Enhancing Char Formation and Flame Retardancy of Ethylene-Vinyl Acetate Copolymer (EVA)/Aluminum Hydroxide (ATH) Composites by Grafting Ladder Phenyl/Vinyl Polysilsesquioxane (PhVPOSS).

The ladder phenyl/vinyl polysilsesquioxane (PhVPOSS) was used to improve the flame-retardancy performances of ethylene-vinyl acetate copolymer (EVA)/aluminum hydroxide (ATH) composites due to the reactivity of its vinyl groups. FTIR, XPS, 1H NMR, and SEM-EDS data demonstrated the PhVPOSS grafting onto EVA molecular chains. The PhVPOSS improved the thermal stability of EVA/ATH composites, as shown by the thermogravimetric analysis (TGA). Furthermore, with the cone calorimeter (CONE) experiments, EVA/ATH/PhVPOSS showed better fire safety than the EVA/ATH composites, with the PHRR, PSPR, and PCOP reduced by 7.89%, 57.4%, and 90.9%, respectively. The mechanism investigations of flame retardancy revealed that the charring behaviors of the EVA/ATH/PhVPOSS composites were improved by the formation of Si-C bonds and Si-O bonds, and a more compact and denser char layer can contribute more to the barrier effect.

Micro-Nanometer Particle Composition and Functional Design of Surface Nano-Structured Ammonium Polyphosphate and Its Application in Intumescent Flame-Retardant Polypropylene.

A novel composite and functional micro-nanometer particle is designed by the hydrolysis of aluminium isopropoxide on the surface of ammonium polyphosphate (APP) to prepare surface nanostructured ammonium polyphosphate (NSAPP). NSAPP is characterised by XPS, XRF, SEM, water solubility tests, and TGA. Results indicate that nanosized aluminium hydroxide is deposited on the surface of NSAPP, which enhanced its water resistance and thermostability. Then, APP and NSAPP coupled with dipentaerythritol (DPER) is used for the flame retardant of polypropylene (PP). The limiting oxygen index (LOI) value of the PP/DPER/NSAPP composite is higher than that of PP/DPER/APP. Besides, the UL 94 vertical burning test of PP/DPER/NSAPP composites can reach the V-0 rating easily. According to the study of the combustion behaviour of FR-PP composites, NSAPP contributes to form a dense and multi-layered char in the combustion process. Thus, such an intumescent char with a ceramic-like, continuous, and dense structure over the PP matrix protects the underlying matrix and enhances the thermal stability of the condensed phase, thereby improving the flame retardant performance of FR-PP.