Amine-terminated Butadiene Acrylonitrile Research Articles

Calorimetric and dielectric effects during polymerization of an elastomer-containing mixture and liquid-liquid phase separation

Calorimetry and dielectric spectroscopy of an elastomer, amine terminated butadiene acrylonitrile (ATBN), dissolved in a stoichiometric mixture of ethylene diamine and diglycidyl ether of bisphenol-A, were studied in real time during the polymerization and phase separation of the mixture. In the two polymer compositions containing 8 w/w % ATBN and 20 w/w % ATBN, the total enthalpy released per mole of DGEBA's reaction was the same, indicating indetectably small changes in molecular interactions before and after the phase separation. The dielectric relaxation spectra showed no evidence for phase separation, which indicated a gradual phase separation with time and the extent of polymerization, and relatively small differences in the permittivity and conductivity between the ATBN particles and the network matrix at the time of phase separation. The equilibrium permittivity and dc conductivity showed a nonideal mixing of ATBN. The stretched exponential relaxation parameter remained at 0.36, but the characteristic dielectric relaxation time and the dc conductivity increased on addition of ATBN. An increase in the temperature had a greater effect on the relaxation time than the increase in the extent of polymerization. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1911–1919, 1999

Layered Silicate/ATBN Nanocomposite

ABSTRACTComposites of amine terminated butadieneacrylonitrile (ATBN) and montmorillonite (MMT) were prepared by ion exchange between the onium salt of the polymer and the interlamellar cation of the mineral following two different preparation approaches. The first carried out the ion exchange in situ and used dioxane, a better solvent for the polymer, and the second administered the onium salt to MMT using dimethylsulfoxide (DMSO). Elemental analysis and IR spectroscopy indicated that all the ionic sites of the mineral have been occupied by polymer end groups. The d (001) spacing and the span between the internal lamelar surface were only expanded to about 14 Å and 5 Å, respectively, suggesting horizontal packing of the polymer molecules. TEM of microtome sections prepared from compression molded composites revealed that the lamellae, laminated with polymers assembled into multiplets of about 5 nm for both preparations. The multiplets clustered into mineral rich domains whose average size was 250 nm for the DMSO preparation. Finer clusters (70 nm) were obtained by the first method. This three fold decrease in the average domain size was attributed to the strong solvation power of dioxane in the binary solvent and to the locale of ion exchange.

Relaxations in thermosets. XXV. Calorimetric studies of the curing kinetics of pure and rubber‐containing epoxy‐based thermosets

AbstractThe curing kinetics of diglycidyl ether of bisphenol‐A, with ethylene diamine, propylene diamine, and hexamethylene diamine, with 60 wt % amine‐terminated butadiene acrylonitrile (ATBN) and without, have been measured under both isothermal and ramp‐curing conditions. The phase separation of ATBN is undetectable by calorimetry, but has a significant effect on both the rate of curing and the extent of cure. In all cases, its presence decreases the extent of cure and lowers the Tg of the thermoset formed. The total heat of reaction for the curing is 445 ± 15 J/g and remains unaffected by both the presence of an elastomer and the increase in the molecular size of the curing agent. None of the formalisms available for the curing kinetics of epoxy‐based thermosets is consistent with the results for the neat thermosets. The average activation energy for the reactions increases from 107 to 150 kJ/mol when ethylene diamine is replaced by hexamethylene diamine, but curing reaches near completion in a shorter time with the latter than with the former. The Tg of the latter thermoset is lower than that of the former and follows a decreasing trend with increase in the molecular size of the curing agent—an effect that is related to the increase in the length of cross‐links in the network structure. © 1993 John Wiley & Sons, Inc.

Relaxations in thermosets: 15. Curing kinetics and dielectric behaviour of butadiene-acrylonitrile-containing epoxide thermosets

The dielectric permittivity, ε′, and loss, ε″, during the crosslinking or curing of diglycidyl ether of bisphenol-A with diamino diphenyl methane and various amounts of an elastomer, amine-terminated butadiene acrylonitrile (ATBN), have been measured from their sol to gel to glass-formation regions. As the elastomer-containing thermoset cures, both ε′ and ε″ initially decrease and then increase with time. ε′ finally decreases to a value near 3, but ε″ goes through a sharp minimum followed by a peak and ultimately decreases to about 10 −3. The initial increase in both ε′ and ε″ has been interpreted as an onset of liquid-liquid phase separation, which becomes nearly complete before the monotonic decrease in ε′ begins as a result of network formation in the curing thermoset. The time for the onset of phase separation is relatively insensitive to the amount of elastomer in the thermoset, and indicates the time of cure at which the network structure reaches a molecular weight when the elastomer becomes immiscible in it. Both the conductivity and permittivity increase with the increase in the elastomer content, with the consequence that the onset of gelation, which is marked by an approach of conductivity to near zero, is masked by the dipolar relaxation process. Corresponding analysis in the electrical modulus formalism confirms these observations and shows further that the conductivity follows a Maxwell relaxation. The ε″ of the cured thermoset plotted against temperature shows broad peaks and shoulders to these peaks. These are a combination of the sub- T g relaxations in both the elastomer and the thermoset's network structure and the α-relaxation of the elastomer which appears at 240 K at 1 kHz. The permittivity and dielectric loss of the cured thermoset increase with an increase in the weight fraction of ATBN.

Relaxations in thermosets: 22. Curing kinetics and the dielectric properties of an elastomer containing epoxide cured with Ancamide

The dielectric properties of homogeneous solutions of amine-terminated butadiene acrylonitrile (ATBN) elastomer, diglycidyl ether of bisphenol-A and Ancamide have been measured during their curing at 298 and 373 K. As curing progresses, the dielectric permittivity, ε′, decreases and dielectric loss, ε″, first decreases and then peaks. The ε′ and ε″ of the cured thermosets increase with increase in the elastomer content but decrease with increase in the temperature of cure for the same elastomer content. The rate of curing becomes slower with increased amount of ATBN in the thermoset. A prominent relaxation process in the cured thermoset is the α-relaxation of the elastomer, whose height increases with increase in the elastomer content. The broad shoulder to the low-temperature side of the peak is due to the γ- and β-relaxation processes of the epoxy. The dielectric properties of the thermosets are relatively insensitive to the inversion of the thermoset matrix to an elastomer matrix as the elastomer concentration is increased.

Synthesis and characterization of elastomer-modified polyimide films

A study has been conducted to determine the effects of added elastomers on the film properties of a linear aromatic polyimide. Polyamic acids have been prepared via reaction of BTDA (3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride) with ODA (4,4′-oxydianiline) and various ATBN (aromatic amineterminated butadiene acrylonitrile) elastomers. Films were prepared and thermally converted to the corresponding polyimides. Optimum cure conditions for BTDA + ODA/ATBN films were evaluated. The effect of elastomer concentration on BTDA + ODA thermal properties, density, tensile properties, morphology and tear resistance were evaluated. Variation of the acrylonitrile content of the ATBN elastomer in BTDA + ODA was performed and properties evaluated. Incorporation of ATBN into BTDA + ODA caused a decrease in the glass transition temperature, thermal stability, tensile strength and modulus of films. Increases of film tear resistance were observed for several formulations of ATBN in the BTDA + ODA polyimide.

Glass Fabric Reinforced Bismaleimide Composites: Effect of Elastomer/ Reactive Diluent on Properties

The paper deals with the effect of additions of amine terminated butadiene/acrylonitrile (ATBN), carboxy terminated butadiene/acrylonitrile (CTBN) elastomers and bismethacryloxy derivative of diglycidyl ether of bisphenol-A (vinyl ester resin, VE) on the properties of glass fabric reinforced bismaleimide resin composites. Flexural and interlaminar shear strength of the laminates increased in the presence of these elastomers (3 or 5%). Optimum mechanical properties were observed at — 3 % of VE resin. Glass transition temperatures of laminates were determined by dynamic mechanical analysis.