Ammonium Polyphosphate with High Specific Surface Area by Assembling Zeolite Imidazole Framework in EVA Resin: Significant Mechanical Properties, Migration Resistance, and Flame Retardancy

Abstract

A zeolite imidazole framework (ZIF-67) was assembled onto the surface of ammonium polyphosphate (APP) for preparing a series multifunctional flame-retardant APP-ZIFs. The assembly mechanism, chemical structure, chemical compositions, morphology, and specific surface area of APP-ZIFs were characterized. The typical APPZ1 and APPZ4 were selected as intumescent flame retardants with dipentaerythritol (DPER) because of their superior unit catalytic efficiency of cobalt by thermogravimetric analysis. APPZ1 and APPZ4 possessed 6.8 and 92.1 times the specific surface area of untreated APP, which could significantly enhance the interfacial interaction, mechanical properties, and migration resistance when using in ethylene-vinyl acetate (EVA). With 25% loading, 25% APPZ4/DPER achieved a limiting oxygen index value of 29.4% and a UL 94 V-0 rating, whereas 25% APP/DPER achieved a limiting oxygen index value of only 26.2% and a V-2 rating, respectively. The peak of the heat release rate, smoke production rate, and CO production rate respectively decreased by 34.7%, 39.0%, and 40.1%, while the char residue increased by 91.7%. These significant improvements were attributed to the catalytic graphitization by nano cobalt phosphate and the formation of a more protective char barrier comprised of graphite-like carbon.

A strategy to construct multifunctional ammonium polyphosphate for epoxy resin with simultaneously high fire safety and mechanical properties

“…ZIF-67, the coordination polymer of 2-methylimidazole and cobalt, as one of the widely used MOFs was also used in flame-retarding polymers. Hao's group [31] had directly chemically modified APP by ZIF-67 particles for flame retarding ethylene-vinyl acetate, and the results displayed synergistic effect between APP and ZIF-67. However, only a few of ZIF-67 particles were deposited on the surface of APP and the dispersion of ZIF-67 was uneven due to the weak reaction ability between APP and ZIF-67 particles.…”

Effect of polyethylene terephthalate fiber reinforced with non‐hydrophilic nano‐silica on the mechanical, thermic, and chemical shielding characteristics of saturated polyurethane composite

“…The aromatic ( C C ) transmittance was observed at 1591 cm À1 , and aliphatic chain ( CH 2 C O) interactions of substrate were recorded at 1271 and 1081 cm À1 . In polyphosphate linkages, 78,79 the phosphate ( P O P ) stretching resonation occurs at 1109-855 cm À1 , as well as P O intensity was observed at 1356-1101 cm À1 . The CH twisting absorption spectrum was discovered at 1133 cm À1 .…”

Composites Filled with Metal Organic Frameworks and Their Derivatives: Recent Developments in Flame Retardants

“…However, the improved effect is different, which may be caused by the different types of substrates and MOFs. In addition to physical mixing, Wang et al [ 56 ] assembled ZIF-67 onto the APP surface, which opened new avenues for MOFs while obtaining excellent flame-retardant properties. The synthesized APPZ4 was added to Ethylene-vinyl acetate (EVA) as a flame-retardant composite, and with the increase of temperature, APPZ4 could be converted to cobalt phosphate nanocatalyst and formed di-micro nano-films and aggregated nano-skeletons.…”