1. The researchers combined biochar, wood flour, and polypropylene to create novel wood-plastic composites (WPCs) and tested their mechanical and physical properties. 2. Adding biochar improved the composites' strength properties, thermal degradation resistance, and reduced water absorption. Composites with 15% biochar showed the highest flexural strength and decomposition temperature. 3. Ongoing research is evaluating how biochar affects other properties like UV degradation resistance, flame resistance, conductivity, and mechanical properties with coupling agents.

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>.