Poly(arylate-phosphonate) copolymers with deoxybenzoin in the backbone: Synthesis, characterization, and thermal properties

Intrinsically flame-retardant polyamide 66 with high flame retardancy and mechanical properties

The key factor in the synthesis of intrinsic flame retardant polymers is the thermal stability and reactivity of phosphorus-based flame retardants. However, it is difficult to realize both thermal stability and high reactivity by using one phosphorus-based flame retardant. Herein, we proposed a strategy to improve the thermal stability of highly reactive flame-retardant, 4-(2-(((2-carboxyethyl)(phenyl)phosphoryl)oxy)ethoxy)-4-oxohexanoic acid (CPPOA), by reacting it with 1,6-diaminohexane to obtain CPPOA salt, which then was copolymerized with PA66 salt to obtain intrinsic flame-retardant polyamide 66 (FRPA66). The thermal stability of CPPOA was significantly improved. The LOI and vertical combustion grade of FRPA66 with 6 wt% CPPOA reached 27.2% and V-0 rating, respectively. Furthermore, the tensile strength and impact strength of the FRPA66 reached 70 MPa and 5.6 kJ m-2, respectively. Our work presents an efficient approach to synthesize polymers having high flame retardancy and good mechanical properties, showing high potential for real applications.

Synthesis, characterization and thermal degradation kinetics of azomethine-based halogen-free flame-retardant polyphosphonates

In this study, azomethine polyphosphonates were synthesized by solution polycondensation of phenylphosphonic dichloride with various azomethine diols such as [4-(4-hydroxy phenyl) iminomethyl] phenol, [(4-(4-hydroxy-3-methoxy phenyl) iminomethyl)] phenol and [4-(4-hydroxy-3-ethoxy phenyl) iminomethyl] phenol using triethylamine catalyst at ambient temperature. The structure of the synthesized polymers was confirmed by Fourier transform infrared and 1H-, 13C- and 31P- nuclear magnetic resonance spectroscopic techniques. Thermal properties of the polymers were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry under nitrogen atmosphere. The TGA data showed that the synthesized polyphosphonates produce high char yield at 600°C due to the presence of phosphorous atom in the polymer chain and hence have good flame-retardant properties. One of the synthesized polyphosphonate was blended with commercial diglycidyl ether of bisphenol-A (DGEBA) resin in various weight percentage and cured with commercial curing agent triethylene tetramine (TETA). The polyphosphonates-blended epoxy thermosets have tensile strength in the range of 5–41 MPa and the percentage of elongation at breaks was 4–18. It was found that the incorporation of polyphosphonates into epoxy thermoset decreased the tensile strength from 41 MPa to 5 MPa, whereas the elongation at break value increased with increase in the weight percentage of polyphosphonate. The influence of polyphosphonates on the flame retardancy of blended thermosets was examined by limiting oxygen index (LOI) and vertical burning (UL-94) tests and found that the polymer samples achieved an increased UL-94 rating and the LOI values were in the range of 24–26. Broido and Horowitz–Metzger methods have been used to study the thermal degradation kinetic parameters.

The effect of aluminum phosphinate on char formation of phosphorus-containing deoxybenzoin polymer

The introduction of aluminum diethlyphosphinate (AlPi; <2% by weight) to 4,4′-bishydroxydeoxybenzoin-polyphosphonates (BHDB-PPNs) increased the char yield rate of BHDB-PPN from about 54% to 63% at 600°C. The increase of char yield rate might be attributed to the reaction among the degraded products from AlPi and BHDB-PPN to form stable intermediates which increased the activation energy of cleavage of P–C bond in the BHDB-PPN and reduced the release of benzene to the gas phase. It was found that the char yielded from BHDB-PPN and BHDB-PPN/AlPi comprised about 90% carbon element, which was characterized as main sp2 carbon structure by Raman spectrum.

Synthesis and characterization of cardo-based phosphorous–containing flame-retardant aromatic polyesters

Phosphorous-containing cardo polyesters were synthesized by interfacial polycondensation of phenylphosphonic dichloride with various bisphenols using a phase-transfer catalyst at ambient temperature. The structure of the synthesized polymers was confirmed using Fourier transform infrared and proton, carbon 13, and phosphorous 31 nuclear magnetic resonance spectroscopic techniques. The thermal properties of the polymers were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry under nitrogen atmosphere. All the polyesters showed high thermal stability, the maximum decomposition temperature being in the range of 475–523°C. The TGA data showed that all the synthesized phosphorous-containing polyesters produce high char yield at 700°C due to the presence of phosphorous atom in the polymer chain and hence have good flame-retardant properties. The synthesized phosphorus-containing polyesters have tensile strength in the range of 38.2–48 MPa, and the percentage of elongation at breaks of 3.3–16.8. The flame retardancy of all synthesized polymers was investigated by limiting oxygen index (LOI) and vertical burning (UL-94) tests. The results showed that the synthesized polymers have excellent flame retardancy, that is, the polymer samples achieved an increased UL-94 rating and the LOI values were in the range of 28.5–34. Broido model has been used to study the thermal degradation kinetic parameters.

Synthesis and characterization of novel post-chain extension flame retardant waterborne polyurethane

Flame-retardant waterborne polyurethanes with a phosphorus-containing flame retardant diamine (AWPUs) were synthesized and characterized by the method of post-chain extension technology.

Synergistic effects of BHDB-IPC with AlPi/MCA on flame retarding TPEE

The deoxybenzoin-based copolyarylate BHDB-IPC with perfect charring ability was synthesized.

Aryl Polyphosphonates: Useful Halogen-Free Flame Retardants for Polymers

Aryl polyphosphonates (ArPPN) have been demonstrated to function in wide applications as flame retardants for different polymer materials, including thermosets, polycarbonate, polyesters and polyamides, particularly due to their satisfactory thermal stability compared to aliphatic flame retardants, and to their desirable flow behavior observed during the processing of polymeric materials. This paper provides a brief overview of the main developments in ArPPN and their derivatives for flame-retarding polymeric materials, primarily based on the authors' research work and the literature published over the last two decades. The synthetic chemistry of these compounds is discussed along with their thermal stabilities and flame-retardant properties. The possible mechanisms of ArPPN and their derivatives containing hetero elements, which exhibit a synergistic effect with phosphorus, are also discussed.