COATINGS FOR THERMOWOOD. Fourth International Woodcoatings Congress October 2004 The Hague Saila Jämsä

Transcription

1 COATINGS FOR THERMOWOOD Fourth International Woodcoatings Congress October 2004 The Hague Saila Jämsä

2 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

3 Current industrial use Estimated ThermoWood production 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

4 Wood species/production m m m3 0 % 20 % 40 % 60 % 80 % 100 % Pine Spruce Birch Aspen Alder Others Source: Finnish Thermowood Association

5 Market area m m % 20 % 40 % 60 % 80 % 100 % m3 Domestic EU Other Source: Finnish Thermowood Association

6 Effect of treatment temperature to tangential swelling of pine Swelling(%) Swelling = 0,087*Tmax - 0,00036*Tmax 2 + 3,4 R 2 = 0, Treatment temperature ( C)

7 Effect of treatment temperature to tangential swelling of pine Confidence bands have been calculated at a risk level of 0,1 %. Swelling (%) Swelling = 0,087*Tmax - 0,00036*Tmax 2 + 3,4 R 2 = 0, 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

8 Class ThermoWood standard classes Thermo-S and Thermo-D Properties of softwood (sapwood) Treatment temperature ( C) Tangential swelling (%) Natural durability class Thermo-S Thermo-D Untreated Source: Finnish Thermowood Association

9 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:

10 Sauna building, Thermo-S pine + sauna protection oil Photo: Finnish Thermowood Association

11 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:

12 Skiing museum Lahti built 1998, photo 1999: Thermo S - D, no coating Photo: Finnish Thermowood Association

13 Music school, Kauniainen 2002: Thermo S- D, WBstain Photo: Finnish Thermowood Association

14 Residential garden decking, Espoo: Thermo-D spruce, WB acrylate stain + WB wood oil Photo: Finnish Thermowood Association

15 Treatment classes m % 20 % 40 % 60 % 80 % 100 % m3 Thermo-S Thermo-D Other Source: Finnish Thermowood Association

16 Heat treated wood needs a protective coating After treatment (pine) After 6 months weathering

17 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

18 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 and the exposure time was August September

19 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

20 Moisture content of spruce panels coated with a waterborne paint: August September Moisture content (%) spruce class S class D

21 Average moisture content of spruce panels during two years natural exposure (exposure August September 2003) 20 No heat treatment Average moisture content during two years of exposure Stained spruce Painted spruce Untreated spruce Class S Class D

22 Cracking of spruce panels 5 No heat treatment Class S Class D Cracking Stained spruce Painted spruce Untreated spruce

23 Mould and blue stain Performance of the coatings no differences between heat treated or untreated panels no differences between pine and spruce

24 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

25 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