High-strength fire- and heat-resistant imide resins containing cyclotriphosphazene and hexafluoroisopropylidene groups

High-strength fire- and heat-resistant polymers were obtained by the thermally induced melt-polymerization of maleimido-phenoxy cyclotriphosphazenes linked by hexafluoroisopropyliden-ediphthalimide groups. These polymers show good thermal stability and high char yields: 78–80% at 800°C in nitrogen and 60–68% in air at 700°C. Graphite-fabric laminates did not burn in pure oxygen, even at 300°C (LOI = 100%), and were tested for shear, flexural, and tensile strengths. Two monomers were synthesized by reacting tris(4-aminophenoxy)-tris(phenoxy) cyclotriphosphazene with maleic anhydride and hexafluoroisopropylidenediphthalic anhydride. The triamine was synthesized by a stepwise reaction of hexachlorocyclotriphosphazene with phenol and 4-nitrophenol to give tris(4-nitrophenoxy)-tris(phenoxy)cyclotriphosphazene and reducing the nitro groups. The structures of cyclic phosphazene-trimeric precursors and the polymers were characterized by FT-IR, ¹H-NMR, ³¹P-NMR, and mass spectroscopy. The curing behaviors of polymer precursors were evaluated by differential scanning calorimetry and thermogravimetric analyses.     

Bis-, tris-, and tetrakis-maleimidophenoxy-triphenoxycyclotriphosphazene resins for fire- and heat-resistant applications

Novel fire- and heat-resistant polymers was obtained by the thermal polymerization of various maleimidophenoxy-triphenoxycyclotriphosphazenes. These polymers, in which the cyclic triphosphazene structure is preserved, have thermal stability to 350°C and char yields of 82–78% at 800°C in nitrogen and 78–71% at 700°C in air. Two groups of monomers were synthesized by reacting tris(4-aminophenoxy)-tris(phenoxy)cyclotriphosphazene with maleic anhydride alone or in combination with benzophenonetetracarboxylic or pyromellitic dianhydride. The structures of cyclic phosphazene-trimeric precursors and the polymers were characterized by Fourier-transform infrared, proton nuclear magnetic resonance, and elemental analysis. The thermal stabilities of the polymers were evaluated by thermogravimetric analysis.     

New polypyromellitimide films based on cyclotriphosphazene and bisaspartimide derived diamines

Three new thermally stable polypyromellitimide films were made by the thermal cyclodehydration of the corresponding polyamic acids obtained by the polymerization of pyromellitic dianhydride with 4,4′-bis{N²-[4-(4-aminobenzyl)phenyl]aspartimido} diphenylmethane, 4,4′-bis{N²-[4-(4-aminophenoxy)phenyl]aspartimido} diphenylether, and bis(4-aminophenoxy)tetrakis (4-phthalamic acid phenoxy)cyclotriphosphazene. The bis(4-aminophenoxy)tetrakis (4-phthalamic acid phenoxy)cyclotriphosphazene was obtained from hexakis(4-aminophenoxy)cyclotriphosphazene involving its reaction with phthalic anhydride. The structure of these materials and precursors were characterized by using Fourier-transform-infrared (FT–IR) and proton nuclear magnetic resonance spectroscopy. The thermal stabilities of the films were evaluated by the thermogravimetric analysis, showing char yields at 800°C ranging from 68% to 58% in a nitrogen atmosphere and 24% in air atmosphere.     

Polybismaleimide containing tetrakisphenoxycyclotriphosphazenes

A heat-resistant polybismaleimide was obtained by the thermal polymerization of bis(maleimidophenoxy)- tetrakis(phenoxy)cyclotriphosphazene. The thermal stabilities of the polybismaleimide were evaluated in nitrogen and in air by thermogravimetric analysis. The polybismaleimide was stable to 340°C and has char yield of 70% at 800°C in nitrogen and of 60% at 700°C in air. The monomer bismaleimide was obtained by the reaction of bis(4-aminophenoxy)tetrakis(phenoxy)cyclotriphosphazene with maleic anhydride. The diamine was synthesized by a stepwise reaction of hexachlorocyclotriphosphazene with phenol and 4-nitrophenol to give bis(4-nitrophenoxy)tetrakis(phenoxy)cyclotriphosphazene and reducing the nitro groups. The structure of the cyclotriphosphazenes were characterized using Fourier transform infrared (IR), proton nuclear magnetic resonance (¹H-NMR) spectroscopy, and elemental analysis.     

Fire- and heat-resistant polymer based on maleimido-substituted 2,2-bis(anilino)-4,4,6,6-tetrakis-(4-aminophenoxy)-cyclotriphosphazene

A fire- and heat-resistant polymer was obtained by the thermal polymerization of bismaleimido-substituted 2,2-bis(anilino)-4,4,6,6-tetrakis-(4-Aminophenoxy)-cyclotriphosphazene. The thermal stabilities of the polymer were evaluated in nitrogen and in air by thermogravimetric analysis. This polymer was stable to 345°C and had char yields of 78% at 800°C in nitrogen and of 71% at 700°C in air. The structures of cyclotriphosphazene precursors and the polymer were characterized using Fourier-transform infrared and proton nuclear magnetic resonance spectroscopy.     

Heat-resistant thermosetting polymers based on a novel tetrakisaminophenoxycyclotriphosphazene

Two heat-resistant thermosetting polymers ( IX and X ) have been developed based on a new cyclotriphosphazene containing tetrakisamine. These polymers were synthesized by the reaction of tetrakisamine ( IV ) with maleic anhydride followed by in situ cyclodehydration and polymerization of the maleimides ( VII and VIII ) at 235–240°C for 1.5 h and 290°C for 0.5 h. The thermogravimetric analyses (TGA) of the developed cyclotriphosphazene containing cyclomatrix polymers showed their thermal stability up to 350°C and char yield of 71% in nitrogen at 800°C and 65% in air at 700°C. The monomer, 2,2,4,4-tetrakis(4′-aminophenoxy) -6,6-diphenylcyclotriphosphazene ( IV ), useful for producing a variety of heat- and fire-resistant polymers, has been synthesized in good yield. Its syntheses involve Friedel-Crafts reaction of hexachlorocyclotriphosphazene ( I ) with benzene followed by the reaction of 2,2,4,4-tetrachloro-6,6-diphenylcyclotriphosphazene ( II ) with potassium 4-nitrophenoxide. The reduction of the obtained 2,2,4,4-tetrakis(4′-nitrophenoxy)-6,6-diphenylcyclotriphosphazene ( III ) with molecular hydrogen in presence of PtO₂ gave the tetrakisamine ( IV ). The structure of the synthesized monomer and intermediates were characterized by FT-IR, ¹H-NMR, ³¹P-NMR, mass spectroscopy, differential scanning calorimetry (DSC), and elemental analysis. These resins are potential candidates for the development of heat- and fire-resistant composites, laminates, and adhesives, useful for space, aerospace, and electronic application. © 1993 John Wiley & Sons, Inc.     

Bismaleimides chain-extended by imidized benzophenone tetracarboxylic dianhydride and their polymerization to high temperature matrix resins

Heat-resistant polymers were obtained by thermal polymerization of several bismaleimides or their substituted derivatives. The chain of the polymer precursors was extended by incorporation of imidized benzophenone tetracarboxylic dianhydride between the maleimide rings in order to impart a degree of flexibility in the polymers. The bismaleimides and their corresponding tetraamic acids were characterized by infrared (IR) and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. The differential thermal analysis (DTA) thermograms of the monomers showed exotherms at 200–340°C attributed to the thermally induced polymerization reactions. The influence of different substituents in the maleic double bond on the curing temperature was investigated. The thermal stability of the cured resins was evaluated by thermogravimetric analysis (TGA) and isothermal gravimetric analysis (IGA). They were stable up to 367–433°C both in nitrogen and air atmosphere and afforded 57–68% char yield at 800°C under anaerobic conditions. The structure of the aromatic and aliphatic diamines utilized for imidization was correlated with the thermal stability of the cured resins. The bismaleimide derived from p-phenylenediamine gave the most heat-resistant resin because of its higher rigidity.     

Synthesis and characterization of aromatic poly(ether ketone)s containing cyclotriphosphazene units

Bis(4-oxybenzoic acid) tetrakis(phenoxy) cyclotriphosphazene (IUPAC name: 4-[4-(carboxyphenoxy)-2,4,6,6-tetraphenoxy-1,3,5,2λ⁵,4λ⁵,6λ⁵-triazatriphosphinin-2-yl]oxy-benzoic acid) was synthesized and direct polycondensed with diphenylether or 1,4-diphenoxybenzene in Eaton's reagent at the temperature range of 80–120°C for 3 hours to give aromatic poly(ether ketone)s. Polycondensations at 120°C gave polymer of high molecular weight. Incorporation of cyclotriphosphazene groups in the aromatic poly(ether ketone) backbone greatly enhanced the solubility of these polymers in common organic polar solvents. Thermal stabilities by TGA for two polymer samples of polymer series ranged from 390 to 354°C in nitrogen at 10% weight loss and glass transition temperatures (T_g) ranged from 81.4 to 89.6°C by DSC. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1227–1232, 1998     

Heat-resistant polymers from melt-processable bisimido-bisphthalonitriles

Heat-resistant polymers which are processable into void-free components and suitable for composite applications have been synthesized by thermal/chemical polymerization of four newly developed bisimido-bisphthalonitriles containing silicon, ether, carbonyl, and hexafluoroisopropylidene groups. Thermal polymerization involving addition reactions was performed at 200–275°C for 2–10 h and then post-curing at 310°C for 10 h. Polymers VI, VII, VIII , and IX were obtained. The thermal polymerization was monitored using infrared spectroscopy. Thermal polymerization was also carried out in the presence of an aromatic diamine. A polyhexasocyclane ( V ) was synthesized by condensation polymerization of ether containing bisimido-bisphthalonitrile with 4,4′-diaminodiphenyl ether in solvent phenol. The synthesized polymers were evaluated for thermal stability using dynamic thermogravimetric analysis (TGA). Polymers VII, VIII, IX , and X showed thermal decomposition temperature in the range of 475–500°C in nitrogen and air atmosphere. The char yield of the polymers was in the range of 60–69% in nitrogen at 800°C. This study indicated that synthesized thermosetting polymers from ether and keto containing bisimido-bisphthalo-nitrile are potential candidates for development of graphite composites. © 1993 John Wiley & Sons, Inc.     

High temperature phosphorylated or nonphosphorylated laminating resins based on maleimido-substituted aromatic s-triazines

Several new phosphorylated or nonphosphorylated maleimide or nadimide systems containing s-triazine rings were synthesized. Their synthesis was accomplished by simple methods utilizing readily available and relatively inexpensive starting materials. All polymer precursors were characterized by infrared (IR) and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. They were thermally polymerized to heat-resistant laminating resins. Thermal characterization of monomers and their cured resins was achieved using differential thermal analysis (DTA), dynamic thermogravimetric analysis (TGA) and isothermal gravimetric analysis (IGA). The cured resins were stable up to 304–330°C both in nitrogen and air atmospheres and formed anaerobic char yield 49–59% at 800°C. The phosphorylated polymers showed a lower temperature of initial weight loss but afforded higher anaerobic char yield than did the corresponding nonphosphorylated polymers. The thermal properties of the polymers were correlated with their chemical structure.     

Studies on metathetical and thermal polymerization of 5-norbornene 2,3-dicarboximide end-capped resins Pt-II

The article deals with synthesis, characterization, and polymerization of 5-norbornene-2,3-dicarboximide end-capped resins (bisnadimides) based on 4,4′-diaminodiphenylether, 1,4/1,3-bis(4′-aminophenoxy) benzene, 2,2′-bis[4-(4′-aminophenoxy)phenyl]propane, and bis[4-(4′-aminophenoxy)phenyl]sulphone. Both exo and endo bisnadimides were prepared by reacting the aromatic diamines with exo or endo nadic anhydride in glacial acetic acid at 120°C. The exo or endo bisnadimides could be distinguished on the basis of differences observed in IR or ¹H-NMR spectra. Both thermal (in solid state) and metathetical polymerization (using WCl₆/tetramethyltin catalyst and chlorobenzene solvent) of bisnadimides was carried out. Only exo bisnadimides could be polymerized using metathesis reaction whereas thermal polymerization of both endo and exo bisnadimide could be successfully carried out at 300°C in static air atmosphere. The polymers were highly crosslinked and insoluble in common organic solvents. The polymers obtained by metathesis polymerization were light brown in color whereas those obtained by thermal polymerization were dark brown in color. Thermal stability of the thermally polymerized exo or endo bisnadimides was comparable. These polymers were stable up to 400°C and decomposed in a single step above this temperature. The char yield at 800°C depended on the structure of the polymer and was in the 39–56% range. The polymers formed by metathesis polymerization showed a 1–3% weight loss in the temperature range 226–371°C and decomposed in a single step above 440°C. The char yields were higher in these polymers (53–71%) compared to those obtained by thermal polymerization. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2323–2331, 1997     

Synthesis and Characterization of a Novel Cyclomatrix Phosphazene Polymer

Novel phosphazene cyclomatrix network polymers were synthesized via the nucleophilic displacement of activated nitro groups of tri(4-nitrophenoxy)tri(phenoxy)cyclotriphosphazene and hexa(p-nitrophenoxy) cyclotriphosphazene with hydroxyls of bisphenol A. Both monomers and polymers were characterized by Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance, and elemental analysis measurements, and their structures were identified. Thermal properties of polymers were investigated using dynamic thermogravimetric analysis in air. The results demonstrated that both cyclomatrix phosphazene polymers 4 and 6 were of excellent thermal stability, and their char yields in air at 800°C were 45.1 and 43.2%, respectively. According to combustion phenomenon, polymer 4 was supposed to be processed with a good flame-retardant property because of its excellent crosslinked structure during pyrolysis or combustion. However, polymer 6 yielded the opposite result. Translated from the Journal of Beijing University of Chemical Technology, 2005, 32(2) (in Chinese) This study was supported by the National High Technology Research and Development Foundation (2002AADF3202)     

Synthesis,thermal property and hydrolytic degradation of a novel star-shaped hexa[p-(carbonylglycinomethylester)phenoxy]cyclotriphosphazene

A novel star-shaped cyclotriphosphazene substituted by glycinomethylesterphenoxy and its intermediates are synthesized from hexachlorocyclotriphosphazene (HCCP). The structures are characterized by ¹H NMR, ¹³C NMR, 31P NMR, FTIR and elemental analysis. Their thermal properties are clarified by thermogravimetric analysis (TGA), differential scanning calorimentry (DSC) and FTIR, while hydrolytic degradation behaviour is studied with UV-vis spectrophotometer and by measuring the weight loss, and the phosphorus content of residue. According to hydrolysis behaviour of hexa[p-(carbonylglycinomethylester)phenoxy]cyclotriphosphazene (HGPCP) under different conditions, it is easy to hydrolyze in hydrochloric acid (pH 1.0) than in phosphate buffer (pH 7.4) at 37°C. And the sample hydrolytic degradation still remains at the stage of side groups’ break. The TGA data show that the thermal stability of the hexa[p-(aldehyde)phenoxy]cyclotriphosphazene (HAPCP), hexa[p-(carboxyl) phenoxy]cyclotriphosphazene (HCPCP) and HGPCP is so high that their char residues are 75%, 47% and 47% at 800°C, respectively, probably due to cross-linking between molecules.     

Crosslinking of polyimides via spirodilactone unit in polymer backbone

A new approach for the crosslinking of polyimides via the lactamization of spirodilactone unit in polyimide backbone was studied by two means: model reaction and the comparison of the properties of the polyimide precursors to those of the crosslinking polymers. Polyimides 4 and 5 were soluble in N,N′dimethylacetamide (DMAc), dimethylformamide (DMF), dimethylsulfoxide (DMSO), N′-methylpyrrolidone (NMP), and other common organic solvents, whereas their corresponding crosslinking polymers were insoluble in these solvents. The glass transition temperatures for polyimide 5 and its crosslinking polymer were 262°C and 291°C, whereas those for polyimide 4 and its crosslinking polymer were 265°C and 360°C. The weight-loss rate of the crosslinking polymers was apparently slower than that of the precursors when the temperature was > 400°C. The 10% weight-loss temperature for the polyimides 4 and 5 was < 500°C, whereas that for the crosslinking polymers was close to or above 600°C. The results indicate that this type of crosslinking polymer has good thermal properties. The temperature for the formation of lactam was above 180°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3680–3686, 1999     

Bis- or tetra-maleimides of substituted s-triazines chain-extended by imide,amide, and urea groups for fire- and heat-resistant applications

Novel phosphorylated bismaleimides and nonphosphorylated tetramaleimides containing substituted s-triazine rings (chain-extended by imide, amide, or urea groups) were prepared and polymerized. These polymer precursors were prepared by reacting 2,4-bis(4-aminophenoxy)-6-diethoxyphosphinyl-s-triazine or 2,4,6-tris(4-aminophenoxy)-s-triazine with maleic anhydride in combination with a bridging agent such as pyromellitic or benzophenone tetracarboxylic dianhydride, terephthaloyl chloride, and tolylene diisocyanate. The structure of polymer precursors was confirmed by infrared (IR) and proton nuclear magnetic resonance (¹H-NMR) spectroscopy and their curing behavior was investigated by differential thermal analysis (DTA). The phosphorylated bismaleimides were thermally polymerized at a lower temperature than did the corresponding nonphosphorylated tetramaleimides. Dynamic thermogravimetric analysis (TGA) showed that the nonphosphorylated and phosphorylated cured resins were stable up to 320–370 and 312–327°C, respectively, in nitrogen or air atmosphere. In addition, the latter afforded a relatively higher char yield. The relative thermal and thermooxidative stability of polymers with regard to the chemical structure of the bridging group was of the order imide > amide > urea. Upon isothermal aging the phosphorylated polymers exhibited a lower weight loss than did the corresponding nonphosphorylated polymers.     

Thermally stable polymers based on bismaleimides containing amide,imide, and ester linkages

Seven new structurally different bismaleimides were synthesized and characterized by infrared and proton nuclear magnetic resonance spectroscopy. The chain of these polymer precursors was extended by incorporating amidized, imidized, and esterified 4-chloroformyl phthalic anhydride. The bismaleimides containing amide and imide linkages were prepared by a simple synthetic route based on the reaction of the monomaleamic acid derived from various aromatic diamines (1 mol) with 4-chloroformyl phthalic anhydride (0.5 mol) and subsequent cyclodehydration of the intermediate triamic acid. In addition, chain extended bismaleimides were prepared by reacting the monomaleamic acid derived from p-phenylenediamine with several dianhydrides such as p-phenylene bis(trimellitamide anhydride), p-phenylene bis(trimellitate anhydride), and bis-phenol A bis(trimellitate anhydride). The differential thermal analysis scans of bismaleimides showed exotherms at 221–304°C associated with their polymerization reactions. The thermogravimetric analysis traces of polymers did not show a weight loss up to 351–393 and 344–372°C in N₂ and air atmospheres, respectively. The anaerobic char yield of polymers at 800°C was 44–61%. These polymers can be used for fabrication of composites having improved properties.     

Synthesis and Characterization of Heat-Resistant Polyamides from Thiadiazacycloheptatriene Dicarboxylic Acid

Novel polyamides containing 2,3,6,7-dibenzo-1-thia-4,5-diazacy-clohepta-2,4,6-triene-4′,4″-dicarboxy-l, l-dioxide (VII) are reported. The acid VII was prepared in several steps from p-chlorobenzoic acid and characterized by spectral data and elemental analysis. Prior to polymer synthesis, a model diamide (MDA) was prepared from VII and p-toluidine. The model diamide and several polyamides were obtained in an overall yield of (75-90%) by direct polycondensation of acid VII with certain diamines through a phosphorylation reaction at 100-110°C employing a solvent mixture of NMP-pyridine. The resulting polyamides and MDA were characterized by spectral, analytical, and thermal methods. The solubility, density, viscosity, and morphology (X-ray) were also studied for the polyamides. These polymers were moderately soluble in conventional polymer solvents, and the inherent viscosities were measured in concentrated sulfuric acid. Integral procedural decomposition temperatures (ipdt) were calculated from their primary thermogram in the temperature range 100-650°C in order to have quantitative data regarding their relative thermal stabilities. The polymers exhibit a 10% weight loss at 500°C in static air.     

Synthesis and characterization of aromatic poly(ether ketone)s containing cyclotriphosphazene units. II

A new monomer di(4‐carboxyphenoxy) tetrakis(4‐fluorophenoxy)cyclotriphosphazene 1 was synthesized in a two‐step reaction sequence. The direct polycondensation of 1 and/or 4,4′‐dicarboxydiphenylether with aromatic ethers was carried out in P₂O₅/methanesulfonic acid (Eaton's reagent) at 120 °C for 3 h to give two series of aromatic poly(ether ketone)s containing cyclotriphosphazene units. The effect of the introduction of the cyclotriphosphazene group on the solubility and thermal properties of these polymers was discussed with relation to the cyclotriphosphazene contents. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2300–2305, 2000     

Studies of Some Newer Polyhydrazides Containing Amide Linkages. Part 1

An attempt has been made to prepare some new polyamide hydrazides of high thermal stability with different dicarboxylic acid chlorides by the solution polymerization technique. The polymerization was carried out at -20°C. Amide linkage was present in each polymer unit. Results of thermal degradation and thermogravimetric analysis indicate that these polymers melt or decompose above 350°C, and the steep weight loss of the polymer takes place in the range 360–390°C. Most of the polyhydrazides are soluble in organic solvents.     

Biaspartimide-diamines as Curing Agents for Epoxy Resins

Various 4,4′ -bis(N²-[4-(4-aminophenoxy)phenyl]aspartimido)diphenylmethane-type bisaspartimide-diamines have been used as solventless curing agents for epoxy resins. The thermal curing was performed at 170, 190, and 230°C to give a tough brown polymer. Thermogravimetric analysis of the polymer obtained showed thermal stability up to 330°C and char yields of 45% in N₂ at 800°C and 12% in air at 700°C. The thermal curing reaction was monitored using FT-IR. The synthesized polymers are useful for making composites, laminates, and adhesives.