Effect of sodium alginate on properties of wheat straw/polylactic acid composites

To investigate the effect of sodium alginate (SA) on the properties of wheat straw/polylactic acid (PLA) composites, four kinds of composites with different SA contents (0 wt%, 5 wt%, 10 wt%, and 15 wt%）were prepared via injection molding. The mechanical properties, moisture absorption, thermal stability, and infrared spectrum of the four kinds of composites were tested and analyzed, and the microstructure of the tensile section of the composites was observed via scanning electron microscopy. The degradability of the composites was also analyzed. The results showed that the wheat straw/PLA composites with 5% SA had better mechanical properties. Their tensile strength was 15.8%, 5.4%, and 19% higher than those of 0%, 10%, and 15% SA, respectively. The impact strength of the 5% SA composites changed to an acceptable degree relative to the non-SA composites, which had an impact strength of 28% lower than that of 0% SA but 51.9% higher than that of the 15% SA composite. The 5% SA composites had less hygroscopicity and better thermal stability, and adding SA enhanced the degradability of the composites. As the SA content increased, degradability increased greatly.