STEAM-EXPLODED WHEAT-STRAW FIBERS AS REINFORCING MATERIAL FOR POLYPROPYLENE-BASED COMPOSITES - CHARACTERIZATION AND PROPERTIES

Composites of wheat straw fibers with polypropylene (iPP) and maleic a nhydride modified polypropylene (iPPMA) were prepared. Before being mi xed with polypropylene matrices, the wheat straw fibers were subjected to a steam explosion process that induces morphological and structura l changes in lignocellulosic materials. Such changes are able to enhan ce the interactions with the thermoplastic matrix. Compared with iPP, the modified matrix (iPPMA) has shown higher mechanical performances ( tensile and impact behavior) and a remarkable decrease of water absorp tion, that is one of the main drawbacks of natural fiber composites. F inally, the presence of covalent bonds between maleic anhydride and st eam-exploded (STEX) fibers, by means of an esterification reaction, pr oduced during the melt-mixing process, can explain the resulting good interfacial adhesion found in iPPMA-based composites.