An urethane-based phosphonate ester for improving flame retardancy and smoke suppression of thermoplastic polyurethane

Significantly suppressing CO release achieved by the catalysis effect of nanostructured rare earth/manganese oxides: Application in flame retardant thermoplastic polyurethane

There is significant smoke and toxic volatiles generated from the combustion of thermoplastic polyurethane (TPU), which has compromised its application and posed a significant threat to human life. Here, the hydrothermal-citrate complexation method synthesised the rare earth Mn-based composite catalyst and blended with TPU to mitigate smoke release and toxic gas generation during TPU combustion. The results demonstrate that the inclusion of 3 wt% Mn-La and Mn-Ce catalysts into TPU leads to a 41.3% and 33.6% decrease in maximum smoke density (Ds max), respectively, along with a 52.4% and 50.5% reduction in peak CO production rate (pCOPR). The mechanism of rare earth Mn-based catalyst-based smoke suppression and toxicity reduction in TPU is explained at a microscopic scale based on density functional theory (DFT) research: the introduction of catalyst bolsters the adsorption of O2 and CO on the surface of TPU nanocomposites and facilitates the oxidation of CO. Additionally, it can expedite the formation of dense carbon layers and impede heat and mass transfer. The TPU nanocomposites exhibit excellent flame retardancy and effective smoke suppression. A feasible strategy for manufacturing fire-safety TPU nanocomposites with favorable comprehensive properties is proposed.

Strategy for Constructing Phosphorus-Based Flame-Retarded Polyurethane Elastomers for Advanced Performance in Long-Term

Polyurethane elastomer (PUE), which is widely used in coatings for construction, transportation, electronics, aerospace, and other fields, has excellent physical properties. However, polyurethane elastomers are flammable, which limits their daily use, so the flame retardancy of polyurethane elastomers is very important. Reactive flame retardants have the advantages of little influence on the physical properties of polymers and low tendency to migrate out. Due to the remarkable needs of non-halogenated flame retardants, phosphorus flame retardant has gradually stood out as the main alternative. In this review, we focus on the fire safety of PUE and provide a detailed overview of the current molecular design and mechanisms of reactive phosphorus-containing, as well as P-N synergistic, flame retardants in PUE. From the structural characteristics, several basic aspects of PUE are overviewed, including thermal performance, combustion performance, and mechanical properties. In addition, the perspectives on the future advancement of phosphorus-containing flame-retarded polyurethane elastomers (PUE) are also discussed. Based on the past research, this study provides prospects for the application of flame-retarded PUE in the fields of self-healing materials, bio-based materials, wearable electronic devices, and solid-state electrolytes.

Impact of a Novel Phosphoramide Flame Retardant on the Fire Behavior and Transparency of Thermoplastic Polyurethane Elastomers

In many application fields of thermoplastic polyurethane (TPU), excellent flame retardancy and transparency are required. However, higher flame retardancy is often at the expense of transparency. It is difficult to achieve high flame retardancy while maintaining the transparency of TPU. In this work, a kind of TPU composite with good flame retardancy and light transmittance was obtained by adding a new synthetic flame retardant named DCPCD, which was synthesized by the reaction of diethylenetriamine and diphenyl phosphorochloridate. Experimental results showed that 6.0 wt % DCPCD endowed TPU with a limiting oxygen index value of 27.3%, passing the UL 94 V-0 rating in the vertical burning test. The cone calorimeter test results showed that the peak heat release rate (PHRR) of the TPU composite was dramatically reduced from 1292 kW/m² (pure TPU) to 514 kW/m² by adding only 1 wt % DCPCD. With the increase of DCPCD contents, the PHRR and total heat release gradually decreased, and the char residue gradually increased. More importantly, the addition of DCPCD has little effect on the transparency and haze of TPU composites. In addition, scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy were carried out to investigate the morphology and composition of the char residue for TPU/DCPCD composites and explore the flame retardant mechanism of DCPCD in TPU.

Improving the Reaction-to-Fire Properties of Thermoplastic Polyurethane by New Phosphazene-Triazinyl-Based Covalent Organic Framework

In this study, an approach to simultaneously improve fire resistance and mechanical performance of thermoplastic polyurethane (TPU) was introduced through the penetration of a conjugated network containing nitrogen and phosphorus elements. For this purpose, a Bg-HCCP COF was synthesized through a solvothermal method from benzoguanamine (Bg) and hexachlorophosphazene (HCCP) monomers. Then, it was combined with TPU using the wet mixing method. The TPU/Bg-HCCP composites showed better mechanical strength than the untreated sample. The fire safety of TPU/Bg-HCCP composites was greatly improved by increasing the Bg-HCCP contents. The reduction of the peak heat release rate and the total heat release for the TPU/Bg-HCCP composite with 3 wt % Bg-HCCP were about 44.8 and 60.4%, respectively. Besides, the results showed that adding Bg-HCCP to TPU significantly improved the suppression of smoke generation so that 3% by weight of the fire retardant reduced the total smoke released by 53.1%. It also decreased the peak of the carbon monoxide production rate by 26.5%. Generally, our research provides a promising strategy for constructing flame-retardant composites with high performance.

Recent Advances in Halogen-Free Flame Retardants for Polyolefin Cable Sheath Materials

With the continuous advancements of urbanization, the demand for power cables is increasing to replace overhead lines for energy transmission and distribution. Due to undesirable scenarios, e.g., the short circuit or poor contact, the cables can cause fire. The cable sheath has a significant effect on fire expansion. Thus, it is of great significance to carry out research on flame-retardant modification for cable sheath material to prevent fire accidents. With the continuous environmental concern, polyolefin (PO) is expected to gradually replace polyvinyl chloride (PVC) for cable sheath material. Moreover, the halogen-free flame retardants (FRs), which are the focus of this paper, will replace the ones with halogen gradually. The halogen-free FRs used in PO cable sheath material can be divided into inorganic flame retardant, organic flame retardant, and intumescent flame retardant (IFR). However, most FRs will cause severe damage to the mechanical properties of the PO cable sheath material, mainly reflected in the elongation at break and tensile strength. Therefore, the cooperative modification of PO materials for flame retardancy and mechanical properties has become a research hotspot. For this review, about 240 works from the literature related to FRs used in PO materials were investigated. It is shown that the simultaneous improvement for flame retardancy and mechanical properties mainly focuses on surface treatment technology, nanotechnology, and the cooperative effect of multiple FRs. The principle is mainly to improve the compatibility of FRs with PO polymers and/or increase the efficiency of FRs.

Metal-organic Framework ZIF-67 Functionalized MXene for Enhancing the Fire Safety of Thermoplastic Polyurethanes

In this work, a novel functionalization strategy for ZIF-67-modified layered MXene was proposed, aiming at improving the fire safety of thermoplastic polyurethanes (TPU). The ZIF-67@MXene was verified by microscopic morphology, elemental composition, functional group species and crystal structure, and then the successfully prepared ZIF-67@MXene was introduced into the TPU material. When ZIF-67@MXene content was only 0.5 wt%, the peak heat release rate, total heat release rate, peak smoke release rate, total smoke release rate, and CO yield of the TPU/ZIF-67@MXene composites were reduced by 26%, 9%, 50%, and 22%, respectively, compared with the pure TPU. The thermogravimetric tests showed that the residual char of TPU/ZIF-67@MXene composites was the most in all samples. In short, the high-quality carbon layer of TPU/ZIF-67@MXene composites acts as a physical barrier to the transfer of heat and toxic gases, greatly improving the flame retardant properties of the TPU polymer.

Comparison of differences in the flame retardancy of cotton fabrics caused by the introduction of cyclic polysiloxane into P/N organic coatings

Cyclic polysiloxane was introduced into P/N flame retardant coating to prepare Si/P/N synergistic FRs (ASPP-Si), which can improve the heat release and smoke release of cotton fabric and enhance the tensile strength of fiber.