Effect of filler gradation on the properties of high-filled unsaturated polyester composites

Abstract

The preparation of high-filled composites by combining inorganic fillers (such as quartz sand and CaCO ₃ ) with resins has garnered significant attention for its ability to effectively reduce composite material costs. Adjusting the ratio of inorganic fillers represents an effective approach to enhancing the properties of high-filled composites. This study incorporated quartz sand fillers of varying grades into unsaturated polyester resin (UPR) to create composites with elevated filler content. The mechanical properties, degree of cure, component distribution, and phase structure of the blends were analyzed using three-point bending tests, compression tests, dynamic thermal analysis, and scanning electron microscopy. The study shows that optimizing the gradation of quartz sand can notably improve the strength of composite materials. The refined composite material structure exhibits increased compactness, leading to a 37.56 % enhancement in bending strength and a 27.53 % rise in average compressive strength. Optimizing the filler gradation improved the UPR conversion rate of the composite material, thereby enhancing its curing degree. Gradation optimization reduced interface defects between the filler and UPR, resulting in a structurally compact and uniformly distributed composite. This study proposes a novel method for preparing composites by integrating the close-packed theory with high-filled composites.