Preparation of Thermosetting and Thermoplastic Composites Reinforced with Natural Fibers

5 Preparation of Thermosetting and Thermoplastic Composites Reinforced with Natural Fibers 

Prepared samples were placed in a glass mold with three independent rectangular plates two whole boards (upper and lower) measuring 140 x 100 x 5 mm and a plate of the same dimensions with a hollow center of 100 x 60 x 5 mm. Before the materials were distributed in the mold, the mold was covered with adhesive to facilitate the removal of the composites. 

Preparation of polyurethane matrix In a Petri dish, 9.0 g of the polyol of castor oil and 6.0 g of the prepolymer based on MDI were combined to obtain a polyol (castor oil) diisocyanate mass ratio of 1.5 1.0 for all composites. The homogenized mixture was distributed in the mold to fill the entire space of the intermediate plate. Then, the upper plate of the mold was closed and sealed with adhesive tape. After the material was cured for approximately 24 h, the mold was opened. 

Preparation of the composites reinforced with cellulose the same mass ratio between polyol and diisocyanate was maintained in all composites. After weighing the polyol, the desired mass of cellulose was added, and this mixture was homogenized. The prepolymer was then added and the mixture was homogenized again. Finally, the mixture was distributed into the mold as described previously. Composites were prepared with varying amounts of cellulose from 10 to 40 wt%. 

Preparation of the composites reinforced with lignin Composites reinforced with lignin were prepared using the same procedure as for composites reinforced with cellulose. Composites were prepared with varying amounts of lignin from 10 to 60 wt%. 

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