Abstract:
Natural fibers such as wood, flax, and hemp are frequently used as fillers in natural fiber-plastic composites (NFPCs). At present, wood fiber is the most commonly used filler in the production of wood-plastic composites (WPCs). The advantages of these fibers compared to conventional inorganic fibers such as glass fiber is that they offer low density, low abrasion, and low materials cost. The properties of the NFPCs depend highly on the filler characteristics, filler volume, and the thermoplastic characteristics. As the NFPC market evolves, the strength requirements of NFPCs become increasingly higher. However, the interface between hydrophobic plastic and hydrophilic wood is typically weak and fails to transfer stress. At present, the interfacial structure and chemistry are still poorly understood. For example, little has been published about the effects of wood extractives on the interfacial adhesion between wood and plastics. The first chapter of this thesis investigated the effect of extractives in wood flour on the mechanical properties of wood-polypropylene (PP) composites. This study found that the extractives in wood lowered the mechanical properties of the composites. At the moment, there is an abundant amount of underutilized grass straw all over the world. Burning is currently a commonly used method for disposing of the grass straw. However, burning causes environmental problems, and the farmers do not benefit from this practice. Therefore, the utilization of the grass straw in NFPCs will be beneficial for the environment and for the farmers. However, the use of the grass straw as a filler in making grass straw-plastic composites (GPC5) has yet to be fully investigated. In particular, little has been published about effects of a compatibilizer on the properties of GPCs, although it has been well-established that a compatibilizer can greatly improve the strength and stiffness of WPCs. The second part of this thesis investigated the effects of several compatibilizers on the flexural properties and water resistance of GPCs.
