The effect of defect-rich molybdenum disulfide nanosheets with phosphorus, nitrogen and silicon elements on mechanical, thermal, and fire behaviors of unsaturated polyester composites

Abstract

The article demonstrates the method of engineering defects into molybdenum disulfide surface to facilitate dithioglycol conjugation. The molybdenum disulfide (MoS2) nanosheets containing phosphorus, nitrogen and silicon elements were successfully synthesized by a “thiol-ene” click reaction between defect-rich MoS2 nanosheets with sulfydryl groups and ene-terminated hyperbranched polyphosphate acrylate (HPA) and characterized by FTIR and XPS to confirm covalent functionalization through C–S bond. The influence of MoS2-HPA on combustion behavior of unsaturated polyester resin (UPR) composites was investigated by cone calorimeter, demonstrating the obvious reduction of 43.2% and 39.6% in Peak Heat Release Rate and Total Heat Release. TG-IR-MS coupling technique was utilized to reveal thermal degradation and identify toxic volatiles such as CO, benzene, methylbenzene. Based on gaseous and condensed phase, we reasonably proposed the flame-retardant mechanism of MoS2-HPA/UPR composites. Moreover, mechanical properties and thermal stability of UPR matrix have significantly improved, due to the incorporation of MoS2-HPA hybrids. It is anticipated to exploit covalent functionalization of MoS2 nanosheets and MoS2-based composites with high performance.