Novel macromolecular flame retardant derived from sulfonated naphthalene monomer for simultaneous fire safety and high performance of polycarbonate

Macromolecular flame retardants possess unique advantages in endowing compatible polymers with simultaneous high performance and functionalization because they may greatly reduce incompatibility-caused damage to overall properties of polymer substrates. To address the contraction between fire safety and high performance of polycarbonate (PC), a novel sulfonated naphthalene monomer-containing copolymer polycarbonate, that is named NSD, was synthesized by melt copolymerization and used as flame retardant of PC. Thermal analysis confirmed that the initial decomposition temperature of NSD was 387 °C under nitrogen atmosphere and met the processing of PC. Burning tests results indicated that incorporation of 2 wt.% NSD enabled PC to achieve UL-94 V-0 rating and the LOI value increased to 28.0%; the peak heat release (PHRR) and smoke release of the PC/NSD showed a decreasing trend. Moreover, flame-retarded PC with 2 wt.% NSD maintained comparable tensile strength and elongation at break to neat PC. The flame-retardant and anti-dripping mechanisms were also investigated. Sulfur-containing substances and sulfate in the condensed phase concentrated in the residue and thus strengthened the char layer, and the sulfur dioxide in the gas phase diluted the combustible gas, thus leading to excellent fire retardance of PC/NSDs. Reasons for excellent tensile property of PC/NSDs were also studied in detail. This work demonstrates that macromolecular flame retardants NSD may enable PC to achieve simultaneous high performance and flame retardation.