Surface functionalization of MoS2with POSS for enhancing thermal, flame-retardant and mechanical properties in PVA composites

Surface functionalization of molybdenum disulfide (MoS2) was prepared by a simple reflux reaction between DITG-MoS2 and octa-vinyl polyhedral oligomeric silsesquioxanes (OvlPOSS). The structure of OvlPOSS-MoS2 was confirmed by XRD, FTIR and TEM. The SEM and TEM results of fracture surface exhibited that OvlPOSS-MoS2 was dispersed well in the matrix due to the good interfacial interaction between the functionalized MoS2 and PVA. The thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) results indicated that the thermal decomposition temperature and the glass transition temperature (Tg) were improved. Compared with pure PVA, the maximum degradation temperature of the PVA/OvlPOSS-MoS2 nanocomposites was increased by 23 °C, and the Tg of the PVA/OvlPOSS-MoS2 was improved by 10.2 °C. Meanwhile, the peak of heat release rate (pHRR) and total heat release (THR) were decreased. The tensile stress was increased by 57% with addition of 2 wt% OvlPOSS-MoS2. Moreover, the addition of OvlPOSS-MoS2 significantly decreased the gaseous products, including hydrocarbons, carbonyl compounds and carbon monoxide, which was attributed to the synergistic effect of OvlPOSS and MoS2: the adsorption and barrier effect of MoS2 inhibited the heat and gas release and promoted the formation of graphitized carbons, while OvlPOSS improved the thermal oxidative resistance of the char layer.