Diethyl Toluene Diamine Research Articles

Morphology, thermal relaxations and mechanical properties of layered silicate nanocomposites based upon high-functionality epoxy resins

This paper investigates the possibility of improving the mechanical properties of high-functionality epoxy resins through dispersion of octadecyl ammonium ion-modified layered silicates within the polymer matrix. The different resins used are bifunctional diglycidyl ether of bisphenol-A (DGEBA), trifunctional triglycidyl p-amino phenol (TGAP) and tetrafunctional tetraglycidyldiamino diphenylmethane (TGDDM). All resins are cured with diethyltoluene diamine (DETDA). The morphology of the final, cured material was probed by wide-angle X-ray scattering, as well as optical and atomic force microscopy. The α- and β-relaxation temperatures of the cured systems were determined using dynamic mechanical thermal analysis. It was found that the presence of organoclay steadily decreased both transition temperatures with increasing filler concentration. Further, the effect of different concentrations of the alkyl ammonium-modified layered silicate on the toughness and stiffness of the different epoxy resins was analyzed. All resin systems have shown improvement in both toughness and stiffness of the materials through the incorporation of layered silicates, despite the fact that it is often found that these two properties cannot be simultaneously achieved.

Highly soluble polyimides from sterically hindered diamines

Polyimides with enhanced solubility have been synthesized from various aromatic tetracarboxylic dianhydrides and sterically hindered diamines. Intrinsic viscosities in 1-methyl-2-pyrrolidinone (NMP) ranged from 0.28 to 1.05 dL/g. Most of the polyimides were soluble in common solvents such as N,N-dimethylacetamide, NMP, chloroform and tetrahydrofuran. Polyimides derived from thianthrene-2,3,7,8-tetracarboxylic dianhydride (TDAN) and diamino mesitylene (DAM) or diethyltoluene diamine (DETDA) were insoluble in all solvents indicating that polyimide solubility decreased as anhydride rigidity increased. Glass transition temperatures ranged from 252 to 398°C and above with the polymers showing little or no weight loss by TGA up to 400°C in both air and nitrogen. The glass transition temperatures of the polyimides increased 15 to 98°C (compared to unhindered polyimide analogs) when one or more methyl group was placed ortho to the imide nitrogen, hindering backbone rotation, chain packing and flexibility. Tough, transparent films of the soluble polyimides were cast from solution.

Mechanical and dynamic mechanical properties of polyurethane and polyurethane/polyurea elastomers based on 4,4?-diisocyanatodicyclohexyl methane

The physical and thermal properties of hand-cast polyurethane and polyurethane/polyurea elastomers prepared from prepolymers of 20 and 97% trans,trans-4,4′-diisocyanatodicyclohexyl methane (t,t-rMDI) and C3- and C4-polyethers chain extended with either 1,4-butanediol (XB) or a commercial mixture of diethyl toluenediamine isomers (DETDA) were determined. The influence of the distribution of geometric isomers of the diisocyanate and of the chain-extender building blocks on these properties is significant. Urethane/ureas are harder and have higher modulus than polyurethanes formed from the same prepolymer. The polyurethane/polyurea elastomers all have somewhat high compression set. Dynamic Mechanical Analysis (DMA) suggests that DETDA extended systems based on 20% t,t-rMDI are phase separated, as illustrated by extended rubbery plateau regions and significantly higher softening points than the corresponding XB extended ones. Uniquely, these elastomers are transparent rather than opaque as typical with most other phase-segregated elastomers. Polyurethanes based on 97% t,t-rMDI are harder and have higher modulus than those based on 20% t,t-rMDI (Desmodur™ W). They have good phase separation and high softening points but they are opaque. Surprisingly, there is not much difference between the physical or thermal properties of polyurethane/polyureas and polyurethanes based on 97% t,t-rMDI. Replacing XB with DETDA gives only moderate improvement in properties, but it does make the elastomers optically clear. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 957–970, 1997

Processing of intractable polymers using reactive solvents: 1. Poly(2,6-dimethyl-1,4-phenylene ether)/epoxy resin

A new processing route for poly(2,6-dimethyl-1,4-phenylene ether) (PPE), an intractable polymer on account of its thermal and oxidative sensitivity, was explored. PPE can be dissolved at elevated temperatures in epoxy resin and these solutions can then be processed at temperatures as low as 175°C. For solutions of PPE with a molecular weight of 10, 20 and 30 kg mol −1, the phase diagram and the flow curves in the homogeneous region were determined. The upper critical solution temperature ( UCST) cloud point curves intersect the glass transition-composition lines at a PPE content of ∼ 70 wt%. Below this composition, thermoreversible gelation is observed upon cooling which prevents complete phase separation. Curing of the homogeneous solutions, using diethyltoluene diamine, resulted in virtually complete phase separation. In the composition range that was studied (30–70 wt% PPE), the chemically induced phase separation is accompanied by phase inversion, yielding a final morphology of epoxy spheres dispersed in a PPE matrix. Thus, after processing, the (reactive) solvent is converted into a dispersed phase. The mechanical and thermal properties of the final materials, such as toughness and glass transition temperature, are dominated by the continuous PPE matrix.

Morphology‐property relationship of segmented polyurethaneurea: Influences of soft‐segment structure and molecular weight

AbstractThe relationships of the morphology and properties of a series of segmented polyurethaneurea (PUU) were studied in film form by using SEM and tensile stress‐strain data. The polyether‐based and polyester‐based PUU block copolymers were synthesized using poly(propylene oxide) ‐ethylene oxide polyether or poly(butylene adipate) polyester with different molecular weights, 4,4‐methylene bis(phenyl isocyanate), and diethyltoluene diamine. The extent of phase separation increased with increasing molecular weight of the soft segment. The polyether‐based PUU showed better phase separation than did polyesterbased PUU with the same molecular weight soft segment. The polyether‐ester‐based PUU showed the morphology of both polyether‐based and polyester‐based PUU but with larger domain size and interface. © 1993 John Wiley & Sons, Inc.

Dielectric and viscoelastic properties of some meta‐tetramethyl xylene diisocyanate‐based polyurethanes as a function of sample composition

AbstractA series of linear segmented polyurethanes were synthesized, based on soft segments of polycaprolactone having an average number molecular weight of 2100, or hydroxy–terminated polybutadiene having an approximate molecular weight of 2800. Hara segments were made of meta–tetramethyl xylene diisocyanate and diethyl toluene diamine. The dynamic Young's modulus and loss tangent, relative permittivity, and dielectric loss, were found to be significantly affected by soft segment polarity and hard segment content. These results are discussed in terms of polymer morphology, such as degree of phase separation and soft segment phase state.

Reaction kinetics of a polyurea reaction injection molding system

AbstractPolyureas have the potential for Improving reaction Injection molding (RIM) productivity through shorter demo Id times and elimination of external mold release agents and post‐cure. Kinetics of urea formation are necessary for process modeling of polyurea RIM systems. Adiabatic temperature rise measurements were used to monitor the extent of reaction of an aliphatic diamine and an aromatic diamine reacting competitively with a single diisocyanate. The aliphatic diamine reacted much faster; essentially complete polymerization occurred in the RIM mixhead. A similar three‐component system was studied in dimethylacetamide and diethylene glycol dimethyl ether, and the sequential nature of the two competing reactions was confirmed. The RIM polymerization of the aromatic diamine, 3,5 diethyltoluene (2,4 and 2,6) diamine and;4,4′‐diphenylmethane diisocyanate was studied using an unreactive poly ether as the solvent. The exotherms could be fit with a third order model. Adiabatic temperature rises for all RIM experiments were in good agreement with the values predicted by heats of reaction measured in solution.

Structure-property relations in non-linear, segmented copolyureas formed by reaction injection moulding, RIM

Segmented copolyureas have been formed by RIM using a MDI-based polyisocyanate (RMA400) and mixtures of a polyether triamine (Jeffamine T5000) and diethyltoluene diamine (DETDA) chain extender. Hard segment (HS) content was varied between 35 and 65% w/w at a constant overall stoichiometric ratio of -NCO to -NH2 groups of 1.03. All the copolyureas were translucent and DSC confirmed their totally amorphous structure.

Relationship between polyurethane composition and viscoelastic properties of model urethane systems

A study was performed to determine the relationship between polyurethane composition and viscoelastic properties in a series of model urethane compounds. The compositional variables studied included the nature of the soft segment, amount of hard segment, and cure stochiometry. Model urethanes were prepared using the aliphatic diisocyanate, metatetramethylene diisocyanate (m‐TMXDI). This aliphatic isocyanate is less reactive than commonly used aromatic isocyanates and does not undergo the secondary cross‐linking reactions commonly observed with aromatic isocyanates. The urethanes chosen for this study contained soft segments based on hydroxy‐terminated polybutadiene (HTPBD) or polycaprolactone (PCL), which is a highly polar material in which extensive phase mixing should occur. In contrast, polyurethanes based on HTPBD should undergo more complete phase separation. Prepolymers were prepared with both of these soft segments and with available isocyanate contents varying from 3.7% to 5.7%. Diethyltoluene diamine (DETDA) was used to cure these prepolymers over a range of cure stochiometries. Thermal transitions attributed to the hard and soft segments were observed in these urethanes using a Perkin‐Elmer DSC‐4. Dynamic mechancial behavior was measured using both a Polymer Labs dynamic mechanical thermal analyzer (DMTA) and a resonance apparatus developed at the NRL‐USRD. [Sponsored by ONT.]

Polyurea RIM-A Versatile High Performance Material

Polyurethane elastomers were the first products to find wide commercial use in the RIM process. Recently, the advent of a new chain extender, diethyltolu enediamine (DETDA), provided another class of commercially useful RIM elas tomers. These materials are best classified as polyurethane/urea elastomers. We have been working on the next logical step in this evolution: amine- terminated polyether resins with amine chain extenders. These are best classi fied as polyurea elastomers. Amine-terminated polyether resins, or polyether polyamines, can replace the polyol in a RIM formulation. These materials are much more reactive than pol yols, and their composition can be varied more easily than conventional RIM polyols. Thus, these products can be tailored to meet the performance require ments of a particular end use more easily than polyols. The use of amine-terminated polyether products in RIM applications brings a new dimension to the RIM process. Depending on the choice of amine termi nated polyether amine, one can formulate systems covering a broad range of properties from elastomeric materials to rigid materials. Elastomeric materials are made by having a small amount of hard segment in a block-copolymer in conjunction with a polyether diamine. These elasto meric materials can be more closely tailored to meet a specific physical prop erty by either adjusting the formulation or by adjusting the density of the polymer. Very rigid materials can also be made by increasing the amount of hard seg ment in the block-copolymer in conjunction with a polyether triamine. High levels of an aromatic diamine chain extender can be used with the polyether triamine.