Natural fiber‐reinforced biodegradable polyester composites were prepared from biodegradable polyesters and surface‐untreated or ‐treated abaca fibers (length ca. 5 mm) by melt mixing and subsequent injection molding. Poly(butylene succinate)(PBS), polyestercarbonate (PEC)/poly(lactic acid)(PLA) blend, and PLA were used as biodegradable polyesters. Esterifications using acetic anhydride and butyric anhydride, alkali treatment, and cyanoethylation were performed as surface treatments on the fiber. The flexural moduli of all the fiber‐reinforced composites increased with fiber content. The effect of the surface treatment on the flexural modulus of the fiber‐reinforced composites was not so pronounced. The flexural strength of PBS composites increased with fiber content, and esterification of the fiber by butyric anhydride gave the best result. For the PEC/PLA composites, flexural strength increased slightly with increased fiber content (0–20 wt.‐%) in the case of using untreated fiber, while it increased considerably in the case of using the fiber esterified by butyric anhydride. For the PLA composite, flexural strength did not increase with the fiber reinforcement. The result of soil‐burial tests showed that the composites using untreated fiber have a higher weight loss than both the neat resin and the composites made using acetylated fiber. Flexural modulus of PBS composites as a function of fiber content.magnified imageFlexural modulus of PBS composites as a function of fiber content.

ABSTRACT:The mechanical properties of poly(3-hydroxybutyrate-co-3-hydroxyvarelate) (PHBV) composites, reinforced with short abaca fibers prepared by melt mixing and subsequent injection molding, were investigated and compared with PHBV composites reinforced with glass fiber (GF). The influences of fiber length, fiber content, and surface treatment of the natural fiber on the mechanical properties were evaluated. Regarding fiber length, the tensile properties had a maximum at a fiber length of about 5 mm. The flexural properties of the PHBV/abaca composite were improved by the surface treatment of abaca with butyric anhydride and pyridine for 5 h because of the increase of interfacial adhesiveness between the matrix polyester and the surfaceesterified fiber, as is obvious from the SEM micrographs. The flexural and tensile properties of PHBV/treated abaca composite were comparable to those of PHBV/GF composite, except for tensile modulus, compared with the same weight fraction of fiber.

Cu/MoS 2 composite material was formed by a novel powder-molding technique, which is termed the compression shearing method at room temperature (COSME-RT). Cu/MoS 2 sample mechanical and tribological properties and microstructures were investigated. Samples were prepared using five different MoS 2 concentrations between 0 to 20 vol.%. No unwanted compounds were generated by the Cu and MoS 2 because a high temperature is unnecessary in COSME-RT. Scanning electron microscopy observations confirmed that the MoS 2 particles were dispersed homogeneously in the Cu host matrix. The indentation hardness of Cu/MoS 2 with 0, 1.0 and 5.0 vol.% MoS 2 was higher than 1.6 GPa, and is higher than that formed by conventional powder metallurgy methods and a pure Cu plate. The indentation hardness of the Cu/MoS 2 decreased with increasing MoS 2 concentration. In contrast, the lubricating performance of MoS 2 became more pronounced at 5.0 vol.% or above. The coefficient of friction of Cu/MoS 2 with 5.0, 10 and 20 vol.% MoS 2 was ~0.20, and is the same as for MoS 2 in air. The sample coefficient of friction was maintained because of lubrication by forming a transferred film of wear debris that contained MoS 2 . Cu/MoS 2 had a low coefficient of friction, but maintained its material strength at 5.0 vol.% MoS 2 .

Poly(butylene succinate) composites reinforced with short sisal fibre were prepared by melt mixing and subsequent injection moulding. The influence of fibre length, fibre content and the surface treatment of the natural fibres on the mechanical properties of the composites were evaluated. Regarding fibre length, the tensile and flexural properties of the composites had maxima at a fibre length of about 5 mm. The flexural and tensile moduli of the composites increased with increasing fibre content. Although the tensile strength hardly changed, the flexural strength increased up to a fibre content of 10 wt%. The dynamic mechanical analysis of the composites showed that the storage moduli at above ca.-16°C (corresponding to the glass transition temperature of the matrix) increased with increasing fibre content.

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