Effect of fiber surface treatments on the fiber-matrix interaction in banana fiber reinforced polyester composites

Cellulosic Ž bers have been used as cost-cutting Ž llers in plastic industry. Among the various factors, the Ž nal performance of the composite materials depends to a large extent on the adhesion between the polymer matrix and the reinforcement and therefore on the quality of the interface. To achieve optimum performance of the end product, sufŽ cient interaction between the matrix resin and the cellulosic material is desired. This is often achieved by surface modiŽ cation of the resin or the Ž ller. Banana Ž ber, the cellulosic Ž bers obtained from the pseudo-stem of banana plant (Musa sepientum) is a bast Ž ber with relatively good mechanical properties. The Ž ber surface was modiŽ ed chemically to bring about improved interfacial interaction between the Ž ber and the polyester matrix. Various silanes and alkali were used to modify the Ž ber surface. ModiŽ ed surfaces were characterized by SEM and FTIR. The polarity parameters of the chemically modiŽ ed Ž bers were investigated using the solvatochromic technique. The results were further conŽ rmed by electrokinetic measurements. Chemical modiŽ cation was found to have a profound effect on the Ž ber–matrix interactions. The improved Ž ber–matrix interaction is evident from the enhanced tensile and  exural properties. The lower impact properties of the treated composites compared to the untreated composites further point to the improved Ž ber–matrix adhesion. In order to know more about the Ž ber–matrix adhesion, fracturedsurfacesof the failed compositeswhere further investigated by SEM. Of the various chemical treatments, simple alkali treatment with NaOH of 1% concentration was found to be the most effective. The Ž ber–matrix interactions were found to be dependent on the polarity of the modiŽ ed Ž ber surface.