Phosphorus-containing Structure Research Articles

Deeper insights into flame retardancy of polymers by interpretable, quantifiable, yet accurate machine-learning model

Fire-safety polymer materials are essential in modern society such as electronics, aerospace, new energy. The quantification and prediction of flame retardancy, determined by the chemical composition and the burning process, has always been a bottleneck challenge. Previous empirical design rules and the existing models show large deviations for predicting flame retardancy and are often unexplainable. Here, this study proposes an interpretable model that can quantify the groups contribution of flame-retardancy and predict the flame retardance of intrinsically flame-retardant polymers. The machine learning model simultaneously considers the group structures and their flame-retardant mechanism in both the gas phase and condensed phase, achieving high prediction accuracy (89.8% for the training set and 83.8% for the testing set). It also quantifies the contribution values of various flame-retardant groups (halogen-containing structures, phosphorus-containing structures, phosphorus-nitrogen-containing structures, aromatic ring-containing structures, etc.) in both phases for the first time. The running script that integrates the model has also been open-sourced, providing an emerging strategy for transitioning flame-retardant research from empirical methods to scientific design.

Multiple free-radical-trapping and hydrogen-bonding-enhanced polyurethane foams with long-lasting flame retardancy, aging resistance, and toughness.

Flexible polyurethane foam (FPUF) is a ubiquitous material utilized in furniture cushions, mattresses, and various technical applications. Despite the widespread use, FPUF faces challenges in maintaining long-lasting flame retardancy and aging resistance, particularly in harsh environments, while retaining mechanical robustness. Here, we present a novel approach to address these issues by enhancing FPUF through multiple free-radical-trapping and hydrogen-bonding mechanisms. A hindered amine phosphorus-containing polyol (DTAP) was designed and chemically introduced into FPUF. The distinctive synergy between hindered amine and phosphorus-containing structures enables the formation of multiple hydrogen bonds with urethane, while also effectively capturing free radicals across a broad temperature spectrum. As a result, incorporating only 5.1 wt% of DTAP led to the material successfully passing vertical burning tests and witnessing notable enhancements in tensile strength, elongation at break, and tear strength. Even after enduring accelerated thermal aging for 168 hours, the foam maintained exceptional flame retardancy and mechanical properties. This study offers novel insights into material enhancement, simultaneously achieving outstanding long-lasting flame retardancy, toughness, and anti-aging performance.

Synthesis and flame inhibition efficiency of a novel Fe-based metal complex with phosphorus-containing structure

Owing to the increased depletion risk and cost of phosphate mines, the demand for low phosphorus or ecological phosphorus flame inhibitor is increasing. This study reports an experimental exploration of the combustion inhibition efficiency of bio-based transition metal complex materials containing iron and phosphorus, namely, iron @ phosphorus complex (Fe-PMC). The aim is to develop a new type of flame inhibitor with an iron-phosphorus interaction effect to replace pure phosphorus extinguishing agents. The synthesis of Fe-PMC was characterized by Fourier-transform infrared spectroscopy, X-Ray diffraction, X-ray photoelectron spectroscopy and Scanning electron microscope. The Fe-PMC (ⅰ) is the mesh porous structure connected by the accumulation of small particles, (ⅱ) is an amorphous structure with many binding sites exposed and excellent interface compatibility, (ⅲ) contains no chloride ions. Suppression tests and thermogravimetric measurements indicate that (ⅰ) Fe-PMC has a higher combustion inhibition ability than MIL-53 containing only iron, especially at low concentrations, (ⅱ) Fe-PMC reduces the laminar flame velocity of cellulose, (ⅲ) Fe-PMC greatly reduces flame temperature. The activation energy (E), pre-exponential factor (A) and char yield (Y) of cellulose pyrolysis were determined by kinetic analysis. It concluded that MIL-53 and Fe-PMC produce combustion inhibition mainly in the solid phase. These findings will contribute to the development of a flame inhibitor with low or no phosphorus and better performance.

Synthesis and Flame Inhibition Efficiency of a Novel Fe-Based Metal-Organic Framework with Phosphorus-Containing Structure

Synthesis and Flame Inhibition Efficiency of a Novel Fe-Based Metal-Organic Framework with Phosphorus-Containing Structure

The improvement of fire safety performance of flexible polyurethane foam by Highly-efficient P-N-S elemental hybrid synergistic flame retardant

Herein, three different phosphorus-containing compounds (methyl phosphoryl dichloride, phenyl phosphoryl dichloride and phenyl dichlorophosphate) were reacted with 2-aminobenzothiazole respectively, and a series of synergistic flame retardants with phosphorus, nitrogen and sulfur elements were synthesized, named MPBT, PPBT and POBT respectively. Then, they were added to prepare flame-retardant flexible polyurethane foam (FPUF). Through the analysis of thermal stability, pyrolysis, heat release and smoke release behavior, the influence of different phosphorus-containing structures on the flame-retardant performance of FPUF was studied, and their flame-retardant mechanism was explored in detail. Among them, MPBT had the highest flame retardant efficiency with the same addition amount (10 wt%). The limiting oxygen index (LOI) value of PU/10.0% MPBT reached 22.5 %, and it successfully passed the vertical burning test. Subsequently, the addition amount of MPBT was increased and the best comprehensive performance of flame-retardant FPUF was explored. The results showed that the LOI value of PU/15.0% MPBT was increased to 23.5%. As for PU/15.0% MPBT, the peak heat release rate (PHRR) was 453 KW/m2, which was reduced by 46.64 %; and the flame retardancy index (FRI) value was also increased to 6.88. At the same time, the mechanical properties of flame-retardant FPUF were studied. The tensile strength of PU/15.0% MPBT reached 170 KPa, and the permanent deformation of FPUF/10% MPBT was only 4 %, showing its excellent resilience. The above results show that this phosphorus-containing element hybrid synergistic flame retardant (MPBT) has a very good application prospect in the field of flame-retardant polymer materials.

Electret Materials Based on Fluoropolymers Modified with Vanadium- and Phosphorus-Containing Structures

Electret Materials Based on Fluoropolymers Modified with Vanadium- and Phosphorus-Containing Structures

Thermal and flame-retardant properties of intrinsic flame-retardant epoxy resin containing biphenyl structures and phosphorus

An intrinsic flame-retardant epoxy resin was synthesized by introducing biphenyl structures and phosphorous into epoxy resin. The biphenyl structures could increase the glass transition temperature by more than 10 °C, as well thermal stability as indicated by the elevation in char yield. They could also enhance mechanical properties as reflected by the increments of 86.4% and 176.5% in tensile strength and breaking elongation, respectively, and offset the negative effects of phosphorus-containing structures. The introduction of elemental phosphorus could improve the flame-retardant properties of epoxy resin. The resulting epoxy resin presented a high limiting oxygen index of 32.4% and a V-0 rating in the UL-94 test. Moreover, it exhibited better flame-retardant parameters than pure epoxy resin in the cone calorimeter test. It could be decomposed to generate PO∙ and PO2∙ radicals to quench active free radicals, reduce toxic and smoke gas generation, and form a dense and stable char layer. It could simultaneously achieve gas and condensed phase flame retardancy. The presence of the biphenyl structure and phosphorus element in the epoxy resin system improved the thermal, mechanical, and flame-retardant properties of epoxy resin simultaneously. This work offered a facile method for preparing intrinsic phosphorus-containing flame-retardant epoxy resin without sacrificing thermal and mechanical properties.

Особенности строения липотейхоевых кислот бифидобактерий по данным ТСХ и ИК-ФТ

Липотейхоевые кислоты (ЛТК) клеточной стенки представителей рода Bifidobacterium проанализированы методом ТСХ и ИК-ФТ. Экстракцию ЛТК из бактериальных клеток разных видов осуществляли смесью хлороформ : гексан. Установлены видовые отличия в хроматографических и спектральных характеристиках ЛТК бифидобактерий. Так, ЛТК B. bifidum характеризуются относительно высоким содержанием полиеновых фрагментов и остатков фосфорной кислоты. В свою очередь ЛТК B. breve отличаются низким содержанием непредельных фрагментов. Для B. longum характерно наличие в структуре ЛТК остатков фосфорной кислоты с тремя электроотрицательными заместителями. Установлены особенности разделения ЛТК разных видов бифидобактерий в условиях ТСХ. Показана возможность сравнительного анализа ЛТК грамположительных бактерий в режиме ТСХ с последующим экстрагированием хроматографических зон и изучением в режиме ИК-ФТ

Flame-retardant effect and mechanism of melamine phosphate on silicone thermoplastic elastomer.

Different from the traditional silicone materials, which are not easily ignited, silicone thermoplastic elastomer (Si-TPE) has poor flame retardant properties due to the existence of the hard segments in its molecular chains. In this paper, melamine phosphate (MP), a kind of halogen free flame retardant, was adopted to improve the flame retardancy of Si-TPE. The results showed that MP played the role of flame retardant in both gas and condensed phases due to its nitrogen–phosphorus-containing structure. Inert gases, including nitrogen, steam and ammonia which were released by the degradation of melamine during burning, could take away the heat and dilute the oxygen in the gas phase, and further working with the phosphoric acid, which was generated in the condensed phase, to form a denser and firmer char layer. In this way, Si-TPE/MP composite with good flame retardancy was obtained. Interestingly, MP had little influence on the thermal processability of Si-TPE, even at 28 wt% content, ascribing to its two opposite effects on Si-TPE, but enhanced the comprehensive mechanical properties of Si-TPE with suitable loadings, e.g. when the MP content was 28 wt%, the composite reached UL94-V0 rating, and its tensile strength and Young's modulus were 3.5 MPa and 37.7 MPa, respectively.

A novel Co(Ⅱ)–based metal-organic framework with phosphorus-containing structure: Build for enhancing fire safety of epoxy

Co–based metal-organic framework with phosphorus-containing structure (P-MOF) was synthesized by a facile hydrothermal reaction and was first added into epoxy resin (EP) to enhance its fire safety, including flame retardancy, toxicity reduction, and smoke suppression. It was found that the values of peak heat release rate and total heat release of EP were decreased by 28% and 18.6% respectively at 2 wt% content of P-MOF. Meanwhile, the notable reductions of total smoke production and total CO yield were also observed from results of cone calorimeter and the steady state tube furnace, decreased by 15% and 52% respectively. Due to the absorption and catalytic effect of P-MOF and its residues, the release of organic volatiles and CO generated during the pyrolysis process of EP was significantly suppressed. Based on the analysis of gas and condensed phase, the possible mechanism of the enhanced fire safety was proposed as the combination of the adsorption and catalytic effect of P-MOF, which provides a promising application of MOFs to enhance the fire safety of polymer materials.

Chemical modification with orthophosphoric acid enhances surface-charge stability on polypropylene electrets

The low surface-charge stability of polypropylene (PP) frequently limits its application as an electret material. In this paper, we demonstrate how the treatment of PP-film surfaces with orthophosphoric acid (H3PO4) enhances their charge stability. To discriminate between the effects of chemical modification and thermal treatment, as-received and annealed PP films are used as reference samples. The electret properties of treated and non-treated PP films are characterized with thermally stimulated discharge (TSD) and isothermal surface-potential decay (ISPD) experiments, from which considerable improvement in thermal and temporal charge stability is observed for samples modified with H3PO4. The half-value temperature (T1∕2) observed on TSD curves of chemically treated PP increases to 131 and 145 °C for positive and negative charges, respectively. The enhancement might be attributed to the phosphoric compounds detected on the H3PO4-modified surfaces via attenuated-total-reflection infrared spectroscopy. Deeper surface traps formed at the “foreign” phosphorus-containing structures are able to capture the charges over longer time periods and at higher temperatures, thus leading to significant improvements in the temporal and thermal surface-charge stabilities of PP electrets.

Main-chain liquid crystalline copolyesters with a phosphorus-containing non-coplanar moiety

A series of phosphorus-containing main-chain thermotropic liquid crystalline copolyesters named poly(4,4′-biphenylene decanedioate-co-4,4′-(phenylphosphoryl)dibenzoate) (PBPDP) were synthesized by random polycondensation from mesogenic diol 4,4′-biphenol (BP), decanedioic acid (DA) and phosphorus-containing non-coplanar diacid named 4,4′-(phenylphosphoryl)dibenzoic acid (PPDBA). Chemical structures and physical properties of PBPDPs were characterized by Fourier-transform infrared spectroscopy (FTIR), proton and 31P nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC) and X-ray diffraction (WAXD). Thermal stability of the copolyesters was determined via thermogravimetric analysis (TGA), and the liquid crystalline behaviours were observed using polarizing optical microscopy (POM). Results showed that the introduction of PPDBA into the copolyester could decrease the liquid crystalline temperature (Tlc) and the isotropic temperature (Ti) as a result of both copolymerization and the non-coplanar structure of PPDBA; furthermore, when the molar ratio of PPDBA reached 15%, the copolyester turned into a semi-crystalline polymer and lost its liquid crystallinity. Thermal stability of the copolyester increased with increasing the content of PPDBA, due to the positive contribution of the phosphorus-containing structure.

Treatment with orthophosphoric acid enhances the thermal stability of the piezoelectricity in low-density polyethylene ferroelectrets

Ferroelectrets have been fabricated from low-density polyethylene (LDPE) films by means of a template-based lamination. The temperature dependence of the piezoelectric d33 coefficient has been investigated. It was found that low-density polyethylene ferroelectrets have rather low thermal stability with the piezoelectric coefficient decaying almost to zero already at 100 °C. This behavior is attributed to the poor electret properties of the polyethylene films used for the fabrication of the ferroelectrets. In order to improve the charge trapping and the thermal stability of electret charge and piezoelectricity, LDPE ferroelectrets were treated with orthophosphoric acid. The treatment resulted in considerable improvements of the charge stability in LDPE films and in ferroelectret systems made from them. For example, the charge and piezoelectric-coefficient decay curves shifted to higher temperatures by 60 K and 40 K, respectively. It is shown that the decay of the piezoelectric coefficient in LDPE ferroelectrets is governed by the relaxation of less stable positive charges. The treatment also leads to noticeable changes in the chemical composition of the LDPE surface. Infrared spectroscopy reveals absorption bands attributed to phosphorus-containing structures, while scanning electron microscopy shows new island-like structures, 50–200 nm in diameter, on the modified surface.

Defect-induced dimer pinning on the Si(0 0 1) surface

Room-temperature STM images frequently show regions of antisymmetric dimer ordering surrounding certain types of defect on the Si(0 0 1) surface. While it has been generally believed that any defect asymmetric with respect to the dimer row would induce this dimer pinning effect, recent experimental results have shown that this is not the case. We present a model, based on a nearest-neighbour Ising treatment of the surface, which allows the extent of pinning caused by a dimer to be predicted from ab initio calculations. We use this model to predict the pinning extent for three phosphorus-containing structures important in a proposed silicon-based quantum computer fabrication scheme, and identify one of these asymmetric features as causing no appreciable pinning. In addition, we use ab initio calculations to identify the effects governing the interaction between neighbouring dimers.

Aluminum Elicits Exocellular Phosphatidylethanolamine Production in Pseudomonas fluorescens

Pseudomonas fluorescens ATCC 13525 was found to grow in a minimal mineral medium supplemented with millimolar amounts of aluminum, a known environmental toxicant. During the stationary phase of growth, the trivalent metal was localized in a phosphatidylethanolamine (PE)-containing residue. The concentration of PE in pellets ranged from 1.7 to 13.9 mg ml of culture(sup-1) in media supplemented with 1 to 30 mM aluminum. Although the gelatinous residue was observed during the stationary phase of growth, ultracentrifugation and dialysis experiments revealed that PE was produced from earlier stages of incubation and was associated with aluminum. A sharp diminution in the levels of PE and aluminum in the spent fluid was concomitant with the formation of the insoluble deposit. The aluminum content of the soluble cellular fraction increased during growth and reached an optimum of 1.85 mM of test metal at 45 h in cultures with 15 mM aluminum. Further incubation, however, led to a marked decrease in the cellular aluminum content, and during the stationary phase of growth, only trace amounts of the trivalent metal were detected in this fraction. When 45-h cells were incubated in fresh citrate medium, most of the intracellular aluminum was secreted in the spent fluid and citrate was rapidly consumed. Aluminum efflux was also observed in cultures in which d-glucose was substituted for citrate. However, no efflux of this trivalent metal was evident in media devoid of either citrate or d-glucose. Scanning electron microscopic studies and X-ray energy-dispersive analyses of the dialyzed supernatant aided in the visualization of nodule-like aluminum- and phosphorus-rich bodies associated with thread-like carbon-, oxygen-, and phosphorus-containing structures. Transmission electron microscopic and electron energy loss spectroscopic analyses revealed the presence of aluminum within bacteria after 45 h of incubation. Cells harvested after aluminum insolubilization did not shown aluminum inclusions. This aluminum-tolerant microbe may have potential application in bioremediation processes.