Research On The Preparation And Performance Of Hybrid Natural Fibers Reinforced Polylactide Biocomposites

With the growing shortage of oil resources and increasingly serious environmental pollution, non-petroleum based biodegradable polymer materials and renewable plant resources has been rapidly developed. Holding lots of advantages which synthetic fibers can hardly compare, sisal fibers can be used to fill and reinforce polylactide(PLA). It can not only reduce the cost of PLA, improving their overall performance and expanding the applied range of composites, but also solve the above issues and achieve sustainable development.Based on the defects of the performance of single sisal fiber, this paper used two kinds of natural fibers(bamboo fiber and coir fiber) with different performance mixing with sisal fiber, to investigate the properties of hybrid natural fiber reinforced PLA composite. Alkali solution was used to treat the three kinds of natural fibers, and hybrid sisal/bamboo fibers reinforced PLA composites and hybrid sisal/coir fibers reinforced PLA composites were prepared respectively. Besides, the effect of hybrid ratio of fibers on the mechanical properties, microstructure, crystallization properties and thermal properties of hybrid composites were researched respectively, and the hybrid effect of hybrid composites was also analyzed. The experimental results show that:The hemicellulose, lignin and other small molecular substances of three kinds of natural fibers were removed for varying degrees. Meanwhile, the diameters of fibers were reduced, and the thermal stability of fibers under N2 environment was enhanced. Among three kinds of single fiber reinforced PLA composites, sisal fiber reinforced PLA composites showed relatively preferable tensile properties, but the impact properties had a small-range improvement; while the impact properties of single bamboo fiber and single coir fiber reinforced PLA composites both had significant improvement. Besides, the crystallization capacity and crystallinity of three single fiber reinforced composites were enhanced after the addition of natural fibers, and compared with unmodified method, alkali treatment could improve the thermal stability of composites.By mixing sisal fiber with bamboo fiber to reinforce PLA, the hybrid composites showed an irregular mechanical properties. Only when the hybrid ratio was 5/5, the hybrid composites had relatively preferable mechanical properties. Compared with pure PLA and single fiber reinforced composites, the tensile properties changed little, while other performance especially impact property had a significant improvement. What’s more, the hybrid ratio had a less effect on the thermal properties of the hybrid composites.By mixing sisal fiber with coir fiber, the mechanical properties of hybrid composites had an obvious variation trend. When the hybrid ratio was 7/3,The hybrid composites had an optimum mechanical properties. Compared with pure PLA and sisal fiber reinforced PLA, the tensile strength of hybrid composites at 7/3 hybrid ratio decreased slightly, but still higher than that of PLA/ACF; while the flexural strength and impact strength increased dramatically, even higher than those of pure PLA and PLA/ASF as well as PLA/ACF. And, all the mechanical properties showed positive hybrid effect except tensile modulus when the hybrid was 7/3. Besides, the hybrid composites had a highest crystallinity and crystallization capacity when the hybrid ratio was 7/3, while the hybrid ratio has little influence on the thermal stability of the hybrid composites.