Biorenewable polymer thermoplastic biocomposites
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Biorenewable fillers have recently gained a greater focus in research to produce composites because of their unique properties, abundance, and diversity. These biorenewable fillers can include various terrestrial based plants naturally grown throughout the world. The focus of this work was on the natural fiber feedstocks that are created as waste streams from a wide range of industries, in particular agave fibers. Creating a composite composed of fibrous materials would have potential benefits that include cutting costs of composite products, decrease in density, increased strength and durability, and utilizing plant fiber waste streams for cost recovery. However, these natural fibers tend to be hydrophilic in nature and do not adhere well to hydrophobic polymer matrices. Directly combining plant fibers with plastics tends to yield poor mechanical properties because of this incompatibility. These plant fibers must first go through treatment(s) to alter their surface properties, mechanically and/or chemically, to promote strong interfacial bonding to occur.
Processing temperatures of polymers for extrusion or molding into a finished part vary based on the polymer used; however, they tend to be higher than the degradation temperatures of the fibers, which can result in brittle fibers. Polymers such as polyethylene and polypropylene have processing temperatures ranging from 140-200 Ã Â°C. To allow processing of fiber-reinforced composites, polymer additives are used to suppress the processing temperatures and thus reduce thermal degradation of the natural fibers. Finding both ideal treatments for fibers and additives for polymers will allow a wide variety of feedstocks to be utilized throughout the world, affecting many industries. Potential industries impacted by this research include automotive, aerospace, and consumer goods.
Early success has been observed in creating biofilled composites displaying significantly improved mechanical properties. Creating functionalized chemical bonding groups to promote surface interactions of biofibers and polymer matrices is important to enhance the properties of these composites. In this project, modified lignin and agave fibers were utilized as fillers in biocomposites with high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), and polypropylene (PP), as the matrix polymers. It was found that with proper pretreatments and processing conditions, it is possible to produce biocomposites with higher specific strength (strength: density) compared to traditional composites, such as glass reinforced composites. It was also seen that at higher filler levels (20-25%), the mechanical properties were maximized as a result of fiber to fiber interaction and entanglement.