XIV SLAP/XII CIP 2014, October 12-16 th , 2014, Porto de Galinhas, Brazil - 1 - PIASSAVA FIBER REINFORCED POLYPROPYLENE COMPOSITES. Claudio Roberto Passatore 1,a , Alcides Lopes Leão 2,b and Derval dos Santos Rosa 1,c 1 Universidade Federal do ABC (UFABC), Santo André, SP, Brazil. 2 Faculdade de Ciências Agronômicas - UNESP, Botucatu, SP, Brazil. a cpassatore@uol.com.br ; c dervalrosa@yahoo.com.br Abstract The mechanical and morphological properties of composites of PP containing different proportions (20, 40 and 60 wt%) of short piassava fiber were prepared and compared with PP composites with CaCO3. Samples were prepared using a K-mixer and the composites were characterized by density, tensile test and the scanning electron microscopy (SEM). The theoretical modeling for Young´s modulus was observed with micromechanical models. The composite with piassava fiber was less dense than composites with filler and in the Young's modulus values showed that the inclusion of fibres reinforced the PP and increased the stiffness. The results showed that the inverse rule of mixtures equation to be an adequate mechanism for predicting the Young`s modulus and micrographs of the composites showed the interaction of the fiber in the matrix even the highest content (60 wt%). Keywords: Composites, Short fiber, Theoretical modelling, Piassava, Polypropylene. 1 INTRODUCTION We last few years there has been an increase in products manufactured with plastics in Brazil and in the World. Most of these materials are produced from commodity polymers, especially polyolefins have been used in the preparation of composites with natural and synthetic fiber as filler, aiming at the improvement of their unique properties without adding cost to the materials, for applications in aerospace, marine and automotive industries, as well as in construction [1, 2]. Some studies have compared methods for obtaining composites with satisfactory properties and in other have evaluated the effect of coupling additives (coupling agents) to improve the interaction at the fiber (hydrophilic character) and matrix (hydrophobic character) interface [1, 3]. To investigate the effect of fiber content in the composites and the need to pretreat the fibers, Elzubair et al. [3] compare the thermal and mechanical properties in composites with PEAD with piassava fiber with NaOH and silane and without treatment and proved that treatments of piassava fibers by NaOH and a silane coupling agent lead to an overall improvement of the mechanical properties of the composites. This was probably, due to an increase in the fiber–matrix adhesion and as such a higher strength, but the piassava fiber composites were found to be suitable for application as a reinforcement phase in thermoplastic matrix composites and presented good potential even without any surface treatment. Bledzki et al. [4] compared the properties of PP composites containing 40% (wt%) coconut fibers, grain and wood in the absence and presence of 5 wt% with PP-g-MA. Analysis of the mechanical, chemical, thermal and morphological properties of these composites showed the importance of PP-g- Ma with compatibilizer and that the tensile strength of a composite containing wheat fiber was 10% higher than a composite containing wood fiber. For elongation at break, the inclusion of coconut fiber resulted in values 80% higher than for wood, whereas for wheat the increase was only 40% compared to wood fiber. The differences in the properties of these composites, including tensile strength, were largely attributed to variations in the morphological form and the surface properties, size and shapes of the fibres. Despite the various studies [4, 5] mentioned above, there are few studies with piassava fiber, at a content > 40 wt% of fiber with PP. In this study, we examined the properties of PP composites containing short piassava fiber at high contents (60 wt%) with not pre treatment of the fibers (fibers in nature). 2 MATERIALS AND METHODS 2.1 Materials