Silatrane based imide resins: synthesis and characterization

A series of silatrane based imide resins having different end-caps were prepared by reacting 1-(3-aminopropyl)silatrane with 5-norbornene-endo-2,3-dicarboxylic anhydride (nadic anhydride), 5-methyl-5-norbornene-2,3-dicarboxylic anhydride (methyl nadic anhydride), hexachloronadic anhydride, maleic anhydride, benzophenone-3,3′,4,4′-tetracarboxylic dianhydride or pyromellitic dianhydride in dimethylacetamide. Structural characterisation of the resins was done by elemental analysis and IR. In DSC traces of these resins, an exothermic transition associated with crosslinking was observed above 230°C. Thermogravimetric studies revealed a multistep decomposition reaction. Residual weight at 800°C in nitrogen was found to depend on the backbone structure and ranged from 32–60%.     

Methyl nadimide resins: Synthesis and characterization

This article describes the synthesis and characterization of several methyl nadimides endcapped resins based on tris(3-aminophenyl)phosphine oxide. These resins were prepared by reacting methyl-5-norbornene 2,3-dicarboxylic anhydride (methyl nadic anhydride) (MNA), pyromellitic dianhydride (PMDA)/3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA)/2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6F), and tris(3-aminophenyl)phosphine oxide (TAP) in glacial acetic acid/acetone. Structural characterization of the resins was done by elemental analysis, IR, and ¹H-NMR. Thermal characterization of uncured resins using DSC and TGA techniques revealed an exothermic transition accompanied by a weight loss in the temperature range of 200–350°C. Residual weight at 800°C in nitrogen was found to be 47–55%. Isothermal curing of the resins was done at 340°C for 1 h in an air atmosphere. The cured resins were stable up to 400 ± 20°C. © 1994 John Wiley & Sons, Inc.     

Synthesis,characterization, and thermal properties of tris (3‐aminophenyl) phosphine oxide‐based nadimide resins

This article describes the synthesis, characterization, and thermal properties of nadimides obtained by reacting endo‐5‐norbornene‐2,3‐dicarboxylic acid anhydride (nadic anhydride) (NA), 4,4′‐oxodiphthalic anhydride (ODA), 1,4,5,8‐naphthalene tetra carboxylic dianhydride (NTDA) in glacial acetic acid/DMF. Structural characterization of the resins was done by elemental analysis, IR, ¹H‐NMR, and ¹³C‐NMR. The DSC scan showed the endothermic transition in the temperature range of 120–270°C. Multistep decomposition was observed in the TG scan of uncured resins in nitrogen atmosphere. Isothermal curing of the resins was done at 250 and 300°C for 1 h in an air atmosphere. These cured resins were stable to (350 ± 30)°C and decomposed in a single step above this temperature. This may be due to the retro Diels Alder (RDA) reaction. The char yield of the resins increased significantly on curing. The char yield was highest for P‐2N resin and this could be due to the presence of rigid skeleton i.e. naphthalene. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Bis(3-aminophenyl)methyl phosphine oxide-based (methyl) nadicimide resins

Ten nadicimide/methyl nadicimide end-capped oligomeric resins were prepared by reacting endo-5-norbornene-2,3-dicarboxylic acid anhydride (methyl nadic anhydride), pyromellitic dianhydride (PMDA)/3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA)/2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6F), and bis(3-aminophenyl) methyl phospine oxide (BAP) in glacial acetic acid/acetone. Structural characterization of the resins was done by elemental analysis, IR, and ¹H-NMR. Multistep decomposition was observed in the TG scan of uncured resins in a nitrogen atmosphere. Residual weight at 800°C depended on the structure and ranged between 25 and 51%. Isothermal curing of the resins was done at 300°C for 1 h in an air atmosphere. These cured resins were stable to 350 ± 30°C and decomposed in a single step above this temperature. The char yield of the resins increased on curing and was in the range 34–70%. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:861–869, 1997     

Curing octaepoxysilsesquioxane with different curing agents

Octaepoxysilsesquioxane (POSS-Ep) was first synthesized by the hydrolysis and condensation of γ-[(2,3)-epoxypropoxy]propyltrimethoxysilicane (KH-560) with the presence of ethanol and HCl at 55°C for 72 h. Then, it was cured with 4,4′-diaminodiphenylsulfone (DDS) and methylnadic anhydride (MNA), respectively. The curing reactions between POSS-Ep and DDS or MNA were investigated by FTIR. Thermal stability of the cured nanocomposites was studied by TGA. The micromophologies of the obtained hybrids were observed by SEM. FTIR results show that POSS-Ep can be cured completely with DDS or MNA to obtain the final organic–inorganic (O–I) hybrids after the same experimental curing cycle: 120°C/2 h + 140°C/2 h + 160°C/2 h + 180°C/2 h + 200°C/2 h. TGA results show that POSS-Ep/DDS hybrid displays better thermal stability than that of POSS-Ep/MNA hybrid. Initial thermal degradation temperature (Tdi) of POSS-Ep/DDS hybrid is 420°C, 195°C higher than that of POSS-Ep/MNA (225°C). SEM images of the fracture surfaces of the hybrids suggest the cured POSS-Ep possesses good mechanical properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and Polymerization of Epoxy Methacrylates, 2. Acylated Epoxy Methacrylates and their Copolymers

Partially (20–75%) acylated isopropylidene‐bis[1,4‐phenyleneoxy(2‐hydroxytrimethylene)] dimethacrylate (BisGMA) was prepared by a single step reaction of 2,2‐bis[4‐(2,3‐epoxypropoxy)phenyl]propane (DGEBA) with methacrylic acid (MAA), methacrylic anhydride (MAAn) and/or acetic anhydride catalyzed by 0.8 mol‐% N‐methylimidazole at 90–100°C. In any case, MAA was substituted by an equimolar quantity of the anhydride. The reaction kinetics of DGEBA with MAA and MAAn follows a first order law up to a conversion of epoxy groups corresponding to the initial molar ratio of MAAn. For different mole fractions x_MAA, the reaction rate was found to be directly proportional to x^0.5_MAA. The viscosity of BisGMA decreased with an increase in the acylation degree. Acylated BisGMA was copolymerized with triethylene glycol dimethacrylate (TEGMA) by use of a redox initiator system at room temperature and with vinyltoluene (VT) initiated by di‐tert‐butyl peroxide at 150–200°C, respectively, both in the presence of 70–76 wt.‐% of quartz filler. Different dependencies of the content of sol and the conversion of C=C double bonds were observed for thermally polymerized composites from VT with acetylated and methacrylated BisGMA, respectively. Methacrylated BisGMA yielded composites with reduced water uptake. The higher network density of the polymer matrix with methacrylated BisGMA resulted in a higher glass transition temperature T_g and a higher storage modulus of the composites. The initial temperature of weight loss of composites with VT was increased from 230°C for composites with BisGMA up to 258°C for composites with BisGMA methacrylated to a degree of 40%.     

Use of Difunctional Compounds During Rapid Steam Hydrolysis (Rash) Pretreatment

Mixed hardwood chips were treated with difunctional compounds as catalysts to study the reaction of wood with steam. The Rapid Steam Hydrolysis (RASH) pretreatment process was used for steam treatment. The difunctional compounds studied were maleic anhydride, phthalic anhydride, isophthalic acid, and terephthalic acid at 1.5% concentration based on dry wood weight. RASH pretreatment was performed for one minute at 180°C, 200°, 220°C, 230°C, 240°C, and 260°C. These compounds strongly modified the RASH pretreated material, especially the physical structure. Overall recovery of the pretreated catalyzed and uncatalyzed solids decreased with an increase in RASH temperatures. Catalyst addition did not make a difference on the recovery of pretreated solids. Cellulose degradation increased with temperature for catalyzed systems. Hemicellulose solubilization and degradation were extremely sensitive to the type of catalyst and RASH temperatures. Almost all of the hemicellulose was lost at higher temperatures. Lignin losses did not appear to be affected by the addition of catalyst except at 260°C. Enzymatic rates were improved by addition of the catalysts, especially at the lower temperatures. The maleic anhydride gave the highest enzymatic rates at all temperatures, and phthalic anhydride gave the second highest. The water solubles generally followed the same trends as the enzymatic hydrolysis rates and increased with the addition of catalysts, especially maleic anhydride.     

Synthesis and comparative study of thermal stabilities of the imidization of some maleic anhydride copolymers

In the present study, first, maleic anhydride‐styrene (MA‐St), maleic anhydride‐allyl phenyl ether (MA‐APhE), maleic anhydride‐heptene‐1(MA‐Hp), and maleic anhydride‐allyl propionate (MA‐AP) copolymers have been synthesized in different solvents in the presence of azobisisobutyronitrile (AIBN) at 70°C. Then, these four copolymers have been reacted with aniline at 60°C in N,N‐dimethyl formamide (DMF), and maleamidic acid derivatives of these copolymers have been synthesized. Next, they have been obtained from their maleimide derivatives by heating under vacuum at 150°C. All these polymers have been characterized by Fourier Transform infrared spectroscopy (FTIR) and investigated their thermal properties by using differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA) methods. The analyses results showed that thermal properties of maleimide derivatives of maleic anhydride copolymers changed as depend on the neighbor monomers of maleic anhydride. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2250–2254, 2006     

Synthesis of LC p-Biphenyl di{4-[2-(2,3-epoxypropyl)ethoxy] benzoate} and Curing Kinetics with Succinic Anhydride

A liquid crystalline (LC) diepoxide of p-biphenyl di{4-[2-(2,3-epoxypropyl)ethoxy] benzoate} (p-BPEPEB) was synthesized from allyl 2-hydroxyethyl ether, 4-hydroxy ethyl benzoate, 4,4-biphenol and m-chloroperoxybenzoic acid (MCPBA). Its structure was characterized by FTIR, ¹HNMR. The thermal properties and liquid crystalline behavior were investigated by using DSC, POM and XRD. The results show that the p-BPEPEB has a smectic liquid crystalline structure, and the melting point is 155°C. The curing kinetics of p-BPEPEB with succinic anhydride was investigated by nonisothermal DSC method. The results show that the cured system's initial temperature T_i is 90.8°C; peak temperature T_p is 128.4°C and finishing temperature T_f is 144.7°C. The apparent activation energy Ea is 213.69 KJ/mol, and with the increase of conversion rate the value reduces.     

Studies on thermosetting bisimide resins based on N,N-(4-aminophenyl)-p-quinone diimine

The paper describes two novel bisimide resins, i. e. MQA and NQA, prepared by reacting N,N'-(4-aminophenyl)-p-benzoquinone diimine (QA) with maleic anhydride or 5-norbornene-2,3-dicarboxylic (nadic) anhydride in glacial acetic acid. These resins were characterised by IR spectroscopy, DSC and thermogravimetric analysis. The char yield (at 800°C) in nitrogen atmosphere for MQA and NQA was found to be 56% and 61%, respectively. Chain extension of bismaleimides containing flexible ether linkages, i. e. 1,3-bis(4-maleimidophenoxy)benzene and 1,4-bis(4-maleimidophenoxy)benzene with QA was also carried out. The thermal stability of the chain-extended bismaleimide resins was lower than that of the neat bismaleimide resins.     

The solvent effect on the sidewall functionalization of multi-walled carbon nanotubes with maleic anhydride

The Diels–Alder cycloaddition of maleic anhydride to multi-walled carbon nanotubes (MWCNT) was performed in dimethyl sulfoxide (DMSO) (190 °C, 24 h) and in 2-chorotoluene (150 °C, 48 h). The functionalized MWCNT were characterized by thermogravimetry, elemental analysis, X-ray photoelectron spectroscopy, and potentiometric titration allowing a clear perception of the solvent involvement on the functionalization reaction. The MWCNT functionalized in DMSO presented acidity arising mostly from reaction with the solvent. The MWCNT modified in 2-chlorotoluene did not evidence chemical transformations that could be assigned to the solvent alone. The cycloaddition of maleic anhydride to anthracene, used as model compound for the MWCNT surface, confirmed that the reaction was fast in DMSO. Hydrolysis of the anhydride was catalyzed by the MWCNT presence, but the cyclic anhydride structure was restored upon heating in this solvent at 185 °C. The work also confirmed the cycloaddition of maleic anhydride to CNT and DMSO was identified as the best solvent for the reaction, at 190 °C.     

Thermal behavior of methacrylic acid–ethyl acrylate copolymers

The thermal degradation behavior of copolymers of methacrylic acid (81.5–17.4 mol%) was studied using thermogravimetry (TGA) and differential scanning calorimetry (DSC) and the degradation products were analyzed using mass spectroscopy and DSC–FTIR. From mass spectroscopy, it was observed that in the copolymers the main degradation products obtained below 280°C included water, ethanol, and methanol, whereas at higher temperature (up to 400°C), CO₂, CO, and small olefins were liberated. Elimination of water and ethanol is attributed to anhydride formation, which is believed to result from two routes: (a) anhydride formation involving adjacent acid groups and (b) anhydride formation involving adjacent acid and ester groups. An endothermic transition in the DSC and percent weight loss in the TGA in the same temperature range (140–280°C) support the above proposal. An increase in weight loss with increase in EA content of the copolymer confirms the participation of EA in the anhydride formation. © 1994 John Wiley & Sons, Inc.     

Maleinization of Soybean Oil Glycerides Obtained from Biodiesel-Derived Crude Glycerol

Glycerides obtained from the glycerolysis of soybean oil with crude glycerol were acylated with maleic anhydride at 80–100 °C. Both uncatalyzed and catalyzed reactions with 2-methylimidazole (2-MI) were evaluated. Formation of maleated glycerides was confirmed by ¹H-NMR and FTIR analyses. Consumption of maleic anhydride as a function of time was followed by acid value titration. High conversion (ca. 95 %) of hydroxyl groups was obtained at 90 °C in 60 min without catalyst. Under these conditions, a product with 1.9 maleate moieties per glyceride molecule was obtained. Catalyzed reactions afforded lower conversions of hydroxyl groups and lower maleate yields compared to uncatalyzed reactions.     

Fabrication and Characterization of Glass Fiber Reinforced Composites from 2,3‐Epoxypropyl 3‐(2‐Furyl)acrylate and Acrylonitrile

The present paper comprises synthesis and characterization of 2,3‐epoxypropyl 3‐(2‐furyl)acrylate (EPFA) from 3‐(2‐furyl)acrylic acid (FAA) and epichlorohydrin, and its subsequent copolymerization with acrylonitrile (AN) by varying the ratio of EPFA:AN and time using benzoyl peroxide as initiator at 80°C in toluene. The resultant pre‐polymers were characterized by epoxy equivalent weight (EEW), viscosity measurement, gel permeation chromatography (GPC), and infrared (IR) spectral studies. The prepolymers were cured by employing two different curing agents viz. chlorosulfonic acid (ClSO₃H) and maleic anhydride/triethanolamine (MAN : TEA). The curing study was performed isothermally at 120 and 160°C, respectively, for the agents employed. Differential scanning calorimetry (DSC) was also employed to study the curing behavior on dynamic runs. The cured samples were analyzed by thermogravimetry for their thermal stability. The glass fiber reinforced composites (GFRC) were fabricated from selected resin samples and were characterized for their mechanical properties, electrical properties and chemical resistance.     

Synthesis and Thermal Study of Cured Epoxy-Acrylate-Maleate,Unsaturated Polyester and Their Interpenetrating Networks of Varying Compositions

Epoxy-acrylate-maleate of bisphenol-C (ECAM), unsaturated polyester resin of phthalic anhydride, maleic anhydride and propylene glycol (PMP) were synthesized. ECAM, PMP and their varying compositions (25–75 wt%) were cured using MEKP and cobalt naphthenate and characterized by IR, DSC and TGA techniques. Interpenetrating networks possess intermediate thermal stability of ECAM (300°C) and PMP (227°C) and followed single step degradation with fractional order kinetics (0.6–2.4) leaving 10–25% residue above 400°C. Low magnitudes of energy of activation and frequency factor of interpenetrating networks indicated improvement in flexibility due to toughening of PMP by ECAM of varying compositions.     

Biocomposites composed of epoxidized soybean oil cured with terpene‐based acid anhydride and cellulose fibers

Epoxidized soybean oil (ESO) was cured with a terpene‐based acid anhydride (TPAn) at 150°C, and the thermal and mechanical properties of the cured product were compared with ESO cured with hexahydrophthalic anhydride (HPAn), maleinated linseed oil (LOAn), or thermally latent cationic polymerization catalyst (CPI). The ESO‐TPAn showed a higher glass transition temperature (67.2°C) measured by dynamic mechanical analysis than ESO‐HPAn (59.0°C), ESO‐LOAn (?41.0°C), and ESO‐CPI (10.0°C). The storage modulus at 20°C of ESO‐TPAn was higher than those of ESO‐LOAn and ESO‐CPI. Also, ESO‐TPAn showed higher tensile strength and modulus than the other cured ESOs. Regarding the biodegradability measured by biochemical oxygen demand in an activated sludge, ESO‐TPAn possessed some biodegradability, which was lower than that of ESO‐LOAn. Next, biocomposites composed of ESO‐TPAn and regenerated cellulose (lyocell) fabric were prepared by compression molding method. The tensile strength of ESO‐TPAn/lyocell composites increased with increasing fiber content. The tensile strength and modulus of ESO‐TPAn/lyocell composite with fiber content 75 wt % were 65 MPa and 2.3 GPa, which were three times higher than those of ESO‐TPAn. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Studies on chemical resistance of polyesters

Chlorendic anhydride based polyester ( I ,) tetrachlorophthalic anhydride based polyester ( II ), dibromoneopentyl glycol based polyester ( III ,) general purpose polyester ( IV ,) blend of dibromoneopentyl glycol based polyester with general purpose polyester ( V ,) chlorendic anhydride and dibromoneopentyl glycol based polyester ( VI ), and a blend of chlorendic anhydride based polyester and dibromoneopentyl glycol based polyester ( VII ) were prepared and their chemical resistance and moisture absorption studied in various reagents, acid, alkali, and water, at 25 and 65°C. It is found that the polyester ( III ) is the least affected in the presence of the acids. In 20% NaOH, there was a decrease in weight for all polyesters at both the temperatures compared to the control except the polyester ( VII ). Increase in weight of all the polyesters was observed during the absorption of moisture both at 25 and 65°C. The increase was higher at higher temperature. Polyester ( III ) thus shows the least absorption of moisture.     

Synthesis of cellulose triacetate-I from microfibrillated date seeds cellulose (<Emphasis Type="Italic">Phoenix dactylifera L.</Emphasis>)

Cellulose triacetate (CTA) has successfully been synthesized from microfibrillated date seeds cellulose. The cellulosic material under study constituted 84.9% amorphous phase with a degree of polymerization of 950. Acetylation was conducted at 50 °C under optimized heterogeneous conditions by acetic anhydride as acetyl donor, acetic acid as solvent and sulfuric acid as catalyst. In this process, cellulose was acetylated without dissolving the material throughout. The acetylated cellulose chains on the surface were dissolved gradually in acetic acid, which created new accessible zones. The yield of cellulose triacetate was studied varying acetic acid, acetic anhydride and catalyst concentrations, as well as reaction times. The ratio between the intensity of the acetyl C=O stretching band at around 1740 cm^?1 and the intensity of C–O stretching vibration of the cellulose backbone at 1020–1040 cm^?1 was used to optimize the reaction time. The optimal reaction conditions of 8% concentration of sulfuric acid, acetic anhydride/cellulose weight ratio of 3:1, acetic acid/cellulose weight ratio of 7:1, reaction time of 3 h and reaction temperature of 50 °C have given highest yield of cellulose triacetate, of about 79%. The obtained date seeds-based cellulose triacetate was characterized thoroughly by Fourier transform infrared (FTIR), X-ray diffraction (XRD), nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The synthesized product was identified as cellulose triacetate-I (CTA-I) characterized by a melting temperature of 217 °C and a decomposition temperature of 372 °C. These results demonstrated that date seeds can be used as potential source of microfibrillated cellulose which can be easily functionalized.     

Tris(3-aminophenyl)Phosphine oxide-based nadimide resins. II

A series of phosphorus-containing nadimide end-capped resins having different backbones was prepared by reacting endo-5-norbornene-2-3-dicarboxylic acid anhydride (nadic anhydride), pyromellitic dianhydride (PMDA)/3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA)/2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6F) and tris(3-aminophenyl)phosphine oxide (TAP) in glacial acetic acid/acetone. Structural characterization of the resins was done by elemental analysis, FTIR, and ¹H-NMR. Thermogravimetric studies revealed a multistep decomposition reaction for uncured resins. Residual weight at 800°C in nitrogen was found to be 50–60%. Resins cured at 300°C for 1 h in air atmosphere were stable up to 440 ± 20°C and decomposed in a single step above this temperature. The char yields of cured resins were in the range 63–71.5%. © 1992 John Wiley & Sons, Inc.     

Synthesis and characterization of new cardo poly(ether imide)s derived from 9,9‐bis [4‐(4‐aminophenoxy)phenyl]xanthene

A series of new cardo poly(ether imide)s bearing flexible ether and bulky xanthene pendant groups was prepared from 9,9‐bis[4‐(4‐aminophenoxy)phenyl]xanthene with six commercially available aromatic tetracarboxylic dianhydrides in N,N‐dimethylacetamide (DMAc) via the poly(amic acid) precursors and subsequent thermal or chemical imidization. The intermediate poly(amic acid)s had inherent viscosities between 0.83 and 1.28 dL/g, could be cast from DMAc solutions and thermally converted into transparent, flexible, and tough poly(ether imide) films which were further characterized by X‐ray and mechanical analysis. All of the poly(ether imide)s were amorphous and their films exhibited tensile strengths of 89–108 MPa, elongations at break of 7–9%, and initial moduli of 2.12–2.65 GPa. Three poly(ether imide)s derived from 4,4′‐oxydiphthalic anhydride, 4,4′‐sulfonyldiphthalic anhydride, and 2,2‐bis(3,4‐dicarboxyphenyl))hexafluoropropane anhydride, respectively, exhibited excellent solubility in various solvents such as DMAc, N,N‐dimethylformamide, N‐methyl‐2‐pyrrolidinone, pyridine, and even in tetrahydrofuran at room temperature. The resulting poly(ether imide)s with glass transition temperatures between 286 and 335°C had initial decomposition temperatures above 500°C, 10% weight loss temperatures ranging from 551 to 575°C in nitrogen and 547 to 570°C in air, and char yields of 53–64% at 800°C in nitrogen. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012