Biocomposites, applications mechanical performance

The mechanical performance required of biocomposites is dependent on specific structural applications. Crude inferences can be made by comparing properties of materials that these biocomposites are intended to substitute. Mechanical data and/or allowable design values of wood and engineered wood products were used to evaluate potential applications of hemp fabric/cellulose acetate composites and hemp fabric/poly (hydroxybutyrate) composites (Table 13.2). From the comparisons, it can be inferred that these biocomposites, despite not passing the design values of wood structural material, can potentially substitute engineered wood products (of the same size) such as plywood and oriented strand boards to partially capture existing markets as crates, pallets, and formwork [38]. 

However, cellulose has an attractive combination of mechanical and thermal properties extracted from various plant sources. Extracted cellulose performs as a raw material in many packaging industry applications such as biocomposites, nanocomposites, coatings, films, etc. The process of converting cellulose to these products is quite complex. For example, to convert wood pulp to film, it rmdergoes a series of chemical processes to break the pulp down to a viscose liquid. This liquid is filtered in order to minimize waste and maximize the purity of the material to ensure the best film quality possible. The viscose is extruded and then cast along a series of rollers and baths, during which the film is cleaned and softened in order to ensure the right optical and mechanical properties. 

All polymer composites absorb substantial amounts of moisture or water in humid environment as well as in water. The most important concern in indoor and outdoor applications of natural fiber-based biocomposites with polymer matrices is their sensitivity to water absorption, which can reduce considerably their mechanical, physical, and thermal properties and performances. The water absorption of biocomposites results in the debonding or gap in the natural fiber-polymer matrix interfacial region, leading to poor stress transfer efficiency from the matrix to the fiber and reduced mechanical and dimensional stabilities as well [158]. It has been known that the hemiceUulose component in cellulose-based natural fibers may be mainly responsible for water absorption because it is more susceptible to water molecules than the crystalline cellulose component. Also, poor interfacial adhesion... 

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