Diaminodiphenyl Sulphone Research Articles

Toughening of epoxy resins by N-phenylmaleimide-styrene copolymers

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 ( M w 345,000 ) which led to a 130% increase in the fracture toughness ( K IC) 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 ( M w 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.

Effect of cross-link density on modification of epoxy resins with reactive acrylic elastomers

The effect of cross-link density on the toughness of modified resins was investigated for modification of epoxy resins with acrylic elastomers with pendant epoxy groups. The elastomers were prepared by terpolymerization of butyl acrylate (BA), glycidyl methacrylate (GMA) and acrylonitrile (AN). The cross-link density of the epoxy matrix was controlled using hybrid hardeners composed of p, p′-diaminodiphenyl sulphone (DDS) as a primary diamine and p, p′-( N, N′-dimethyl)-diaminodiphenyl sulphone (MDS) as a secondary diamine. The terpolymers were effective as modifiers for toughening of difunctional epoxy resins (bisphenol A diglycidyl ether). The addition of 20 wt% of the terpolymer (62 mol% BA, 25 mol% GMA and 13 mol% AN, M n 7900 ) led to a 100% increase in the fractural toughness of the resin cured with the hybrid hardener (DDS/MDS, 48:52 mol ratio, 65:35 NH ratio). The lower the cross-link density, the larger was the fracture toughness and the lower was the glass transition temperature. On the other hand, the terpolymers were less effective in the modification of trifunctional epoxy resins of higher cross-link density (triglycidyl aminocresol) even when using the hybrid hardener (DDS/MDS, 48:52 mol ratio). Both modified systems afforded cured resins with two-phase morphologies. The toughening mechanism is discussed in terms of the morphological and dynamic mechanical behaviours of the modified epoxy resin systems. It is concluded that the ductility of the epoxy matrix contributes greatly to toughening of epoxy resins with acrylic elastomers.

Influence of a two-step process and of different cure schedules on the generated morphology of a rubber-modified epoxy system based on aromatic diamines

Toughened epoxy networks based on diglycidyl ether of bisphenol A (DGEBA) prepolymer, 4,4′-diamino diphenyl sulphone (DDS) curing agent and epoxy-terminated butadiene-acrylonitrile copolymer-2,2′-bis(4-aminophenoxy)phenyl propane (ETBN-BAPP) adduct were prepared using a two-step process and compared to DGEBA-DDS-ETBN networks prepared using a one-step process. The kinetics of the reaction was followed by size exclusion chromatography and differential scanning calorimetry: the extent of reaction was found to be higher at the cloud point and lower at gelation in the two-step process. The morphology was studied by transmission and scanning electron microscopy. For the same initial rubber content, large differences were observed: when a two-step process was used, the dispersed particles showed irregular contours with a broad diameter distribution, but the volume fraction of dissolved rubber in the rigid matrix was independent of the process. The effect of the cure cycle on the morphology, mechanical and viscoelastic properties was examined. All of the samples had the same impact strength ( ⋍30 kJ m −2 ) with an identical modulus and glass transition temperature. These results confirm that the most important parameter is the volume fraction rather than the diameter of the dispersed-phase particles.

Epoxy resin toughened with thermoplastic

AbstractHighly crosslinked, brittle epoxy resin based on tètraglycidyl‐4,4′‐diaminodiphenyl methane (TGDDM) cured with 4,4′‐diaminodiphenyl sulphone (DDS) is widely used as a matrix material for aerospace composite applications. This work describes how inclusion of a polyetherimide (PEI) thermoplastic rich phase can significantly toughen the resin without a fall in apparent stiffness, which accompanies the more traditional method of rubber toughening. Dynamic mechanical analysis and scanning electron microscopy are used to characterize morphology, while fracture toughness and flexural modulus measurements are also performed on the cured resins. The extent of toughening is found to be dependent upon PEI concentration and test temperature. It is observed that the PEI rich phase toughens through ductile drawing across the faces of the advancing crack tip, and that this is the dominant toughening mechanism in the material.

Toughening of epoxy resins by modification with reactive elastomers composed of butyl acrylate and glycidyl (meth)acrylate

Acrylic elastomers with pendant epoxy groups were used to reduce the brittleness of bisphenol-A diglycidyl ether epoxy resin cured with p, p′-diaminodiphenyl sulphone. The elastomers were prepared by copolymerization of butyl acrylate (BA) with glycidyl acrylate (GA) or methacrylate. These copolymers were effective for toughening of the epoxy resin system. The addition of 20 wt% of copolymer (74 mol% BA and 26 mol% GA) led to 60% increase in the fracture toughness of the cured resin at slight expense of its mechanical properties. The glass transition temperatures of cured resins were comparable to that of the parent epoxy resin. The toughening mechanism is discussed in terms of the morphological and dynamic viscoelastic behaviour of the modified epoxy resin system.

Chemical modification of matrix resin networks with engineering thermoplastics: 1. Synthesis, morphology, physical behaviour and toughening mechanisms of poly(arylene ether sulphone) modified epoxy networks

Bisphenol A-based epoxy resins were modified with either phenolic hydroxyl or aromatic amine functionally-terminated poly(arylene ether sulphone) oligomers and thermally cured with 4,4′ diaminodiphenyl sulphone. The resulting networks displayed significantly improved fracture toughness, with little sacrifice in modulus. The bisphenol A-based polysulphones were molecularly miscible with the epoxy precursors over the entire range of compositions and molecular weights investigated, but developed a two phase structure upon network formation. The molecular weights and composition of polysulphone chemically incorporated into the network were varied and their effect on several important physical properties was investigated. The dynamic mechanical analysis and scanning electron microscopy (SEM) studies showed that it is possible to generate a two-phase morphology in the cured networks wherein polysulphone composite particles are dispersed in the epoxy matrix. Despite the two-phase structure, the modified crosslinked systems are nearly transparent, due to a similarity in component refractive index values. The fracture toughness of these modified networks under plane strain conditions improved significantly with minimal sacrifice of the flexural modulus.

Radiation resistance of polymer composites at 77 K: effects of reinforcing fabric type, specimen thickness, radiation type and irradiation atmosphere

Polymer matrix composites having different reinforcing fabrics and specimen thickness were prepared by using an epoxy of tetraglycidyldiaminodiphenylmethane (TGDDM) cured with diaminodiphenyl sulphone (DDS) and a polyimide of polyaminobismaleimide as matrix resins. The composites obtained and the pure TGDDM - DDS epoxy and polyimide resins were irradiated with 60Co γ-rays or 2 MeV electrons at room temperature in an atmosphere of air or argon. Three-point bend tests were then carried out at 77 K. Comparison of the degradation behaviour among the E-glass and T-glass fabric composites revealed that the dose dependence of the composite strength is almost independent of the composite specifications such as the type of fabric weave, the kind of glass fibres, the specimen thickness and the volume fraction of fibres. This result is in accord with a degradation mechanism such that the dose dependence of the composite strength is virtually determined by a change in the matrix ultimate strain due to irradiation. As to the effects of γ-ray and electron irradiation in air or in argon, the dose dependence of the composite strength follows an identical pattern regardless of the radiation type and the irradiation atmosphere. The dose dependence of the pure resin strength, however, follows completely different patterns between the γ- and electron irradiation in air. These results are interpreted in terms of the oxidative degradation and the flaw sensitivity at the specimen surface of pure resins and composites.

Histopathological findings in the iris of dapsone treated leprosy patients.

From 43 Nepalese leprosy patients skin smear negative, and treated with dapsone (diamino diphenyl sulphone), and without any sign of active leprosy or iritis, specimens from iridectomy during cataract surgery were studied histopathologically. Of 49 iris specimens only six (12%) were found to be without any histopathological change. Atrophy of the iris stroma was seen in 63% and neovascularisation in 6% of all cases. In 16% in which the dilator muscle could be detected, it was atrophic, and in 11% the pigmented epithelium was thinned and atrophic. Cellular inflammatory infiltrations were seen in 88% of all specimens. They were mostly slight in eyes which before operation had been without posterior synechiae of the iris. In most of the eyes in which posterior synechiae had been present moderate or heavy inflammatory cell infiltrates composed of lymphocytes and plasma cells, often associated with macrophages, neutrophils, or eosinophils, were found. In five iris specimens acid fast bacilli were present. This raises the question whether these can survive systemically despite dapsone chemotherapy in the iris, thus leading to dapsone-resistant leprosy and to recurrent iritis.

Mecanismes reactionnels, cinetique et structure du reseau de systemes thermodurcissables type TGDDM-DDS

Liquid and solid CP MAS 13C NMR techniques were used to analyse model compounds characteristic of the main chemical groups present or created during polycondensation of tetrafunctional epoxide prepolymer in the presence of an aromatic amine (diaminodiphenyl sulphone). The main results agreed with published data that certain intramolecular reactions occurred and could become predominant, depending on the purity of the resin. Kinetic study (isothermal) in the 100–180°C range of several resins with the same chemical groups showed the role of impurities in autocatalysis. Structural data obtained in relationship with the stoichiometry, the catalysts and the impurities have been correlated with thermal data.

Toughening of epoxy resins by modification with acrylic elastomers containing pendant epoxy groups

New acrylic elastomers with pendant epoxy groups were used to reduce the brittleness of bisphenol-A diglycidyl ether epoxy resin cured with p, p′-diaminodiphenyl sulphone. The elastomers were prepared by copolymerization of butyl acrylate (BA), vinylbenzyl glycidyl ether (VBGE) and styrene (St) or acrylonitrile (AN). These terpolymers were effective for toughening of the epoxy resin system. The addition of 20 wt% of the terpolymer (74 mol% BA, 18 mol% VBGE and 8 mol% St) resulted in an 80% increase in the fracture toughness ( K 1c) of the cured resin at the slight expense of its mechanical properties. The modified epoxy resins had two-phase morphology in which the volume fraction and average diameter of the dispersed elastomer particles were dependent on the structure and concentration of the terpolymer. The toughening mechanism is discussed in terms of the morphological and dynamic mechanical behaviour of the modified epoxy resin system.

Toughening mechanisms in elastomer-modified epoxies

The role Of matrix ductility on the toughenability and toughening mechanism of elastomer-modified, diglycidyl ether of bisphenol A (DGEBA)-based epoxies is investigated. Matrix ductility is varied by using epoxide resins of varying epoxide monomer molecular weights. These epoxide resins are cured using 4,4′ diaminodiphenyl sulphone (DDS) and, in some cases, modified with 10 vol% carboxyl-terminated copolymer of butadiene and acrylonitrile (CTBN). Fracture toughness values for the neat epoxies are found to be almost independent of the monomer molecular weight of the epoxide resin used. However, the fracture toughness of the elastomer-modified epoxies is found to be very dependent upon the epoxide monomer molecular weight. Tensile dilatometry indicates that the toughening mechanism, when present, is similar to the mechanism found for piperidine cured, elastomer-modified epoxies studied previously. Scanning electron microscopy and optical microscopy techniques corroborate this finding.

Toughening tetrafunctional epoxy resins using polyetherimide

Toughened epoxy resins have been prepared by dissolving polyetherimide (PEI) in a tetraglycidyl-4,4′-diaminodiphenyl methane (TGDDM) based resin with 30 p.h.r. diaminodiphenyl sulphone (DDS) as curing agent. The polyetherimide forms a separate phase, with a dynamic loss peak which varies between 200 and 212°C. The loss peak of the resin occurs at about 265°C. Three-point bend tests show a linear increase in K IC with PEI content, from 0.5MPa√m in the parent resin to 1.42MPa√m at 25 p.h.r. of PEI. Young's modulus at 23°C shows a modest reduction from 3.6 to 3.5 GPa over the same composition range.

Synthesis and characterization of thermally stable polymers: poly(keto-amines)

Poly(keto-amines) have been prepared by condensing 4,4′-dichloroacetyldiphenyl ether (DDE) with ethylene diamine, hexamethylene diamine, 1,4-phenylene diamine, 4,4′-diaminodiphenyl sulphone, o-toluidine, o-dianisidine and 1,5-diaminonaphthalene. The polycondensations were carried out at 80–85° using benzene as solvent and pyridine as acid acceptor. The poly(keto-amine) samples have been characterized by i.r. spectral studies; values of bar M n were estimated by non-aqueous conductometric titration and viscometric study in formic acid. The polymers were examined by thermogravimetry. Poly(ketoamine) samples were reduced by the Wolf-Kishner method. The characteristics of reduced poly(ketoamines) i.e. poly(amines), have been compared with those of the parent polymers.

Thermomechanical properties and structure of polyamidoimide blends and copolymers

The phase-aggregate state of polyamidoimide films, and their blends and copolymers based on dicarboxypphenylphthalimide dichloride and 4,4′-diaminodiphenyl etherm 4,4′-bis-amino phenoxydiphenylsulphone and 3,3′-bis aminophenoxydiphenylsulphone is studied by diffraction and thermomechanical methods. The homopolymers have a mesomorphic X-ray with the exception of polyamidoimides based on 3, 3′-bis aminophenoxydiphenyl structure. The copolymers under study have a block structure, the 4,4′-diaminodiphenyl sulphone. ments having a dominant role. When the content of these fragments is 30 mole %, ether fragrearrangements are observed in both the copolymers and mechanical blends of the structural polyamidoimides.

Leprosy and immunity: genetics and immune function in multiple case families.

Genetic susceptibility to infection with M. leprae was studied in 10 multiple case families of Australian Aborigines. Of the 87 members available for study, 24 had proven stable clinical leprosy which had been or was still being treated with diamino diphenyl sulphone. Evidence of contact with M. leprae in the remaining 63 members as assessed by ELISA to M. leprae sonicate and phenolic glycolipid (PGL) or by indirect immunofluorescence antibody assay was found in 78%, 64% and 71%, respectively. By contrast, in vitro assays of T cell function (LMAT and LTT) were less reliable indicators of exposure. Evidence was sought for possible linkages between human leucocyte antigen (HLA) or non-HLA genes and four marker phenotypes including clinical leprosy, clinical subtype of leprosy and lymphocyte transformation or leucocyte migration inhibition factor (LIF) production in response to M. leprae antigen. No associations were found with any particular HLA or non-HLA gene. On the other hand, sequential analysis of the data from the 10 families was strongly suggestive of a linkage between HLA haplotype and non-responsiveness to M. leprae as manifest by lack of LIF production but not lymphocyte transformation. The model which best fits the data is for a gene on chromosome 6 in close linkage with the HLA haplotype, with two alleles, autosomal recessive inheritance and penetrance of 90%. On this basis, it can be suggested that disease type (lepromatous leprosy) rather than disease susceptibility may be controlled by genes within or closely linked to the major histocompatibility gene complex.

Inverse gas chromatography used to follow kinetics of epoxy-amine reactions in the molten state

Polycondensation kinetics of epoxy-amine model systems were investigated with inverse gas chromatography. The results obtained were applied to the study of cross-linking kinetics of two epoxy prepolymers, tetraglycidyl diamino diphenyl methane and diglycidyl ether of bisphenol A, with diamino diphenyl sulphone. Data furnished by inverse gas chromatography showed zones of gelation and of vitrification. Based on kinetics established by isothermal microcalorimetry, it was possible to determine reaction advancement in these transition zones. The results show that advancement of both reaction systems to the transition points T 1 and T 2 is very sensitive to curing temperature and to the stoichiometry of the mixture. Finally, the vitreous transition temperatures of the cross-linked systems were determined and compared to those determined with differential scanning calorimetry.

Proton Magnetic Resonance Investigation of the Interaction of the Antileprosy Drug, Dapsone, with the Model Membrane, Dipalmitoyl Phosphatidyl Choline-Water

Proton magnetic resonance studies of the binding of the antileprosy drug, diamino diphenyl sulphone (dapsone or DOS) with the model membrane, dipalmitoyl phosphatidyl choline (DPPC) in water, have been undertaken. The results indicate that the drug molecules bind to the head group of DPPC, reducing thereby, the number of sites available for water to bind to DPPC. This results in the sharpening of the proton magnetic resonance line of water on addition of the drug. The results also indicate that the motion of the alkyl chain, as also that of the head group, become more restricted as a result of the binding of the drug with DPPC.

Hygrothermal Aging Effects in Cured Epoxies

The effect of relatively severe hygrothermal aging on the sorption and also the diffusion of water at 40°C has been studied for a number of epoxy networks comprising tetraglycidyl 4,4′-diaminodiphenyl methane, and the curing agent 4,4′-diaminodiphenyl sulphone, 4,4′-diaminodiphenyl methane and 2,2′-dichloro-4,4′-diaminodiphenyl methane. Aging at high temperatures is accompanied by a pronounced increase in sorptive capacity at 40°C consistent with a significant expansion of the network. Dry annealing of the aged network at sub- Tg temperatures collapses the expanded structure to recover the sorptive capacity of the unaged network. Preliminary studies of the sorption-desorption kinetics for aged networks indicate that the effective diffusion coefficient is not markedly affected.

Statistical structural model for the build-up of epoxy-amine networks with simultaneous etherification

A statistical structural model is developed to describe a diepoxy-diamine cure, taking into account the possibility of simultaneous epoxy-hydroxy reaction (etherification). Expressions for the number- and weight-average molecular weights, gel conversion, sol fraction, mass fraction of pendant and elastically active network chains (EANC) and concentration of EANC are derived. The different reactivity of primary and secondary amine hydrogens is taken into account, but intramolecular reactions in the pregel stage are neglected. The model is applied to the cure of bisphenol A diglycidyl ether with diaminodiphenyl sulphone, where a previous kinetic analysis showed the presence of etherification. It is shown that, for stoichiometric formulations, etherification acts to decrease both the gel conversion and the concentration of EANC at full epoxy conversion. However, the elastic modulus of the material is not expected to change significantly. Instead, for formulations containing a 100% epoxy excess, the predicted elastic modulus at full epoxy conversion is 50% higher than that predicted for a stoichiometric mixture.

Minimum inhibitory concentration of drugs againstMycobacterium leprae as determined by anin vitro assay

The observations that liveMycobacterium leprae after entry into cultured peritoneal macrophages from mice, reduced the EA rosetting macrophages, have been exploited to determine the minimum inhibitory concentration of diamino diphenyl sulphone and rifampicin. Diamino diphenyl sulphone showed a minimum inhibitory concentration of 0.028 μg/ml and rifampicin 0.11μg/ml when given externally. However, there was accumulation of diamino diphenyl sulphone inside the macrophages. At an external concentration of 0.028 μg/ml the concentration inside the macrophage was 0.5μg/ml. The minimum inhibitory concentration for diamino diphenyl sulphone in this assay system is higher by several folds and that for rifampicin is slightly lower, than what is reported earlier with mice foot pad experiments. The minimum inhibitory concentration reported in this assay system is quite close to what is observed forin vitro inhibition ofMycobacterium lufu with both the drugs