Structural and Thermal Characterisation of Nadimide Resins

A series of hexachloronadimides containing phosphine oxide in the backbone were synthesized by the reaction of bis(3-amino phenyl) methyl phosphine oxide (BAP) with pyromellitic dianhydride (PMDA)/3,3’,4,4’-benzophenone tetracarboxylic acid dianhydride (BTDA)/2,2-bis(3,4-dicarboxy phenyl) hexafluoropropane dianhydride (6F) and hexachloronadic anhydride in glacial acetic acid/acetone. Structural characterisation of the resins was carried out by infrared, nuclear magnetic resonance spectroscopy and elemental analysis. Thermal characterisation of uncured resin was done by differential scanning calorimetry and thermogravimetric analysis. The decomposition temperature of uncured resins were above 310±10°C with T _max 330±10°C in nitrogen atmosphere. Char yield at 800°C ranged from 37–42%. This revised version was published online in July 2006 with corrections to the Cover Date.     

Curing kinetics and thermal stability of diglycidyl ether of bisphenol

Curing kinetics of diglycidyl ether of bisphenol-A (DGEBA) in the presence of varying molar ratios of aromatic imide-amines and 4,4′-diaminodiphenylsulfone (DDS) were investigated by the dynamic differential scanning calorimetry. The imide-amines were prepared by reacting 1 mole of benzophenone 3,3′,4,4′-tetracarboxylic acid dianhydride (B) with 2.5 moles of 4,4′-diaminodiphenyl ether (E)/ or 4,4′-diaminodiphenyl methane (M)/ or 4,4′-diaminodiphenylsulfone (S) and designated as BE/ or BM/ or BS. The mixture of imide-amines and DDS at ratio of 0:1, 0.25:0.75, 0.5:0.5, 0.75:0.25 and 1:0 were used to investigate the curing behaviour of DGEBA. The multiple heating rate method (5, 10, 15 and 20°C min⁻¹) was used to study the curing kinetics of epoxy resins. The peak exotherm temperature was found to be dependent on the heating rate, structure of imide-amines as well as on the ratio of imide-amine: DDS used. A broad exotherm was observed in the temperature range of 180–230°C on curing with mixture of imide-amines and DDS. Curing of DGEBA with mixture of imide-amines and/or DDS resulted in a decrease in characteristic curing temperatures. Activation energy of curing reaction as determined in accordance to the Ozawa’s method was found to be dependent on the structure of amine. The thermal stability of the isothermally cured resins was also evaluated using dynamic thermogravimetry in a nitrogen atmosphere. The char yield was highest in case of resins cured using mixture of DDS: BS (0.25:0.75; EBS-3), DDS: BM (0.5: 0.5; EBM-2) and DDS: BE (0.5: 0.5; EBE-2).     

Phosphorus-containing imide resins. III

Three imide monomers were prepared by reacting maleic anhydride; 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride, bis(m-aminophenyl) methyl phosphine oxide, and tris(m-aminophenyl) methyl phosphine oxide, and tris (m-aminophenyl) phosphine oxide. The characterization was done by elemental analysis and infrared spectroscopy (IR). These monomers were soluble in acetone. Their thermal polymerization was investigated by differential scanning calorimetry (DSC). The temperature of the exothermic peak position was influenced by the presence of free amino group in the monomer and was about 50°C higher in monomers that did not contain amino group. Anaerobic char yield of imide monomers cured at 270 ± 2°C for 30 min ranged from 58 to 64%. Graphite cloth laminate fabricated from one of these resins had a limiting oxygen index of 100.     

Synthesis and thermal characteristics of bisimides. I

Ten structurally different bisimide resins were prepared by reacting maleic anhydride/citraconic anhydride and benzophenone tetracarboxylic dianhydride with aromatic diamines and fused aromatic structures or heterocyclic groups. The amines included were 1,5-diaminonaphthalene, 2,5-bis(p-aminophenyl)1,3,4-oxadiazole, 3,3-bis(p-aminophenyl)phthalide, 9,9-bis(p-aminophenyl)fluorene. and 10,10-bis(p-aminophenyl)anthrone. These monomers were characterized by infrared (IR). ¹H-NMR, mass spectroscopy, and elemental analysis. Thermal polymerization of these monomers was investigated by differential scanning calorimetry. Broad exothermic peaks were observed for a temperature range of 225–380°C. Temperature of exothermic peak position was influenced by the presence of substituents at the olefinic bond, and in biscitraconimides it was 40–50°C lower than in the corresponding bismaleimides. Anaerobic char yields of cured bisimide resins ranged from 44 to 64%. Oxadiazole-containing bisimides had low thermal stability. Increase in formula weight between the imide groups did not influence the char yields in a systematic manner. Graphite cloth laminates with two of these bisimide resins were fabricated and tested for a number of physical properties. Their limiting oxygen index was 70–72%.     

Polyphenols and acids of Ulugbekia tschimganica

From the herbage ofUlugbekia tschimganica (B. Fedtsch.) Zak two new phenolcarboxylic acids have been isolated in the form of their methyl derivatives: methyl ulugbekate C₁₉H₁₈O₆ (I) and methyl ulugbinate acid C₂₀H₂₂O₇ (II), mp 228°C. It has been established that (I) most probably has the structure of 1,5-bis(3′,4′-dihydroxyphenyl)-3-methoxycarbonylpent-1-ene and (II) that of 1,5-bis(2′,4′-dihydroxyphenyl)-3-methoxycarbonylpent-1-ene and (II) that of 1,5-bis(2′,4′-dihydroxyphenyl)-3-methoxycarbonyl-4-methoxypent-2-ene.     

Polyimides containing nonaromatic nitrogen linkages

Two diamines, 2,5-bis (4-aminophenyl)-2,5-diazahexane and 1,4-bis (4-aminophenyl)-1,4-diazacyclohexane were chosen as components for polyimidizations because they have melting points that differ by nearly 200°C (66–67 and 229–230°C, respectively) and are relatives of p-nitro-N,N-dimethylaniline. The melting points of the model compounds (phthalic anhydride) do not differ by as much as those of the free amines [303–304 and 386°C (DSC), respectively]. Six polyimides were prepared by a two-step polycondensation of the diamines with pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride, and 5,5'-[2,2,2-trifluoro-1-(trifluoromethyl) ethylidene] bis-1,3-isobenzofurandione. DSC thermograms failed to indicate any distinct transitions up to 450°C, however, the polyimide prepared from 2,5-bis (4-aminophenyl)-2,5-diazahexane and pyromellitic dianhydride shows a slight break in its DSC curve at 233°C.     

Thermal stability and dynamic mechanical thermal analysis of epoxy thermosets possessing N,N′-disubstituted pyromellitimide units

Abstract

In this work, three epoxy resins including diglycidyl ethers of N,N′-bis(2-hydroxyethyl)pyromellitimide (DIDGE), bisphenol-A (BADGE), and polyethylene glycol (PEDGE) were isothermally cured by an amine curing agent possessing N,N′-disubstituted pyromellitimide units (denoted by DIDAM). DIDGE resin was synthesized from the reaction of N,N′-bis(2-hydroxyethyl)pyromellitimide with an excess of epichlorohydrin. Also, DIDAM curing agent was prepared from the reaction of pyromellitic dianhydride with an excess of ethylene diamine. Completion of the isothermal curing processes was approved by both Fourier transform-infrared spectroscopy and non-isothermal differential scanning calorimetry (DSC). The DSC traces showed only the phase transitions related to the thermal degradation of the resulting thermosets. According to the thermogravimetric analyses, the DIDGE/DIDAM thermoset showed higher thermal stability at temperatures above 425?°C than the other two thermosets. While BADGE/DIDAM and PEDGE/DIDAM thermosets showed about 70% weight loss in the thermal range of 400–850?°C, DIDGE/DIDAM thermoset was encountered with only about 40% weight loss. The glass transition temperatures (T_g ) of the resulting thermosets were determined using tan δ vs temperature plots obtained from dynamic mechanical thermal analysis. The T_g values of BADGE/DIDAM, DIDGE/DIDAM, and PEDGE/DIDAM thermosets were found to be 211?°C, 189?°C, and 81?°C, respectively.     

Synthesis of p,p ′-Phenolphthaleinbis(trimellitic) Dianhydride

p,p′-Phenolphthalein-bis(trimellitic) dianhydride was obtained by the reaction of diacetyloxyphenolphthalein with trimellitic anhydride. The structure of the new compound was proved by elementary analysis, infrared spectroscopy, and acid value determination. The course of acidolysis reaction was examined in the temperature range of 240–280°C. The compound obtained is a powder having a melting point of 135–138° C, has high thermal stability, and is easily soluble in many organic solvents and low-molecular epoxy resins. Application of p,p′-phenolphthalein-bis(trimellitic) dianhydride in synthesis of soluble polyester-imides and as a hardening agent for low molecular weight epoxy resins is proposed.     

Curing and thermal behaviour of epoxy resin in the presence of a mixture of imide-amines

The curing behaviour of diglycidyl ether of bisphenol-A (DGEBA) was investigated by the dynamic differential scanning calorimetry using varying molar ratios of aromatic imide-amines and 4,4′-diaminodiphenylsulfone (DDS). The imide-amines were prepared by reacting 1 mole of naphthalene 1,4,5,8-tetracarboxylic dianhydride (N) and 4,4′-oxodiphthalic anhydride (O) with 2.5 moles of 4,4′-diaminodiphenyl ether (E) or 4,4′-diaminodiphenyl methane (M) or 4,4′-diaminodiphenylsulfone (S) and designated as NE/OE or NM/OM or NS/OS. The mixture of the imide-amines and DDS at ratio of 0:1, 0.25:0.75, 0.5:0.5, 0.75:0.25 and 1:0 were used to investigate the curing behaviour of DGEBA. A single exotherm was observed on curing with mixture of imide-amines and DDS. This clearly shows that the two amines act as co-curing agents. Curing temperatures were higher with imide-amines having sulfone linkage irrespective of anhydride. Curing of DGEBA with mixture of imide-amines and or DDS resulted in a decrease in characteristic curing temperatures. The thermal stability of the isothermally cured resins was also evaluated using dynamic thermogravimetry in a nitrogen atmosphere. The char yield was higher in case of resins cured imide-amines based on N and E. The activation energy of decomposition and integral procedural decomposition temperature were also calculated from the TG data.     

Syntheses and properties of poly (amide–imide)s based on 5,5′-bis[4-(4-trimellitimidophenoxy)phenyl]-hexahydro-4,7-methanoindan and aromatic diamines

 A novel polymer-forming diimide–diacid, 5,5′-bis[4-(4-trimellitimido phenoxy)phenyl]-hexahydro-4,7-methanoindan (II), was prepared by the condensation reaction of 5,5′-bis[4-(4-aminophenoxy)phenyl]-hexahydro-4,7-methanoindan with trimellitic anhydride. A series of novel aromatic poly(amide–imide)s (PAIs) containing polycyclic cardo groups was prepared by the direct polycondensation of II with various aromatic diamines using phosphorylation techniques. The polymers had inherent viscosities between 0.71 and 0.96 dl/g. The polymers were soluble in polar solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide (DMAc) and N,N-dimethylformamide, and could be cast from their DMAc solutions into transparent, flexible, and tough films, except for III _a . These films had yield strengths of 85–114 MPa, tensile strengths of 77–102 MPa, an elongation at break of 8–17%, and initial moduli of 2.0–2.7 GPa. Wide-angle X-ray diffraction revealed that the polymers are amorphous. The glass-transition temperatures of the polymers were in the range 242–312 °C. All the PAIs exhibited no appreciable decomposition below 430 °C, and their 10%-weight-loss temperatures were in the range 484–507 °C in nitrogen and 494–515 °C in air. Received: 26 January 1999 Accepted in revised form: 11 May 1999     

Preparation and properties of new soluble aromatic polyimides from 2,2′-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride and aromatic diamines

A new aromatic tetracarboxylic dianhydride having a crank and twisted noncoplannar structure, 2,2′-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, was synthesized by the reaction of 4-nitrophthalonitrile with biphenyl-2,2′-diol, followed by hydrolysis and cyclodehydration. The biphenyl-2,2′-diyl-containing aromatic polyimides having inherent viscosities up to 0.66 dL/g were obtained by the conventional two-step procedure starting from the dianhydride monomer and various aromatic diamines. Most of the polyimides were readily soluble in amide-type solvents such as N,N-dimethylacetamide and N-methyl-2-pyrrolidone. The aromatic polyimides had glass transition temperatures in the range of 205–242°C, and began to lose weight around 415°C, with 10% weight loss being recorded at about 500°C in air. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2021–2027, 1998     

Cyclothiomethylation of heterochain α,ω-diamines with formaldehyde and H<Subscript>2</Subscript>S

Cyclothiomethylation was performed of heterochain (O, S-S, NH) α,ω-diamines with formaldehyde and H₂S in aqueous medium at 20–60°C to obtain new α,ω-bis(1,3,5-dithiazinanes). The cyclocondensation of N-(3-aminopropyl)butane-1,4-diamine (spermidine), formaldehyde, and H₂S proceeds efficiently in the medium of BuOH-H₂O at 0°C and leads to the formation of previously unknown O,S-containing macroheterocycle, 1,7-dioxa-3,5,9,11-tetrathiacyclododecane. A fungicidal activity was found in 5,5′-(3,6-dioxaoctane-1,8-diyl)bis-1,3,5-dithiazinane with respect to microscopic fungi affecting agriculture.     

Cure mechanism of novel bismaleimide resins based on fluorene cardo moiety and their thermal properties

In this paper, two novel bismaleimide resins based on 9, 9-bis[4-(4-maleimidophenoxy) phenyl] fluorene (PFBMI), 9, 9-bis[4-(4-maleimidophenoxy)-3-methylphenyl]fluorene (MFBMI), and 2, 2’-diallyl bisphenol A (DABPA) were prepared. Their curing mechanism and curing kinetic were carefully investigated by Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The thermal mechanical properties of the composites based on these BMI resins and the glass cloth were obtained by Dynamic mechanical analysis (DMA), displaying that the novel resins whose T_g were 296°C and 289°C had excellent thermal performance. In addition, Thermogravimetric analysis (TGA) results showed that both the cured PD and MD resins possessed good thermal stability, and their T_5% were all higher than 410°C.     

Curing and thermal behaviour of DGEBA using mixture of biuret and 4,4′-diaminodiphenylsulfone

Curing behaviour of DGEBA was investigated in the presence of varying molar ratio of biuret and 4,4′-diaminodiphenylsulfone (DDS) by means of Differential scanning calorimetery. The multiple heating rate method (5, 10, 15 and 20 °C min⁻¹) was used to study the curing behaviour of epoxy resins. The peak exotherm temperature was found to be dependent on the heating rates, structure of biuret as well as on the ratios of biuret:DDS used. Ozawa method was used for calculating the activation energy of curing reaction. The thermal stability of the isothermally cured resins was evaluated by recording the thermogravimetric traces in nitrogen atmosphere. All the samples were stable up to 330 °C.     

Potentiometric determination of acidity constants of some Schiff bases in tetrahydrofuran-water mixtures

Using potentiometric measurements, dissociation constants of two Schiff bases, N,N′-bis(1′-hydroxy-2′-acetonaphthone)propylenediimine (L₁) and bis(1′-hydroxy-2′-acetonaphthone)-3,3′-diiminodpropaneamine (L₂) were determined in binary mixtures of tetrahydrofuran-water at 25.0 ± 0.1°C and an ionic strength of 0.100 M tetrabutylammonium perchlorate (TBAP). The results show that the pK _a values of these acids increases as the percentages of the tetrahydrofuran increase in solvent mixtures. There is a linear relationship between acidity constants and the mole fraction of tetrahydrofuran in the solvent mixtures. Effect of solvent composition on acidity constants is also discussed.     

Phenylethynyl-terminated imide oligomers and polymers therefrom

Two new phenylethynyl endcapping compounds, 3- and 4-amino-4′-phenylethynylbenzophenone, were synthesized and used to terminate imide oligomers from 3,4′-oxydianiline and 4,4′-oxydiphthalic anhydride at a calculated molecular weight of 9000 g/mol and from 3,4′-oxydianiline (0.85 mol), 1,3-bis (3-aminophenoxy) benzene (0.15 mol), and 3,3′,4,4′-biphenyltetracarboxylic dianhydride at a calculated molecular weight of 5000 g/mol. Glass transition temperatures for the cured oligomers were ～ 249°C for the former and 272°C for the latter. Films cured at 350°C for 1 h were tough and flexible and provided high tensile properties. The uncured oligomers were readily compression molded to provide tough, solve nt-resistant moldings. © 1994 John Wiley & Sons, Inc.     

Thermally Stable Spiropolymers

Abstract

The condensation of the aliphatic spirotetraamine 2,2-bis(aminomethyl)-1,3-diaminopropane (I) or 1,4-bis(aminomethyl)-1,4-diaminocyclohexane (II) with pyromellitic dianhydride (III) or 1,4,5,8-naphthalenetetracar-boxylic dianhydride (IV) was studied. It was found that in polyphos-phoric acid at temperatures greater than 200°C and after long reaction times, either tetraamine produced the desired spiropolymer with the dianhydride (IV), but only tars could be isolated when the dianhydride (III) was used. Although these condensations proceed through a polyimide precursor which then cyclizes by elimination of water, condensations of (II) with (IV) only yielded the fully cyclized material and all attempts to isolate the imide precursor failed. Strong evidence for total cyclization was obtained by comparing the infrared and ultraviolet spectra of the polymer and of model compounds that were representative of the fully cyclized and imide forms. Condensations of (I) and (IV) yielded polymers that were only 50% cyclized. The polymer based on spirotetraamine (I) started to lose weight at 300°C in both air and vacuum, while the polymer based on amine (II) showed no weight loss until 500 C in vacuum and 400°C in air.     

Synthesis of novel bismaleimide monomers based on fluorene cardo moiety and ester bond: Characterization and thermal properties

Two novel bismaleimide monomers based on fluorene cardo moiety and ester bonds, namely 9, 9-bis[4-(4-maleimidobenzoate) phenyl]fluorene (PEFBMI) and 9,9-bis[4-(4-maleimidobenzoate)-3-methylphenyl]fluorene (MEFBMI) were designed and synthesized. Their structures were confirmed by FTIR, ¹H-NMR, ¹³C-NMR spectroscopy and Elemental analysis. Both monomers obtained have excellent solubility in some organic solvents with low boiling point, including acetone, chloroform and dichloromethane. The curing process of the monomers were investigated by DSC, displaying that the melting point of the monomers were 157.1°C and 193.6°C respectively, and all processing windows exceed 30°C. DMA results showed the glass transition temperature of the cured PEFBMI/glass cloth composite was higher than 390°C while that of the cured PEFBMI composite was 349.2°C. TGA results indicated that the cured BMI resins have good thermal stability and their 5% weight loss temperatures were both higher than 410°C.     

Thermosetting polyimides

Linear polyimides prepared from m-phenylene diamine (MPD) and 3,4,3′,4′-benzophenonetetracarboxylic dianhydride (BTDA) were modified so as to be thermosetting. This was done by replacing a portion of the MPD with either 2,4-diaminoacetanilide or p-(2,4-diaminophenoxy) acetanilide and 3,5-diaminobenzoic acid; it is thought that during final processing of the laminates the carboxyl group and the acetamido group react, forming amide crosslinks. Alternatively, excess anhydride was incorporated into the polymer to react with some of the attached acetamido groups; these would give imide crosslinks. A series of resins and glass-reinforced laminates incorporating these resins was prepared. The laminates were aged and tested at 315°C. Flexural strength at 315°C. versus hours aged at 315°C. is presented. Flexural strength after 100 hr. at 315°C. for two of the better laminates from modified polymers was about 48,000 psi, compared to 24,000 psi for the straight linear polymer. The flexural strength of the modified polymers decreased more rapidly, however, and after 1000 hr. of aging at 315°C. the flexural strength of the best laminates, including the linear polymer, was 12,000 psi.     

Studies on the curing kinetics of epoxy resins using mixture of nadic/or maleic anhydride and 4,4′-diaminodiphenyl sulfone

Curing kinetics of diglycidyl ether of bisphenol-A (DGEBA) in the presence of maleic anhydride (MA)/or nadic anhydride (NA) or mixture of MA/NA: 4,4′-diaminodiphenyl sulfone (DDS) in varying molar ratios were investigated using differential scanning calorimetry. Curing behaviour of DGEBA in the presence of varying amounts of DDS:MA/NA was evaluated by recording DSC scans at heating rates of 5, 10, 15 and 20°C min⁻¹. The peak exotherm temperature depends on the heating rate, structure of the anhydride as well as on the ratio of anhydride: DDS. Thermal stability of the isothermally cured resins was evaluated by thermogravimetry. The char yield was highest in case of resins cured using mixture of DDS:MA (0.75:0.25; sample EM-1) and DDS:NA (0.75:0.25, sample EN-1).