Interfacial Adhesion in Natural Fiber-Reinforced Polymer Composites

Interfacial Adhesion in Natural Fiber-Reinforced Polymer Composites 19... 

One of the most important focus areas of research in the development of natural fiber-reinforced polymer composites is characterisation of the fiber-matrix interface, since the interface alone can have a significant impact on the mechanical performance of the resulting composite materials, in terms of the strength and toughness. The properties of all heterogeneous materials are determined by component properties, composition, structure and interfacial interactions [62]. There have been a variety of methods used to characterize interfacial properties in natural fiber-reinforced polymer composites, however, the exact mechanism of the interaction between the natural fiber and the polymeric matrix has not been clearly studied on a fundamental level and is presently the major drawback for widespread utilization of such materials. The extent of interfacial adhesion in natural fiber-reinforced polymer composites utilizing PLA as the polymer matrix has been the subject of several recent investigations, hence the focus in this section will be on PLA-based natural fiber composites. 

Optimization of interfacial adhesion in the development of natural fiber-reinforced polymer composites has been the subject of extensive research of the past two decades. Many techniques have been developed and tested and the principal aim of various modification strategies has been to reduce the fiber-fiber interaction through aiding improved wetting and dispersion, as well as improving interfacial adhesion and the resulting stress transfer efficiency from the matrix to the fiber. 

Natural fibers-reinforced polymer matrixes provide more alternatives in the materials market due to their unique advantages. Poor fiber-matrix interfacial adhesion may affect the physical and mechanical properties of the resulting composites due to the surface incompatibihty between hydrophilic natural fibers and non-polar polymers. The results presented in this chapter focus on the properties of palm and pineapple fibers in terms of their physical and chemical structure, mechanical properties and processing behavior. The final properties of these fibers with thermoplastics matrixes are also presented, paying particular attention to the use of physical and chemical treatments for the improvement of fiber-matrix interaction. 

As mentioned previously, the main bottleneck in the broad use of these fibers in thermoplastics is the poor compatibility between the fibers and the matrix. The inherent high moisture sorption of lignocellulosic fibers certainly has an effect on their dimensional stability [28]. This may lead to the microcracking of the composites and degradation of mechanical properties [28]. Like other natural fibers, kenaf absorbs moisture due to its hydrophilicity. The key issue related to the development and production of natural fiber-reinforced composites is the interfacial adhesion between the fiber and polymer matrix. Because of their inherent dissimilarities, natural fibers/polymer matrix composites are not compatible and interfadal adhesion in these composites tends to be poor. The weak bonding at the interfaces between natural fibers and polymer matrix is surely a critical cause of the reduction of useful properties and performance of the... 

The enhanced compressive mechanical properties in these composites were attributed to the development of better hydrophobic character, which results in increased interfacial adhesion between G. optiva fibers and hydrophobic matrix phase. The better performance of raw fibers-reinforced polymer composites at 20% of loading in comparison to 30% loading is because of hydrophilic nature of raw fibers which at high loading causes agglomeration of particle fibers and hence poor dispersability of reinforcement with matrix. 

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