Interfacial Properties of Biocomposites

An inspection of the fracture surfaces of composites composed of reinforcing fibers and polymer matrices provides qualitatively useful information on the interfacial adhesion between the fiber and the matrix and also gives rise to an indication of the effect of fiber surface treatment on the mechanical and thermal properties of resulting composites [137-139]. 

Interlaminar shear strength (ILSS) depends primarily on the matrix properties and fiber-matrix interfacial adhesion rather than on the fiber properties [141]. The ILSS, measured by the short-beam shear test, can be enhanced by increasing the tensile strength and volume fraction of the matrix as well as by increasing the interfacial adhesion in the laminates. 

It was reported that the efiect of surface modification of flax on the ILSS of two-directional flax fabric/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) biocomposites [121]. The ILSS values of the surface-treated flax fabric/PHBV biocomposites were greater than that of with untreated fabric. The plasma-treated specimen exhibited ILSS values greater than those for the acetylated one in comparison with the untreated specimens. The explanation for this was that aliphatic moieties with greater hydrophobicity may be formed on the fiber surfaces by ethylene plasma. It was noted that both acetylation and plasma treatment played an important role in improving the interfacial properties of flax/PHBV biocomposites, suggesting that the ethylene plasma treatment was more efiective. 

It has been concluded from a number of studies that cellulose-based natural fibers must be chemically or physically surface treated to improve the interfacial properties of the biocomposites and consequently to increase their mechanical, thermal, and/or other relevant properties. 

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Many research efforts to enhance the interfacial properties of biocomposites and ultimately to improve the mechanical and thermal properties and so forth have been performed more extensively by treating or modifying natural fibers before composite processing than by modifying polymer matrices. Natural fibers can be treated by chemical and physical approaches. 

Han, S.O., Cho, D., Park, W.H., and Drzal, L.T. (2006) Henequen/ poly(butylene succinate) biocomposites electron beam irradiation effects on henequen fiber and the interfacial properties of biocomposites. Compos. Interfaces, 13, 231-247. 

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