Diaminodiphenyl Sulphone Research Articles

Synthesis and Properties of Interpenetrating Polymer Networks Composed of Epoxy Resins and Polysulphones with Cross-linkable Pendant Vinylbenzyl Groups

Polysulphones with cross-linkable pendant vinylbenzyl groups (PSF-VB) were prepared via chloromethylation of commercial polysulphones. The curing reactivity of PSF-VB was investigated by differential scanning calorimetry. Interpenetrating polymer networks (IPNs) were prepared based on bisphenol A diglycidyl ether (DGEBA) and PSF-VB, where DGEBA was cured by 4,4'-diaminodiphenyl sulphone and VB groups of PSF-VB were radically polymerized using dicumyl peroxide (DCP). Polysulphones having pendant benzyl groups (PSF-Bz) were also prepared and used as non-reactive modifiers. The fracture toughness (K 1C ) for the resulting epoxy/PSF-VB IPN increased by 65% with no loss of mechanical properties on 10 wt% addition of PSF-VB (7.9 mol% VB unit, MW 74000). Non-reactive PSF-Bz was less effective than PSF-VB. Although the PSF-Bz modified resin had a particulate structure, the morphologies of the PSF-VB/epoxy IPNs were not clear from scanning electron micrographs. Furthermore, the epoxy/PSF-VB IPNs had higher solvent resistance than the epoxy/PSF-Bz blends. Morphological behaviour, modification results and high solvent resistance of the cured epoxy/PSF-VB resins indicate that crosslinked PSF-VB and the epoxy network entangled fully in the presence of DCP.

Shear ductility and toughenability study of highly cross-linked epoxy/polyethersulphone

The objective of the present study was to determine whether the ductility and toughenability of a highly cross-linked epoxy resin, which has a high glass transition temperature, T g, can be enhanced by the incorporation of a ductile thermoplastic resin. Diglycidyl ether of bisphenol-A (DGEBA) cured by diamino diphenyl sulphone (DDS) was used as the base resin. Polyethersulphone (PES) was used as the thermoplastic modifier. Fracture toughness and shear ductility tests were performed to characterize the materials. The fracture toughness of the DDS-cured epoxy was not enhanced by simply adding PES. However, in the presence of rubber particles as a third component, the toughness of the PES–rubber-modified epoxy was found to improve with increasing PES content. The toughening mechanisms were determined to be rubber cavitation, followed by plastic deformation of the matrix resin. It was also determined, through uniaxial compression tests, that the shear ductility of the DDS-cured epoxy was enhanced by the incorporation of PES. These results imply that the intrinsic ductility, which had been enhanced by the PES addition, was only activated under the stress state change due to the cavitation of the rubber particles. The availability of increasing matrix ductility seems to be responsible for the increase in toughness.

Correlation between stress-whitening and fracture toughness in rubber-modified epoxies

Fracture toughness of rubber modified epoxy systems was evaluated in relation to stresswhitening. The epoxy systems consisted of diglycidyl ethers of bisphenol A (DGEBA)-based epoxy resin, 4,4′ diaminodiphenyl sulphone (DDS) as curing agent, and carboxylterminated butadiene-acrylonitrile (CTBN) rubber. It was found that a peak value of fracture toughness occurs at a small amount of rubber content (∼ 4 phr) and closely corresponds to that of stress-whitening size. Other properties such as flexural strength and flexural modulus were also found to display maxima at a similar amount of rubber content. © 1996 John Wiley & Sons, Inc.

Chemical reactions, thermal and mechanical properties of epoxy ? Polycarbonate blends cured with aromatic amines

Bisphenol-A polycarbonate (PC) has been incorporated into epoxy resin cured with 4,4′-diaminodiphenyl sulphone (DDS) and 4,4'-diaminodiphenyl methane (DDM). IR spectra reveal that transesterification and transamidation occur between the carbonate group of PC and the hydroxyl group of cured epoxy resin for the DDM-cured system, and that only transesterification occurs for the DDS-cured system. Scanning electron micrographs (SEM) show no evidence of phase separation in these cured systems, which is an indication of full miscibility between the bisphenol-A monomers and PC-oligomers with the copolymer network. The mechanical strength and glass transition temperature (Tg) fluctuate with PC content, whereas the flexural modulus shows a steadily increasing tendency.

Eosinophilic pustular folliculitis effectively treated with recombinant interferon-γ: suppression of mRNA expression of interleukin 5 in peripheral blood mononuclear cells

Eosinophilic pustular folliculitis (EPF) is characterized clinically by pruritic grouped follicular papules and pustules on the trunk, limbs, and face, and, histologically, by follicular infiltration with eosinophils. The blood eosinophil count is elevated in most patients. Oral minocycline, nonsteroidal anti-inflammatory drugs, diaminodiphenylsulphone, and corticosteroids may induce remission. We report two Japanese men with EPF who responded poorly to the usual therapy. Intravenous injections of recombinant interferon-gamma (rIFN-gamma), 5 x 10(5) to 2 x 10(6) Japan Reference Unit (JRU) (1 JRU roughly corresponds to 4 NIH units) daily for 7 days, cleared the skin lesions and returned the peripheral eosinophil counts to normal in both patients. However, the lesions recurred 2-3 days after rIFN-gamma was stopped. Both patients have received intravenous rIFN-gamma once or twice a week for nearly 1 year without systemic side-effects. Reverse transcriptase-polymerase chain reaction revealed a decreased expression of interleukin 5 (IL-5) mRNA in peripheral mononuclear cells after the rIFN-gamma therapy. rIFN-gamma may become the treatment of choice in recalcitrant EPF, although further studies are needed. It may work by interfering with the immunological function of type 2 T-helper cells, including IL-5 production responsible for the growth and differentiation of eosinophils.

Polyurethane-modified epoxy resin and their polymer particle filled epoxies

Hydroxyl-terminated polyurethane (HTPU) prepolymer and crystalline polymer particles were used to modify the toughness of diglycidyl ether of bisphenol-A (DGEBA) epoxy cured with diaminodiphenyl sulphone (DDS). For the crystalline polymers, poly(butylene terephthalate) (PBT) and poly(hexamethylene adipamide) (Nylon 6,6), with particle size under 401 μm were employed. The PU-modified epoxies exhibit a significantly improved fracture toughness. The β-relaxation of cured epoxy resin shows a more clear two-phase separation as the polyurethane content increases. Besides, the addition of crystalline polymer particles could further enhance the toughness of PU-modified epoxy at low particle content. Scanning electron microscopy (SEM) shows that PU-modified epoxy has a two-phase structure. The fracture properties of PBT particle filled epoxy are found to be better than those of Nylon 6,6 particle filled epoxy. Nevertheless, the toughening effect of these crystalline polymer particles is much less efficient than that of PU modification.

The effect of crosslink density on the fracture toughness of core-shell modified epoxy resins

It has long been recognized that many epoxy resins offering a high glass transition temperature are inherently brittle materials absorbing insignificant amounts of energy during the fracture process. In an attempt to trigger energy-dissipating mechanisms in brittle epoxy resins, a number of workers have investigated the potential benefits of incorporating small inclusions such as rubber particles [1-5], thermoplastic spheres [6-8] and, more recently, core-shell particles consisting of a rubbery core surrounded by a thermoplastic shell [9]. Core-shell modified epoxies have recently attracted interest since an unusual craze-like damage has been observed in such systems [9]. At present, however, it is not clear if similar toughening mechanisms operate in highly crosslinked epoxy resins similar to those currently used in the aerospace industry. A number of workers have shown that the degree of toughness enhancement in a particle-modified epoxy depends upon the crosslink density of the network structure [10-12]. It is generally recognized that epoxy resins which have a high crosslink density, and therefore a high glass transition temperature Tg, are more difficult to toughen than their low crosslink density counterparts. This difficulty in achieving high toughness in certain epoxies appears to be related to the materials' inability to undergo appreciable plastic flow in high stress fields. The objective of this work was to investigate the influence of crosslink density of the toughness and the failure mechanisms in a series of core-shell modified epoxy resins. The materials examined and the curing procedures employed in this study are summarized in Table I. Two epoxide phenolic novolac resins, Araldite ® EPNl138 and Araldite®EPNl139, and two hardeners, bisphenol A (4,4'-isopropylidenediphenol) and DDS (4,4'-diamino diphenyl sulphone), were used. The bisphenol A cured systems resulted in materials A, B and C and the DDS-cured systems in materials D and E. The average crosslink density within each of the five epoxy systems was determined from rubber elasticity theory following the procedure used by Fischer [13], as well as from stoichiometry. The glass transition temperature of each polymer was measured by differential scanning calorimetry (DSC) at a heating rate of 20 Kmin -1. The core-shell modifier was supplied in powder form consisting of an acrylic/styrene shell and a butadiene-styrene core. The diameters of the particles lay in the range 0.1-0.2~tm. The modifier was added to the pre-polymer and stirred with a high speed mixer prior to the addition of the hardener. In general, a good distribution of the particles was achieved although large agglomerations were occasionally observed. For simplicity, the core shell modified systems are prefixed by the letter M. The mode I critical strain energy release rate Gic for each material was determined using the compact tension specimen geometry in accordance with the

96/00347 Effect of detector size and position on measured vibration spectra of strings and rods

N-Phenylmaleimide (PMI)-styrene (St) alternating copolymers were used to improve the toughness of bisphenol-A diglycidyl ether epoxy resin cured with p,p′-diaminodiphenyl sulphone (DDS). The most suitable composition for the modification was inclusion of 10 wt% of the copolymer (Mw 345,000) which led to a 130% increase in the fracture toughness (KIC) of the cured resin with a medium decrease of its mechanical properties. The glass transition temperatures of the modified resins were equal to or higher than that of the parent epoxy resin. The morphologies of the modified resins were dependent on the copolymer molecular weight and concentration. On addition of up to 7 wt% of the copolymer (Mw 345,000) the modified resins had two-phase morphologies with the copolymer-rich dispersed particles in the epoxy matrix. On addition of 8 wt% of the copolymer, the morphologies of the cured resins changed drastically and showed a tendency to form co-continuous phases. The toughening mechanism is discussed in terms of the morphological characteristics of the modified epoxy resin systems.

Toughening of aromatic diamine‐cured epoxy resins by modification with hybrid modifiers composed of N‐phenylmaleimide–styrene copolymers and N‐phenylmaleimide–styrene–p‐hydroxystyrene terpolymers

AbstractHybrid modifiers composed of N‐phenylmaleimide–styrene copolymers (PMS), and N‐phenylmaleimide–styrene–p‐hydroxystyrene terpolymers (PMSH) containing pendent p‐hydroxyphenyl groups as functionalities, were used to improve the toughness of bisphenol‐A diglycidyl ether epoxy resin cured with p,p′‐diaminodiphenyl sulphone. The hybrid modifiers were effective in toughening the epoxy resin. When using the modifier composed of 10 wt% PMS (M̄w 313000) and 2.5 wt% PMSH (2.5 mol% p‐hydroxystyrene units, M̄w 316000), the fracture toughness (KIC) for the modified resins increased 100% with no deterioration in the flexural properties and the glass transition temperature. The improvement in toughness of the epoxy resins was attained because of the co‐continuous phase structure and the improvement in interfacial adhesion. The toughening mechanism is discussed in terms of the morphological characteristics of the modified epoxy resin systems.

Solvatochromism and prototropism of diaminodiphenyl sulphones and 2-aminodiphenyl sulphone: a comparative study by electronic spectra

A comparative study of absorption and fluorescence maxima of 4,4′-diaminodiphenyl sulphone (4DADPS), 3,3′-diaminodiphenyl sulphone (3DADPS) and 2-aminodiphenyl sulphone (2ADPS) in different solvents reveals that (i) solvatochromic shifts are found to be mainly due to interaction of solvents with amino group, (ii) in any one solvent the net solvatochromic shifts of two amino groups are less than that of one amino group, (iii) fluorescence shift from cyclohexane to water is a maximum for 4DADPS and a minimum for 2ADPS and (iv) 4DADPS and 3DADPS possess more twisted intramolecular charge transfer character than 2ADPS. The excited-state acidity constants, determined by fluorimetric titration and Förster cycle methods, have been reported and discussed.

Toughening of aromatic diamine-cured epoxy resins by modification with N-phenylmaleimide-styrene-p-hydroxystyrene terpolymers

N-phenylmaleimide-styrene-p-hydroxystyrene terpolymers (PMSH), containing pendant p-hydroxyphenyl groups as functionalities, were prepared and used to improve the toughness of bisphenol-A diglycidyl ether epoxy resin cured with p,p′-diaminodiphenyl sulphone. The terpolymers were effective as modifiers for toughening the epoxy resin. When using more than 10 wt% of PMSH with < 3.0 mol.% p-hydroxystyrene (HSt) units, the fracture toughness ( K IC ) for the modified resins increased > 100% with a medium loss of flexural strength and with a retention in flexural modulus and the glass transition temperature. For example, inclusion of 12.5 wt% of PMSH (1.0 mol.% HSt unit, M w 291,000) led to a 130% increase in K IC . The most effective modification for the modified resins could be attained because of the co-continuous structure of the modified resins. The toughening mechanism is discussed in terms of the morphological behaviours of the modified epoxy resin systems.

Chemiluminescence measurement of gel times for amine-cured epoxy resins

The cross-linking reactions of 4,4'-diaminodiphenyl sulphone (DDS) with stoichiometric quantities of glycidyl ether- or tetraglycidyl amine-based epoxy resins were monitored using chemiluminescence (CL) and rheometry. It was found that, when a sample was cured isothermally in air, the CL profile increased to a maximum, then decreased again. The maximum was found to correspond well with the gel time (tgel), as measured by rheometry. This observation is discussed in relation to the chemical reactions occurring within the material and the physical state of the matrix. The effect of impurities in DDS on the gel time of these epoxy resins is reported.

Toughening of aromatic diamine-cured epoxy resins by poly(ethylene phthalate)s and the related copolyesters

Aromatic polyesters, prepared by the reaction of aromatic dicarboxylic acids and 1,2-ethanediol, were used to improve the toughness of bisphenol-A diglycidyl ether epoxy resin cured with p,p′-diaminodiphenyl sulphone. These polyesters contained poly(ethylene phthalate)s, poly(ethylene phthalate-co-ethylene isophthalate)s (PEPI), poly(ethylene phthalate-co-ethylene terephthalate)s, and poly (ethylene phthalate-co-ethylene 2,6-naphthalene dicarboxylate)s. All the aromatic polyesters used in this study were soluble in the epoxy resin without solvents and were found to be effective as modifiers for toughening the epoxy resin. For example, the inclusion of 20 wt% of PEPI (10 mol.% isophthalate unit, MW 7400) led to a 100% increase in the fracture toughness ( K IC ) of the cured resin with no loss of mechanical and thermal properties. The modified resins had a two-phase morphology and the polyesterrich dispersed particles in the epoxy matrix. The toughening mechanism was discussed in terms of the morphological and dynamic viscoelastic behaviours of the modified epoxy resin system.

Effect of processing variables on thermal and viscoelastic properties in TGDDM/DDS epoxy system

Abstract The effects of processing temperature and mechanical mixing speed on glass transition temperature, and pot life, activation energies for chemical reaction and molecular relaxation of diaminodiphenyl sulphone (DDS) cured tetraglycidyl diaminodiphenyl methane (TGDDM) epoxy have been evaluated. Viscometry study indicates that the pot life of TGDDM/DDS resin mixtures is significantly affected by the cure temperature and mixing speed. The anomalous behavior at the mixing speed of 900 rpm is likely to be due to a result of poor mixing. Differential scanning calorimetry (DSC) studies show that the glass transition temperature of uncured resin exhibits a Tgo of 5 ‐ 19 °C, which decreases with increasing mixing speed. In general, a higher mixing speed would create a higher mixing power of the system, is a result of increasing fluid molecular friction and shear stress. This may be a consequence of molecular chain scissions of oligomer that probably reduce the average molecular weight, and therefore reduce the glass transition temperature. The activation energy for the curing reaction of this epoxy system, around 91 ‐ 98 kJ/mole, was found to be only slightly affected by the mixing speed. Dynamic mechanical analysis (DMA) studies show that two main relaxations can be ob‐ served for this epoxy system. The low temperature relaxation at ‐20 ‐ ‐50 °C is the β transition, with a low activation energy of about 56 ‐ 59 kJ/mole under increasing mixing speed, whereas the high temperature relaxa‐tion at 230 ‐ 260 °C is the a transition, which is associated with the glass transition temperature, with an activation energy of 240 ‐ 400 kJ/mole, and was strongly affected by the mixing speed. It is believed that these activation energies provide a unique method of characterizing the molecular segmental motion of epoxy networks which were affected by the mixing process.

Kinetic studies by FT-NIR of the curing reactions of two glycidyl ether epoxy resins mixed with stoichiometric quantities of 4,4′ - DDS

The crosslinking reactions of 4,4'-diaminodiphenyl sulphone with stoichiometric quantities of multifunctional epoxy resins were monitored using Fourier transform near infrared (FT-N1R) spectrophotometry. Manipulation of the pectral data enabled the concentrations of reactive groups throughout isothermal cure to be profiled. A kinetic model which included catalytic and diffusion-controlled reactions was developed to fit the data. Two glycidyl ether resins (Shell 1153 and Tactix 742) were chosen for this study to give an overview of this approach to commercial systems.

Positive-working photosensitive polyimide precursor based on polyisoimide using nifedipine as a dissolution inhibitor

A positive-working photosensitive polyimide precursor based on polyisoimide (PFII) and nifedipine (1,4-dihydro-2,6-dimethyl-4-(nitrophenyl)-3,5-pyridinedicarboxylic acid dimethylester) (DHP) as a photosensitive compound has been developed. P11 was prepared by the ring-opening polyaddition of oxydiphthalic anhydride (ODPA) and 3,3' diamino diphenylsulphone (3,3'-DDS), followed by the treatment of trifluoroacetic anhydridetriethylamine in N-methyl-2-pyrrolidone (NMP). PII film showed excellent transparency at 365 nm and 436 nm. The dissolution behaviour of PII film containing 20 wt% of DHP after exposure and post-exposure bake (PEB) has been studied. It was found that the dissolution rate of the exposed area was about six times faster than that of the unexposed area due to the photochemical reaction of DHP in P11 film. The photosensitive polyimide precursor containing 20 wt% of DHP showed a sensitivity of 45 mJ cm- 2 and a contrast of 2.4 with 365 nm light when post-baked at 150C for 10 min and developed with cyclohexanone at 50C.

Fibre reinforced composites of multifunctional epoxy resins

AbstractGlass and carbon fibre reinforced epoxy composites were fabricated for N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenyl methane (TGDDM) and its formulated systems with tri‐ and di‐functional reactive epoxy diluents using 30% diaminodiphenyl sulphone (DDS) as a curing agent. The epoxy laminates were evaluated for their physical, chemical and mechanical properties [at room (26°C) and high (100°C) temperatures]. A marginal increase (&lt;20%) in the mechanical properties of CFRP was found compared with GFRP laminates. Incorporation of epoxy diluents altered the mechanical properties of the composites significantly. The incorporation of triglycidyl‐4‐aminophenol diluent to TGDDM systems resulted in an improvement in mechanical properties of about 2–6%.

Effect of cross-link density on modification of epoxy resins by N-phenylmaleimide-styrene copolymers

The effect of cross-link density on the toughening of modified resins was investigated for the modification of epoxy resins with N-phenylmaleimide-styrene alternating copolymers (PMS). The cross-link density of the epoxy matrix was controlled by a combination of two kinds of epoxy resins [diglycidyl ether of bisphenol-A (DGEBA) or triglycidyl aminocresol (TGAC)] and hybrid hardeners composed of p, p′-diaminodiphenyl sulphone (DDS) and p, p′-( N, N′-dimethyl)-diaminodiphenyl sulphone (MDS). The addition of 10 wt% of PMS ( M w 214,000 ) led to 120% increase in the fracture toughness ( K 1C) of the DGEBA resin cured with the hybrid hardener (DDS: MDS, 67:33 mol ratio). On addition of 15 wt% of PMS ( M w 214,000 ), K 1C for the modified resin increased 110% in the TGAC/hybrid hardener (DDS: MDS, 67:33 mol ratio) system. Morphologies of the modified resins depended on PMS molecular weight and concentration, and the cross-link density of the matrix. The toughening of epoxies could be explained by the cocontinuous phase structure in every case.

Kinetics of curing reactions for epoxy-amine/polyethersulphone resins

Differential scanning calorimetry (DSC) was used to indicate the relative extents of the different cure reactions of the 4-glycityloxyl-N, N-diglycidylaniline (MY0510), polyglycidyl ether of phenol formaldehyde novolac (DEN431) and 3,3 diamino diphenylsulphone (3,3 DDS) resin systems and how these were affected by the presence of polyethersulphone (PES). The extent of reactions at any given time decreased with increasing PES concentration and the reaction rate maximum shifted to longer times. The cured resin systems were examined using dynamic mechanical analysis (DMA). Broader β-transitions of lower intensities were observed in specimens containing PES, suggesting an increased range of relaxations within the transition.

Treatment of Behçet's disease with diamino-diphenyl sulphone (DDS)

Diamino-diphenyl sulphone (DDS) was given to three patients with Behcet's disease. One patient was treated with DDS for orogenital ulcers, cutaneous symptoms and arthralgia. The other two were being treated with oral corticosteroid, and DDS was added. In all cases, DDS therapy improved cutaneous manifestations of Behcet's disease, and enabled a lowering of the dosage of oral corticosteroids in one case.