CHEMICAL FORCE MICROSCOPY ANALYSIS OF WOOD-PLASTIC COMPOSITES PRODUCED FROM DIFFERENT WOOD SPECIES AND COMPATIBILIZERS
Keywords:Alien invasive species, compatibiliser, adhesive force, chemical force microscopy, tensile strength
Alien invasive species are posing a serious and direct threat to biodiversity, water security, and productive use of land in South Africa. Most of these species need to be cleared and are therefore regarded as waste material, which could become raw material for wood-plastic composites (WPCs). WPCs containing wood from Pinus radiata, Eucalyptus grandis, Acacia mearnsii, Acacia longifolia, Acacia saligna, and Casuarina cunninghamiana trees, low-density polyethylene (LDPE) and three different compatibilizers: namely the commercially available ethylene vinyl alcohol (EVOH), polyethylene graft-maleic anhydride (PE-g-MA), and thermally degraded LDPE (dPE)—were studied. The determined properties included MC, density, tensile strength, and adhesive forces between the wood and compatibilizer components. The adhesive forces were determined using chemical force microscopy with functionalized, coated tips. WPC samples were compounded and injection molded. EVOH as compatibilizer proved to be very sensitive to the wood species incorporated into the WPC blend. Composites containing PE-g-MA and dPE as compatibilizer had a higher tensile strength for all the wood species. Composites containing dPE as compatibilizer showed less variation in all samples for tensile strength and adhesive force measurements. The densities and tensile strengths of the samples compares well with some commercial WPCs. The study shows that the inexpensive dPE outperforms commercially available compatibilizers and effectively promotes adhesion in WPCs. It was also shown that the studied invasive wood species can be incorporated into WPCs, if the correct compatibilizer is chosen. The differences in the results of the study seem difficult to relate due to the many factors such as the wood species, MC, density, compatibilizers, and processing method. However, the micro properties can give enough information regarding the macro properties of WPCs.
ASTM (2007) D4442-07. Standard test methods for direct
moisture content measurement of wood and wood-base
materials. ASTM, West Conshohocken, PA.
ASTM (2010) D638-10. Standard test method for tensile
properties of plastics, ASTM, West Conshohocken, PA.
Awaja F, Gilbert M, Kelly G, Fox B, Pigram PJ (2009)
Adhesion of polymers. Prog Polym Sci 34(9):
Balasuriya PW, Ye L, Mai YW (2001) Mechanical properties of wood flake-polyethylene composites. Part I: effects of processing methods and matrix melt flow behaviour. Composites Part A: Applied Science and Manufacturing 32(5):619-29.
Basson NC (2013) The effect of molecular composition on the properties of polyolefin-wood composites (Doctoral dissertation, Stellenbosch: Stellenbosch University).
Bastidas JC, Venditti R, Pawlak J, Gilbert R, Zauscher S, Kadla JF (2005) Chemical force microscopy of cellulosic fibers. Carbohydrate Polymers 62(4):369-78.
Drabeck GW Jr., Bravo J, DiPierro M, Andrews AC,
McKinney JM, Hollo B, Chundury D (2005) US Patent
No. 6,942,829. US Patent and Trademark Office
Drummond KM, Hopewell JL, Shanks RA (2000) Crystallization
of low-density polyethylene and linear lowdensity
polyethylene-rich blends. J Appl Poly Sci
Feifel S, Stübs O, Seibert K, Hartl J (2015) Comparing
wood-polymer composites with solid wood: The case
of sustainability of terrace flooring. Eur J Wood Wood
Hodzic A, Shanks R (2014) Natural fiber composites:
Materials, processes and properties. Woodhead Publishing,
ISSA (Invasive Species South Africa) (2016) Celebrating National Invasive Species Week. Invasive species South Africa. www.invasives.org.za/component/k2/item/1125-celebrate-national-invasive-species-week (Accessed 26/01/2016).
Kazemi-Najafi S, Nikray SJ, Ebrahimi GA (2012) Comparative study on creep behavior of wood-plastic composite, solid wood, and polypropylene. Journal of Composite Materials doi: 0021998311410499.
Kim JP, Yoon TH, Mun SP, Rhee JM, Lee JS (2006) Wood–polyethylene composites using ethylene–vinyl alcohol copolymer as adhesion promoter. Bioresource technology 97(3):494-9.
Klash A, Ncube E, Du Toit B, Meincken M (2010) Determination of the cellulose and lignin content on wood fibre surfaces of eucalypts as a function of genotype and site. European journal of forest research 129(4):741-8.
Klyosov AA (2007) Wood-plastic composites. John Wiley & Sons.
Lee SH, Wang S, Pharr GM, Xu H (2007) Evaluation of
interphase properties in a cellulose fiber-reinforced
polypropylene composite by nanoindentation and finite
element analysis. Compos, Part A Appl Sci Manuf
Ndlovu SS, Van Reenen AJ, Luyt AS (2013) LDPE–wood composites utilizing degraded LDPE as compatibilizer. Composites Part A: Applied Science and Manufacturing 51:80-8.
Niska KO, Sain M (2008) Wood-polymer composites. Elsevier.
Petinakis E., Yu L, Simon GP, Dai XJ, Chen Z, & Dean K (2014) Interfacial adhesion in natural fiber‐reinforced polymer composites. Lignocellulosic polymer composites: processing, characterization, and properties, 17-39.
Sarifuddin N, Ismail H (2015) Applications of Kenaf‐Lignocellulosic Fiber in Polymer Blends. Lignocellulosic Polymer Composites: Processing, Characterization, and Properties 499-521.
Schneider MH (2007) Wood polymer composites. Wood
Fiber Sci 26(1):142-151.
Shebani A, Van Reenen A, Meincken M (2012) Using
extractive-free wood as reinforcement in wood-LLDPE
composites. J Reinf Plast Compos 31(4):225-232.ss
Shebani AN, Van Reenen AJ, Meincken M (2009) The
effect of wood species on the mechanical and thermal
properties of wood—LLDPE composites. J Compos
Stark NM, Rowlands RE (2007) Effects of wood fiber
characteristics on mechanical properties of wood/polypropylene composites. Wood Fiber Sci 35(2):167-174.
Stokke DD, Wu Q and Han G (2013) Introduction to wood and natural fiber composites. John Wiley & Sons.
Stokke DD, Gardner DJ (2003) Fundamental aspects of
wood as a component of thermoplastic composites.
J Vinyl Additive Techn 9(2):96-104
Teuber L, Militz H, Krause A (2013) Characterisation of
the wood component of WPC via dynamic image analysis.
Pages 46-54 in J Geldermann and M Schumann (Hg.).
First International Conference on Resource Efficiency in
Interorganizational Networks-ResEff Universitätsverlag
Göttingen/Universitätsdrucke, Göttingen, At Göttingen,
Yang HS, Kim HJ, Park HJ, Lee BJ, Hwang TS (2007) Effect of compatibilizing agents on rice-husk flour reinforced polypropylene composites. Composite Structures 77(1):45-55.
The copyright of an article published in Wood and Fiber Science is transferred to the Society of Wood Science and Technology (for U. S. Government employees: to the extent transferable), effective if and when the article is accepted for publication. This transfer grants the Society of Wood Science and Technology permission to republish all or any part of the article in any form, e.g., reprints for sale, microfiche, proceedings, etc. However, the authors reserve the following as set forth in the Copyright Law:
1. All proprietary rights other than copyright, such as patent rights.
2. The right to grant or refuse permission to third parties to republish all or part of the article or translations thereof. In the case of whole articles, such third parties must obtain Society of Wood Science and Technology written permission as well. However, the Society may grant rights with respect to Journal issues as a whole.
3. The right to use all or part of this article in future works of their own, such as lectures, press releases, reviews, text books, or reprint books.