Polymer/Wood Composites

Abstract

The use of thermoplastic composites reinforced with natural fibers is a mature technology now with a considerable growth rate. The properties of all polymer/wood composites are determined by four factors: component properties, composition, structure, and interfacial interactions. Matrix stiffness determines the extent of reinforcement, while aspect ratio and particle size are the most important characteristics of the wood. Wood content is usually very large in order to achieve maximum effect and lowest possible price. At large fiber content, wood particles can touch each other purely from geometrical reasons resulting in a kind of aggregation which decreases composite strength. Alignment of the fibers, that is, orientation is the other structural factor that influences composite properties considerably. Interfacial interactions are inherently weak in most commodity thermoplastic/wood composites. External load initiates various micromechanical deformation processes in these materials: shear yielding of the matrix, debonding, fiber pullout, or fiber fraction may occur simultaneously or consecutively. Because of easy debonding, interactions must be modified usually by coupling in most composites. In the case of strong interfacial adhesion, the inherent strength of the wood particles may limit the maximum strength of the composites. A brief summary of processing technologies and main application areas are also presented at the end of the article.

Deformation and failure of sugarcane bagasse reinforced PP

“…The mechanical properties were characterized by tensile and impact testing. characteristics and adhesion very much, but mainly on the amount of fiber added to the matrix [21,32]. The presence of MAPP does not influence stiffness indeed, but fiber characteristics seem to have an effect [32]; the modulus of composites containing the bagasse fibers is smaller than that prepared with wood flour.…”

“…The properties of heterogeneous polymers including fiberreinforced composites are determined by four factors, by component properties, composition, structure and interfacial interactions [20]. In the case of wood flour and other natural fibers, the main factor proved to be the size and aspect ratio of the particles [21]. Larger aspect ratio improves stress transfer and reinforcement, but it makes processing more difficult [21].…”

“…In the case of wood flour and other natural fibers, the main factor proved to be the size and aspect ratio of the particles [21]. Larger aspect ratio improves stress transfer and reinforcement, but it makes processing more difficult [21]. The surface energy of natural fibers is small, thus their adhesion to the polymer matrix is weak, especially in polyolefins, which do not contain any polar functional groups [16,22,23].…”

“…In the case of large particles, the transvers strength, i.e. the strength of the fiber vertically to its axis, proved to be small, which led to small tensile strength and impact resistance [21]. Various fibers coming from a variety of sources can have a wide range of characteristics and thus the properties of the composites prepared from them can vary considerably [16,25].…”

Impact modification of PP/wood composites: A new approach using hybrid fibers

“…Stiffness usually increases as a result of the addition of wood fibers into a polymer matrix [11][12][13][14][15]. The strength of WPCs' cannot be predicted easily, as it depends on numerous factors: the particle characteristics of wood (size, shape), the inherent strength of the natural reinforcement [16], the orientation of fibers [17] and interfacial interactions [18,19]. For some applications, especially in the automotive industry, the impact resistance of composite parts is also a crucial factor.…”