Yanlu Sun,Zhengqi Wang,Dequn Wu,Xueli Wang,Jianyong Yu,Ruchao Yuan,Faxue Li
The absence of inherently flame-retardant polyamide 6 (FR-PA6) with enhanced anti-dripping and melt spinnability has significantly limited its further application in textiles. In this work, a binary reactive flame retardant composed of commercial 9,10-dihydro-10-[2,3- di ( hydroxycarbonyl ) propyl ]-10-phosphaphenanthrene-10-oxide (DDP) and synthesized polydiphenylsiloxane (PDPS) was employed to fabricate FR-PA6 through a facile synthetic route. The prepared FR-PA6 containing 5 wt% DDP and 5 wt% PDPS (FR-PA6-5-5) exhibited a UL94 V-0 rating with no melt-droplets during combustion, a 31.0% reduction in heat release rate and a 18.8% decrease in total heat release compared to pure PA6 in cone calorimetric tests. The improved fire safety of FR-PA6-5-5 was contributed to the gas-phase quenching and dilution effect and the condensed-phase barrier effect, which was enhanced by the synergistic charring effect achieved through the formation of P(= O )-O-Si. Additionally, FR-PA6-5-5 exhibited excellent melt spinnability as demonstrated by the successful preparation of filaments with a tensile strength of approximately 2.27 cN/dtex.
Li Kaiqian,Zhang Xupeng,Li Xianghong,Chang Qiaowen,Deng Shuduan,Zhu Gang
Introducing novel bimetallic metal–organic frameworks (Cu/Zr-MOF) into wood cellulose scaffolds via an in situ growth strategy represents an effective approach to enhance the fire retardancy of wooden products. This work evaluates the effects of Cu/Zr-MOF loading content embedded in wood composite on the MOF morphology and flame retardancy of natural wood (NW). We discovered that MOF loading has a significant impact on the morphology of Cu/Zr-MOF. Specifically, with an increase in the amount of MOF precursors, the morphological transformation is from spherical to regular octahedra. Furthermore, the incorporation of high MOF loading remarkably enhanced the thermal stability at the early stage and exhibited significantly improved residual content. With 24 mass% loading of Cu/Zr bimetallic MOF, the highly flame-retardant wood composite (Cu-U-W-3) was obtained. Compared to pure NW, the peak heat release rate (pHRR) and total heat release (THR) were reduced to 25.25 W g −1 and 5.0 kJ g −1 , respectively. The limiting oxygen index (LOI) of the treated sample reached 24.81%, showing outstanding self-extinguishing ability. According to the char residue analysis, it was found that Cu-Zr bimetallic MOF anchored on the cell wall exhibited catalytic carbon-forming effect, thereby facilitating the generation of high-quality residual char. The enhanced fire safety of natural wood can be attributed to the oxygen barrier and the reduced heat transfer characteristics of the dense carbon layer. This work presents a novel methodology for the fabrication of bimetallic MOF hybrid flame retardants, with the objective of enhancing the flame retardancy of wooden products.
Bo Xu,Simiao Wei,Yanting Liu,Siheng Zhao,Lijun Qian
An organo-cobalt coordination complex (Co-H4APD), based on phosphonitrile-azacycles, was prepared by hydrothermal method . The flame retardancy, smoke suppression and thermal stability of epoxy (EP) composites were investigate by means of limited oxygen index (LOI), cone calorimeter test (CONE) and thermogravimetric analysis (TGA). The flame retardant modes of action of Co-H4APD in EP were confirmed by experiments, such as thermogravimetry-Fourier transform infrared spectroscopy-gas chromatograph/mass spectrometer (TG-FTIR-GC/MS), exploring condense and gas-phase products after composites pyrolysis or combustion. Results revealed that the introduction of 6 wt.% Co-H4APD increased LOI value to 29.8% and effectively suppressed heat/smoke release of EP composites. The synergistic charring effect of Co-H4APD improved the thermal stability and char-forming ability of composites. The char strength may be well-correlated with gas release for EP/Co-H4APD, conducive to form dense and regularly expanded char layer, with more phosphorus-rich graphitic structures and cross-linking structures catalyzed by cobalt ions . This high-quality char layer was regarded as the most critical side in improving the flame retardant and smoke suppression performance of EP composites. The gas-phase function of Co-H4APD should not be overlooked due to releasing phosphorous-based radicals during pyrolysis, exhibiting flame inhibition effect in gas phase. More efficient interactions between phosphazene and cobalt within one molecule unit of Co-H4APD contributed to its more obvious reduction of the combustion and smoke production than those of the physical mixing system of CoO + H4APD.
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