Biofiber-Reinforced PLA Composites

Biofiber-reinforced PLA composites are now among the most well-established biocomposites in the industry. Some of the examples of the products made from these biocomposites are urns, mobile phone shells and spare tire covers in automobiles. They are also the most widely researched of all biocomposites as is evident from Table 10.5, which lists mechanical properties of a selection of such composites. 

Oksman et al. [26] reported that the tensile strength of flax fiber-reinforced PLA composites was improved by 50% compared to similar PP/fiax fiber composite at fiber loading of 30-40%. Similarly, modulus of PLA-based composites was increased from 3.4 GPA for neat PLA to 8.4 GPa for the composite. PLA was also not degraded by the compounding process used during manufacturing of composites. 

Shih et al. [27] fabricated green composites with fiber recycled from disposable chopsticks and PLA matrix by melt-mixing method. Mechanical tests showed that the tensile strength of the composites markedly increased with the fiber content, reaching 115 MPa in the case of being reinforced with 40 phr fibers, which was about three times higher than the neat PLA. 

Plackett et al. [29] reported that the tensile strength and stiffness of PLA could be approximately doubled when jute fiber reinforcement (40 wt%) was used. Results of electron microscopy showed brittle failure of jute fibers under tension and void spaces between fiber and polymer matrix, indicating that the strength 

Similarly, Tao et al. [30] reported that neat PLA had a lower tensile strength than PLA-based ramie and jute short fibers composites. However, an optimum fiber content of 30% was reported above which the tensile strength of composites decreased and was even lower than that of neat PLA. They also reported that the impact strength of PLA/ramie composites was higher than that of PLA/jute composites due to the higher strength of ramie fiber. 

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