Mechanical properties: wood lumber versus plastic lumber and thermoplastic composites

Abstract

Abstractlastic lumber and thermoplastic composites are sold as alternatives to wood products. However, many technical standards and scientific studies state that the two materials cannot be considered to have the same structural behaviour and strength. Moreover, there are many compositions of thermoplastic-based products and plenty of wood species. How different are their mechanical properties? This study compares the modulus of elasticity and the flexural, compressive, tensile and shear strengths of such materials, as well as the materials' specific mechanical properties. It analyses the properties of wood from the coniferae and dicotyledon species and those of commercialized and experimental thermoplastic-based product formulations. The data were collected from books, scientific papers and manufacturers' websites and technical data sheets, and subsequently compiled and presented in Ashby plots and bar graphs. The high values of the compressive strength and specific compressive and tensile strengths perpendicular to the grain (width direction) shown by the experimental thermoplastic composites compared to wood reveal their great potential for use in compressed elements and in functions where components are compressed or tensioned perpendicularly to the grain. However, the low specific flexural modulus and high density of thermoplastic materials limit their usage in certain civil engineering and building applications. Keywords

Compósitos De Madeira Plástica/Carga Inorgânica: Influência Do Tipo De Carga

“…Apesar da série de vantagens apresentada pela madeira plástica, pelo fato dela ser fabricada primordialmente por poliolefinas, que são materiais intrinsecamente mais facilmente combustíveis, há preocupação com a resistência térmica desses materiais, tendo sido encontrados registros da ocorrência de empenamento destes materiais durante o uso, devido, provavelmente, a sua exposição ao calor do sol e outras intempéries (MARTINS, 2017;REZENDE, 2015;DIAS;ALVAREZ, 2017).…”

Processing and Properties of Plastic Lumber

“…Although the composition of plastic lumber varies, the market consists primarily of companies that manufacture HDPE-based plastic lumber and those that use plastic composites and wood waste [16]. This has contributed to greater interest in the search for wood-plastic composite (WPC) processing technologies.…”

“…The physical and mechanical properties of plastic lumber differ from natural wood parts with the same dimensions [6,16,17]. One of the most significant differences is the lower stiffness (modulus of elasticity) of plastic lumber.…”

“…Following the abovementioned efforts in equipment design, attention turned to the composition of plastic lumber, and wood-plastic composites (WPC) emerged in the 1990s to replace wood with recycled plastic lumber in decking and fencing [16,18]. Also in the 1990s, pioneering studies on plastic recycling for the development of plastic lumber began at the Institute of Macromolecules of the Federal University of Rio de Janeiro, under the supervision of Professor Eloisa Biasotto Mano, the first line of research in the area at university level.…”

“…Despite the development of technology to obtain recycled PL, lack of standardization prevented its use by the construction industry in the early 1990s, particularly in structural applications. The Plastic Lumber Trade Association worked to establish a set of ASTM standards initially applicable to plastic lumber made from high-density polyethylene (HDPE) [16,20].…”