1. Thermal, Mechanical, and Physical
Properties of Wood-Plastic
Composites with Added Biochar
David DeVallance,
Gloria Oporto,
George Cheng, and
Patrick Quigley

2. GOALS & OBJECTIVES
The long-term goal of this research:
• Integrate bio-energy related by-products,
particularly biochar, with plastics and wood by-
products to create sustainable composite products
The objective in this project:
• To combine biochar with wood flour and polymeric
materials (i.e., plastics) to fabricate a novel
composite material

3. BACKGROUND
• Wood and most polymers (i.e., plastics) are not
compatible
• Polymers – hydrophobic (i.e., non-polar)
• Wood – hydrophilic (i.e., polar)
• Traditional WPC’s use coupling agents
• Most WPCs undergo some UV degradation and
lighten over time (Falk et al. 2001)
• Carbon black – additive to reduce UV degradation
• There is a need to identify alternative,
environmentally friendly materials that can replace
the currently used additives in WPCs
• Biochar - Viable replacement for WPC
additives?

4. BACKGROUND
Biochar
• By-product of slow pyrolysis
processes used to produce
gas and bio-oil (Sohi et al., 2009)
• Exhibits a hydrophobic
nature (Maciejewska, et al. 2006)
• Should reduce UV
degradation in WPCs
• Has a higher ignition temperature, as opposed to
wood fiber (Antal and Gronli, 2003)
• Should be more thermal resistant than wood

5. EXPERIMENTAL
 Wood (yellow-poplar), Biochar (mixed hardwoods), and
Polypropylene (with lubricant) were combined to form
composites

6. EXPERIMENTAL
 Component were mixed using a Haake PolyDrive blender
 Composite specimens for physical and mechanical
analysis prepared using a Carver Hot press (Temp.
200°C, Pressure 8.9 kN)

7. EXPERIMENTAL
 Mechanical properties evaluated using an Instron
Universal Test Machine
 Water absorption and swelling were measured after
24 and 48 hours
 Thermogravimetric analysis (TGA, DTGA) was
performed

8. TEST RESULTS: Bending
 Composites with biochar Box-and-Whisker Plot
Flexural Strength (MPa)
included resulted in a 24
statistically significant 20
higher flexure strength 16
(MOR), as compared to 12
the composites without 8
biochar Exp. 1 Exp. 2 Exp. 3 Exp. 4 Exp. 5
Group
Summary Modulus of Rupture, MOR (MPa)
Statistic 40/0/60 35/5/60 25/15/60 15/25/60 0/40/60
Average 16.1 19.4 20.4 21.3 19.5
St. Dev. 4.3 1.4 1.6 1.5 2.3
COV % 26.7 7.1 7.7 7.2 11.8
Minimum 8.7 17.0 17.6 18.4 15.8
Maximum 23.6 21.6 23.0 23.6 22.4

9. TEST RESULTS: Tension
Box-and-Whisker Plot
 While two composites
Tensile Strength (MPa)
15.9
that included biochar
13.9
(5% and 15%) resulted in
higher average tensile 11.9
strengths, the 9.9
differences were not 7.9
statistically significant Exp. 1 Exp. 2 Exp. 3 Exp. 4 Exp. 5
Group
Summary Tensile Strength, Ft (MPa)
Statistic 40/0/60 35/5/60 25/15/60 15/25/60 0/40/60
Average 11.2 12.5 12.0 10.8 11.0
St. Dev. 1.4 1.3 1.3 1.3 0.9
COV % 12.6 10.1 11.1 12.3 8.1
Minimum 9.4 10.2 9.6 7.9 9.0
Maximum 14.3 14.4 14.9 12.5 12.4

10. TEST RESULTS: Water Absorption
 Water absorption is reduced by 25%, 51% and 73%
after the incorporation of 5%, 15% and 25% biochar

11. TEST RESULTS: Swelling
 Although reduction in swelling is observed after the
addition of biochar, no statistically significant
difference was found

12. TEST RESULTS: Thermogravimetric
Analysis (TGA & DTGA)
 Considering a 10% of weight loss, biochar increase
the composite decomposition temperature from
315°C to 360°C when 15% is added to the mixture

13. Major Conclusions
Addition of biochar appears to have:
1. Improved strength properties,
2. Improved thermal degradation properties, and
3. Reduced water absorption
On-going research
Research is underway to evaluate:
1. Potential improvements in UV degradation,
2. Flame resistance,
3. Conductivity,
4. Mechanical properties with the incorporation of
coupling agent, and
5. Microbial degradation after the incorporation of
biochar in wood-plastic composites (WPCs)

14. Questions?
Further Information: david.devallance@mail.wvu.edu
Acknowledgments:
Dr. Rakesh Gupta, Chair of the Chemical Engineer
Department at West Virginia University, for giving us
access to some laboratory equipment

15. References:
Antal, M.J. and Gronli, M. 2003. The art, science, and technology of charcoal
production. Ind. Eng. Chem. Res. 2003(42):1619-1640.
Falk, R.H., T. Lundin, and C. Felton, 2001. Accelerated weathering of natural
fiber-thermoplastic composites: Effects of ultraviolet exposure on bending
strength and stiffness. In: Proc. Sixth International Conference on Woodfiber-
Plastic Composites. Forest Prod. Soc., Madison, WI. pp. 87-93.
Maciejewska, A., H. Veringa, J. Sanders, and S.D. Peteves. 2006. Co-firing of
biomass with coal: Constraints and role of biomass pre-treatment. DG JRC
Institute for Energy. Retrieved October 21, 2010, from
<http://www.techtp.com/Cofiring/Cofiring%20biomass%20with%20Coal.pdf>
Sohi, S., E. Lopex-capel, E. Krull, and R. Bol. 2009. Biochar, climate change
and soil: A review to guide future research. CSIRO Land and Water Science
Report. Retrieved April 28, 2010, from, <http://www.csiro.au/files/files/poei.pdf>.