Physical and tensile properties of chemically modified wheat straw/poly lactic acid composites

Abstract

In the present study poly lactic acid (PLA) and wheat straw fibers are used to make biocomposites. For a better compatibility between the two phases, wheat straw fibers were treated by silane and acetylation. Twin screw extruder was used to mix the substances, and compression molding was used to produce standard samples.Physical properties testing including water absorption and thickness swelling were studied to analyze the composites produced. Order to analyze changes occurred in samples after their immersion in water for 1,440 hours, pictures were made from the surfaces of the samples, using SEM. Results of water absorption and thickness swelling showed that the use of acetylated fibers in PLA composites resulted in the least water absorption and thickness swelling. SEM pictures showed that composites of PLA/ acetylated wheat straw fibers did not indicate a certain change after 1,440 hours of immersion in water. While composites of PLA/ untreated fibers showed noticeable gaps and cracks on the surfaces of the samples, PLA composites treated with silane showed only minute cracks on the surface of the sample. Analysis of tensile properties indicated that the tensile modulus of composites of PLA/ treated fibers showed a meaningful increase compared to pure PLA. The highest level of tensile properties was recorded for composites of PLA/ fibers treated with silane.