Dynamic Mechanical Properties of Grafted Polypropylene Composites Reinforced with Acetylated Wheat Straw Fibers
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Dynamic Mechanical Properties of Grafted Polypropylene Composites Reinforced with Acetylated Wheat Straw Fibers Ramón Sánchez 1, Jacobo Aguilar 1, Silvia Y. Martínez 2, Reyes J. Sanjuan 3, Gerardo A. Mejía 4, Emma R. Macías 5, J Félix A. Soltero 5 and Víctor V. A. Fernández 1 1 Departamento de Ciencias Tecnológicas, Universidad de Guadalajara, Ocotlán, Jalisco, 47820, México. 2 Departamento de Ciencias Médicas y de la Vida, Universidad de Guadalajara, Ocotlán, Jalisco, 47820, México. 3 Departamento de Fundamentos del Conocimiento, Universidad de Guadalajara, Colotlán, Jalisco, 46200, México 4 Departamento de Bienestar y Desarrollo Sustentable, Universidad de Guadalajara, Colotlán, Jalisco, 46200, México 5 Departamento de Ingeniería Química, Universidad de Guadalajara, Guadalajara, Jalisco, 44430, México ABSTRACT Dynamic mechanical properties of polypropylene (PP) and grafted polypropylene (PP-gMA) composites reinforced with acetylated wheat straw fibers (WSF) is reported in this work. The materials were prepared with different fiber particle sizes (40, 80 and 140 U.S. mesh) and at different fiber contents (5, 10 and 15 wt.%). The PP and PP-g-MA composites, where anhydride maleic (MA) was used as coupling agent, were obtained using a twin-screw extruder; whereas an injection-molding machine molded the composite pellets into testing specimens. To observe the morphology of the composites, micrographs were taken with an optical microscope. The Dynamic mechanical properties were analyzed using a torsional rheometer. The morphological analysis showed a high porous structure somehow similar to foamed materials. The storage modulus (Gc) increased by increasing the fiber content, and decreased with fiber particle sizes for the PP composites. Meanwhile, the use of the coupling agent additive promoted a modulus increase due to higher fiber-polymer interaction, from better adhesion and chemical bonds formation between the fibers-coupling agent-PP. INTRODUCTION The utilization of lignocellulosic fibers as reinforcement fillers in thermoplastics polymers and elastomers composites have been attracting attention recently because the naturals fibers provide to the composites a low density, biodegradability, strength and add a sustainable value, because they could be obtained from agricultural residues [1-4]. Among the lignocellulosic agricultural sustainable residues commonly used are i.e., stalks of cereal crops, rice husks, coconut fibers (coir), bagasse, maize cobs, peanut shells, etc. [5]. The wheat straw fiber (WSF) is a natural fiber, available, renewable, nontoxic, low density, and his low cost is of industrial and economic interest. Natural fibers have less negative impact on the environment due to its biodegradability and recyclability, however, the weak interfacial adhesion of natural fibers has a negative influence on interfacial bonding between fiber and polymer matrix affecting
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the mechanical properties of composites. Several studies have been carried out to modify natural fibers by using acetic anhydride, a chem
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