Polystyrene cellulose fiber composites: effect of the processing conditions on mechanical and dynamic mechanical properties

The usage of natural fibers on the composites development has grown rapidly in the recent years due to the fibers plentiful availability, renewable source, low density and biodegradability. However, there are some drawbacks, for instance, the fiber dispersion on a polyolefin matrix. In this work, the influence of processing speed on the mechanical and dynamic mechanical properties of polystyrene (PS) filled with cellulose fiber composites was investigated. The composites were processed on a twin-screw co-rotating extruder, using screw speeds of 200 rpm, 400 rpm and 600 rpm. The dynamic mechanical properties and the mechanical properties were investigated as a function of fiber content. The composites processed on a screw speed of 400 rpm had presented an increase on flexural and impact strength, compared to the composites processed at 200 rpm. The flexural and storage modulus had increased when increasing the fiber content, as well as increasing the processing speed. The greater fiber dispersion obtained at a screw speed of 400 rpm hinders the agglomeration arrangement and distributes the fibers more equally on the matrix. The increase on processing speed probably generates a fiber size reduction, increasing the fiber superficial area and generating a greater contact with the matrix as well. Therefore, the efforts transference of matrix to fibers is improved, originating an increase on the evaluated properties.