Marek Gnatowski PhD Polymer Engineering Company Ltd wwwpolymerengineeringca 10 th International Conference on Wood amp Biofiber Plastic Composites Madison WN May 1113 2009 Water in the Environment ID: 271787
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Slide1
Water Absorption and Durability of Wood Plastic Composites
Marek Gnatowski, Ph.D.Polymer Engineering Company Ltd.www.polymerengineering.ca
10
th
International Conference on Wood &
Biofiber
Plastic Composites
Madison, WN
May
11-13, 2009Slide2
Water in the EnvironmentSlide3
Water in Exterior ExposureSlide4
Wood Plastic Composites
Exposed to Water
Wood particles are encapsulated in plastic
Polyethylene water saturation ~0.01%
Wood fiber water saturation ~25%Slide5
Wood Plastic Composites Exposed to WaterSlide6
Experimental WPC
Ingredients
Formulation ID #
1
3
4
5
6
8
10
11
12
13
27
28
31
33
Wood - Pine
50
50
50
50
50
65
65
656565Wood - Oak50506565HDPE4545454545303030303045453030Talc %11111111111111Lubricants %33333333333333UV StabilizerYesYesYesNoNoYesYesYesNoNoYesYesYesYesZinc Borate %02303023033000Board Cross-section (inches)6 x ½ 6 x ½ 6 x ½ 6 x ½6 x ½ 6 x 16 x 16 x 16 x 16 x 16 x ½6 x ½6 x 16 x 1
Quantities are approximateSlide7
Experimental WPCSlide8
Experimental WPCSlide9
Exposure Location
Vancouver, BC
Annual precipitation: 44 inches
Annual minimum temperature: 8
o
F
Annual maximum temperature: 72
o
F
Annual hours of sunshine: 1950
Pan evaporation: 22
(Bellingham, WA)
Scheffer
index: ~50
Hilo, Hawaii
Annual precipitation: 129 inchesAnnual minimum temperature: 53o
F
Annual maximum temperature: 93
o
F
Annual hours of sunshine: 2100
Pan evaporation: 91
(Honolulu)
Scheffer
index: ~330Slide10
Sample Evaluation
a
c
d
b
a
b
c
d
Specimen preparation
#5 and #6
Specimen preparation
#12 and #13
8th International Conference on Woodfiber-Plastic Composites, Madison, WI, May 23-25, 2005
www.polymerengineering.ca
Author: M. Gnatowski
"Water Absorption by Wood-Plastic Composites in Exterior Exposure"
Slide11
Sample Evaluation
bc
Water Absorption
Moisture ContentSlide12
Factors Affecting
Water Absorption Period of exposure Wood content in WPC
Exposure location (sun and shadow)
Exposure geographical location
Wood species
Presence of additives
-
UV Stabilizers
- Biocides (Zinc Borate)Slide13
Period of Exposure
Sunny Exposure in Vancouver, BC 5A
12ASlide14
Wood Content in WPCSunny Exposure in Vancouver, BC
5A & 12A 21 months5A & 12A
70 months
46 Months
70 MonthsSlide15
Exposure Location Sun and Shadow
Exposure in Vancouver, BC70 months 1A & 1B
8A & 8BSlide16
Exposure Geographical Location
Exposure in Vancouver, BC (46 months)and Hilo, Hawaii (51 months)
Shadow
SunSlide17
Wood Species
Sunny Exposure in Vancouver, BC (70 months)Slide18
Presence of Additives
UV StabilizersSunny Exposure in Vancouver, BC (70 months)
1A & 5A
8A & 12ASlide19
Presence of Additives
Zinc Borate
Sunny Exposure in Vancouver, BC (70 months)Slide20
Water Absorption
Mechanical PropertiesVancouver exposure 70 monthsSlide21
Water Absorption
Mechanical PropertiesConditioning: 6 days at 23oC and 50% RHFinal MC change: >0.1% per 24 hrs
Moisture content before and after conditioning
for WPC samples tested
Distribution of moisture content in
WPC samples tested
Sun and Shadow Exposure in Vancouver, BC (70 months)Slide22
Water Absorption
Biological ActivityDecay – Hilo, Hawaii 28 months exposure Sample #8Slide23Slide24
Conclusions
Wood Plastic Composites (WPC) boards absorb a significant quantity of water during exterior exposure. Moisture content distribution in the board cross-sections have a characteristic U-shape, frequently exceeding the concentration required for decay initiation. A major factor in water absorption by WPC was the ratio of wood to plastic binder
Another factor in water absorption is the material composition of WPC. Certain
additives may significantly increase or decrease water absorption
(for example zinc borate decreased water absorption in the tested formulations)
Water absorption is a long process, and even after 6 years exposure in a moderate
climate, equilibrium has likely not been reached
Climate and sample location (sun or shadow) may not be a major factor in water
absorption
It was shown that water absorption in exterior exposure most likely influenced
MOE of selected samples (decrease ~30%). It was observed that some
experimental samples with a significant amount of water absorption underwent
decay in exterior exposure. Slide25
Acknowledgements
Polymer Engineering staff involved in this research: Cecilia Stevens, Ph.D. Mathew Leung, B.Sc. Kate Mao, B.Eng. David Lesewick Christine
Mah
, B.Sc.
Beverly Start
Washington State University
(Wood Materials and Engineering Lab)