Synthesis and properties of novel flame‐retardant poly(amide‐imide)s containing phosphine oxide moieties in main chain by microwave irradiation

Eight new flame‐retardant poly(amide‐imide)s with high inherent viscosities containing phosphine oxide moieties in main chain were synthesized from the polycondensation reaction of N,N′‐(3,3′‐diphenylphenylphosphine oxide) bistrimellitimide diacid chloride 7, with eight ;aromatic diamine 8a–h by two different methods such as solution and microwave‐assisted polycondensation. Results showed that the microwave‐assisted polycondensation by using a domestic microwave oven proceeded rapidly, compared with solution polycondensation and were completed within about 10–12 min. The resulting poly(amide‐imide)s 9a–h showed high thermal stability and flame‐retardant properties. All of the obtained polymers were fully characterized by means of elemental analysis, viscosity measurements, solubility test, and FTIR spectroscopy. Thermal properties of the PAIs 9a–h were investigated by using thermal gravimetric analysis (TGA), derivative thermogravimetric analysis (DTG), and differential scanning calorimetry (DSC). Char yield measurements at 600°C demonstrated that incorporating phosphine oxide moieties in polymer backbone markedly improves their flame retardancy. All of the earlier polymers were soluble at room temperature in various organic solvents such as NMP, DMF, DMSO, DMAc, and concentrated sulfuric acid. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4263–4269, 2006     

Synthesis and characterization of novel heat resistance poly(amide‐imide)s from N,N′‐[2,5‐bis(4‐aminobenzylidene) cyclopentanone] bistrimellitimide acid and various aromatic diamines

A new‐type of dicarboxylic acid was synthesized from the reaction of 2,5‐bis(4‐aminobenzylidene)cyclopentanone with trimellitic anhydride in a solution of glacial acetic acid/pyridine (Py) at refluxing temperature. Six novel heat resistance poly(amide‐imide)s (PAIs) with good inherent viscosities were synthesized, from the direct polycondensation reaction of N,N′‐[2,5‐bis(4‐aminobenzylidene)cyclopentanone]bistrimellitimide acid with several aromatic diamines, by two different methods such as direct polycondensation in a medium consisting of N‐methyl‐2‐pyrrolidone (NMP)/triphenyl phosphite (TPP)/calcium chloride (CaCl₂)/pyridine (Py) and direct polycondensation in a p‐toluene sulfonyl chloride (tosyl chloride, TsCl)/pyridine (Py)/N,N‐dimethylformamide (DMF) system. All of the above polymers were fully characterized by ¹H NMR, FTIR, elemental analysis, inherent viscosity, solubility tests, UV‐vis spectroscopy, differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), and derivative of thermaogravimetric (DTG). The resulted poly(amide‐imide)s (PAIs) have showed admirable good inherent viscosities, thermal stability, and solubility. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

New photosensitive poly(amid‐imide)s containing chalcone moiety and hydantoin derivatives in the main chain: Synthesis and characterization

Six new poly(amid‐imide)s containing chalchone and hydantoin moieties in the main chain were synthesized through the polycondensation reaction of 1,3‐bis[4,4′‐bis(trimellityimido)phenyl]‐2‐propenone 6 with six hydantoin derivatives 7a‐f in a medium consisting of triphenyl phosphite, calcium chloride, pyridine, and N‐methyl‐2‐pyrrolidone. The polycondensation reaction produced a series of novel poly(amid‐imide)s 8a‐f in high yields with inherent viscosities between 0.26 and 0.42 dL/g. The resulting polymers were characterized by elemental analysis, viscosity measurements, solubility test, thermo gravimetric analysis (TGA and DTG), FTIR, and UV‐Vis spectroscopy. 1,3‐bis[4,4′‐bis(trimellityimido)phenyl]‐2‐propenone 6 was prepared from a three‐step reaction by using 4‐nitro benzaldehyde 1 and 4‐nitro acetophenone 2 as precursors. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Novel optically active poly(amide‐imide)s with tetrahydropyrimidinone and tetrahydro‐2‐thioxopyrimidine moieties by microwave‐assisted polycondensation

Rapid and highly efficient synthesis of novel poly(amide‐imide)s (PAIs) were achieved under microwave irradiation by using a domestic microwave oven from the polycondensation reactions of 4,4′‐carbonyl‐bis(phthaloyl‐L ‐alanine) diacid chloride [N,N′‐(4,4′‐carbonyldiphthaloyl)] bisalanine diacid chloride (1) with six different derivatives of tetrahydropyrimidinone and tetrahydro‐2‐thioxopyrimidine compounds (2a–2f) in the presence of a small amount of a nonpolar organic medium that acts as a primary microwave absorber. Suitable organic media was o‐cresol. The polycondensation proceeded rapidly and was almost completed within 10 min, giving a series of PAIs with inherent viscosities of about 0.25–0.45 dL/g. The resulting PAIs were obtained in high yield and are optically active and thermally stable. All of the above compounds were fully characterized by means of Fourier transform infrared spectroscopy, elemental analyses, inherent viscosity (η_inh), solubility test, and specific rotation. Thermal properties of the PAIs were investigated using thermogravimetric analysis. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2416–2421, 2001     

Improving thermal and flame‐retardant properties of epoxy resins by a new imine linkage phosphorous‐containing curing agent

A new reactive phosphorus‐containing curing agent with imine linkage called 4, 4′‐[1, 3‐phenyl‐bis(9, 10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐yl)dimethyneimino)]diphenol (2) was synthesized both via two‐pot and one‐pot procedure. The chemical structure of this curing agent was confirmed by FTIR, ¹H, ¹³C, and ³¹P NMR spectra. A series of thermosetting systems were prepared by using conventional epoxy resins (E51), 4, 4′‐diaminodiphenyl methane (DDM) and (2). Resins with different phosphorus contents were obtained by changing the DDM/(2) molar ratios. Their dynamic mechanical thermal, thermal and flame‐retardant properties were evaluated by dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), and limiting oxygen index (LOI), respectively. All samples had a single T_g, which showed that these epoxy resins were homogeneous phase. Both the two char yields under nitrogen and air atmospheres increased with increasing content of (2) and the LOI values increased from 24.5 for standard resin to 37.5 for phosphorus‐containing resin, which indicated that incorporation of (2) could impart good thermal stability and excellent flame retardancy to the conventional epoxy thermosets. POLYM. ENG. SCI., 56:441–447, 2016. © 2016 Society of Plastics Engineers     

Synthesis and characterization of new polyamides containing p‐phenylenediacryloyl moieties in the main chain

Six new polyamides 8a–f containing p‐phenylenediacryloyl moieties in the main chain were prepared by the direct polycondensation reaction of bis(p‐amidobenzoic acid)‐p‐phenylene diacrylic acid 6 with 1,4‐diphenylene diamine 7a , 1,3‐diamino toluene 7b , 1,5‐diamino naphthalene 7c , 4,4′‐diamino diphenyl ether 7d , 4,4′‐diamino diphenyl sulfone 7e , and 3,3′‐diamino diphenylsulfone 7f by using thionyl chloride, N‐methyl‐2‐pyrolidone, and pyridine as condensing agents. These new polymers 8a–f were obtained in high yield and inherent viscosity between 0.35–0.65 dL/g. The resulting polyamides were characterized by elemental analysis, viscosity measurements, thermal gravimetric analysis (TGA and DTG), solubility test, FTIR and UV–vis spectroscopy. Diacid acid 6 as a new monomer containing p‐phenylenediacryloyl moiety was synthesized by using a three‐step reaction. First, p‐phenylenediacrylic acid 3 was prepared by reaction of terephthal aldehyde 1 with malonic acid 2 in the presence of pyridine, then diacid 3 was converted to p‐phenylenediacryloyl chloride 4 by reaction with thionyl chloride. Finally, bis(p‐amidobenzoic acid)‐p‐phenylene diacrylic acid 6 was prepared by the condensation reaction of phenylenediacryloyl chloride 4 with p‐aminobenzoic acid 5 . © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Facile synthesis of novel optically active poly(amide‐imide)s containing N,N′‐(pyromellitoyl)‐bis‐l‐phenylalanine diacid chloride and 5,5‐disubstituted hydantoin derivatives under microwave irradiation

Pyromellitic dianhydride (1,2,4,5‐benzenetetracarboxylic acid 1,2,4,5‐dianhydide) (1) was reacted with L‐phenylalanine (2) in a mixture of acetic acid and pyridine (3 : 2) at room temperature, then was refluxed at 90–100°C and N,N′‐(Pyromellitoyl)‐bis‐L ‐phenylalanine diacid (3) was obtained in quantitative yield. The imide‐acid (3) was converted to N,N′‐(Pyromellitoyl)‐bis‐L ‐phenylalanine diacid chloride (4) by reaction with thionyl chloride. Rapid and highly efficient synthesis of poly(amide‐imide)s (6a–f) was achieved under microwave irradiation by using a domestic microwave oven from the polycondensation reactions of N,N′‐(Pyromellitoyl)‐bis‐L ‐phenylalanine diacid chloride (4) with six different derivatives of 5,5‐disubstituted hydantoin compounds (5a–f) in the presence of a small amount of a polar organic medium that acts as a primary microwave absorber. Suitable organic media was o‐cresol. The polycondensation proceeded rapidly, compared with the conventional melt polycondensation and solution polycondensation, and was almost completed within 10 min, giving a series of poly(amide‐imide)s with inherent viscosities about 0.28–0.44 dL/g. The resulting poly(amide‐imide)s were obtained in high yield and are optically active and thermally stable. All of the above compounds were fully characterized by means of FTIR spectroscopy, elemental analyses, inherent viscosity (η_inh), solubility test and specific rotation. Thermal properties of the poly(amide‐imide)s were investigated using thermal gravimetric analysis (TGA). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 516–524, 2004     

Preparation of a novel phosphorus‐ and nitrogen‐containing flame retardant and its synergistic effect in the intumescent flame‐retarding polypropylene system

A novel phosphorus‐ and nitrogen‐containing flame retardant (melamine phytate) was synthesized via the reaction between melamine and phytic acid. The chemical structure of melamine phytate (MPA) was confirmed by Fourier transform‐infrared spectra (FT‐IR) and elemental analysis. And the thermal behavior of MPA investigated by thermogravimetric analysis (TGA) demonstrates that MPA possesses a good char‐forming ability at high temperature. Besides, limiting oxygen index (LOI) and vertical burning tests (UL‐94) illustrate that polypropylene/melamine phytate/dipentaerythritol (PP/MPA/DPER) (70/22.5/7.5) can reach the LOI value of 28.5% and achieve V‐0 rating at the flame retardant loading of 30 wt%. Except that, the thermal weight loss of MPA and DPER in PP composites was investigated by TGA in detail. Moreover, the char residue of PP composite after combustion was systematically analyzed by FT‐IR, scanning electron microscope (SEM) and X‐ray photoelectron spectroscopy (XPS), which can further propose and confirm the flame retardant mechanism. POLYM. COMPOS., 36:1606–1619, 2015. © 2014 Society of Plastics Engineers     

Synergistic effects of exfoliated LDH with some halogen‐free flame retardants in LDPE/EVA/HFMH/LDH nanocomposites

The synergistic effects of exfoliated layered double hydroxides (LDH) with some halogen‐free flame retardant (HFFR) additives, such as hyperfine magnesium hydroxide (HFMH), microencapsulated red phosphorus (MRP), and expandable graphite (EG), in the low‐density polyethylene/ethylene vinyl acetate copolymer/LDH (LDPE/EVA/LDH) nanocomposites have been studied by X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermal analysis (TGA and DTG), mechanical properties, limiting oxygen index (LOI), and UL‐94 tests. The XRD results show that EVA as an excellent compatilizer can promote the exfoliation of LDH and homogeneous dispersion of HFMH in the LDPE/EVA/HFMH/LDH nanocomposites prepared by melt‐intercalation method. The TEM images demonstrate that the exfoliated LDH layers can act as synergistic compatilizer and dispersant to make the HFMH particles dispersed homogeneously in the LDPE matrix. The results from the mechanical, LOI, and UL‐94 tests show that the exfoliated LDH layers can also act as the nano‐enhanced and flame retardant synergistic agents and thus increase the tensile strength, LOI values, and UL‐94 rating of the nanocomposites. The morphological structures of charred residues observed by SEM give the positive evidence that the compact charred layers formed from the LDPE/EVA/HFMH/LDH nanocomposites with the exfoliated LDH layers play an important role in the enhancement of flame retardant and mechanical properties. The TGA and DTG data show that the exfoliated LDH layers as excellent flame retardant synergist of MRP or EG can apparently increase the thermal degradation temperature and the charred residues after burning. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and characterization of new optically active poly(amide‐imide)s derived from N,N‐(4,4′‐Oxydiphthaloyl)‐bis‐(s)‐(+)‐valine diacid chloride and aromatic diamines

4,4′‐Oxydiphthalic anhydride (1) was reacted with (s)‐(+)‐valine (2) in acetic acid and the resulting imide‐acid 3 was obtained in high yield. This compound 3 was converted to diacid chloride 4 by reaction with excess amount of thionyl chloride. The polycondensation reaction of diacid chloride 4 with several aromatic diamines such as 4,4′‐sulfonyldianiline (5a), 4,4′‐diaminodiphenyl methane (5b), 4,4′‐diaminodiphenylether (5c), p‐phenylenediamine (5d), m‐phenylenediamine (5e), and 4,4′‐diaminobiphenyl (5f) was performed by two conventional methods: low temperature solution polycondensation and a short period reflux conditions. To compare conventional solution polycondensation reaction methods with microwave‐assisted polycondensation, the reactions were also carried out under microwave conditions in the presence of small amount of o‐cresol that acts as a primary microwave absorber. The reaction mixture was irradiated for 4 min with 100% of radiation power. Several new optically active poly(amide‐imide)s with inherent viscosity ranging from 0.26–0.44 dL/g were obtained with high yield. All of the above polymers were fully characterized by ¹H‐NMR, FTIR, elemental analyses, and specific rotation techniques. Some structural characterizations and physical properties of these new optically active poly (amide‐imide)s are reported. POLYM. ENG. SCI. 46:558–565, 2006. © 2006 Society of Plastics Engineers     

Effect of nano‐titanium nitride on thermal insulating and flame‐retardant performances of phenolic foam

In this work, titanium nitride (TiN) nanoparticles were employed to achieve enhanced thermal insulation and flame retardance of phenolic foam (PF)/TiN nanocomposites (PFTNs) via in situ polymerization. The morphologies of PFTNs were observed by scanning electron microscope and the images showed that the PFTNs have more uniform cell morphologies compared with pure PF. Thermal insulating properties of PFTNs were evaluated by thermal conductivity tests. The introduction of TiN obviously decreased the thermal conductivities of PF over a wide temperature range (?20 to 60 °C). Significantly, the thermal conductivity of PFTNs gradually decreased as the temperature increased from 30 to 60 °C, showing a contrary tendency with that of pure PF. Moreover, the thermal stability and flame‐retardant properties of PFTNs were estimated by thermogravimetric analysis (TGA), UL‐94 vertical burning and limited oxygen index (LOI) tests, respectively. The TGA and LOI results indicated that PFTNs possess enhanced thermal stabilities and fire‐retardant performances with respect to the virgin PF. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43765.     

Morphology,thermal, and mechanical properties of flame‐retardant silicone rubber/montmorillonite nanocomposites

Flame‐retardant methyl vinyl silicone rubber (MVMQ)/montmorillonite nanocomposites were prepared by solution intercalation method, using magnesium hydroxide (MH) and red phosphorus (RP) as synergistic flame‐retardant additives, and aero silica (SiO₂) as synergistic reinforcement filler. The morphologies of the flame‐retardant MVMQ/montmorillonite nanocomposites were characterized by environmental scanning electron microscopy (ESEM), and the interlayer spacings were determined by small‐angle X‐ray scattering (SAXS). In addition to mechanical measurements and limited oxygen index (LOI) test, thermal properties were tested by thermogravimetric analysis (TGA). The decomposition temperature of the nanocomposite that contained 1 wt % montmorillonite can be higher (129°C) than that of MVMQ as basal polymer matrix when 5% weight loss was selected as measuring point. This kind of silicone rubber nanocomposite is a promising flame‐retardant polymeric material. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3275–3280, 2006     

Construction of novel silicon‐phosphorus linear polymers with DDSQ and DOPO derivatives for effective flame retardancy of PC/ABS

Two kinds of novel silicon‐phosphorus linear polymers were synthesized by the hydrosilylation reaction of double‐decker‐shaped silsesquioxane (DDSQ) and 9,10‐dihydro‐9‐oxa‐10‐ phosphaphenanthrene‐10‐oxide (DOPO) derivatives and characterized using ¹H NMR, ³¹P NMR, and ²⁹Si NMR. Flame‐retardant polycarbonate/acrylonitric‐butadiene‐styrene (PC/ABS) blends were prepared with different contents of silicon‐phosphorus linear polymers. The flame‐retardant properties of silicon‐phosphorus linear polymers as well as the morphology were investigated in detail by using thermogravimetric analysis (TGA), limiting oxygen index (LOI), (Underwriters Laboratory) UL‐94, microscale combustion calorimetry (MCC), and scanning electron microscopy (SEM), respectively. The silicon‐phosphorus linear polymers containing DDSQ and DOPO units can synergistically improve the flame retardancy and thermal stability of PC/ABS blends. Flame‐retardant polymers with different linkers between DDSQ and phosphate units show comparable effect on the flame retardancy of PC/ABS.     

The flame retardant group‐synergistic‐effect of a phosphaphenanthrene and triazine double‐group compound in epoxy resin

A flame retardant tri‐(phosphaphenanthrene‐(hydroxyl‐methylene)‐phenoxyl)‐1, 3, 5‐triazine (Trif‐DOPO) and its control samples are incorporated into diglycidyl ether of bisphenol‐A (DGEBA) and 4, 4′‐diamino‐diphenyl sulfone (DDS) to prepare flame retardant thermosets, respectively. According to the results of limited oxygen index (LOI), UL94 vertical burning test and cone calorimeter test, the Trif‐DOPO/DGEBA/DDS thermoset with 1.2 wt % phosphorus possesses the LOI value of 36% and UL94 V‐0 flammability rating, and Trif‐DOPO can decrease the peak of heat release rate (pk‐HRR) and reduce the total heat release (THR) of thermosets. All these prove better flame retardant performance of Trif‐DOPO than that of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide(DOPO). The residue photos of thermosets after cone calorimetry test disclose that Trif‐DOPO can promote the formation of thick and tough melting char layer for combined action of the flame retardant groups of Trif‐DOPO. The results from thermo gravimetric analysis (TGA) and pyrolysis‐gas chromatography‐mass spectrometry(Py‐GC/MS) show that the groups in Trif‐DOPO can be decomposed and produce PO₂ fragments, phosphaphenanthrene and phenoxy fragments, which can jointly quench the free radical chain reaction during combustion. Therefore, the excellent flame retardancy of Trif‐DOPO is attributed to its flame retardant group‐synergic‐effect. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39709.     

Microwave assisted polycondensation of polyimides by [4,4′‐(hexafluoroisopropylidene)diphthalic anhydride,pyromellitic dianhydride] and [2,4,6‐trimethyl‐m‐phenylenediamine]. Power,time, and solvent effect

The microwave assisted polycondensation of two polyimides were studied using pyromellitic dianhydride (PMDA), and 4,4′‐(hexafluoroisopropyliden)diphthalic anhydride (6FDA) as dianhydride monomers and 2,4,6‐trimethyl‐m‐phenylenediamine (TrmPD), as diamine monomer, under microwave irradiation in DMF and DMSO solvents. The structure and performance of polymers were characterized by Fourier Transform Infrared Spectroscopy (FTIR), viscosity, density, and Thermogravimetric Analysis (TGA). The results show that the polyimides can be obtained in a short reaction time with high intrinsic viscosity and high yield. The effect of the presence of a bridging group, ? C(CF₃)₂? , in the monomer structure is apparent in the permeability parameters of the macromolecules as polymer (6FDA‐TrmPD) always presents better results than polymer (PMDA‐TrmPD). Properties as density and T_g increases with the time exposition to the microwave irradiation. Polyimides obtained present good thermal properties because they began to lose weight in a range of 8–16% at high temperature as 450°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis,characteristic of a novel flame retardant containing phosphorus and its application in poly(ethylene‐co‐vinyl acetate)

A novel flame retardant (SPDH) containing phosphorus was synthesized through the reaction of 10‐(2, 5‐dihydroxyphenyl)‐9, 10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO‐HQ) and synthesized intermediate product 3, 9‐dichloro‐2, 4, 8, 10‐tetraoxa‐3, 9‐diphosphaspiro(5.5)undecane‐3, 9‐dioxide (SPDPC). The structure and properties of SPDPC and SPDH were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) spectroscopy and thermogravimetric analysis (TGA). After blending with poly(ethylene‐co‐vinyl acetate) (EVA), the flame‐retardant properties of EVA/SPDH composites were estimated by cone calorimeter, limited oxygen index (LOI) and UL‐94 tests, whereas the thermal stabilities were investigated using TGA. The morphological microstructure of the char formed by EVA/SPDH composite after combustion in cone calorimeter was investigated by scanning electron microscopy (SEM). The results indicate that the flame retardant and thermal stability were improved by incorporation of SPDH. The rich foamy char layers were observed from the residues after combustion in a cone calorimeter, which exactly benefits the improvement of thermal stability and flame retardant property of materials. Copyright © 2010 John Wiley & Sons, Ltd.     

Application of a novel halogen‐free intumescent flame retardant for acrylonitrile‐butadiene‐styrene

A novel intumescent flame retardant (IFR), containing ammonium polyphosphate (APP) and poly(tetramethylene terephthalamide) (PA4T), was prepared to flame‐retard acrylonitrile‐butadiene‐styrene (ABS). The flame retardation of the IFR/ABS composite was characterized by limiting oxygen index (LOI) and UL‐94 test. Thermogravimetric analysis (TGA) and TGA coupled with Fourier transform infrared spectroscopy (TG‐FTIR) were carried out to study the thermal degradation behavior of the composite and look for the mechanism of the flame‐retarded action. The morphology of the char obtained after combustion of the composite was studied by scanning electron microscopy (SEM). It has been found the intumescent flame retardant showed good flame retardancy, with the LOI value of the PA4T/APP/ABS (7.5/22.5/70) system increasing from 18.5 to 30% and passing UL‐94 V‐1 rating. Meanwhile, the TGA and TG‐FTIR work indicated that PA4T could be effective as a carbonization agent and there was some reaction between PA4T and APP, leading to some crosslinked and high temperature stable material formed, which probably effectively promoted the flame retardancy of ABS. Moreover, it was revealed that uniform and compact intumescent char layer was formed after combustion of the intumescent flame‐retarded ABS composite. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of novel optically active poly(amide–imide)s containing N,N′‐(pyromellitoyl)‐bis‐L‐valine diacid chloride and 5,5‐disubstituted hydantoin derivatives under microwave irradiation

Pyromellitic dianhydride (1,2,4,5‐benzenetetracarboxylic acid 1,2,4,5‐dianhydide) was reacted with L ‐valine in a mixture of acetic acid and pyridine (3:2) at room temperature, and then was refluxed at 90–100 °C, N,N′‐(pyromellitoyl)‐bis‐L ‐valine diacid was obtained in quantitative yield. The imide–acid was converted to N,N′‐(pyromellitoyl)‐bis‐L ‐valine diacid chloride by reaction with thionyl chloride. Rapid and highly efficient synthesis of a number of poly(amide–imide)s was achieved under microwave irradiation using a domestic microwave oven by polycondensation of N,N′‐(pyromellitoyl)‐bis‐L ‐valine diacid chloride with six different derivatives of 5,5‐disubstituted hydantoin compounds in the presence of a small amount of a polar organic medium that acts as a primary microwave absorber. A suitable organic medium was o‐cresol. The polycondensation proceeded rapidly, compared with conventional melt polycondensation and solution polycondensation and was almost completed within 8 min, giving a series of poly(amide–imide)s with inherent viscosities in the range 0.15–0.36 dl g^?1. The resulting poly(amide–imide)s were obtained in high yield and are optically active and thermally stable. All of the above compounds were fully characterized by Fourier‐transform infrared (FT‐IR) spectroscopy, elemental analysis, inherent viscosity (η_inh) measurements, solubility testing and specific rotation measurements. The thermal properties of the poly(amide–imide)s were investigated by using thermogravimetric analysis. Copyright © 2004 Society of Chemical Industry     

Flame‐retarding mechanism of organically modified montmorillonite and phosphorous‐Nitrogen flame retardants for the preparation of a halogen‐free,flame‐retarding thermoplastic poly(ester ether) elastomer

In this study, thermoplastic poly(ester ether) elastomer (TPEE) nanocomposites with phosphorus–nitrogen (P–N) flame retardants and montmorillonite (MMT) were prepared by melt blending. The fire resistance of the nanocomposites was analyzed by limiting oxygen index (LOI) and vertical burning (UL 94) tests. The results show that the addition of the P–N flame retardants increased the LOI of the material from 17.3 to 27%. However, TPEE containing P–N flame retardants only obtained a UL 94 V‐2 ranking; this resulted in a flame dripping phenomenon. On the other hand, TPEE containing the P–N flame retardant and organically modified montmorillonite (o‐MMT) achieved better thermal stability and good flame retardancy; this was ascribed to its partially intercalated structure. The synergistic effect and synergism were investigated by Fourier transform infrared spectroscopy and thermogravimetry. The introduction of o‐MMT decreased the inhibition action of the P–N flame retardant and increased the amount of residues. The catalytic decomposition effect of MMT and the barrier effect of the layer silicates are discussed in this article. The residues after heating in the muffle furnace were analyzed by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and laser Raman spectroscopy. It was shown that the intercalated layer silicate structure facilitated the crosslinking interaction and promoted the formation of additional carbonaceous char residues in the formation of the compact, dense, folded‐structure surface char. The combination of the P–N flame retardant and o‐MMT in TPEE resulted in a better thermal stability and fire resistance because of the synergistic effect of the mixture. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41094.     

Flammability and thermal degradation of epoxy acrylate modified with phosphorus‐containing compounds

A series of UV‐curable flame‐retardant resins was obtained by blending phosphate acrylate (BTP) in different ratios with epoxy acrylate resin (EA). The flammability was characterized by limiting oxygen index (LOI), UL 94 flammability rating and cone calorimeter, and the thermal degradation of the flame‐retardant resins was studied using thermo gravimetric analysis (TGA), and real‐time Fourier transform infrared (RTFTIR). The results indicated that the flame‐retardant efficiency increases with the addition of BTP. The heat release rate with the addition of BTP decreases greatly. The TGA data showed that EA/BTP blends have lower initial decomposition temperatures and higher char residues than pure EA, whereas BTP has the lowest initial decomposition temperature and the highest char residue. The RTFTIR study indicates that the EA/BTP blends have lower thermal oxidative stability than the pure EA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010