Research on the fabrication of composite materials based on unsaturated polyester resin matrix and modified rice husk reinforcement

In this study, rice husks (RHs) were utilized as fillers to create a reinforcing phase during the fabrication of composites based on an unsaturated polyester (UPE) resin matrix. The aim was to maintain the mechanical properties of the materials at a certain level and partially replace the amount of thermosetting resin used, thereby reducing negative environmental impacts. Sodium hydroxide (NaOH) and 3-methacryloxypropyltrimethoxysilane (MPS) were employed in the modification process of the RHs. The structure and morphology of the modified RHs were investigated using Fourier-transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy (FESEM). Additionally, the mechanical properties of composite samples were evaluated according to international standards, such as ISO 527:2012, ISO 178:2019, ISO 604:2002, and ASTM D256. The results showed that the RHs sequentially modified by a NaOH solution and a MPS-dissolved mixture significantly improved the mechanical properties of the respective composites, compared to the composites with untreated RHs and RHs chemically modified by one solution. Specifically, compared to the reference samples formed by raw RHs, the best composite among ones with two-stage-treated RHs demonstrated flexural strength with an increase of 34.1% (reaching 45.1 MPa), compressive strength with a climb of 51.6% (reaching 33.8 MPa), tensile strength rising by 44.6% (at 34.3 MPa), and impact strength of 6.3 kJ/m² (18.9% higher). These results indicate that modified RHs can meet the research objectives and pave the way for further studies on RH-based composites.