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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.

There is critical concern about meeting future global demand for materials because of the depletion of natural resources. In particular, the balance between future demand and sustainable supply will require a great deal of attention in years to come. The interest in the long term sustainability of material resources has led to advancements in bio-composite or polymer composite materials that are made from natural fibers and resin. Pinecones and chestnut waste are most often used as the biomass/biochar source. Nature proposes, and man disposes; we have to find or create new forms of pinecone and chestnut waste to increase their value and for environmental reasons. That is why the current waste was processed and transformed to filler in an up-graded state. In this study, composites were manufactured using chestnut waste and pinecone powder as filler and polyester as the polymer matrix. In addition, methyl ethyl ketone peroxide as hardener and cobalt naphthenate as accelerator were used to produce polyester composite. Raw materials of the fillers were treated with sodium hydroxide solution. The polyester amount was kept constant while the filler ratio was increased from 3% to 12% by weight. The similarities and differences between composites with different fillers and chemical pre-treatments were assessed by evaluating certain mechanical properties such as flexural strength, elastic modulus and hardness and various physical features such as density, open porosity percentage and water absorption. According to the experimental results, increasing the ratio of both chestnut and pinecone powder led to a decrease in the bending strength and an increase in the elastic modulus. Higher properties were associated with the chestnut waste/polyester composite than the pinecone powder/polyester composite.