Wood-plastic composites properties

The improved physical and mechanical properties of the wood-plastic composites lead to a diversity of applications, e.g., automotive parts, furniture, construction (e.g., building panel, flooring veneers), toys, cutlery handles, industrial pattern, sports equipment, musical... 

In addition, ABS that has been recovered can be recycled into high value composites without separation from impurities. This has been exemplified with wood-plastic composites that contain ABS as matrix polymer. Both virgin ABS and recycled ABS were used and the properties of the materials were compared (126). In order to increase the performance, coupling agents were used, all based on grafted maleic anhydride. 

Fifteen years ago, when wood-plastic composites were first introduced many people predicted that this process would solve the problem of wood dimensional stability and great claims were made for its future use. Now that the physical properties of wood-polymer composites are better understood, specific commercial products are being produced which take advantage of the desirable aesthetic appearance, the high compression strength, increased hardness and abrasion resistance and improved dimensional stability. Future use of wood-polymer composites will depend upon the imagination of the producer and the market place. 

This research project represents initial studies into a new approach to blending thermoplastic materials like polystyrene with wood materials, leading to a new class of wood-plastic composites. Traditional wood-plastic composites have involved the impregnation and subsequent in situ polymerization of vinyl monomers. This procedure has been adopted for selected products for which improved physical properties justify increased production costs. While producing mixtures or blends of wood and plastics, these types of composites do not demonstrate significant chemical bonding between the wood and plastic components. 

When wood meals are kneaded with synthetic thermoplastic resins, the mixture shows hot-melting behavior as these plastics act as external plasticizers [20]. However, such wood plastic composites lack a fibrous construction and do not show the excellent properties of solid wood such as beautiful grain and color, tactility, or insulation. 

Let us take a look at a generic wood-plastic composite (WPC) deck, preferably of a premium quality. What should be done in order to avoid the deck owner complaints and, god forbid, a lawsuit Which properties of the deck should we consider, in order to extend its lifetime as much as possible, preferably longer than that of a common pressure-treated lumber deck In other words, what is required to make a material that is both durable enough to meet the warranty guidelines and at the same time cost-efflcitive to be competitive in the marketplace What can happen to the WPC deck in use, and how to prevent it Which properties of the composite material should we aim at, what should we study in that regard, what shonld we test and how, what shonld we optimize in order to make a premium product, or, at least—for a less ambitious manufacturer—to pass the building code ... 

This chapter is not a comprehensive description of thermoplastics because those readings are abundant in the literature. This chapter aims at a brief description of plastic properties directly related to behavior of wood-plastic composites and at a comparison of these properties for thermoplastics currently used in making WPC. Besides, this comparison is extended to Nylon and ABS as prospective—apparently—plastics for future brands of WPC possessing superior properties. 

Thermal expansion-contraction of plastics will be considered in detail in Chapter 10, Temperature-driven expansion-contraction of wood-plastic composites. Linear coefficient of thermal expansion-contraction. Here it can be briefly mentioned that this property is about the same with HDPE, polypropylene, PVC, ABS, and Nylons 6 and 6/6, and the respective coefficients of thermal expansion are all overlapping in the range of 2-7 X 10 1/°F (4-13 X 10 1/°C). Only with LDPE the coefficient is noticeably higher and equal to 6-12 X 10 1/°F (10-22 1/°C) [12]. 

M. A. Svoboda. Property profiles and structure-property relationships of polypropylene-wood composites with high wood content. In Wood-Plastic Composites, A Sustainable Future. The International Conference, Vienna, Austria, May 14-16, 2002. 

EFFECT OF COUPLING AGENTS ON MECHANICAL PROPERTIES OF WOOD-PLASTIC COMPOSITES EXPERIMENTAL DATA... 

DENSITY (SPECIFIC GRAVITY) OF WOOD-PLASTIC COMPOSITES AND ITS EFFECT ON WPC PROPERTIES... 

Note of the author This procedure was one of the most widely used of the mechanical property tests for wood-plastic composite (WPC) materials, as the specimen geometry is very simple as well as the testing equipment. However, it became more and more obvious that material properties, tested by this method, were not necessarily corresponding to the product properties, such as composite deck board. 

The standard method was withdrawn in 2002. The main reason to describe it in this chapter is that this method was referenced in ASTM D 7031 ( Standard guide for evaluating mechanical and physical properties of wood-plastic composite products ), issued in 2004, and in ASTM D 7032 ( Standard specification for establishing performance ratings for wood-plastic composite deck boards and guardrail systems (guards or handrails) ), issued in 2005. 

TABLE 13.13 Effect of Folpet on flexural properties of HDPE-based wood-plastic composite [14]... 

M.W. Chastagner, M.P. Wolcott and K.R. Englund. Characterizing the Rheological Properties of Wood-Plastic Composite Formulations. Wood Materials and Engineering Laboratory, Washington State University, 2005. 

Naghipour B. Effects of extreme environmental conditions and fungal exposure on the properties of wood-plastic composites [dissertation]. Toronto (ON) University of Toronto 1996. 

FIGURE 5.97 Effect of plastic type (polyethylene o, polypropylene A, polystyrene X) and wood loading levels on properties of wood plastic composites. (After Chelsea Center for Recycling and Economic Development (CCRED), 2000. Technical Report 19, An Investigation of the Potential to Expand the Manufacture of Recycled Wood Plastic Composite Products in Massachusetts, Univ. of Massachusetts, Massachusetts.)... 

The mechanical properties of Wood-Plastic-Composites substantially depend on the quality of the raw material, the composite and the manufacturing process. The density of WPC lies between 0.9 and 1.4 g cm and is higher than that of one of the two components, plastic and wood, alone. The porous wood structure is densified during the production process and plastics and additives partly penetrate into the cavities. Thus, water absorption is made harder, and the material swells less and more slowly. ... 

D.P. Kamdem et al., Properties of wood plastic composites made of recycled HOPE and wood flour from CCA-treated wood removed from service. Compos. Part A AppL Sci. Manuf. 35(3), 347-355 (2004)... 

This chapter first gives an overview of cellulose raw materials and their molecular and supermolecular structures. The principles of shaping cellulose into fibres, films, and nonwovens by means of solution techniques are then outlined followed by a section on properties and market applications of these materials. Derivatives of cellulose are presented with special emphasis on thermoplastic cellulose esters, typical plasticizers, and promising reinforcing materials. Finally, recent developments and future prospects of cellulose materials are reviewed as far as the above applications are concerned. This book does not cover the important applications of cellulose and ligno cellulose fibres for reinforcing thermoplastics, like wood plastic composites (WPC) and natural fibre reinforced plastics (NFRP), since in these cases cellulose does not substitute a thermoplastic. 

As shown in Table 11.1, mechanical properties of a wood-plastic composite are generally improved in comparison with those of an untreated wood. The major improvements are in compressive strength (increased by a factor of up to 1.5 x), shear strength (2 x), hardness (11 x), and abrasion resistance (8 x) (Hills et al, 1969 Langwig et a/., 1968, 1969 Meyer, 1965 Siau and Meyer, 1966 Siau et a/., 1965a, 1965h, 1968). 

Lee C-H, Hung K-C, Chen Y-L. Effects of polymeric matrix on accelerated UV weathering properties of wood-plastic composites. Holzforschung 2012 66 (8) 981-987. 

Leu SY, Yang TH, Lo SF, Yang TH. Optimized material composition to improve the physical and mechanical properties of extruded wood-plastic composites (WPCs). Construct Build Mater 2012 29 120-127. 

Ndmberg B, BorchardtE, LuinstraGA, Fromm J. Wood plastic composites from polyfpropylene carbonate) and poplar wood flour—mechanical, thermal and morphological properties. Eur Polym J 2014 51 167-176. 

Suzhou Y, Rials TG, Wolcott MP (1999) Crystallizatirat behavior of polypropyltare and its effect on woodfiber composite properties, pp. 139-146. Proceedings of 5th International Conference on Wood-Plastic Composites, Forest Products Society (Eds) Madison, WI, USA... 

Shebani et al. [20] noted that removing extractives improved the thermal stability of different wood species. Therefore, using extracted wood for the production of wood-plastic composite (WPCs) would improve the thermal stability of WPCs. Because wood and other bio-fibres easily undergo thermal degradation beyond 200°C, thermoplastic matrix used in the composites is mainly limited to low-melting-temperature commodity thermoplastics like polyethylene (PE) and polypropylene (PP). However, the inherently unfavourable thermomechanical and creep properties of the polyolefin matrix limit some structural applications of the materials. 

Singh B, Gupta M, Verma A (1996) Influence of fiber surface treatment on the properties of sisal fiber reinforced polyester composites. Polym Compos 17 910-918 Schirp A, Wolcott M (2005) Influence of fungal decay and moisture absorption on mechanical properties of extruded wood-plastic composites. Wood Fiber Sci 37 643-652 Winfield AG (1979) Jute reinforced polyester project for UNIDO/Govt, of India Blast Rubber Int 4 23-28... 

Chapters 15-18 focus on the weathering/mechanical study of lignocellulosic fiber-reinforced polymer composites. The effect of different environmental conditions on the physico-chemical and mechanical properties of the polymer composites is discussed in detail in these chapters. Chapter 15 mainly focuses on the effect of weathering conditions on the properties of lignocellulosic polymer composites. Most of the focus of this chapter is the effect of UV radiation on different properties of composites. Chapter 16 describes the effect of layering pattern on the physical, mechanical and acoustic properties of luffa/coir fiber-reinforced epoxy novolac hybrid composites, and Chapter 17 summarizes the fracture mechanism of wood plastic composites. Chapter 18 focuses on the mechanical behavior of biocomposites xmder different environmental conditions. 

J.S. Fabiyi and A.G. McDonald, Effect of wood species on property and weathering performance of wood plastic composites. Compos. A, 41, 1434-1440 (2010). 

---