An Environmentally Friendly Nanohybrid Flame Retardant with Outstanding Flame-Retardant Efficiency for Polypropylene

A facile method to fabricate nanohybrid flame retardants has become increasingly important to enhance the flame-retardant efficiency and adhesion in interfaces between polymer matrix and the flame retardants. Polypropylene (PP) is a vital thermoplastic polymer family member; however, its flame retardancy remains a big challenge because of its other seriously deteriorated properties. In this present work, an environmentally friendly nanohybrid expandable graphite (nHEG) has been successfully designed and synthesized in situ via a one-pot strategy of the first flame-retardant PP by introducing nano-SiO2 particles into the surface and interlamination of graphite lamellas. The performance of PP composites is modulated through regulating nHEG content and nano-SiO2 distribution as the catalytic charring agent, and expandable graphite (EG) is used to be the flame-retardant unit in the synthesis process. PP composites obtain the UL-94 V0 rating by the UL-94 test. The enhanced flame retardancy can be attributable to the formation of continuous and tight char residues. The sample with the highest flame retardancy maintains a tensile strength of 32.7 MPa and 9.3 kJ/m2 of notched impact strength, respectively. Therefore, the nanohybrid flame-retardant PP composites show extensive applications.