Isothermal Gravimetric Analysis Research Articles

Aromatic polyamides and polyimides with benzimidazole or benzoxazinone pendent groups prepared from 5-(2-benzimidazole)- or 5-(2-benzoxazinone)-1,3-phenylenediamine

Abstract New aromatic polyamides and polyimides containing benzimidazole or benzoxazinone pendent groups were prepared from 5-(2-benzimidazole)- or 5-(2-benzoxazinone)-1,3-phenylenediamine. They were characterized by inherent viscosity and water absorption measurements, Fourier transform infra-red, 1 H nuclear magnetic resonance, X-ray, thermomechanical, thermogravimetric and isothermal gravimetric analyses. Their properties were compared with those of the parent polymers derived from 1,3-phenylenediamine. The modified polymers displayed better solubility than the unmodified ones and dissolved in polar aprotic solvents and certain inorganic and organic acids. The polyamides bearing benzimidazole or benzoxazinone pendent groups exhibited higher or lower, respectively, hydrophilicity than the reference polyamide. All modified polymers were amorphous and showed lower glass transition temperatures and thermal stability than the corresponding unmodified ones. Some of them softened in the region of 133–205°C.

Poly-schiff bases—II. Synthesis and characterization of polyetherketoimines

Six new poly-Schiff bases have been synthesized by solution polycondensation of six different diamines with 4,4′-aryl bis-(oxy)-bis acetophenone. The synthesized polymers were characterized by viscosity measurement, elemental analyses, i.r., X-ray diffraction, and differential scanning calorimetry. The thermal stability of the polymers was evaluated by thermogravimetric and isothermal gravimetric analysis. The polymers cured at a high temperature by the opening of C(CH 3)N linkages. The electrical conductivities of the virgin and iodinedoped polymers are as high as 10 −11 – 10 −16 and 10 −9 − 10 −6 S/cm, respectively, at 30 °C. Variation in the electrical conductivity (σ) with temperature followed the empirical relation σ = σ 0e −E a RT .

Soluble, Rigid-Rod Polyamide, Polyimides, and Polyazomethine with Phenyl Pendent Groups Derived from 4,4‘‘-Diamino-3,5,3‘‘,5‘‘-tetraphenyl-p-terphenyl

The reaction of 4,4‘-(1,4-phenylene)bis(2,6-diphenylpyrylium tetrafluoroborate) with nitromethane afforded 4,4‘‘-dinitro-3,5,3‘‘,5‘‘-tetraphenyl-p-terphenyl, which was catalytically hydrogenated to the corresponding diamine. The latter was used as starting material for the preparation of new rigid-rod polyamide, polyimides, and polyazomethine bearing phenyl pendent groups as well as the respective model compounds. Characterization of polymers was accomplished by inherent viscosity measurements, elemental analysis, 1H-NMR, 13C-NMR, X-ray, DTA, TMA, TGA, and isothermal gravimetric analysis. The polymers were amorphous and soluble in polar aprotic solvents. Polyamide showed an outstanding solubility, being soluble even in o-dichlorobenzene and chloroform. Polyamide displayed Tg and softening temperature at 135 and 155 °C, respectively, whereas other polymers showed only Tg above 265 °C. The polymers were stable up to 397−441 °C in N2 and 344−363 °C in air and afforded anaerobic char yields of 68−77% at 800 °...

Modified polyisophthalamides bearing furamido pendant groups

A new series of modified polyisophthalamides containing pendant furamido groups was prepared from 5-(furamido)isophthalic acid and various aromatic diamines by the phosphorylation method. The chemical, physical and thermal properties of these polyamides were compared to those of the analogous unmodified ones. The modified polyamides exhibited better solubility in certain solvents such as m-cresol, cyclohexanone and trichloroacetic acid than their unmodified counterparts. In addition, the incorporation of the pendant furamido groups in the polyisophthalamide backbone brought about some substantial increase of the thermal stability as measured by TGA and isothermal gravimetric analysis. The crosslinked modified polyamides obtained upon curing at 300 °C for 20 hr were stable up to 321–340 °C in N 2 or air and afforded anaerobic char yields of 61–67% at 800 °C. Water absorption and X-ray measurements were also performed.

Aromatic Polyamides and Polyimides with Benzoxazole or Benzothiazole Pendent Groups Prepared from 5-(2-Benzoxazole)- or 5-(2-Benzothiazole)-1,3-phenylenediamine

A series of polyamides and polyimides containing pendent benzoxazole or benzothiazole pendent groups were prepared from two new monomers, 5-(2-benzoxazole)- or 5-(2-benzothiazole)-1,3-phenylenediamine. In addition, model compounds were synthesized and characterized by elemental analyses, FT-IR, and 1 H-NMR. Characterization of polymers was accomplished by inherent viscosity measurements, FT-IR, X-ray, DTA, TGA, and isothermal gravimetric analysis. Water absorption studies were also carried out for the polyamides. The properties of the modified polymers were correlated with those of the corresponding unmodified ones. The solubilities of modified polyamides in common organic solvents as well as their hydrophilicities were enhanced compared to these of the corresponding unmodified polyamides. The synthesized polyamides softened between 200 and 300 °C, but no softening was observed for the polyimides. The modified polyamides and polyimides suffered less weight loss under TGA and isothermal gravimetric analysis than the parent structures. Their initial decomposition temperatures in N 2 or air and the anaerobic char yields at 800 °C were, respectively, 24-68 °C and 5-9% higher than those of the unmodified polymers.

Polyisophthalamides with pendent phthalimide groups

Certain structurally different polyisophthalamides containing pendent phthalimide groups were synthesized from 5-(phthalimide)isophthalic acid and aromatic diamines by the phosphorylation method. Their chemical, physical and thermal properties were determined and compared with those of the corresponding unsubstituted polyisophthalamides. The polymers were characterized by FTi.r., 1H n.m.r., thermogravimetric analysis, isothermal gravimetric analysis and inherent viscosity measurements. The modified polyisophthalamides showed enhanced solubilities in some solvents, such as 1,4-dioxane, m-cresol and trichloroacetic acid, in comparison to the unmodified analogues. In addition, the incorporation of the pendent phthalimide groups in the polyisophthalamide backbone increased remarkably the thermal stability of the polymer. The modified polyamides were stable up to 317–351°C in N2 or air and afforded anaerobic char yields of 55–66% at 800°C. Water absorption and X-ray measurements were also performed.

Unsaturated polyamides with pendent cyano groups derived from 1,4-bis(2-cyano-2-carboxyvinyl)benzene

Various homopolyamides and copolyamides bearing olefinic bonds and pendent cyano groups were prepared by reacting aromatic diamines with the acid chloride of 1,4-bis(2-cyano-2-carboxyvinyl)benzene. In addition, the latter reacted with aniline to afford a model diamide. The monomers were characterized by infra-red and 1H nuclear magnetic resonance spectroscopy, as well as by elemental analyses. Characterization of polyamides was accomplished by infra-red spectroscopy, differential thermal analysis, thermogravimetric analysis, isothermal gravimetric analysis and inherent-viscosity measurements. The synthesized homopolyamides were soluble in polar aprotic solvents and certain strong inorganic and organic acids. Upon thermal curing, crosslinked polymers were obtained. The thermal stabilities of cured resins were correlated with the curing conditions and their composition. They were stable up to 391–407°C in N 2 or air and afforded anaerobic char yield of 64–70% at 800°C.

Polyamides containing olefinic bonds

AbstractThe reaction of 2,5‐dimethylpiperazine with a double molar amount of maleic anhydride afforded a new unsaturated dicarboxylic acid that was characterized by IR and 1H‐NMR spectroscopy. It was condensed with various aromatic diamines by the phosphorylation method to yield polyamides bearing olefinic bonds. They were readily soluble in polar aprotic solvents and certain acids. The DTA traces of polyamides showed exotherms above 250°C attributable to their cross‐linking through the olefinic bonds and a partial thermal degradation. Evidence for the cross‐linking of polyamides attained during their heat‐curing was obtained from the IR spectra of the uncured and cured samples. Thermal stabilities of cured (at 300°C for 15 h) polyamides were evaluated by TGA and isothermal gravimetric analysis. They were stable up to 321–336°C in N2 or air and afforded an anserobic char yield of 61–71% at 800°C. © 1993 John Wiley & Sons, Inc.

Synthesis and curing of heat-resistant homopolyamide and copolyamides containing enamino nitrile segments

A new aminocarboxylic acid bearing an enamino nitrile segment was used as starting material for the preparation of modified homopolyamide and various copolyamides. The polycondensations were carried out by the phosphorylation method. Poly(benzamide) was also prepared under the same experimental conditions for comparative purposes. Polyamides were characterized by i.r. and 1H-NMR spectroscopy as well as by inherent viscosity measurements. The modified polyamides showed higher solubility in common organic solvents than poly(benzamide). Their solubility was increased with increasing concentration of the enamino nitrile segments. Thermal stability of cured (at 300° for 15 hr) polyamides was evaluated by TGA and isothermal gravimetric analysis. The modified polyamides displayed higher heat resistance than poly(benzamide) attributable to a rearrangement, at least in part, of the enamino nitrile segments to 4-aminoquinoline. They were stable up to 381–415° in N 2 or air and afforded anaerobic char yields of 64–70% at 800°. Thermal stability of copolyamides was correlated with the concentration of enamino nitrile units.

Polyimides derived from diels‐alder polymerization of furfuryl‐substituted maleamic acids or from the reaction of bismaleamic with bisfurfurylpyromellitamic acids

AbstractCertain AB or AA and BB Diels‐Alder polymer precursors bearing maleimide and furan segments were synthesized, characterized, and polymerized. Particularly, the monomaleamic acid derived from 4,4'‐diaminodiphenylmethane, reacted with the monofurfurylpyromellitamic acid to yield a triamic acid which was cyclodehydrated to the corresponding triimide. A polyimide was obtained upon heat‐curing of triimide or the intermediate triamic acid. In addition, equimolar amounts of N,N'‐bismaleimido‐4,4'‐diphenylmethane (BMDM) and bisfurfurylpyromellitimide or their intermediate diamic acids were cured to afford a polyimide. The polymer precursors were characterized by IR and 1H‐NMR spectroscopy and their curing behavior was investigated by DTA. It was shown that the Diels‐Alder polymerization of monomers took place at lower temperature than that required for crosslinking of BMDM. The thermal stabilities of polymers were ascertained by TGA and isothermal gravimetric analysis (IGA). The synthesized Diels‐Alder polymers were remarkably more heat‐resistant than the crosslinked polymer obtained from BMDM or its intermediate bismaleamic acid. They were stable up to about 360°C in N2 or air and afforded anaerobic char yield of 58% at 800°C. © 1992 John Wiley & Sons, Inc.

Synthesis, characterization, and curing of unsaturated polyamides derived from 2,6‐di(4‐carboxystyryl)pyridine and 2,6‐bis(4‐carboxybenzylidene) cyclohexanone

AbstractTwo new series of heat‐curable polyamides were prepared utilizing the unsaturated dicarboxylic acids 2,6‐di(4‐carboxystyryl)pyridine (DCSP) and 2,6‐bis(4‐carboxybenzylidene)cyclohexanone (BCBC) as starting materials. They were prepared from the condensation of 4‐carboxybenzaldehyde with a half molar amount of 2,6‐dimethylpyridine or cyclohexanone, respectively. The dicarboxylic acids reacted with various aromatic diamines, utilizing triphenyl phosphite and pyridine as condensing agents, to yield polyamides. In addition, two model diamides were prepared by condensing the dicarboxylic acids with aniline. Characterization of starting materials, polyamides, and model compounds was accomplished by IR and 1H–NMR spectroscopy. The curing behavior of polyamides was investigated by DTA. Upon heat‐curing, the unsaturated polyamides were crosslinked through their olefinic bonds to afford insoluble, heat‐resistant resins. The thermal stability of the resins was evaluated by TGA and isothermal gravimetric analysis (IGA). The cured resins were stable up to 310–322°C in N2 or air and afforded anaerobic char yield of 57–69% at 800°C.

Synthesis and characterization of poly(imidine-amides)

New poly(imidine-amides) were synthesized by the polycondensation of two dicarboxylic acids bearing benzylidene-substituted pyromellitimide or trimellitimide segments with various diamines. Polymerization was carried out using triphenyl phosphite and pyridine as condensing agents. The dicarboxylic acids used as starting materials as well as their intermediate compounds were characterized by i.r., DTA and inherent viscosity measurements. They were soluble in polar aprotic solvents such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methyl-2-pyrrolidone. Thermal stabilities of heat-cured polymers were evaluated by TGA and isothermal gravimetric analysis. They showed thermal stability up to 351-300° in N 2 or air and afforded char yields of 64-55% at 800° in N 2.

Furyl‐maleimidein situ generated ab‐monomers: Synthesis, characterization, and Diels‐Alder polymerization

Abstract2‐Furoyl chloride reacted with the monomaleamic acids 1a‐1d derived from a aromatic diamine to yield a new series of maleamic acids 2a–2d. The latter were cyclodehydrated to afford maleimides 3a‐3d which behaved as AB‐monomers for a Diels‐Alder polymerization. In addition, the monomaleamic acid 4 derived from 4‐aminophenol reacted with 2‐furoyl chloride to yield maleamic acid 5. It was cyclodehydrated to maleimide 6 which is a novel polymer precursor. The monomers were characterized by IR and 1H‐NMR spectroscopy. Their thermal polymerization was investigated by DTA. Maleamic acids 2a–2d and 5 were cured at 280°C for 22 h to yield polymers which were characterized by TGA and isothermal gravimetric analysis (IGA). They were stable up to 340–376°C and afforded anaerobic char yield of 55–64% at 800°C. © 1992 John Wiley & Sons, Inc.

High-Temperature Resins Obtained From Bismaleamic Acids of β,β′-Dichloroterephthalyl Dimalonitrile

Abstract A novel class of bismaleamic acids was synthesized from the reactions of β,β′-dichloroterephthalyl dimalonitrile with a double molar amount of the monomaleamic acid derived from an aromatic diamine utilizing triethylamine as an acid acceptor. Both monomaleamic and bismaleamic acids were characterized by IR and 1H-NMR spectroscopy as well as elemental analyses. Bismaleamic acids were soluble in various organic solvents. Upon curing at 300°C for 15 h, they yielded insoluble network polymers by dehydration to the corresponding bismaleimides and subsequent crosslinking through their olefinic bonds. It was shown by IR spectroscopy that curing of bismaleamic acids rearranged, at least in part, the enamino nitrile units to 4-aminoquinoline. The cured resins were characterized by DTA and TGA. They showed excellent thermal stability because they were stable up to 355–389°C in N2 and air and afforded an anaerobic char yield of 57–66% at 800°C. In addition, the thermal stability of a typical cured resin was evaluated by isothermal gravimetric analysis.

Synthesis and diels–alder polymerization of furfurylidene and furfuryl‐substituted maleamic acids

AbstractThe reactions of monomaleamic acid derived from an aromatic diamine with furfural afforded a novel class of furfurylidene‐substituted maleamic acids 2a–2d. The latter were cyclodehydrated to yield maleimides 3a–3d which are AB‐monomers for a Diels–Alder polymerization. In addition, N‐furfurylmaleamic acid (4) was synthesized by reacting furfurylamine with maleic anhydride at ambient temperature. Cyclodehydration of 4 afforded N‐furfurylmaleimide (5). The polymer precursors were characterized by IR and 1H‐NMR spectroscopy. Their curing behavior was investigated by DTA and correlated with chemical structures. Diels–Alder polymerization of monomers occurred at the temperature range of 113–210°C. Thermal stability of monomers was evaluated by TGA and isothermal gravimetric analysis (IGA). It was shown that thermal stability of the polymer derived from maleamic acid 4 was dramatically improved upon curing at high temperatures due to the formation by dehydration of a stable aromatic structure.

New crosslinking end caps for polyquinoline prepolymers: synthesis, processing, and thermal properties

Flexible quinoline oligomers were end-capped with 4-acetylbenzocyclobutene (BCB), 6-acetyl-8-phenyl-1,2-dihydro[3,4]cyclobuta[1,2-b]quinoline (CBQ), and 8-acetyl-6b-10b-dihydrobenzo[j]cyclobut-[1,2-a]acenaphthylene (BCBAN) and were melt-processed under various conditions. The best conditions afforded high-quality films that exhibited good flexural moduli (E'). Oligomers capped with CBQ and BCBAN gave insoluble cured films of comparable quality under the same cure conditions. The BCBAN-capped oligomer gave a cured film with superior stability by isothermal gravimetric analysis (IGA) in air at 400°C

Polystyrylpyridine bearing pendant maleimide groups

Poly(styrylpyridine) (PSP) bearing pendant maleimide groups in various concentrations was synthesized. The synthesis was based on the maleamic acid (MA) derived from 2-amino-4,6-dimethylpyridine and characterized by elemental analyses and by i.r. and 1H-NMR spectroscopy. MA was used as comonomer in various proportions (0, 10, 40, 70 and 100%) together with 2,6-dimethylpyridine to react with 1,4-benzenedicarbaldehyde in acetic anhydride. All polymers were characterized by i.r. spectroscopy and their curing behaviour was investigated by DTA. The onset temperature for curing of PSP fell with increasing concentration of maleimide groups in the resin. The thermal stabilities of cured resins were evaluated by dynamic TGA in N 2 and air and by isothermal gravimetric analysis. The attachment of maleimide groups to the PSP backbone reduced the initial decomposition temperature of cured resins but increased their anaerobic char yield at 800°, when the proportion of maleimide moieties was below 40%.

Epoxides bearing azomethine linkages

AbstractSeven structurally different diepoxides, triepoxides or tetraepoxides bearing azomethine linkages were synthesized and characterized. The reactions of 4‐hydroxybenzaldehyde or 3,4‐dihydroxybenzaldehyde with 4‐aminophenol or 4‐aminobenzoic acid afforded azomethines, which reacted subsequently with excess of epichlorohydrin in the presence of benzyltrimethylammonium bromide to yield diepoxides or triepoxides. Triepoxides were prepared by reacting 4‐hydroxybenzaldehyde with 5‐aminoisophthalic acid or 4‐amino‐2‐hydroxybenzoic acid again to yield azomethines, which were subsequently reacted with epichlorohydrin. In addition, a tetraepoxide was prepared from the reaction of 1,4‐benzenedicarbaldehyde with a double molar amount of 4‐amino‐2‐hydroxybenzoic acid to afford a bisazomethine followed by reaction with epichlorohydrin. The epoxy compounds were characterized by IR and 1H NMR spectroscopy. Their thermal polymerization in the presence of 4,4‐diaminodiphenylsulfone (DDS) was investigated by DTA. Thermal stabilities of cured resins were ascertained by TGA and isothermal gravimetric analysis (IGA) in N2 or air. The polymer derived from the tetraepoxide was the most heat‐resistant. It was stable in N2 up to 313°C and afforded an anaerobic char yield of 58% at 800°C.

Synthesis and evaluation of photolytically and thermally crosslinkable polyimide copolymers with diacetylene functionality

The polyimide block copolymers with diacetylene functionality were prepared in a two-step process: (1) oligomeric imide formation terminated with 1-amino-3-ethynylbenzene, and (2) oxidative coupling of the acetylene-terminated polyimides with p- and/or m-diethynylbenzene or bispropargyl ether of Bisphenol A to form block copolymers, or oxidative coupling within themselves in the presence of a copper (I) catalyst. The resulting copolymers were crosslinked with UV irradiation or thermal treatment. The thermal crosslinking process and the thermal stability of the crosslinked materials were studied by differential scanning calorimetry (DSC) and isothermal gravimetric analysis (IGA), respectively.

Crosslinkable aromatic polyketones with maleimide pendent groups

AbstractA novel class of crosslinkable aromatic polyketones with maleimide pendent groups were synthesized by Friedel–Crafts polymerization from 5‐maleimido‐isophthaloylchloride and various aromatic reagents. The synthesized polyketones showed a poor solubility. They were characterized by inherent viscosity measurements and infrared (IR) spectroscopy. Differential thermal analysis (DTA) revealed that their crosslinking occurred at relatiively lower temperatures (167–253°C) than did thermal polymerization of ordinary bismaleimides. The thermal‐and thermooxidative stability of crosslinked resins were evaluated by dynamic thermogravimetric analysis (TGA) as well as by isothermal gravimetric analysis (IGA). They were stable in N2 up to 303–329°C and formed anaerobic char yield 50–62% at 800–C. The thermal stability of crosslinkable polyketones was significantly increased after curing.