Vertically Aligned Nickel 2‑Methylimidazole Metal–Organic Framework Fabricated from Graphene Oxides for Enhancing Fire Safety of Polystyrene

In this work, flowerlike nickel 2-methylimidazole metal–organic framework (Ni-MOF) was prepared by a solvothermal method. Vertically aligned Ni-MOF was fabricated from graphene oxide (GO) solution in the same way. The combination of GO and Ni-MOF (GOF) obviously suppressed the agglomeration of Ni-MOF sheets. As-synthesized, GOF has bigger pore volume and specific surface area, which are beneficial for volatile degradation products adsorption. It is noteworthy that the addition of GOF obviously reduced the fire hazard of polystyrene (PS). More than 33% decrease in the peak heat release rate for the PS/GOF composite was obtained when the content of the additives is only 1.0 wt %. Meanwhile, the reductions of total smoke and CO production were also prominent during the combustion of PS/GOF, respectively 21% and 52.3% decreases compared with that of pure PS. The synergism effects between layered GO and porous Ni-MOF realized the improved performances of PS. Thus, this work paves a feasible pathway to design efficient flame retardants for enhancing fire safety of polymers

Synthesis of Phosphorus–Sulfur-Containing Polyols for Intrinsic Flame Retardant Flexible Polyurethane Foams with Enhanced Mechanical Properties

The development and preparation of intrinsic flexible polyurethane foam (FPUF) with low-load flame retardancy and high mechanical properties are challenging. Herein, a reactive flame retardant, poly(ethylene methylphosphonothioate) (PEMPT), was synthesized by the polycondensation of methylphosphonothioic dichloride and ethylene glycol. Subsequently, PEMPT was chemically bound to the FPUF chain. When the PEMPT content was 2.5 wt % polyols, the FPUFs exhibited self-extinguishing properties in less than 3 s after removing the igniter and passed the TB 117-2000 vertical burning test. Furthermore, the flame retardant FPUF with only 10 wt % PEMPT loading (FPUF10) showed an oxygen index value of 23.5%. Also, its peak heat release and total heat release rates were reduced by 25.8 and 24.0%, respectively. Concurrently, the incorporation of PEMPT improved the compressive and reversible properties of the foams. These results indicate that PEMPT is a promising flame retardant to endow FPUF with excellent flame retardancy and mechanical properties

Facile Synthesis of a Highly Efficient, Halogen-Free, and Intumescent Flame Retardant for Epoxy Resins: Thermal Properties, Combustion Behaviors, and Flame-Retardant Mechanisms

A novel branched poly­(phosphonamidate-phosphonate) (BPPAPO) oligomer was synthesized from the polycondensation of phenylphosphonic dichloride and tri­hydroxy­methyl­phosphine oxide followed by end-capping with aniline in a one-pot synthesis. BPPAPO exhibited excellent flame-retardant efficiency in epoxy resins (EP). With only 5.0 wt % loading, the EP composite reached UL-94 V-0 rating with a limiting oxygen index (LOI) value of 35.5%. BPPAPO catalyzed the early degradation of EP and promoted the formation of more char residue. Glass transition temperatures were partially lowered. When 7.5 wt % BPPAPO was incorporated, the peak heat release rate and total heat release were decreased by 66.2% and 37.3%, respectively, with a delayed ignition and the formation of a highly intumescent char residue. Combination of gas-phase and condensed-phase flame-retardant mechanisms was verified

Construction of Bimetallic ZIF-Derived Co–Ni LDHs on the Surfaces of GO or CNTs with a Recyclable Method: Toward Reduced Toxicity of Gaseous Thermal Decomposition Products of Unsaturated Polyester Resin

This work proposed an idea of recycling in preparing Co–Ni layered double hydroxide (LDH)-derived flame retardants. A novel and feasible method was developed to synthesize CO–Ni LDH-decorated graphene oxide (GO) and carbon nanotubes (CNTs), by sacrificing bimetal zeolitic imidazolate frameworks (ZIFs). Organic ligands that departed from ZIFs were recyclable and can be reused to synthesize ZIFs. ZIFs, as transitional objects, in situ synthesized on the surfaces of GO or CNTs directly suppressed the re-stacking of the carbides and facilitated the preparation of GO@LDHs and CNTs@LDHs. As-prepared hybrids catalytically reduced toxic CO yield during the thermal decomposition of unsaturated polyester resin (UPR). What is more, the release behaviors of aromatic compounds were also suppressed during the pyrolysis process of UPR composites. The addition of GO@LDHs and CNTs@LDHs obviously inhibited the heat release and smoke emission behaviors of the UPR matrix during combustion. Mechanical properties of the UPR matrix also improved by inclusion of the carbides derivatives. This work paved a feasible method to prepare well-dispersed carbides@Co–Ni LDH nanocomposites with a more environmentally friendly method

Innovative Design and Preparation of Hierarchical BP–OH@HAP Structure: Study on Flame Retardancy and Mechanical Characteristics of UPR Nanocomposites

The flammability and brittleness of unsaturated polyester resin (UPR) were two serious problems that limited its application in high-precision fields. Here, the rod-shaped hydroxyapatite (HAP) was anchored on the surface of hydroxylated black phosphorus nanosheets (BP–OH) through a hydrothermal reaction to obtain a highly stable black phosphorus-based nano flame retardant (BP–OH@HAP). Owing to the exposure of many hydroxyl groups, BP–OH@HAP was well dispersed in the UPR matrix, and UPR nanocomposites with 0.5 wt % BP–OH@HAP realized a 71% increase in impact strength. The presence of BP–OH@HAP also greatly inhibited the combustion of UPR nanocomposites. In detail, the UPR composites with 2 wt % BP–OH@HAP achieved a 47.0% decrease in peak heat release rate (PHRR) along with 23.1% reductions in total heat release (THR), revealing the excellent ability of BP–OH@HAP to inhibit polymer combustion. In addition, UPR/BP–OH@HAP 2.0 achieved a 46 s increase in the time to PHRR (tPHRR) and a 62% reduction in the fire growth index (FGI), indicating that the fire spread of UPR/BP–OH@HAP 2.0 was significantly suppressed. Therefore, this work obtained the UPR/BP–OH@HAP nanocomposite with high fire safety through the innovation of inorganic nanotechnology, which provided new research ideas for improving the toughness and flame-retardant properties of UPR-based nanocomposites

Boron-Based Polyphosphazene-Functionalized Mxene Nanosheets for Polypropylene Composites with Improved Mechanical Properties and Flame Retardancy Applications

Developing high-performance resins with exceptional thermal oxidation stability, flame retardancy, smoke release suppression, and mechanical properties is an important industrial challenge. However, current flame-retardant design strategies often compromise other composite material properties. Especially when using polyolefin, unsaturated polyester, and other noncharred materials, it is usually necessary to add large amounts of flame-retardant fillers. In this study, a nanosynergist (Ti3C2Tx@PPD) for functionalizing Ti3C2Tx nanosheets with boron-based polyphosphazene was designed and adopted for a piperazine pyrophosphate/polypropylene (PAPP/PP) system as an application example. By controlling the chemical environment of cyclotriphosphazene, the condensed phase characteristics of polyphosphazene were preserved, but also an atypical vapor phase flame-retardant mechanism was activated. The combination of P/N/B elements and Ti3C2Tx exhibited excellent catalytic char-forming performance compared to others in the literature. Only 2% of incorporated Ti3C2Tx@PPD reduced the total heat released from the composite by 66.3%, the total smoke released by 71.8%, and the fire growth index by 49.4%. The incorporation of Ti3C2Tx@PPD inhibited deterioration of the mechanical properties of the composite. In addition, the pyrolysis path of Ti3C2Tx was revealed under a special environment. This study lays the foundation for the functional design of Ti3C2Tx nanomaterials that can be used in various applications that require high-performance resins

Effect of Functionalized Graphene Oxide with Organophosphorus Oligomer on the Thermal and Mechanical Properties and Fire Safety of Polystyrene

A novel organophosphorus oligomer was synthesized to functionalize graphene oxide. Subsequently, the functionalized graphene oxide (FGO) was incorporated into polystyrene (PS) to enhance the integration properties of the matrix. The effect of FGO on the thermal properties, fire safety, and mechanical properties of PS nanocomposites was investigated. The results showed that the introduction of FGO significantly increased the maximum decomposition temperature (<i>T</i>_max) (25 °C increase), reduced the total heat release (20.8% reduction), and peak heat release rate (38.2% reduction) of PS. In addition, the thermogravimetric analysis/infrared spectrometry analysis results indicated that the amount of organic volatiles and toxic carbon monoxide of PS was remarkably reduced. The physical barrier effect of FGO and the synergistic effects between the organophosphorus oligomer and FGO were the main causations for these properties improvements. Homogeneous dispersion of FGO into the polymer matrix improved the mechanical properties of FGO/PS nanocomposites, as demonstrated by tensile tests results