Metal Phosphinates Research Articles

Aluminum Diethylphosphinate as a Flame Retardant for Polyethylene: Investigation of the Pyrolysis and Combustion Behavior of PE/AlPi-Mixtures

The popularity of organic polymers despite their high flammability forces the introduction of flame retardants (FR) such as metal phosphinates into the combustible material. The thermal behavior of aluminum diethylphosphinate (AlPi) as FR in the widely used polymer ultra-high molecular weight polyethylene (UHMWPE) is investigated here. The study focuses on the effect of the FR on the gas phase activity when a polymer is pyrolyzed or burned. For this purpose, the fast pyrolysis of AlPi was investigated by differential mass-spectrometric thermal analysis (DMSTA). Also, the thermal and chemical structures of diffusion flames of UHMWPE + AlPi specimens were investigated using micro thermocouples and molecular beam mass spectrometry, respectively. Small amounts of AlPi (2.5 wt.%) decrease the gas temperature significantly by a maximum of 155 K related to FR-free polymer flames, indicating a retardancy effect of the additive on the flame. From the results of subsequent limiting oxygen index (LOI) tests, it is obvious that a PE burn-up cannot be achieved in a self-sustained flame when an additive content above 10 wt.% is used as FR. In the mass-spectrometric studies, the phosphorus-containing species produced in the pyrolysis experiments (DMSTA) of the neat AlPi as well as the species which are formed in flames during combustion experiments can be detected. In the flames, the concentration of the phosphorus containing compounds peaks at low heights above the polymer surface which indicate a gas phase activity of AlPi or its pyrolysis products. Besides a charring layer on top of the burning surface could be noticed. The use of AlPi as a FR for UHMWPE shows flame retardant effects in both the condensed and the gas phase.

Synthesis and electrochemical properties of metal(ii)-carboxyethylphenylphosphinates.

We report herein the synthesis, structural characterization and electrocatalytic properties of three new coordination polymers, resulting from the combination of divalent metal (Ca2+, Cd2+ or Co2+) salts with (2-carboxyethyl)(phenyl)phosphinic acid. In addition to the usual hydrothermal procedure, the Co2+ derivative could also be prepared by microwave-assisted synthesis, in much shorter times. The crystal structures were solved by ab initio calculations, from powder diffraction data. Compounds MII[O2P(CH2CH2COOH)(C6H5)]2 {M = Cd (1) or Ca (2)} crystallize in the monoclinic system and display a layered topology, with the phenyl groups pointing toward the interlayer space in a interdigitated fashion. Compound Co2[(O2P(CH2CH2COO)(C6H5)(H2O)]2·2H2O (3) presents a 1D structure composed of zig-zag chains, formed by edge-sharing cobalt octahedra, with the phenyl groups pointing outside. Packing of these chains is favored by hydrogen bond interactions via lattice water molecules. In addition, H-bonds along the chains are established with the participation of the water molecules and the hydrophilic groups from the ligand. However, the solid exhibits a low proton conductivity, attributed to the isolation of the hydrophilic regions caused by the arrangement of hydrophobic phenyl groups. Preliminary studies on the electrocatalytic performance for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) have been conducted for compound 3 and its pyrolytic derivatives, which were previously thoroughly characterized. By comparison, another Co2+ phosphinate, 4, obtained by microwave-assisted synthesis, but with distinct stoichiometry and a known structure was also tested. For the OER, the best performance was achieved with a derivative of 3, prepared by heating this compound in N2 at 200 °C. This derivative showed overpotential (339 mV, at a current density of 10 mA cm-2) and Tafel slope (51.7 mV dec-1) values comparable to those of other Co2+ related materials.

Isothermal pyrolysis investigation of aluminum diethylphosphinate mixed as a flame retardant additive into ultra-high molecular weight polyethylene

Aliphatic polymers such as polyethylene or polypropylene are widely used in spite of their high flammability and forces the introduction of flame retardants (FR), e.g. metal phosphinates, into the polymers. These flame retardants usually act in the condensed phase or may influence the gas phase mechanism of combustion. However, the modes of action are not yet understood in detail and require increasing research. In this study a contribution to the latter is made. The thermal decomposition behavior of aluminum diethylphosphinate (AlPi) as FR, mixed in ultra-high molecular weight polyethylene (UHMWPE) is investigated here by molecular beam mass spectrometry (MBMS) in an oxygen-free atmosphere. The isothermal pyrolysis experiments for this system have been systematically studied by first concentrating on each neat compound, FR and polymer, respectively, followed by the analysis of doped polyethylene blends. The aim is to detect phosphorus-containing species in the gas phase, which is the minimum requirement for a gas phase active FR. It was found that the main product of AlPi is diethylphosphinic acid, which subsequently degrades to lighter species or dimerizes. In the mixture, although the AlPi decomposition is influenced by the polymer in the condensed phase, most of the species responsible for a flame suppressant effect are still present in the gas phase.

Coordination Compounds of 9,10‐Dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐Oxide (DOPO) Ligands: Extremely High Thermostability and Ligand Oxidation in the Solid State

Different metal phosphinates and phosphonates were obtained containing zinc, calcium and magnesium as cations by means of a salt metathesis reaction with sodium salts of DOPO and DOPO‐OH. The synthesized complexes [Zn(DOPO)2]n, [Zn(DOPO‐OH)2]n and [Ca(DOPO)2(H2O)]n are featured a polymeric structure. The open‐ring metal phosphinate coordination compound [Zn(DOPO)2]n is able to undergo a non‐reversible thermally induced oxidative cyclisation to the corresponding metal phosphonate [Zn(DOPO‐OH)2]n. The magnesium and calcium phosphinates cannot be oxidized to their corresponding metal phosphonate complexes. All organophosphorus compounds were analyzed by means of X‐ray crystallography, NMR, TGA and TDMS. The oxidative cyclisation reaction of [Zn(DOPO)2]n was investigated by DSC. Additionally, the coordination polymer [Zn(DOPO)2]n can be transformed into a molecular complex by adding nitrogen ligands such as N‐methylimidazole, whereby the phosphonate ligand changes from a bridging to a monodentate ligand. The synthesized coordination compounds exhibit very high thermostabilities of up to 520 °C.

Intumescent formulations based on lignin and phosphinates for the bio-based textiles

This study investigates new intumescent formulations based on lignin and phosphinates to improve the flame retardant properties of Polyamide 11, while preserving the bio-based characteristics of this latter. Lignin has the advantage of being a bio-based compound and can be effectively used as carbon source for the design of intumescent systems in combination with other flame retardant additives. Metal phosphinates belong to a novel class of phosphorus flame retardants. Despite their increasing use, there is lack of scientific understanding as far as their fire retardancy mechanism is considered, especially in char forming polymeric materials. In this context, Polyamide 11 was melt blended with lignin and metal phosphinates. The possibility of melt spinning the prepared blends were assessed through melt flow index (MFI) tests; thermogravimetric (TG) analyses and cone calorimetry tests were exploited for investigating the thermal stability and the combustion behaviour of the obtained products, respectively. MFI results indicate that some formulations are suitable for melt spinning processes to generate flame retardant multifilament. Furthermore, the combination of lignin and phosphinates provides charring properties to polyamide 11. Finally, cone calorimetry data confirmed that the designed intumescent formulations could remarkably reduce PHRR through formation of protective char layer, hence slowing down the combustion process.

Flame retardancy and mechanical properties of poly(decamethylene terephthalamide) filled with metal phosphinates

Flame retardancy and mechanical properties of poly(decamethylene terephthalamide) (PA10T) containing aluminum diethlyphosphinate (BEPAL) were investigated. The influence of BEPAL on the thermal degradation behavior of PA10T was studied using thermogravimetry, flammability test and chemical analysis. A decomposition model was given on the basis of Lewis acid-base interaction. The introduction of BEPAL led to reduced decomposition temperature, while the limiting oxygen index was greatly improved. The investigation of mechanical properties of PA10T/BEPAL composites indicated that the tensile strength firstly increased when low content BEPAL was added, then decreased with further increasing the concentration of BEPAL due to the agglomeration of filler particles. Dynamic mechanical analysis (DMA) results revealed that the presence of BEPAL hindered the movement of molecular chain.

A New Type of Flame Retarded Epoxy Resin Based on Metal Phosphinates

Exolit OP930 (abbreviate OP930) product based on aluminum (diethyl phosphinate) is a new class of flame retardants for the use in epoxy resin (EP). In this paper, the mechanical properties, the morphologies of fracture surfaces, thermal stability, glass transition temperature (Tg) and flame retardant of OP930-EP composites with different composition have been studied. The composites exhibit satisfying thermal properties and a high limiting oxygen index (LOI) value as well as good compatibility with the matrix. Compared to neat resin, the mechanical properties of composites are also on a very good level.

Cobalt and copper phosphinates based on N-(phosphinomethyl)iminodiacetic acid: supramolecular layered structures and magnetic properties

Reactions of N-(phosphinomethyl)iminodiacetic acid (H3L) and cobalt or copper salts in aqueous solutions result in two new metal phosphinates, [Co(H2O)6][Co2L2]·2H2O (1) and [Cu(H2O)4][Cu2L2] (2). Both compounds exhibit different supramolecular layered structures, which result from the assembly of cationic and anionic moieties through hydrogen bond interactions. In 1, {Co2O2} dimers are linked through O–P–O units into a {[Co2L2]}n2n− double chain and [Co(H2O)6]2+ serve as a counterion. Compound 2 contains two kinds of chain-like moieties, i.e. {[Cu2L2]}n2n− and {[Cu(H2O)4]}n2n+. The former is made up of corner-sharing {CuO4N} square pyramids and {PHO2C} tetrahedra and the latter is formed through edge-sharing connections of {CuO6} octahedra. Magnetic studies reveal a dominant ferromagnetic interaction mediated between the magnetic centers in 1, while antiferromagnetic interactions are dominant in 2.

Hydrothermal Synthesis of Chiral Metal(II) Phosphinates Derived from Camphor

AbstractThe diastereoselective synthesis of bis(3‐endo‐camphoryl)phosphinic acid (1) and its 2‐bornen‐2‐yl ester 2 from the reaction of lithium camphor enolate with phosphorus trichloride and the hydrothermal synthesis of three chiral molecular metal(II) phosphinates of the type M(O2PR2)2·2R2P(O)OH [M = Co (3); Ni (4); Pb (5); R = 3‐endo‐camphoryl] from the reaction of 1 with metal(II) acetates or nitrates is described. The molecular structures of 1–5 are reported.

Flame retardancy mechanisms of metal phosphinates and metal phosphinates in combination with melamine cyanurate in glass‐fiber reinforced poly(1,4‐butylene terephthalate): the influence of metal cation

AbstractThe pyrolysis and fire behavior of glass‐fiber reinforced poly(butylene terephthalate) (PBT/GF) with two different metal phosphinates as flame retardants in combination with and without melamine cyanurate (MC) were analyzed by means of thermogravimetry, thermogravimetry coupled with infrared spectroscopy, flammability, and cone calorimeter tests as well as scanning electron microscopy/energy dispersive X‐ray spectroscopy and X‐ray fluorescence spectroscopy. In PBT/GF, dosages of 13–20% of the halogen‐free flame retardant aluminum phosphinate or aluminum phosphinate in combination with MC fulfill the requirements for electrical engineering and electronics applications (UL 94 = V‐0; LOI > 42%), whereas the use of the same amount of zinc phosphinate or zinc phosphinate in combination with MC does not improve the fire behavior satisfactorily (UL 94 = HB; LOI = 27–28%). The performance under forced flaming conditions (cone calorimeter) is quite similar for both of the metal phosphinates. The use of aluminum and zinc salts results in similar flame inhibition predominantly due to the release of the phosphinate compounds in the gas phase. Both metal phosphinates and MC interact with the polymer changing the decomposition characteristics. However, part of the zinc phosphinate vaporizes as a complete molecule. Because of the different decomposition behavior of the metal salts, only the aluminum phosphinate results in a small amount of thermally stable carbonaceous char. In particular, the aluminum phosphinate‐terephthalate formed is more stable than the zinc phosphinate‐terephthalate. The small amount of char has a crucial effect on the thermal properties and mechanical stability of the residue and thus the flammability. Copyright © 2008 John Wiley & Sons, Ltd.

Mononuclear Metal Phosphinates with Ancillary Pyrazole Ligands. Synthesis and X‐ray Crystal Structures of [M(Ph2PO2)2(3,5‐DMPZ)2] (M = Co, Zn)

AbstractThe reaction of diphenylphosphinic acid, [Ph2P(O)(OH)], with CoCl2 or ZnCl2 and 3,5‐dimethylpyrazole (DMPZ) in the presence of triethylamine affords the mononuclear phosphinates, M(Ph2PO2)2(DMPZ)2 (M= Co(1), Zn(2)). The molecular structures of 1 and 2 reveal a tetrahedral environment around the metal. The phosphinate ligands are monoanionic and bind to the metal in a monodentate manner, while the pyrazole ligands act as neutral monodentate ligands. Intermolecular C‐H‐O and π–π interactions in 1 and 2 result in the generation of two dimensional supramolecular polymeric sheets in the solid state.

Hybrid Organic—Inorganic Materials Based on Organophosphorus Derivatives

AbstractFor Abstract see ChemInform Abstract in Full Text.

Inorganic coordination polymers, 20. Zinc(II) phosphinate polymers and copolymers containing phenyl sulfone side groups

AbstractThe syntheses and characterizations of a series of new phosphinic acids and the zinc polymers and copolymers prepared from them are reported. These compositions are characterized by the presence of phenyl sulfone side groups. The zinc derivatives were found to be among the thermally most stable tractable poly(metal phosphinates) yet studied.

Specific heat of disordered antiferromagnetic chains: Poly(metal phosphinates)

The inorganic transition-metal polymers, poly(metal phosphinates), comprise a unique and versatile class of new materials. In particular, three poly(chromium phosphinates) have been shown to form linear polymeric molecules, which may be described in terms of spin chains with antiferromagnetic interactions. The specific heats of these materials and of their nonmagnetic analogs, poly(zinc phosphinates), have been measured in the temperature range $1.6\ensuremath{\lesssim}T\ensuremath{\lesssim}10$ K. The vibrational contribution to the specific heat is consistent with the polymeric nature of the materials, changing from ${T}^{3}$ to ${T}^{\frac{5}{2}}$ dependence as the temperature increases. The magnetic specific heat can then be extracted and is found to be in qualitative agreement with a model which includes disorder in the spin chains. We believe that this is the first measurement of the specific heat of a disordered one-dimensional magnetic system.

Magnetic properties of poly(metal phosphinates): The effects of structural disorder on one-dimensional antiferromagnetic chains

The magnetic properties of several materials from the class poly(metal phosphinates) have been measured. In particular ESR spectra and the temperature dependence of the static susceptibility of three poly (chromium phosphinates) imply that these polymers comprise a class of one-dimensional antiferromagnetic chains with $\frac{J}{k}\ensuremath{\sim}4$ K and with a varying degree of crystallinity. Structural disorder is found to limit the range of spin correlations and, in the extreme case, prohibits extended short-range order. The data are analyzed in terms of a model of chains of constant exchange but finite length. Comparison is made with an alternative model of infinite chains with Heisenberg exchange $J$ varying randomly about a mean. The width of the distribution of $J$ provides a direct measure of the disorder in each system.

Inorganic coordination polymers. XI. A new family of chromium(III) bis(phosphinate) polymers, [Cr(OH)(OPRR′O)2]x

AbstractHeating hydroxyaquochromium(III) bis(phosphinates) at temperatures up to 200°C under vacuum yields the corresponding anhydrous polymers [Cr(OH)(OPRR'O)2]x. The infrared and visible spectra and solution properties lead to the following conclusions. When R and R′ are phenyl groups, the hydroxyl groups appear to bridge between adjacent chromium atoms in the chain together with the phosphinate ligands to yield a linear, triple‐bridged polymer. When at least one substituent on the phosphorus is an alkyl group, some of the hydroxyl groups crosslink between chains to yield less soluble polymers. Comparison of the properties of these new polymers with the parent polymers suggests that the latter should be formulated [Cr(H2O)n(OH)(OPRR′O)2]x·pH2O and that they contain more than one kind of monomer unit. The parent polymers can be readily prepared by a new method which involves reaction of a soluble chromium(III) salt with alkali metal phosphinates or of chromium(III) hydroxide with phosphinic acids in a water–tetrahydrofuran mixture.

Coordination Polymers with Inorganic Backbones Formed by Double- Bridging of Tetrahedral Elements

Abstract : Typical modes of preparation are reported for some novel polymeric metal phosphinates, among which are included /Be(OPPh2O)2/x, /Zn(OPPh2O)2/x, and /Zn(OP(Ph)(Me)O)2/x.