A comparative study and evaluation of methodologies used for ...

A comparative study and
evaluation of methodologies used
for determining wood
preservative penetration
Radu Craciun, Ralf Moeller, Joachim Wittenzellner, Thomas Jakob,
and Joerg Habicht
Dr. Wolman GmbH / BASF Group,
Sinzheim, Germany
IRG 42-nd Annual Meeting
Queenstown, New Zeeland
May 08-12, 2011
18.03.2009 INTERN 1

18.03.2009
Key steps for evaluating new wood
preservative systems
Treatment
Process
Environment/
exposure
conditions
Chemical
stability
Efficacy - wood protection
Biostability/
bio
degradation
Fixation/
Leaching
INTERN
Penetration
UV stability/
weathering
2

18.03.2009
Overview – why penetration studies ?
� Review various method to determine the wood
preservative/product penetration into the core part of the
wood:
- Indirect color indicator/tracers,
- Direct treating solution uptake
- Gradient analysis: solvent
extraction/chromatography analysis
- Laboratory microbiology methods/what really works!
� Correlation studies between various methods used in
penetration studies (color vs. gradient vs. microbiology)
� Concluding remarks/what the industry needs !?
INTERN
3

18.03.2009
Indirect penetration color indicator
- copper/quat/other additives/traces profiles -
(A) for -a Br-phenol quat-based for system, quats (a) and Cr-azurol (B) for foracopper copper (b); based and other system,
indicators for Cu-modified systems (c - other type of matrix)
(a)
(b)
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4

Direct gradient analysis
- Solvent extraction/chromatography at various depths -
18.03.2009
(a) Scots pine wood blocks used in this penetration study.
(b) Cross sections of the wood blocks showing the marked
analytical zones (A, C) and the sealed cross section (B).
(a) (b)
- Wood grinding corresponding to each zone followed by solvent
extraction or acid digestion
- AAS/ICP for metal analysis (Cu, B, As) or HPLC/GC for organic
biocides (e.g. tri-azoles) in metal-organic systems
INTERN
5

Test set up: wafers taken for ende sealed pine boards samples (20 x 4
x 4 cm³) DV or VPT impregnated. Wafer cut out from the centre of the
treated wood (as shown in the picture below).
•
18.03.2009
Direct microbiology penetration method
- methodology setup/test design -
40 mm
40 mm
Samples for EN 113
Petri dish
fungal mycelium
growth medium
200 mm
EN113 EN113
fungi fungi
analytics
wood
section
sample holder
INTERN
Cross sections sealed
Samples for screening II
6

Microbiology penetration method
- results from various types of fungi used in the test -
18.03.2009
(a) P.p. exposed treated wafers with Cu-based and organic systems
(b) Exposed untreated control wafer
(c) Exposed and dreid untreated control wafer
(a)
(b)
(c)
INTERN
7

18.03.2009
Indirect penetration color indicator
- copper profile in modified systems -
(A) for a- quat-based Cr-azurol forsystem, copper; and penetration (B) for aprofiles copperfor based Cu-amine system,
modified systems – matrix effect
(a) – no penetration enhancement additive
(b) – with penetration enhancement additive
(a) (b)
INTERN
8

Direct microbiology penetration method
- copper depth profile with 2 different fungi (Cp/Gt) -
18.03.2009
- Cu penetration profiles for Cu-amine systems – matrix effect,
(where Coniophora puteana, Cp – top/Gloeophyllum trabeum, Gt – bottom)
(a) – no penetration enhancement additive
(b) – with penetration enhancement additive
(A) for a quat-based system, and (B) for a copper based system,
(a) (b)
INTERN
9

Correlation between the direct analytical
gradient and microbiology profile methods
- for VPT using organic-based systems -
(A)
(a)
(A) for a quat-based system, and (B) for a copper based system,
18.03.2009
(b)
Organic a.i. retention [mg/g wood]
600
400
200
Gradient of organic a.i. in the vacuum-treated wood blocks
- penetration data for Organic - I versus Organic - I + Penetration Enhancement Additive -
0
0 2 4 6 8 10 12 14
Penetration depth [mm]
Organic - I
Organic - I + Additive C1
Organic - I + Additive C2
(B)
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10

Double vacuum/envelop penetration studies
- microbiology penetration profile method -
18.03.2009
(A) (B)
(A) - experimental exposure
conditions - initial
(B) - various application procedures -
after exposure
(C) - Effect of DV pressure profile -
after exposure
- Blue stain used:
Aureobasidium pullulans
and Sydowia polyspora
INTERN
11

18.03.2009
Conclusions
� The key parameter to be monitored = distribution of active
ingredients in the treated wood/penetration gradient
� Penetration gradient depends directly of matrix/product composition,
wood species, type of treatment, pressure profile, concentration
� Even if laborious, the direct solvent extraction/chromatography the
most reliable (when interferences from wood components solved)
� Microbiology method – proven to be a direct, quick and useful R&D
tool for evaluating product penetration in new formulation development
� Industry needs: simple, easy to use, reliable, preferable directed
toward the active component; for indirect methods data should be
generated to proof or correlate penetration of product/actives with the
direct methods
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12

18.03.2009
Questions ????
INTERN
13