Effect of pressurized steam treatment on selected properties of wheat straws

Wheat straw fibers were modified via a pressurized steam treatment. The effect of steam pressure (i.e., 0.2, 0.4, 0.6, 1.0 MPa) and treatment time (i.e., 5 and 10 min) on chemical composition, sorption isotherm, thermal and mechanical properties of the treated fibers was investigated. Differential scanning calorimetry analysis showed that thermal characteristics of the treated straw samples were shifted indicating the improved thermal stability. The ash and extractive content of the treated straw was reduced; and the materials were likely removed when the steam was released. The removal of ash and extractives could improve the wettability of wheat straw when it is used in combination with polymer matrices. Sorption behavior study showed that steam treatment reduced the hydrophilic characteristic of wheat straw. Tensile strength of the treated straw was significantly enhanced. The tensile strength of straw after treatment at a steam pressure of 1.0 MPa for 5 min was more than twice higher than that of the control group. The study demonstrated that pressurized steam treatment is an effective pre-treatment process for wheat straw fibers as possible reinforcement element in polymer matrices.