1. EFFECT OF RESIN ACIDS AND OTHER
EXTRACTIVES ON DIMENSIONAL
STABILITY AND DECAY
SUSCEPTABILITY OF SYP LUMBER IN
ABOVE GROUND EXPOSURE
Tor P. Schultz, Joseph
Dahlen and Darrel
Nicholas
Mississippi State
University

2. 1. Examine effect of resin acids on dimensional
stability of outdoor SYP decking
2.Examine effect of resin acids and other
extractives on decay susceptibility of SYP in
two above ground exposures

3. 1st Study – RESIN
ACIDS/DIMENSIONAL STABILITY
•TOR is the common acronym for resin acids that
are isolated from Tall Oil, obtained by the Kraft
pulping of pines
•Safe – modified TOR is chewing gum base,
GRAS for paper in food contact
•Inexpensive - $0.25 to 0.40/lb, bulk
•Other folks have examined potential of
solventborne TOR in Wood Preservation, so-so
results
•We developed a waterborne system

5. Materials & Methods
 Defect free sapwood  Roof, MSU Campus,
slanted towards sun, very
 5/4 Flatsawn Decking hot in summer, ~165F
• Untreated control  Δ MC%: Rain: before & after,
• 3% waterborne resin acid plus other times
 Laminated Quartersawn  Flatsawn: checking
• Untreated control  Quartersawn: cupping
• 3% waterborne resin acid
• 3% paraffin wax, toluene

6. Flatsawn

7. Quartersawn

8. Flatsawn
Control TOR
ΔMC% 26.1% (A) 18.9% (B)
Checking 3.17 (A) 2.1(B)

9. Quartersawn
Control TOR Wax
ΔMC% 33.4% (A) 26.2% (B) 5.2% (C)
Cupping 4.17 (A) 3.41(A) 1.25 (B)

11. Materials and Methods
 KD sapwood 5/4 flatsawn decking
 Two Above Ground Exposures

12. AWPA Gnd Prox, E-18,
Saucier, AWPA 5 Decay Hazard

13. Roof Setup
 Starkville: AWPA 4 Decay Hazard, very hot

14. Regression Factors & Results
 Extractives
• Fatty and resin acids
 Initial water permeability Avg. Decay Ratings,
 Moisture content averages 21 months’ exposure
before/after rain • Roof = 7.85
 Checking • Ground = 7.35
 Relative density
 Growth rate
 Mold
 Gnd Prox vs. Roof
 Simple sugars

15. Ground Prox Decay
Predicted vs Actual Ground Decay
r2 = 0.41
12
+ = less decay
10
Palmitic -
Predicted Ground Decay
8 Dehydroabietic +
Neoabietic -
6
4
2
0
0 1 2 3 4 5 6 7 8 9 10
Actual Ground Decay

16. Roof Decay
Predicted vs Actual Roof Decay
r2 = 0.76
12
+ = less decay
10
Permeability +
Predicted Roof Decay
8 Rain Absorption –
C=87%, collinear -
6
Check Rating +
4 Dehydroabietic +
2
0
0 1 2 3 4 5 6 7 8 9 10
Actual Roof Decay

17.  Decay is complex
 Both tests above ground and had about the
same extent of decay [which was not expected]
– but different results as should be anticipated
 Roof Test – Decay extent appears related to
moisture availability
 Ground Prox Test – decay appears related to
extractives which inhibit decay