Mechanical behavior of sugarcane bagasse cellulose composites using lignin as coupling agent

Natural fibers polymer composites occupy a significant position in the engineering market. There are benefits of using this kind of materials such as light weight, high mechanical properties, drop of environmental problems and recycling. However, the hydrophilic character of natural fibers leads to low compatibility with hydrophobic polymer matrices.The objective of this work was to investigate the use of lignin as coupling agent in polypropylene (PP) composites reinforced with sugarcane bagasse cellulose. Sugarcane bagasse was pretreated by diluted acid, delignified, treated with xylanase and bleached. All lignocellulosic materials were chemically characterized to evaluate the extent of pre-treatment, delignification, enzymatic treatment, alkaline extraction and chemical bleaching. PP composites reinforced with 5 to 40 (%wt/wt) of bleached cellulose fibers and with 5 to 20%(wt/wt) of lignin from sugarcane bagasse were prepared in a thermokinetic mixer at 5250 rpm. After mixing, the composites were cooled with water and after that, ground to 13 mm. The milled composites were submitted to an injection molding under vacuum process. The obtained specimens were tested according to ASTM D-6110 specification. Results revealed that the route chosen for obtaining cellulose was promising, but changes in the process must be carried in order to avoid losing large amounts of cellulose. At the final of the process of obtainment of bleached cellulose, the material had a great portion of cellulose and small portions of hemicelluloses and lignin. The mechanical tests are still in development, indicating the positive effect of lignin in the composites. [Acknowledgements due to FAPESP, CNPq and CAPES]