A novel charring agent containing caged bicyclic phosphate and its application in intumescent flame retardant polypropylene systems

The Flame-Retardant Mechanisms and Preparation of Polymer Composites and Their Potential Application in Construction Engineering

Against the background of people's increasing awareness of personal safety and property safety, the flame retardancy (FR) of materials has increasingly become the focus of attention in the field of construction engineering. A variety of materials have been developed in research and production in this field. Polymers have many advantages, such as their light weight, low water absorption, high flexibility, good chemical corrosion resistance, high specific strength, high specific modulus and low thermal conductivity, and are often applied to the field of construction engineering. However, the FR of unmodified polymer is not ideal, and new methods to make it more flame retardant are needed to enhance the FR. This article primarily introduces the flame-retardant mechanism of fire retardancy. It summarizes the preparation of polymer flame-retardant materials by adding different flame-retardant agents, and the application and research progress related to polymer flame-retardant materials in construction engineering.

Preparation of Mn2+ Doped Piperazine Phosphate as a Char-Forming Agent for Improving the Fire Safety of Polypropylene/Ammonium Polyphosphate Composites

A piperazine phosphate doped with Mn2+ (HP-Mn), as a new char-forming agent for intumescent flame retardant systems (IFR), was designed and synthesized using 1-hydroxy ethylidene-1,1-diphosphonic acid, piperazine, and manganese acetate tetrahydrate as raw materials. The effect of HP-Mn and ammonium polyphosphate (APP) on the fire safety and thermal stability of polypropylene (PP) was investigated. The results showed that the combined incorporation of 25 wt.% APP/HP-Mn at a ratio of 1:1 endowed the flame retardant PP (PP6) composite with the limiting oxygen index (LOI) of 30.7% and UL-94 V-0 rating. In comparison with the pure PP, the peak heat release rate (PHRR), the total heat release (THR), and the smoke production rate (PSPR) of the PP6 were reduced by 74%, 30%, and 70%, respectively. SEM and Raman analysis of the char residues demonstrated that the Mn2+ displayed a catalytic cross-linking charring ability to form a continuous and compact carbon layer with a high degree of graphitization, which can effectively improve the flame retardancy of PP/APP composites. A possible flame-retardant mechanism was proposed to reveal the synergistic effect between APP and HP-Mn.

Chitosan-based flame retardant coatings for polyamide 66 textiles: One-pot deposition versus layer-by-layer assembly

Chitosan (CS) and phosphorylated chitosan (PCS) were deposited onto the polyamide 66 (PA66) fabric surfaces along with poly-acrylate sodium (PAS) via 'one pot' and layer by layer (LbL) assembly methods in preparing flame retardant coatings. Subsequently, to stabilize the deposited coatings, some of the fabric samples were treated under the UV-irradiation and additionally, a thermal treatment was also carried out for the remaining fabric samples. The LbL assembled fabrics showed a better homogeneity in the coating structure over the one pot deposited fabrics as appeared in scanning electron microscopy (SEM). Nonetheless, the LbL treated fabric sample (i.e., PA66-10BL-UV) with a higher weight gain% exhibited a greater improvement in limiting oxygen index (LOI) (i.e., 23%), and a reduced peak heat release rate (pHRR) (i.e., 25%). Yet more, only the LbL assembled and thermally cross-linked fabric sample could able to retain the flame retardant behavior in the vertical burning test even after 5 washing cycles.

Synergistic effects of intumescent flame retardant and nano-CaCO3 on foamability and flame-retardant property of polypropylene composites foams

Synergistic effects of intumescent flame retardant and nano-CaCO3 on foamability and flame retardant property of polypropylene composites and their foams were carefully investigated. The differential scanning calorimetry results showed that the intumescent flame retardant played a plasticizing effect on the polypropylene/intumescent flame-retardant composites and accelerated the crystallization rate. The rheological properties and supercritical CO2-assisted molding foaming behaviors of the polypropylene/intumescent flame retardant/nano-CaCO3 composites showed that the nano-CaCO3 could enhance their foamability. Scanning electron microscopy pictures and mechanical properties of the polypropylene/intumescent flame-retardant composites foams indicated that the agglomeration of intumescent flame retardant would reduce the cell uniformity and even cause the cell collapse. Furthermore, the stress concentration, caused by the agglomeration, could reduce the mechanical properties of the PP composites foams. The synergistic effect of the nano-CaCO3 could improve the cell uniformity and reduce the stress concentration so that the mechanical properties of the polypropylene/intumescent flame retardant /nano-CaCO3 composites foams were improved. Moreover, the polypropylene/intumescent flame retardant/nano-CaCO3 composites foams had the higher limit oxygen index values than the polypropylene/intumescent flame-retardant foams. TGA results also showed that the nano-CaCO3 could improve the thermal stability of the polypropylene composites foams by forming compact carbon layer. The experimental results indicated that the foamability of the polypropylene composites and the flame-retardant property of their foams could be improved by the synergistic effects of intumescent flame retardant and nano-CaCO3.

Functionalized allylamine polyphosphate as a novel multifunctional highly efficient fire retardant for polypropylene

In this study, an efficient novel allylamine polyphosphate (AAPP) as a flame retardant (FR) crosslinker is used to improve the thermal stability of flame retarded polypropylene (PP) composites under electron beam treatment.

Fire retardant and charring effect of cyclic phenolphthalein (phenylene phosphonate) oligomer on polybutylene terephthalate

A novel solid flame retardant cyclic phenolphthalein (phenylene phosphonate) (CPPA) oligomer was synthesized in high yields through the reaction of phenylphosphonic dichloride with phenolphthalein under pseudo-high dilution conditions via polycondensation.

Synthesis of a highly efficient phosphorus-containing flame retardant utilizing plant-derived diphenolic acids and its application in polylactic acid

A highly efficient phosphorous-containing flame retardant for PLA is synthesized from plant-derived diphenolic acids.

Novel PEPA-functionalized graphene oxide for fire safety enhancement of polypropylene

Polypropylene (PP) is a general-purpose plastic, but some applications are constrained by its high flammability. Thus, flame retardant PP is urgently demanded. In this article, intumescent flame retardant PP (IFRPP) composites with enhanced fire safety were prepared using 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane (PEPA) functionalized graphene oxide (PGO) as synergist. The PGO was prepared through a mild chemical reaction by the covalent attachment of a caged-structure organic compound, PEPA, onto GO nanosheets using toluene diisocynate (TDI) as the intermediary agent. The novel PEPA-functionalized graphene oxide not only improves the heat resistance of GO but also converts GO and PEPA from hydrophobic to hydrophilic materials, which leads to even distribution in PP. In our case, 7 wt% addition of PGO as one of the fillers for IFRPP composites significantly reduces its inflammability and fire hazards when compared with PEPA, by the improvement of first release rate peak (PHRR), total heat release, first smoke release rate peak (PSRR) and total smoke release, suggesting its great potential as the IFR synergist in industry. The reason is mainly attributed to the barrier effect of the unburned graphene sheets, which protects by the decomposition products of PEPA and TDI, promotes the formation of graphitized carbon and inhibits the heat and gas release.

Effect of chlorinated phosphate ester based on castor oil on thermal degradation of poly (vinyl chloride) blends and its flame retardant mechanism as secondary plasticizer

The synthesis and application of a novel flame retardant chlorinated phosohate ester based on castor oil.

Flame-Retardant and Thermal Degradation Mechanism of Caged Phosphate Charring Agent with Melamine Pyrophosphate for Polypropylene

An efficient caged phosphate charring agent named PEPA was synthesized and combined with melamine pyrophosphate (MPP) to flame-retard polypropylene (PP). The effects of MPP/PEPA on the flame retardancy and thermal degradation of PP were investigated by limiting oxygen index (LOI), vertical burning test (UL-94), cone calorimetric test (CCT), and thermogravimetric analysis (TGA). It was found that PEPA showed an outstanding synergistic effect with MPP in flame retardant PP. When the content of PEPA was 13.3 wt% and MPP was 6.7 wt%, the LOI value of the flame retardant PP was 33.0% and the UL-94 test was classed as a V-0 rating. Meanwhile, the peak heat release rate (PHRR), average heat release rate (AV-HRR), and average mass loss rate (AV-MLR) of the mixture were significantly reduced. The flame-retardant and thermal degradation mechanism of MPP/PEPA was investigated by TGA, Fourier transform infrared spectroscopy (FTIR), TG-FTIR, and scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDXS). It revealed that MPP/PEPA could generate the triazine oligomer and phosphorus-containing compound radicals which changed the thermal degradation behavior of PP. Meanwhile, a compact and thermostable intumescent char was formed and covered on the matrix surface to prevent PP from degrading and burning.

Synthesis and characterization of a novel organophosphorus oligomer and its application in improving flame retardancy of epoxy resin

A novel organophosphorus oligomer (PCPBO) was synthesized and the incorporation of PCPBO into epoxy resin (EP) significantly improved their flame retardancy and thermal stability.

Preparation, thermal stability and flame-retardant properties of halogen-free polypropylene composites

A flame retardant containing phosphorus and nitrogen was prepared. This halogen-free flame retardant was blended with polypropylene (PP) by hot melting to improve the flame-retardant capability and thermal stability of the composites. Fourier transform infrared spectroscopy, energy dispersive X-ray measurements, thermogravimetric analysis, limiting oxygen index (LOI) measurements, and UL-94 measurements were applied to characterize the structure and thermal and flame-retardant properties of the composites. When the flame-retardant concentration was 40 wt%, the LOI value of the composite was 40, passing the V-0 rating of the UL-94 test. The LOI and UL-94 data showed the composites have an excellent flame-retardant property. For a kinetic study of thermal degradation, Ozawa’s method was applied to calculate the activation energies of pure PP and the composites. Analytical results indicate that the composites had higher values, meaning they have better thermal stability.