Effect of surface chemistry on the interfacial adhesion and mechanical properties of natural fiber reinforced polymer composites

The fiber-matrix adhesion between cellulose fiber and polymer matrix was studied to understand the interfacial bonding mechanism in a natural fiber reinforced composite system. The effects of fiber surface modification, both physical and chemical, on the interfacial adhesion were observed and quantified using AFM and XPS analysis. Both natural and regenerated cellulose fiber were utilized in this research to improve the applicability of the experimental results.; Various fiber and matrix modifications were used to alter the interfacial chemistry between cellulose fibers and polymer matrix, hence changing the bonding characteristic at the composite interface. It's concluded that the matrix properties, such as crystallinity and matrix shear modulus can have an effect on the interfacial adhesion when interfacial chemistry is kept the same. For the same matrix material, chemical bonding at the fiber-matrix interface is much more dominant than physical interlocking mechanism with respect to fiber-matrix adhesion. Whenever covalent bonding is introduced to the fiber-matrix interface, the interfacial adhesion improved.; Unidirectional natural fiber reinforced polypropylene and epoxy composite were also fabricated to gain an insight on how the fiber-matrix adhesion affects the composite mechanical properties. Strong interfacial adhesion usually improves the tensile properties of the composites. However, for the henequen and polypropylene system studied, the impact strength can be lowered by the improvement in the interfacial adhesion. Voids and processing condition can also have an impact on the interfacial adhesion and composite mechanical performance. Therefore, in selecting surface treatment, an optimized approach must be taken in conjunction with chemical and physical properties of the materials.