Diaminodiphenyl Sulfone System Research Articles

Binary systems based on aromatic amines with a view of development of novel hardeners for epoxy resins

Three binary systems based on aromatic amines [4,4′-diaminodiphenylmethane (DDM), 4,4′-diaminodiphenyl sulfone (DDS), 4,4′-diaminodiphenyl ether (DDE) and m-phenylenediamine (MPDA)] were investigated by differential scanning calorimetry (DSC). Phase diagrams for different compositions were constructed. The DSC results showed that all binary systems form simple eutectic mixtures. Formation of eutectic physical mixture of MPDA–DDM and MPDA–DDS was confirmed by powder XRD study. In the case of DDE–DDS system, it was found that besides the eutectic mixture a small amount of the charge transfer complex forms with the novel crystal structure.

Micro phase separated epoxy/poly(ε-caprolactone)-block-poly(dimethyl siloxane)-block-poly(ε-caprolactone)/4,4′-diaminodiphenylsulfone systems: Morphology, viscoelasticity, thermo-mechanical properties and surface hydrophobicity

Epoxy resin/4,4′-diaminodiphenylsulfone (DDS) system was modified by the incorporation of poly(ε-caprolactone)-block-poly(dimethyl siloxane)-block-poly(ε-caprolactone) (PCL–PDMS–PCL) triblock copolymer (TBCP). Morphology, viscoelasticity, thermo-mechanical and surface properties of these blends were investigated. All the blends were opaque after curing. PCL blocks of the TBCP were miscible with epoxy resin while the PDMS fraction was immiscible. However in the cured state, both PCL and PDMS blocks were phase separated from epoxy/DDS matrix. The blends exhibited matrix-droplet morphology in which TBCP phase dispersed as spherical domains in epoxy matrix. Addition of TBCP had profound impact on the cure reaction kinetics. Storage modulus and glass transition temperature (Tg) decreased while impact strength significantly increased. Incorporation of 15 phr of TBCP resulted in 80% improvement in impact strength. Further, thermal stability was unaffected while surface hydrophobicity of the blends increased.

Structural and material properties of a rapidly cured thermoplastic‐toughened epoxy system

AbstractThermoplastic‐toughened epoxy resins are widely used as matrices in modern composite prepreg systems. Rapid curing of thermoplastic‐toughened epoxy matrix composites results in different mechanical properties. To investigate the structure–property relationship, we investigated a poly(ether sulfone)‐modified triglycidylaminophenol/4,4′‐diamino diphenyl sulfone system that was cured at different heating rates. An intermediate dwell was also applied during the rapid heating of the thermoplastic‐modified epoxy system. We found that a higher heating rate led to a larger domain size of the phase‐separated macrostructure and also facilitated more complete phase separation. The intermediate dwell helped phase separation to proceed even further, leading to an even larger domain size of the macrostructure. A carbon‐fiber‐reinforced polymer matrix composite prepreg based on the poly(ether sulfone)‐modified multifunctional epoxy system was cured with the same schedule. The rapidly heated composite laminates exhibited higher mode I delamination fracture toughness than the slowly heated material. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Novel dibutyltin oxide–tributyl phosphate condensate as accelerator for the curing of the epoxy resin/4,4′‐diamino diphenyl sulfone system. I. Chemical reactions and properties of the cured resin

AbstractA crystalline condensate of dibutyltin oxide and tributyl phosphate (Sn‐P‐c) was more effective than the stannous octoate and dibutyltin dilaurate in accelerating the curing of the epoxy resin/4,4′‐diamino diphenyl sulfone (DDS) system, based on an equal tin concentration. Water took part in the reaction and played an important role in the morphology and mechanical properties of the cured resin when Sn‐P‐c was used as the accelerator. In the presence of Sn‐P‐c, water first reacted with glycidyl ether to yield glycerol ether; the yielded hydroxyl group may further catalyze the amino/epoxy group reaction. In the absence of water or polar hydroxyl additives, Sn‐P‐c did not completely dissolve in the resin systems, and the cured resin was translucent material with poor mechanical strength. In the presence of a small amount of water, the cured material became transparent. Both flexural strength and maximum deflection were increased greatly. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1229–1236, 2001

Novel dibutyltin oxide‐tributyl phosphate condensate as accelerator for the curing of the epoxy resin/4,4′‐diamino diphenyl sulfone system. II. Toughening of the resin with hydroxyl‐terminated poly(tetramethylene) glycols

AbstractWhen a crystalline Bu2SnO‐Bu3PO4 condensate was used as a catalyst for the curing of the Epon 828/DDS system, the addition of hydroxyl group to epoxy group took place. On the basis of this reaction, direct employment of poly(tetramethylene) glycols (PTMG) as toughener for the epoxy resin system was successful. Morphology of the modified resin depended on the molecular weight and the concentration of PTMG. With the incorporation of a small amount of PTMG, the critical fracture energy of the cured resin was improved greatly, while the flexural strength and the modulus were less influenced. A slight enhancement in glass transition temperature (Tg) of the modified resin was found up to the PTMG concentration of 5 phr; further increase of the PTMG concentration caused a significant lowering of Tg. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1237–1242, 2001

A systematic study of the microwave and thermal cure kinetics of the TGDDM/DDS and TGDDM/DDM epoxy‐amine resin systems†

AbstractThe microwave and thermal cure processes for the epoxy‐amine systems N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenyl methane (TGDDM) with diaminodiphenyl sulfone (DDS) and diaminodiphenyl methane (DDM) have been investigated. The DDS system was studied at a single cure temperature of 433 K and a single stoichiometry of 27 wt% and the DDM system was studied at two stoichiometries, 19 and 32 wt%, and a range of temperatures between 373 and 413 K. The best values of the kinetic rate parameters for the consumption of amines have been determined by a least squares curve fit to a model for epoxy‐amine cure. The activation energies for the rate parameters for the MY721/DDM system were determined as was the overall activation energy for the cure reaction which was found to be 62 kJ mol−1. No evidence was found for any specific effect of the microwave radiation on the rate parameters, and the systems were both found to be characterized by a negative substitution effect. Copyright © 2001 John Wiley & Sons, Ltd.

Curing kinetics and thermal property characterization of a bisphenol-S epoxy resin and DDS system

The kinetics of the cure reaction for a system of bisphenol-S epoxy resin (BPSER), with 4,4′-diaminodiphenyl sulfone (DDS) as a curing agent was investigated with a differential scanning calorimeter (DSC). Autocatalytic behaviour was observed in the first stages of the cure which can well be described by the model proposed by Kamal, using two rate constants, k1 and k2, and two reaction orders, m and n. The overall reaction order, m + n, is in the range 2∼2.5, and the activation energy for k1 and k2 was 86.26 and 65.13 kJ mol−1, respectively. In the later stages, a crosslinked network was formed and diffusion control was incorporated to describe the cure. The glass transition temperature (Tg) of the BPSER/DDS samples partially cured isothermally was determined by means of torsional braid analysis (TBA) and the results showed that the reaction rate increased with increasing Tg, in terms of rate constant, but decreased with increasing conversion. It was also found that the SO2 group both in the epoxy resin and in the hardener increases the Tg values of the cured materials compared with that of BPAER. The thermal degradation kinetics of this system was investigated by thermogravimetric analysis (TGA). It illustrated that the thermal degradation of BPSER/DDS has nth order reaction kinetics. © 2000 Society of Chemical Industry

Curing of Epoxy Resin with Phosphorylated Diamine

Abstract The diglycidyl ether of Bisphenol-A (DGEBA), suitable for the manufacture of epoxy-glass fiber laminates, has been cured with bis(m-aminophenyl)methylphosphine oxide (BAPO), and the results have been compared with a commercially available 4,4′-diaminodiphenyl sulfone (DDS). DSC studies indicated that an increase in the concentration of diamine resulted in an increase in the extent of the curing reaction even above the optimum level of diamine. Cured resins were stable up to 300°C and started losing weight above this temperature. Glass fabric-reinforced laminates based on DGEBA:BAPO exhibited a higher limiting oxygen index (LOI), as well as higher shear and flexural strength than those based on the DGEBA:DDS system. Thermal aging at 185°C for 100 h did not affect the mechanical properties of laminates. However, a significant decrease was observed in interlaminar shear strength by boiling in water for 100 and 200 h.

Moisture absorption by tetraglycidyl 4,4′ ‐diaminodiphenyl methane/4,4′‐diaminodiphenl sulfone epoxies containing brominated epoxy copolymers

AbstractThe effect on moisture absorption of introducing bromine into epoxy resins is investigated. The research is carried out with a tetraglycidyl 4,4′‐diaminodiphenyl methane/4,4′‐diaminodiphenyl sulfone system, and compared with a reference system of diglycidyl ether of bisphenol A/diaminodiphenyl methane epoxy, both systems containing brominated reactive epoxy additives. The results indicate that the presence of bromine reduces drastically the rate and the maximum level of moisture absorption. The presence of bromine is shown to have only a small effect on the high‐temperature properties and on the glass‐transition temperatures of the dry resins. Moreover, due to their lower moisture absorption capacity, the glass‐transition temperatures of the wet brominated resins are higher than the counterparts of the original bromine‐free epoxies.