Microstructural evolution and hardness properties of coir-coconut husk powder reinforced polymer composites subjected to an acidic environment

In this study, coir-coconut husk powder reinforced polymer composite (CCHPRC) prepared by the simultaneous application of heat and pressure, was subjected to an acidic environment and its morphological and hardness properties were investigated. Four test conditions were selected to elucidate the short-term effect of the exposure of the composites to an acidic environment which was achieved by simulating an acidic condition of Sulfuric Acid (H₂SO₄) solution with a pH of 2.2 at room temperature (27 ^oC). Exposure periods of 3, 6 and 9 days (3PA, 6PA, 9PA) were considered, while samples not exposed to the acid solution were used as control (NP). In order to measure the possible surface degradation and hardness variation of the CCHPRC due to immersion in the acid solution, scanning electron microscopy in addition to energy dispersive spectroscopy (SEM/EDS), and hardness tests were carried out. As a result, the gradual material degradation and poor adhesion between reinforcement and matrix was observed which was confirmed by SEM/EDS analysis. Prolonged acid immersion time seemed to promote an increase in terms of the composites' hardness. It is possible to conclude that the hardness characteristics of the composite (NP- 12.98 HV; 3PA- 7.27 HV; 6PA- 14.40 HV; 9PA- 19.07 HV) increased after immersion on exposure for 6 and 9 days, in comparison with the control sample.