Hydrophilic and hydrophobic silica‐based nanocomposites of chemically recyclable thermoset

• Published in: Polymer international 2022-07, Vol.71 (7), p.884-896
• Main Authors: Souza, Eduarda C, Bello, Roger H, Coelho, Luiz AF
• Format: Article
• Language: English
• Subjects: BAPP; Dielectric constant; Electrical conductivity; Electrical properties; Electrical resistivity; Glass transition temperature; hydrophilic silica; Hydrophilicity; hydrophobic silica; Hydrophobicity; Mechanical properties; Nanocomposites; Nanohardness; Nanoparticles; NMR; Nuclear magnetic resonance; Permittivity; PHT; Polymers; Recycling; Silica; Silicon dioxide; Thermodynamic properties; Triazine
• ISSN: 0959-8103; 1097-0126
• DOI: 10.1002/pi.6359

In this study we evaluated the effect of the addition of hydrophilic and hydrophobic silica nanoparticles on the electrical properties of polyhexahydro‐s‐triazine (PHT), a new chemically recyclable thermoset produced from 2,2‐bis[4‐(4‐aminophenoxy)phenyl]propane and paraformaldehyde. Chemical recycling as well as thermal and mechanical properties were also investigated. Regarding the electrical properties, electrical conductivity near 10−8 S m−1 at 100 Hz and dielectric constant close to 4.00 at 1 kHz were observed for neat PHT polymer. Better results for electrical properties were observed with the addition of hydrophobic silica nanoparticles. After the addition of the highest concentration (4.5 wt%) the dielectric constant increased about 8% at 1 kHz. Concerning the thermal properties, PHT polymer exhibited a glass transition temperature (Tg) of 185 °C. The addition of hydrophilic or hydrophobic nanoparticles into the neat matrix did not lead to significant variations of thermal properties, but Tg values were decreased compared to the neat resin. Additionally, for mechanical properties, values of reduced modulus (4.58 GPa) and nanohardness (0.38 GPa) were observed. Besides, for all nanocomposites, there was an increase in the reduced modulus for all samples studied. Finally, the chemical recycling of both neat polymer and all nanocomposites after acid treatment was successfully characterized via NMR analysis. © 2021 Society of Industrial Chemistry. The change of dielectric constant of SiO2 nanoparticles modified the dielectric properties of polyhexahydro‐s‐triazine (PHT) nanocomposites. Better results for nanocomposites with hydrophobic SiO2 nanoparticles were observed due to strong interactions with the matrix and homogeneous dispersion.