NTR approval of modified wood

Transcription

1 NTR approval of modified wood

2 Basic principles of NTR The approval system of the preservatives involving efficacy testing in lab. and field trials and the evaluation by the technical group The classification (NTR classes) fit to purpose Internal proces control and the external inspection by the control bodies.

3 What is modified wood? General accepted definition Modification of wood involves a chemical, biological or physical treatment of the wood material, resulting in an improvement of the properties in service. The modified wood must be non-toxic in service and no leaching of toxic substances is allowed in use, at disposal or when recycled. NTR definition The modified wood must be treated by a non-biocidal system (not listed in annex A in BPD) resulting in an improvement of the durability in service.

4 Can a common criterion for quantifying the decay resistance of modified wood be established?

5 Method Review of the performance of three types of wood modification: - Bulking (acetylation, furfurylation) - Cross-linking (DMDHEU, glutaraldehyde, glyoxal) - Thermal Three performance parameters are evaluated: - Anti-swelling efficiency (ASE) - Moisture exclusion efficiency (MEE) - Durability in laboratory and field tests

6 Performance parameters Anti-swelling efficiency (ASE) ASE = (S unmod S mod )/S unmod x 100 % Moisture exclusion efficiency (MEE) MEE = (EMC unmod EMC mod )/EMC unmod x 100 %

7 Moisture content [%] 25 Acetylated (21 % WPG) EMC R EMC Untreated softwood Relative humidity [%]

8 MEE [%] MEE MEE R Acetylated (21 % WPG) Relative humidity [%]

9 Decay threshold Modification Threshold MEE ASE ASE * Acetylation 20 % WPG 40 % 63 % 61 % Furfurylation 35 % WPG 40 % 80 %? DMDHEU 25 % WPG 43 % 45 % 43 % Glutaraldehyde 10 % WPG 30 % 57 % 55 % Glyoxal > 50 % WPG??? Thermal 15 % WL? 37 %? 45 %?? modification +

10 A common criterion of 40 % MEE could be established However MEE should be based on the reduced moisture content, EMC R = EMC (1 + WPG/100) and The durability of modified wood must also include field testing

11 Efficacy testing of modified wood Modified wood is to be considered as a new wood species EN 113 (including ageing EN 84 and EN 73) but with reduced requirements for weight loss compared to preservative treated wood. Requirement corresponding to natural durability class 1 and 2 in EN 350. Based on work by van Acker et al (1998). Test of Moisture Exclusion Efficiency (MEE). Requirements for NTR MOD classes for MEE are included. Field test similar (ref. material is identical) to existing tests for normal NTR classes EN 252, EN 330, TS 12037, ENv 807 and EN 275.

12 Work by van Acker et al (1998). E.g. IRG/WP Durability class (EN 335) Description Mass loss (%) Criteria value* From EN Very durable Durable Moderately durable Slightly durable Not durable MLP < 5 5 < MLP < < MLP < < MLP < 30 MLP > 30 < < < < < < < 0.90 > 0.90

13 Test Schedule Requirements for Testing: EN 73 + EN 113 EN 73 + EN 113 with Coriolus versicolor EN 84 + EN 113 EN 84 + EN 113 with Coriolus versicolor EN 330 CEN/TS NTR A NWPC Wood Preservation class NTR NTR NTR NTR AB MOD B MOD AB MOD A MLP<3% MLP<3% MLP<10% MLP<10% MLP<3% MLP<3% MLP<10% MLP<10% Ref. TBTO Ref. CCA Ref TBTO Ref. TBTO Ref. CCA NTR MOD M MLP<5% MLP<5% MLP<5% MLP<5% ENV 807, Part 2 (optional) EN 252 ( 5 years three test sites two in Nordic countries) EN 275 ( 5 years one Nordic test site) MEE (65% RH to 85% RH) after ageing according to EN 73 and EN 84 BRV (CCA) >40% >40% >40% >40% + +

14 Use classes vs NTR classes Penetration class NP1 to NP6 according to EN Relationship between Use Classes UC1 UC5 according to EN and NTR Classes Class Requirement for penetration UC1 UC2 UC3 UC4 UC5 NP1 None (3 mm analytical zone) GW GRAN NP2 Min 3 mm lateral in the sapwood NP3 Min 6 mm lateral in the sapwood B MOD B NP4 Min 25 mm lateral in the sapwood NP5 Full penetration or treatment of sapwood AB MOD AB A MOD A M MOD M NP6 Full penetration of the sapwood min 6 mm in exposed heartwood

15 NTR Classes for modified wood N T R MOD M N T R MOD B N T R M OD A N T R MOD AB

16 Quality control Quantitative chemical analyses of all components in the treatment or in the treated wood Indirect methods (FTIR, WPG, MEE, WL etc.) Determination of the concentration if the chemicals are mixed on the site Determination of the penetration and distribution of chemicals/treatment in the modified wood Proces control vs external control

17 Incomplete list of commercial products in Scandinavia: Thermowood - long list of produceres Bitus-Linax Organo-Click (Organowood) Kebony Eastman - acetylation Koskisen Oy Iki Timber Accoya, Accsys Technology Stora Enso QT (water glass and heat treatment combination) BT WOOD Belmadure BASF (DMDHEU) Vacu3 (heat treated VTT) Sabado Group, Vital protect