Synthesis of activated carbon and different types phosphomolybdate ionic liquid composites for flame retardancy of poly(vinyl chloride)

The flammability, poor mechanical properties, and high smoke production of poly(vinyl chloride) (PVC) have limited its practical applications in industry. In this work, activated carbon/phosphomolybdate 1-butyl-3-methylimidazolium (AC/PIL4) and activated carbon/phosphomolybdate 1-hexadecy-3-methylimidazolium (AC/PIL16) were prepared by direct precipitation and used to improve the flame retardancy and mechanical properties of PVC. Owing to their special structures and compositions, AC/PIL4 and AC/PIL16 triggered PVC crosslinking to form a dense char residue during thermal degradation, prevented smoke generation, and reduced heat transfer to protect the matrix. AC/PIL4-PVC exhibited the lowest peak heat release rate (179.0 kW m−2) and peak smoke production rate (0.091 m2 s−1), which are 45.7% and 75.2% lower, respectively, than those of pure PVC. Further, AC/PIL4-PVC and in particular AC/PIL16-PVC (which has long organic chains) can improve the mechanical properties of PVC. The impact strengths of AC/PIL4-PVC (10.76 kJ m−2) and AC/PIL16-PVC (12.25 kJ m−2) were 34.5% and 53.1% higher, respectively, than that of pure PVC (8.00 kJ m−2).