paint/sb alkyd paint cladding, fence planed and sawn pine and spruce 5 WB stain/ 2 x WB paint door and window planed pine system 6 staining system door and window planed pine 7 WB acrylic paint door and window planed pine 8 WB undercoat and WB door and window planed pine lacquer 9 WB undercoat and WB paint garden furniture planed pine 10 WB stain + WB lacquer garden furniture planed pine 11 ICP reference planed and sawn pine and spruce pressure impregnated (CCA) pine 10.11.2004 19
Moisture content of spruce panels coated with a waterborne paint: August 2001 - September 2003 24 22 20 18 16 Moisture content (%) 14 12 10 8 6 4 2 0 9.8.01 17.9.01 16.10.01 15.11.01 5.4.02 2.5.02 3.6.02 9.7.02 12.8.02 10.9.02 29.10.02 23.04.03 4.6.03 30.09.03 spruce class S class D 10.11.2004 20
Average moisture content of spruce panels during two years natural exposure (exposure August 2001 - September 2003) 20 No heat treatment Average moisture content during two years of exposure 15 10 5 Stained spruce Painted spruce Untreated spruce Class S Class D 0 10.11.2004 21
Cracking of spruce panels 5 No heat treatment Class S Class D Cracking 0-5 4 3 2 1 0 Stained spruce Painted spruce Untreated spruce 10.11.2004 22
Mould and blue stain Performance of the coatings no differences between heat treated or untreated panels no differences between pine and spruce 10.11.2004 23
Conclusions Heat treated wood should be coated if the original colour is preferred The recommendations for the painting are the same as for normal wood The endprotection is important to decrease water absorption through the end-grains 10.11.2004 24
Advantages in using modified wood as a substrate for coatings Heat treated wood has lower moisture content than untreated wood smaller dimensional changes no twisting or cupping - expected better long term durability of the coatings and longer periods without maintenance 10.11.2004 25