Characterization and multi-response optimization of epoxy–castor oil composites reinforced with coconut shell and marsh barbel powders

The increasing demand for sustainable polymer composites has led to the use of agricultural waste and natural materials as alternative reinforcements. The present work deals with the characterization and multi response optimization of epoxy castor oil composites reinforced with coconut shell powder (CSP) and marsh barbel powder (MBP). Hand lay-up casting technique was used to prepare six formulations with different loadings of natural powder and with 20 wt% castor oil, cured at room temperature. The composites were evaluated for mechanical, tribological, electrical voltage, water absorption, chemical, morphological and soil-burial properties. Preliminary electrical voltage measurements, water absorption test and Fourier Transform Infrared (FTIR) spectroscopy were used to evaluate the composite properties. The electrical voltage of the unfilled epoxy–castor oil matrix (S1) was low, from 15 to 20 V. General performance of MBP reinforced composites was inferior to CSP reinforced composites. The optimum formulation, S6 with 60 wt% epoxy resin, 20 wt% castor oil and 20 wt% CSP had maximum tensile strength of 39.3 MPa, impact strength of 4.35 kJ/m 2 , hardness of 29.7 BHN and interlaminar shear strength of 39.8 MPa. Also, S6 exhibited minimum specific wear rate of 0.018 mm 3 /Nm, coefficient of friction of 0.55 and water absorption of 1.5%. The FTIR analysis revealed the presence of functional groups. SEM showed relatively uniform distribution of the filler and improved interfacial contact. Multi-response optimization showed that S6 is the best formulation, indicating the potential of coconut shell powder in the development of sustainable particulate polymer composites.