Thermal, Mechanical, and Physical

Properties of Wood-Plastic

Composites with Added Biochar

David DeVallance,

Gloria Oporto,

George Cheng, and

Patrick Quigley

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

GOALS & OBJECTIVES

• 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?

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

BACKGROUND

• Has a higher ignition temperature, as opposed to

wood fiber (Antal and Gronli, 2003)

• Should be more thermal resistant than wood

EXPERIMENTAL Wood (yellow-poplar), Biochar (mixed hardwoods), and

Polypropylene (with lubricant) were combined to form

composites

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)

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

TEST RESULTS: Bending

Composites with biochar

included resulted in a

statistically significant

higher flexure strength

(MOR), as compared to

the composites without

biochar

Box-and-Whisker Plot

Fle

xu

ral S

tre

ng

th (

MP

a)

Group

Exp. 1 Exp. 2 Exp. 3 Exp. 4 Exp. 5

8

12

16

20

24

Modulus of Rupture, MOR (MPa)

Summary 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

TEST RESULTS: Tension Box-and-Whisker Plot

Te

ns

ile

Str

en

gth

(M

Pa

)

Group

Exp. 1 Exp. 2 Exp. 3 Exp. 4 Exp. 5

7.9

9.9

11.9

13.9

15.9

While two composites

that included biochar

(5% and 15%) resulted in

higher average tensile

strengths, the

differences were not

statistically significant

Tensile Strength, Ft (MPa)

Summary 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

TEST RESULTS: Water Absorption

Water absorption is reduced by 25%, 51% and 73%

after the incorporation of 5%, 15% and 25% biochar

TEST RESULTS: Swelling

Although reduction in swelling is observed after the

addition of biochar, no statistically significant

difference was found

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

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)

Major Conclusions

Addition of biochar appears to have:

1. Improved strength properties,

2. Improved thermal degradation properties, and

3. Reduced water absorption

Acknowledgments:

Dr. Rakesh Gupta, Chair of the Chemical Engineer

Department at West Virginia University, for giving us

access to some laboratory equipment

Questions? Further Information: david.devallance@mail.wvu.edu

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>.