Abstract:

Flame retardant polyvinyl alcohol(PVA) grafted with acrylonitrile(AN)(FR-PVA-g-AN) was prepared via grafting copolymerization of AN onto PVA (PVA-g-AN) using K₂S₂O₈-NaHSO₃ as initiator followed by the chemical modification reaction with phosphoric acid and urea. The structure of FR-PVA-g-AN was characterized by Fourier transform infared spectroscope(FTIR), X-ray photoelectron spectroscopy(XPS) and X-ray diffraction(XRD), and the thermal property was studied by thermogravimetric analysis(TGA). The results show that the grafting percent reaches 190% under the condition of the mass fraction of initiator being 1% of the total reactant, the molar ratio of K₂S₂O₈ to NaHSO₃ being 5:1, the mass ratio of AN to PVA being 3.5:1, and reaction temperature being 70 ℃, and the reaction time of 4 h. The FR-PVA-g-AN with excellent fire retardancy can be obtained with the mass ratio of phosphoric acid to urea being 5:1 and reaction temperature of 85 ℃ for 4 h. There is about 63% char residue left after FR-PVA-g-AN was treated at 700 ℃ with muffle. The TGA curves indicate that the thermo-oxidative degradation of FR-PVA-g-AN is slower than that of PVA, and the char residue of FR-PVA-g-AN increases to 54.3% at 800 ℃, while the char residue of PVA is only 3.12%, which fully proves that FR-PVA-g-AN has better thermal stability and char forming capability.

Key words: Polyvinyl alcohol, Acrylonitrile, Graft, Flame retardant, Thermal property