Effect of Modification of Flax Fibers with Silanes and Polysiloxanes on the Properties of PLA-Based Composites

Natural fibers can be an effective filling of composites and improve their properties. The aim and novelty of the research was to investigate the effect of modifying natural fibers with silanes and, especially synthesized, polysiloxanes with various functional groups in combination with alkali treatment on the properties of composites based on polylactic acid. For this purpose, composites with a 20% content of flax fibers were produced. Scanning electron microscopic (SEM) tests of the composites showed that the modification of the fibers had a positive effect on the adhesion to the polymer. Their thermal stability (TGA) was slightly improved by the addition of modified fibers, especially by polysiloxane with long alkyl chain. Flammability (PCFC) of composites was also improved up to 36% HRR reduction for mercerized fibers. The mechanical properties of the composites were tested on the basis of a tensile test. It has been shown that properly modified flax fibers can be a good filling for biocomposites, and especially synthesized polysiloxanes used to modify can be more effective than silanes.