Biodegradable Polyesters Reinforced with Surface-Modified Vegetable Fibers

✍ Scribed by Elisa Zini; Massimo Baiardo; Lidia Armelao; Mariastella Scandola

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 295 KB
• Volume: 4
• Category: Article
• ISSN: 1616-5187
• DOI: 10.1002/mabi.200300120

✦ Synopsis

Abstract

Summary: Flax fibers are investigated as reinforcing agents for biodegradable polyesters (Bionolle and poly(lactic acid) plasticized with 15 wt.‐% of acetyltributyl citrate, p‐PLLA). The composites are obtained either by high temperature compression molding fiber mats sandwiched between polymer films, or by batch mixing fibers with the molten polymer. Fibers in composites obtained by the latter method are much shorter (140–200 μm) than those of the mats (5 000 μm). Flax fibers are found to reinforce both p‐PLLA and Bionolle (i.e. tensile modulus and strength increase) when composites based on fiber mats are investigated. Conversely, analogous composites obtained by batch mixing show poor mechanical properties. The observed behavior is attributed to the combined effect of fiber length and fiber‐matrix adhesion. If flax fibers with a modified surface chemistry are used, the strength of short fiber composites is seen to improve significantly because the interface strengthens and load is more efficiently transferred. Appropriate surface modifications are performed by heterogeneous acylation reactions or by grafting poly(ethylene glycol) chains (PEG, molecular weight 350 and 750). The highest tensile strength of p‐PLLA composites is reached when PEG‐grafted flax fibers are used, whereas in the case of Bionolle the best performance is observed with acylated fibers.

SEM micrograph of the fracture surface (from side to side) of a freeze fractured composite sheet of A‐p‐PLLA with A2 fibers.

imageSEM micrograph of the fracture surface (from side to side) of a freeze fractured composite sheet of A‐p‐PLLA with A2 fibers.