Syntheses of Metallic Cyclodextrins and Their Use as Synergists in a Poly(Vinyl Alcohol)/Intumescent Flame Retardant System

Maleated cyclodexdrin (MC) and its metal salts (Metal MC) were synthesized and added into poly(vinyl alcohol)–intumescent flame retardant (PVA–IFR) composites as synergists. Results of thermogravimetric analysis (TGA) and differential thermal analysis (DTG) showed that the thermal stability of the composites was greatly improved. The initial decomposition temperature of PVA–IFR composites was increased by 16 °C with the addition of metal MC. UL-94 vertical burning test indicated that the metallic cyclodextrin (metal MC) can catalyze the PVA–IFR system to form strong intumescent char and reach V0 rating at the proper proportion. The morphology and compositions of the char residue of PVA–IFR composites were characterized by scanning electron microscopy (SEM), Raman spectra, FTIR, and X-ray photoelectron spectroscopy (XPS). The results demonstrated that the metal ions could boost the formation of organized and compact char layer in the condensed phase during the degradation of PVA.