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 degrees 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.