Low-dielectric and hydrophobic thermotropic liquid crystalline polyester composites reinforced with hollow glass microspheres for next-generation electronic board materials

Abstract

In this study, composites based on thermotropic liquid crystalline polymers (TLCP) and incorporated with hollow glass microspheres (HGM) were prepared via a melt compounding technique facilitated by masterbatch dilution, followed by subsequent shaping through injection molding. The influence of HGM loading (2–10 wt%) on the microstructure, thermal behavior, rheological and mechanical properties, dielectric performance, and hydrophobicity of the composites was comprehensively investigated. Electron microscopy and infrared spectroscopy confirmed uniform dispersion of HGM and strong interfacial hydrogen bonding with the TLCP matrix. X-ray diffraction revealed that HGM disrupts TLCP crystallinity, while differential scanning calorimetry demonstrated a decrease in crystallization and melting temperatures with increasing filler content. Thermogravimetric analysis showed excellent thermal stability, with char yields increasing from 38.2 % for neat TLCP to 48.8 % for TLCP/HGM10. Rheological testing revealed enhanced melt viscosity and viscoelastic moduli, and dynamic mechanical analysis indicated restricted chain mobility and increased glass transition temperatures. Importantly, the dielectric constant (D_k ∼2.43) and loss (D_f ∼0.0284) at 2 MHz decreased by approximately 20 % and 59 %, respectively, for TLCP/HGM10 compared to neat TLCP, and these experimental values correlated well with theoretical predictions based on the Maxwell-Garnett model. Water contact angle tests further showed improved surface hydrophobicity, increasing from 77.4° to 88.8° with HGM addition. These results collectively demonstrate that the incorporation of HGM simultaneously enhances the thermal, dielectric, and moisture-resistance characteristics of TLCP composites, making them promising candidates for high-frequency and moisture-resilient electronic applications.