Modification of solid wood with glutaraldehyde to improve the outside weathering performance

Transcription

1 COST Action FP1006 Modification of solid wood with glutaraldehyde to improve the outside weathering performance Carsten Mai, Zefang Xiao, Yanjun Xie Content Reaction mechanism of glutaraldhyde (GA) Water-related properties Fungal resistance Weathering performance Conclusion 1

2 Reaction mechanism Treatment of wood Scots pine (Pinus sylvestris L.) sapwood Treatment solutions 0.4, 1.2, 2.0 mol l -1 glutaraldehyde (GA) 6.0% MgCl 2. 6H 2 O related to GA (molar ratio) in aqueous acetate buffer (0.1 M, ph 4.5) Impregnation vacuum (100 mbar, 30 min) and pressure (10 bar, 1 h) Drying / curing one week air drying 24 h pre-curing at 80 C 48 h final curing at 120 C 2

3 Water related properties (summery) GA-treatment reduced... the degree of moisture sorption by ca. 40% capillary water uptake ca. 50% swelling / shrinking ASE up to 75% ASE up to 35% Maximum swelling in water reduced ca. 35% Fungal resistance 3

4 Blue stain infection Assessed following EN 152 Spore suspension of Aureobasidium pullulans Wood species: Scots pine (Pinus sylvestris L.) European beech (Fagus sylvatica L.) Treatment concentration: 0.4, 1.2, 2.0 mol l -1 (n = 14) Classification Surface infection [%] 0 clean 1 slight 2 less than 20% 3 20% - 50% 4 50% - 75% 5 more than 75% Evaluation of blue stain on pine sapwood blocks Conc. WPG (%) Bottom surface (vermiculite contact) Blue stain infection Top surface Control -1.3 (0.1) 5.0 (0.0) 4.9 (0.4) 0.4 M GA 2.0 (0.4) 3.8 (1.4) 2.8 (1.2) 1.2 M GA 10.9 (0.4) 1.3 (0.6) 0.0 (0.0) 2.0 M GA 19.2 (1.0) 1.6 (1.1) 0.3 (0.7) Evaluation of blue stain on beech wood blocks Conc. WPG (%) Bottom surface (vermiculite contact) Top surface Control -1.7 (0.1) 4.6 (0.5) 3.1 (1.7) 0.4 M GA -0.2 (0.2) 4.9 (0.4) 2.3 (0.5) 1.2 M GA 3.3 (0.2) 4.2 (0.9) 0.3 (0.5) 2.0 M GA 7.0 (0.4) 3.4 (1.7) 0.1 (0.4) 4

5 Blue stain infection Cross section view Scots pine untreated WPG 2% WPG 11% WPG 19% Beech wood untreated WPG -0,2% WPG 3 % WPG 7% Basidiomycete decay resistance Test following EN 113 Coniophora puteana Scots pine European beech Trametes versicolor European beech Sample size: 30 *30 *5 mm 3 (R * L * T) Treatment concentration: 0.4, 0.8, 1.2, 1.6, 2.0, 2.8 mol l -1 Test duration: 16 weeks Replicates: 6 per treatment, fungus Coniophora puteana Trametes versicolor 5

6 Basidiomycete decay resistance Mass loss after 16 weeks incubation T. versicolor (beech) C. puteana (beech) C. puteana (pine) Mass loss [%] GA-treated control WPG of treated samples [%] Weathering properties 6

7 Wood species: Scots pine Sample size: 100 mm 15 mm 80 µm (L R T) Treatment concentration: 0.4, 1.2, 2.0 M (ph 4.5, acetate buffer) Test duration : 0, 48, 72, 96, 144, and 168 h UV-A light 340 nm; 0.77 W m -2 nm -1 One cycle: 2.5h UV (60 C) 30 min (cold water spray 6-7l min -1 ) Replicates: 8 Artificial weathering (QUV) Artificial weathering (QUV) FT-IR spectra of weathered veneers: a b (a) treated by acetate buffer (b) treated with 0.4 M (c) treated with 1.2 M (d) treated with 2.0 M 0 h 2 4 h 7 2h 9 6h h 1 6 8h c a b c d 0 h 2 4 h 7 2 h 9 6 h h h d a b c d 0 h 2 4 h 7 2h 9 6h h 1 6 8h a b c d 0 h 2 4 h 7 2 h 9 6 h h h a b c d W avenum b er [cm -1 ] W avenum b er [cm -1 ] 7

8 Tensile strength (Zero-span) Artificial weathering (QUV) Strength retention [%] 110 untreated MgCl 2 alone M GA 1.2 M GA M GA Strength loss [%] by weathering by modification Time [h] 0 untreated MgCl2 0.4 M GA 1.2 M GA 2.0 M GA Treatment of wood Natural weathering (EN ) Wood species: Scots pine Sample size: mm 3 (L R T) Treatment concentration: 0.4, 1.2, 2.0 M Test duration: 18 months Replicates: 4 Evaluation method: Moisture content Surface crack ranking Blue stain penetration 8

9 Natural weathering (EN ) untreated 0.4 M GA 1.2 M GA 2.0 M GA untreated 0.4 M GA 1.2 M GA 2.0 M GA Moisture content [%] Water uptake [kg m -2 ] (cond.) Exposure time [mm-yy] Submersion time [h] Moisture content of panels during outdoor exposure Water uptake determined in a submersion test after 18 months exposure Natural weathering (EN ) Surface cracks evaluation (ISO , 1982) Treatment Surface crack ranking (CR) after x month untreated M GA M GA M GA CR = 0: no cracks; CR = 5: a considerable amount of cracks 9

10 Natural weathering (EN ) Surface appearance after 18 months of weathering Untreated 0.4 M 1.2 M 2.0 M Natural weathering (EN 927-3) Surface appearance after 18 months of weathering Untreated 2.0 mol l-1 GA Untreated 2.0 mol l-1 GA 10

11 Natural weathering (EN ) Penetration of blue stain after 18 months of weathering Untreated 0.4 mol l -1 GA 1.2 mol l -1 GA 2.0 mol l -1 GA Conclusions GA-treatment reduced... the colonisation by blue stain fungi and the decay threshold (basidiomycetes) photo-degradation of lignin water uptake during outdoor exposure and in periodical submersion tests formation of surface crack GA is a suitable modifying agent to improve the performance of wood used outdoors 11

12 Thank you for your attention! 12