Pine Cone and Boron Compounds Effect as Reinforcement on Mechanical and Flammability Properties of Polyester Composites

Abstract

In recent years focus on the development of natural fiber composites has been increased due to their superior properties such as light-weight, high strength and stiffness. Natural fibers are known environmentally friendly and they can be used alternatively to glass and carbon fibers because of their low-cost. Pine cone fibers are good preference to use for composite manufacturing because they are mainly consisted with cellulose, hemicelluloses and lignin macromolecules which provide a hydrophilic character. Potential pine cone forest reserve of Turkey is 54,000 ha and its total stone pine cone production is annually 3500 tons. Boron compounds such as borax, boric acid and zinc borate are generally used for their flame reterdant effect. These compounds can inhibit mass transfer of combustible vapors by blocking its contact with oxygen. In this study three kinds of boron compounds such as boron oxide, borax pentahydrate and borax decahydrate were used to provide better mechanical properties and better incombustibility. Synergistic effect of both waste pine cone and boron compounds were sampled to manufacture the polyester composites by using casting process. Some mechanical (bending strength, flexural modulus, izod impact), flame retardancy (limiting oxygen index (LOI)), and physical properties (water absorption, swelling thickness, open porosity, bulk density) were obtained at different fiber content. SEM analysis of the final products was performed to observe morphological structure. According to mechanical test results boron oxide showed better bending strength and flexural modulus compared with the other boron compounds. LOI of composites with boron compound was higher than the composites with only pine cone reinforcement.