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The polymethacrylimide/silicate (PMI/silicate) composites were successfully prepared from the monomers of acrylonitrile (AN) and methacrylic acid (MAA) via the monomer in situ intercalation polymerization and free foaming. The formation of imide groups was monitored by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results of FTIR and XPS indicated that the imide groups were gradually formed and cyano groups were dwindling but still existed during foaming and thermal treatment. The thermogravimetric analysis results revealed that the thermal stability of the PMI/silicate composites was improved, the rate of thermal degradation was reduced, and the residue was increased because of the addition of silicates. The results of dynamic mechanical analysis revealed that the rigidity and the glass transition temperature of the composites were improved.The limit oxygen index (LOI) and cone calorimeter (CONE) test showed that the fire-retardant properties were improved because of the barrier effect of silicates.The cell morphologies of the PMI/silicate composites were characterized by scanning electron microscopy (SEM), and the results showed that the silicate particles were distributed on the cell walls, but the cells slightly cracked. The mechanical properties were measured by tensile, flexural, and compressive strength. The mechanical strength, especially flexural strength, was significantly improved. The flexural strength of PMI/MMT, PMI/kaolin, and PMI/talc containing 8 wt% silicates was improved to 172%, 240%, and 233%.

In this article, a monomolecular intumescent flame retardant 1,4-bis (diethyl methylenephosphonate) piperazine defined as BDEMPP was introduced into epoxy resins (EP) thermosets. The fire safety, combustion behavior, thermal properties, mechanical performance, transparency, and flame-retardant mechanism of EP/BDEMPP thermoset were investigated systematically. The EP thermosets passed UL-94 V-1 level with the limit oxygen index value of 28.3%, and the release of heat and smoke were inhibited when 9 wt% BDEMPP was added. Moreover, the tensile strength and modulus, flexural strength and modulus, charpy impact strength of EP/9 wt% BDEMPP were increased by 15.0%, 22.4%, 15.4%, 15.6%, and 22.6% in comparison of pure EP thermosets, respectively. EP/BDEMPP composites possessed good transparency and the transmittance of EP/9 wt% BDEMPP was 87.1% at 600 nm UV irradiation. The investigation of flame retardant mechanisms demonstrated BDEMPP exerted flame retardant effect both in gaseous and condensed phase. BDEMPP exhibited good compatibility, flame retardancy, smoke suppression, and mechanical enhancement for EP thermosets.

A novel mono‐component flame‐retardant additive poly (dimethylol melamine piperazine pyrophosphate) defined as PDMPP was synthesized from formaldehyde, melamine, and piperazine pyrophosphate. Its chemical structure was well characterized by Fourier transform infrared spectroscopy, 13C and 31P solid‐state nuclear magnetic resonance, and elemental analysis tests. PDMPP was incorporated into polypropylene (PP) matrix, and the fire‐retardant performance, thermal properties, and water resistance of PP composites were investigated in detail. PP/23 wt% PDMPP composites before and after water resistance tests both achieved UL‐94V‐0 grade during vertical burning tests, and the limiting oxygen index was slightly declined from 26.7% to 26.3%. Small amount of PDMPP was extracted by hot water, and the weight loss percentage was 0.67% during water resistance tests. The piperazine and triazine rings in PDMPP contributed to a much better char‐forming capability, and then a greatly expanded and coherent char residue was generated during combustion and exhibited excellent isolation effect. The heat release rate, carbon monoxide production, and smoke production rate of the flame‐retarded PP composites before and after water resistance tests were effectively suppressed to a low level. Consequently, the introduction of PDMPP apparently improved the fire safety of PP composites as well as excellent water‐resistant performance.

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