On Mechanical Behavior of Pine Nut Shell and Polyurethane Derived from Castor Oil Green Composite

Abstract

Natural fibres reinforced polymeric composites are examples of green composites. Commodities polymers derived from fossil sources have volatile organic compounds in their compositions. Polyurethane derived from castor oil is produced from renewable sources, it has no volatile organic compounds in its composition and presents biodegradability. This study aims to evaluate physical-, mechanical- and thermal properties of composites of Araucaria pine nut shell vegetable fibres as reinforcement and polyurethane derived from castor oil (PU) as matrix. The composites were produced with 20 wt.%, 35 wt.% and 50 wt.% of PU. The 100% PU (used as control samples) properties were assessed by flexural strength, thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR). Composites panels properties were assessed by the following techniques/approaches volumetric density, water absorption, thickness swelling, flexural strength, TGA, FTIR and scanning electron microscopy (SEM). Composites with 35%PU presented flexural strength of 51.55 MPa, a density of 1018 kg/m³, water absorption of 7.95% and swelling in thickness over 24 hours of 5.36%, these results are better when compared to similar composites made with pine nut shell and thermoset polymer. The study focused on how the fibre-matrix adhesion at the interface plays a role in the composite reinforcement.

Keywords

• composite
• polyurethane
• castor oil
• pine nut shell
• mechanical properties
• fiber/matrix interface