Diaminodiphenyl Methane Research Articles

Preparation of 4‐(4‐hydroxyphenoxy)phenol diglycidyl ether with improved toughness behavior

ABSTRACTA high‐performance difunctional epoxy resin, 4‐(4‐hydroxyphenoxy)phenol diglycidyl ether (DHPOP), was synthesized by a two‐step method. The curing behavior of DHPOP was investigated by nonisothermal differential scanning calorimetry method and the curing kinetics results revealed that the introduction of ether linkage could improve the activity of epoxy groups, leading to a lower curing temperature and apparent activation energy compared with that of the commercial bisphenol‐A diglycidyl ether (DGEBA). A series of copolymers were then prepared by varying the mass ratio of DHPOP and DGEBA, which were cured with 4,4′‐diaminodiphenyl methane. The effect of DHPOP contents on thermal and mechanical properties and fracture morphology was studied. As expected, with the increase of DHPOP in the network, the impact strength and char yield were significantly enhanced, while the glass transition temperature (Tg) remained unchanged because of the increase of crosslink density. The excellent toughness endows the DHPOP with the promising potential for the application as high‐performance resin matrix. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46458.

The mechanical behaviors of epoxy-terminated hyperbranched polyester (E-HBP) as toughener in different epoxy resins

Using epoxy-terminated hyperbranched polymer (E-HBP) to modify epoxy resin (EP) is an effective way to improve the toughness of EP. In the present study, two different epoxy resin systems with E-HBP are researched: a commercial diglycidyl ether bisphenol A (DGEBA) resin with anhydride as curing agent and a tetraglycidyl diaminodiphenyl methane (TGDDM) resin with diamine as curing agent. Characterization results show that the addition of E-HBP could improve the mechanical properties of the two epoxy resin systems, such as tensile strength, elongation, and modulus of elasticity. Meanwhile, the glass transition temperature (T g ) of the two systems does not decrease. However, the morphology of the tensile fracture surfaces of the two modified systems shows different behaviors. Significant plastic deformation could be observed in the fracture surfaces of the modified DGEBA/anhydride system, and particle cavitations are clearly shown in the fracture surfaces of the modified TGDDM/diamine systems. The analysis of the tensile fracture surfaces suggests that firstly E-HBP participates in the curing process of the modified resin systems, followed by the chemical-induced phase separation; finally, a gradient transition interface layer (GTIL) is formed. Apart from these, during the external loading process, the mechanical behaviors (deformation or cavitation) of the separated E-HBP particles in the modified epoxy resins are affected by the properties of the epoxy matrix itself.

Mechanochemical changes in absorption and fluorescence of DDM-containing epoxies

Mechanochemical changes in absorption or fluorescence in solid polymers are important for the development of new methods of damage sensing, and must be demonstrated in structural polymers such as epoxies for widespread use. With this in mind, we have observed that diamine-cured epoxies containing 4,4′-diaminodiphenyl methane (DDM) framework display mechanochemical changes in both absorption and fluorescence. Samples change from original “blue” to mechanochemically activated “red” fluorescence in response to uniaxial compressive deformation beginning in the early stages of strain hardening. Accompanying the “red” fluorescence is an increase in radical concentration; both are impermanent in time, suggesting the reactive intermediate as the fluorophore. Orange and green chromophores are generated by compression as well; the orange chromophore is the red-emitting fluorophore while the green chromophore is non-fluorescent at ambient conditions. Our work indicates that the DDM structure is the origin of the mechanochromic responses, and stoichiometric variation and degree of cure are strong determinants for whether orange or green chromophores will form. Based on these results the red-emitting orange chromophore is proposed as a reactive radical intermediate of core DDM structure, generated by bond scission reactions on the epoxy network. The green chromophore is a quinoidal methine resulting from the intermediates.

Photochemical changes in absorption and fluorescence of DDM-containing epoxies

Photochemical changes in the optical characteristics of solid polymers form the basis for many important technologies, but few examples are demonstrated in diamine-cured epoxy, one of the most important structural polymer systems. We have observed that diamine-cured epoxies containing the 4,4′-diaminodiphenyl methane (DDM) framework display changes in both absorption and fluorescence in response to UV light. The change from original “blue” to photo-activated “red” emission can be accomplished by illuminating samples of DDM-containing epoxy with photons of 254 nm or 370 nm wavelengths, followed by excitation of the newly-generated red-emitting fluorophore with 350–400 nm light. Studies of the monomer constituents and of many formulations of diamine-cured epoxy identify the DDM structure as the responsive moiety, both from the epoxy or diamine monomer. The fluorescence change is accompanied by the formation of orange and green chromophores; the orange chromophore is the fluorophore, with a broad 410 nm excitation and 607 nm emission. Our work shows the “blue-to-red” transition to be irreversible and independent of atmospheric oxygen; the fluorophore’s impermanence with time and its radical spectral signature identify it as a reactive intermediate rather than a photo-oxidation product. The central methylene radical of the benzoidal DDM structure is proposed as a red-emitting fluorophore/orange chromophore, with the green chromophore being a quinoidal methine resulting from the DDM radical.

Two high-efficient DOPO-based phosphonamidate flame retardants for transparent epoxy resin

In this work, two kinds of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-based phosphonamidate flame retardants named 4,4′-diamino-diphenyl methane (DDM)-DOPO and morpholine (MPL)-DOPO are successfully synthesized by the classic Atherton–Todd reaction, and their chemical structures are characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). Epoxy composites containing DDM-DOPO or MPL-DOPO are prepared, which still retain relatively high transparency compared with pure epoxy resin (EP). Its fire behavior is studied in terms of vertical burning test (UL-94), limiting oxygen index (LOI), and cone calorimeter tests. The LOI values can achieve 30% and UL-94 test past V-0 rating for DDM-DOPO-modified epoxy composites with 0.25 wt% phosphorus content. The cone calorimeter results indicate that the modified epoxy composites can release less heat and smoke compared with pure EP. Also, thermal degradation behavior and flame-retardant mechanism of epoxy composites are investigated by thermogravimetric analysis and thermogravimetric analysis/infrared spectrometry. The results indicate that two DOPO-based phosphonamidates show a significant gaseous-phase effect on reducing the release of combustible volatiles.

Multivariate curve resolution using a combination of mid-infrared and near-infrared spectra for the analysis of isothermal epoxy curing reaction

Multivariate curve resolution (MCR) was applied to a hetero-spectrally combined dataset consisting of mid-infrared (MIR) and near-infrared (NIR) spectra collected during the isothermal curing reaction of an epoxy resin. An epoxy monomer, bisphenol A diglycidyl ether (BADGE), and a hardening agent, 4,4′-diaminodiphenyl methane (DDM), were used for the reaction. The fundamental modes of the NH and OH stretches were highly overlapped in the MIR region, while their first overtones could be independently identified in the NIR region. The concentration profiles obtained by MCR using the hetero-spectral combination showed good agreement with the results of calculations based on the Beer-Lambert law and the mass balance. The band assignments and absorption sites estimated by the analysis also showed good agreement with the results using two-dimensional (2D) hetero-correlation spectroscopy.

Synthesis of a novel reactive flame retardant containing phosphaphenanthrene and piperidine groups and its application in epoxy resin

A novel reactive flame retardant (DPT) for epoxy resin (EP) was successfully synthesized through the reaction between 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), 1,4-phthalaldehyde and triacetonediamine. DPT was used as co-curing agent of 4,4′-diaminodiphenyl methane (DDM) to prepare intrinsic flame-retardant EP (EP/DDM/DPT) thermosets. DSC results indicated that DPT was capable of curing EP and only a slight decline in glass transition temperatures of EP/DDM/DPT thermosets (162–173 °C) was observed. The incorporation of DPT led to the improvement of the char yields for EP/DDM/DPT thermosets at 800 °C. The EP/DDM/DPT-4 sample displayed a LOI value of 38.3% and a UL94 V-0 rating when the phosphorus content was only 1.0 wt %. Compared with comparable values for a EP/DDM sample, the peak of heat release rate (pk-HRR), average of heat release rate (av-HRR) and total heat release (THR) for EP/DDM/DPT-4 sample were decreased by 38.7%, 31.6% and 36.4%, respectively. During combustion, DOPO groups decomposed to generate phosphorus-containing compounds which promoted the formation of protective char layers in the condensed phase, and produced phosphorus-containing radicals which quenched the active radicals in the gaseous phase. Large quantities of hindered amine radicals with quenching effect and incombustible gases with diluting effect were released into the gaseous phase from the pyrolysis of piperidine groups. The presence of piperidine groups served to reinforce the action of phosphaphenanthrene groups. The piperidine and DOPO groups exerted flame retardant effect in both gaseous and condensed phases to endow EP thermosets with excellent flame retardancy.

Eugenol-based non-isocyanate polyurethane and polythiourethane

Global resource crisis and severe environmental problems have compelled world scientists to develop sustainable and green chemical materials. In this work, eugenol, a cheap and renewable phenol derivative found in cloves, is successfully utilized to prepare hydroxyl non-isocyanate polyurethanes (HNIPU), with number-average molecular weights (M n) from several to dozens of kilodaltons. First, a diepoxide intermediate is synthesized through three steps in 43.9% total yield. Second, this diepoxide reacts with CO2 at atmospheric pressure to form an intermediate possessing two cyclic carbonate groups in moderate yield. Third, the cyclic carbonate-containing intermediate further reacts, with compounds such as 4,4′-diaminodiphenyl methane, 1,6-hexanediamine and p-xylene diamine by nucleophilic ring-opening to obtain the desired HNIPUs. Furthermore, the diepoxide intermediate and CS2 undergo addition reaction to form cyclic dithiocarbonate intermediate that further reacts with 4,4′-diaminodiphenyl methane to afford polythiourethane (PTU). The resulting PTU contains mercapto groups in its each unit. Number-average molecular weight of PTU is Mn 2800 Da. Finally, crosslinking reactions occur between the mercapto groups of PTU and crosslinkers (1,6-hexanediol acrylate and/or cardanol) by thiol-ene reactions under UV (λ = 365 nm) irradiation conditions, leading to their corresponding crosslinked polymers. The optimized conditions for preparing crosslinked polymers include: PTU/cardanol/1,6-hexanediol acrylate = 1:1:0.05 (mass ratio), and UV irradiation time for 30 min. This work is expected to expand applications of eugenol and to provide a new route to NIPUs and PTUs using various diamines.

Rheological and molecular characterization of long-chain branched poly(ethylene terephthalate)

Reactive extrusion with pyromellitic dianhydride (PMDA) and tetraglycidyl diamino diphenyl methane (TGDDM) was conducted to create long-chain branched poly(ethylene terephthalate) (LCB-PET). The mechanical and molecular properties were analyzed by linear and non-linear viscoelastic rheology in the melt state and by size-exclusion chromatography measurements with triple detection. The two tetra-functional chain extenders lead to strong viscosity increases, increasing strain hardening effects, and increasing LCB with increasing chain extender concentration. Molecular stress function model predictions show good agreement with the elongational data measured and allowed a quantification of the strain hardening. Analysis of SEC triple detection data shows a strong increase of the average molar mass, polydispersity, radius of gyration, and hydrodynamic radius with increasing chain extender concentration. Branching was confirmed by a decreasing Mark-Houwink exponent, and the analysis of the contraction of the molecule revealed either star-like, comb-like, random tree-like or hyperbranched structures depending on concentration and type of chain extender.

Pyrolysis and flame retardant behavior of a novel compound with multiple phosphaphenanthrene groups in epoxy thermosets

A novel flame retardant compound (TDBA) with multiple phosphaphenanthrene groups was synthesized and confirmed by chemical structural and elemental characterization. Contrastive analysis on thermal decomposition behavior showed that the two kinds of bridge bonds linking phosphaphenanthrene groups in TDBA caused a wider decomposition temperature range, contributing to inhibiting combustion in relatively longer time. The application of TDBA in epoxy thermosets suggested that, TDBA capacitated the limited oxygen index of thermosets to surpass 35% and 4wt.% or more loadings of TDBA made 4,4′-diamino-diphenyl methane curing thermosets pass UL94 V-0 rating especially. During combustion, the incorporated TDBA induced the matrix to decompose earlier, reduced the fuels production, reduced burning intensity and inhibited the combustion reaction of fuels in gaseous phase, and promoted the charring behavior of thermosets in condensed phase. The pyrolysis of TDBA proceeded along two main directions, namely substituted phosphaphenanthrene and bisphenol-A. Through releasing massive phenolic derivatives, PO free radicals and other certain phosphorus-containing substances, TDBA is capable to exert free radical quenching effect in gaseous phase, and to promote charring behavior to form compact residue with barrier effect on heat and fuels transportation in condensed phase. This bi-phase joint action mode from TDBA endowed epoxy thermosets with excellent flame retardancy.

Photo-Induced Vertical Alignment of Liquid Crystals via In Situ Polymerization Initiated by Polyimide Containing Benzophenone.

Vertical alignment of liquid crystal (LC) was achieved in an easy and effective way: in situ photopolymerization of dodecyl acrylate (DA) monomers initiated by polyimide based on 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 3,3′-dimethyl-4,4′-diaminodiphenyl methane (BTDA-DMMDA PI). The alignment behavior and alignment stabilities were characterized by a polarizing optical microscope (POM), which showed a stable vertical alignment after 12 h of thermal treatment. The chemical structures, morphology, and water contact angles of alignment films peeled from LC cells with and without DA monomers were analyzed by means of a Fourier transform infrared spectrometer (FTIR), a scanning electron microscope (SEM), and a contact angle tester, separately. The results confirmed that the DA monomers underwent self-polymerization and grafting polymerization initiated by the BTDA-DMMDA PI under ultraviolet irradiation, which aggregated on the surfaces of PI films. The water contact angles of the alignment films were about 15° higher, indicating a relative lower surface energy. In conclusion, the vertical alignment of LC was introduced by the low surface free energy of PI films grafted with DA polymer and intermolecular interactions between LC and DA polymers.

Synthesis and characterization of thermally stable poly(ether-azomethine)s derived from 1,1-bis[4-(4-benzaldehyde oxy)-3-methyl phenyl] cyclopentane

ABSTRACTA new dialdehyde 1,1-bis[4-(4-benzaldehyde oxy)-3-methyl phenyl] cyclopentane (BBMPC) was synthesized starting from cyclopentanone and O-cresol to give 1,1-bis(4-hydroxy-3-methyl phenyl)cyclopentane (BHMPC); followed by reaction with 4-fluorobenzaldehyde in N, N-dimethyl formamide (DMF), containing anhydrous potassium carbonate. New series of poly(ether-azomethine)s were synthesized from (BBMPC) with different diamines such as 4,4′- diamino diphenyl ether (ODA); 4,4′-diaminodiphenyl methane (MDA); 4-aminophenyl sulfone (SDA); p-phenylene diamines (p-PDA), etc. in N, N’- dimethyl acetamide (DMAc) with 5 wt% LiCl by the solution polycondensation method. Inherent viscosities of these polymers were in the range 0.20 to 0.38 dL/g indicating formation of moderate molecular weights. These polymers exhibited good solubility in various polar aprotic solvents such as N-methyl-2-pyrrolidone (NMP), DMAc, DMF, etc. However some polymers showed partial solubility in DMF and DMAc. X-Ray diffraction pattern of polymers showed amorphous nature. Thermal stability was assessed by 10% weight loss temperature and the degradation temperature of the resultant polymers falls in the ranges from 444-501°C in nitrogen. The glass transition temperature was in the range of 155-205°C. The structure-property correlation among these polyazomethines were studied; in view of their potential applications as high performance polymers.

Epoxy hybrid networks with high mass fraction molecular-level dispersion of pendant polyhedral oligomeric silsesquioxane (POSS)

A novel high shear continuous reactor method was developed to obtain molecular level incorporation of polyhedral oligomeric silsesquioxane (POSS) containing one amine group and seven isobutyl groups into epoxy network as pendant cage. The method consisted of optimizing reaction time and temperature for the synthesis of POSS-epoxy precursor in a high shear continuous reactor. A full conversion of POSS into POSS-epoxy precursor was achieved within 30–40 s of reaction time in a continuous reactor for all molar compositions from 1:140 to 1:1.05 in comparison to a batch process with the reaction time of 18 h. The structure of this precursor at the end of the reaction, determined by silicon Nuclear Magnetic Resonance spectroscopy (29Si NMR), was close to the ideal one. The distribution of reaction product was determined by size exclusion chromatography (SEC). The reaction product containing up to 1:3-mol ratio of POSS: epoxy molecules showed ‘epoxy-POSS-epoxy’ precursor as a primary product in comparison to 1:2 and 1:1.05-mol ratios with higher molecular weight precursor as the primary product. Hybrid networks containing up to 50 wt % POSS were prepared by curing these precursors with an aromatic amine curative 4, 4'diamino diphenyl methane (DDM). The resulting networks are completely transparent and no phase separation was observed by SEM and TEM in the course of polymerization despite the incompatibility of the isobutyl groups attached to the POSS with the aromatic epoxy-amine networks. In addition to that, DMA and TGA results prove that the introduction of high shear continuous reactor promotes the dispersion of pendant POSS to a molecular level into epoxy networks.

High performance polyurea coatings based on cardanol

Present research work deals with synthesis of phenalkamines and their use as curing agents for blocked polyisocyanates to yield high performance polyurea coatings. In this work, several phenalkamines were synthesized by conventional Mannich reaction; selecting various structural amines such as hexamethylene diamine (HMDA), isophorone diamine (IPDA), diaminodiphenyl methane (DDM), Jeffamine D-400 and Jeffamine T-403. Structures of these phenalkamines were confirmed by FTIR, 1H NMR spectroscopy and evaluation of amine value. These curing agents were mixed with HDI and IPDI based blocked polyisocyanates to obtain polyurea coatings which were subsequently characterized for mechanical, chemical, optical, thermal and anticorrosive properties. In addition, structure property relationship of all the systems was studied and compared with commercial phenalkamine (AG-141). Anticorrosive properties evaluated by salt spray test and electrochemical impedance spectroscopy (EIS) revealed significant improvement in anticorrosive performance when compared with commercial phenalkamine. All polyurea coatings exhibited excellent performance properties irrespective of the isocyanates used.

Study on flame retardancy of TGDDM epoxy resin blended with inherent flame-retardant epoxy ether

In this article, inherent flame-retardant epoxy ether, 9,10-dihydro-9-oxa-10-[1,1-bis(4-glycidyloxyphenyl)ethyl]-10-phosphaphenanthrene 10-oxide (DPBAEP), with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide moieties was synthesized via an economical method and was used to improve the flame retardancy of 4,4′-tetradiglycidyl diaminodiphenyl methane (TGDDM). A series of epoxy resins were prepared and cured with 4,4′-diaminodiphenyl sulfone. The glass transition temperatures ( Tg) of resin composites were above 243°C and decreased only slightly after DPBAEP was added. The thermal stabilities under the nitrogen (N2) and air atmosphere were also measured using thermogravimetric analysis. The results indicated that DPBAEP had a high decomposition temperature and affected the thermal degradation and promoted the charring of resins. When only over 5 wt% of DPBAEP was introduced, the thermosets obtained a high limiting oxygen index value of around 33.0%, achieved vertical burning V-0 rating and presented fast-swelling char barriers. In order to better understand the flame-retardant mechanisms, the residual char was investigated by scanning electron microscopy observation and Fourier transform infrared spectra. We inferred that the phosphorus (P) moieties reacted with the resin matrix, which played a significant role in promoting the formation of char with special structure, as well as making it rich and tough enough. This kind of char barrier could protect the underlying resin matrix against oxygen and heat transfer and inhibited volatile combustible from diffusing to the flame. Hence, thanks to the synergistic effect of P–N and the excellent compatibility, DPBAEP could impart excellent flame retardancy to TGDDM epoxy resin.

Synthesis, solubility and thermal behavior of novel Diamino-diphenyl methane and caprolactam based different polyimide matrix for antibacterial applications

Novel polyimides (PIs) are synthesized by N, N ‘-(4, 4′-methylene bis (4, 1-phenylene)) bis (6-aminohexanamide) (CPA), pyromellitic dianhydride (PI-1), benzophenone dianhydride (PI-2), naphthalene dianhydride (PI-3), and perylene dianhydride (PI-4) in presence of 1-methyl-2-pyrrolidone (NMP) medium using thermal imidization method. As-synthesized polyimides were physicochemical characterization done by FTIR, XRD, TGA, DSC and the surface morphology and particle in size of polyimides by SEM analysis. The PIs synthesized in the present work exhibit good solubility in organic solvents such as NMP, dimethylformamide (DMF), and dimethyl sulfoxide (DMSO). The PI-4 based imide possesses better solubility with the highest glass transition temperature value of 206° C, highest char yield of 31.5%, and improved antibacterial activity than those of other PIs. Furthermore, the good solubility and thermal stability make them also useful for aerospace and industrial applications.

Development of epoxy-urethane hybrid coatings via non-isocyanate route

Non-isocyanate route of urethane synthesis based on reaction of cyclic carbonated compound with amines is well known. Taking inspiration from this, we have synthesized a monomer containing urethane linkage through the reaction of propylene carbonate with ethylene diamine. This monomer was further reacted with commercial epoxy polymer to obtain hybrid epoxy-urethane adduct. Synthesized adduct was then cured with various structural amines such as isophorone diamine (IPDA), Jeffamine T-403 and diaminodiphenyl methane (DDM). The resultant epoxy-urethane hybrid coatings were characterized for mechanical, chemical, thermal and anticorrosive properties. The hybrid coatings exhibited at par mechanical, chemical and corrosion resistance as compared to that of commercial epoxy coatings. DSC and TGA analysis revealed that glass transition temperature, thermal stability and char yield of hybrid coatings was higher than that of commercial epoxy coatings.

Miscibility, Phase Morphology, Thermomechanical, Viscoelastic and Surface Properties of Poly(ε-caprolactone) Modified Epoxy Systems: Effect of Curing Agents

In this paper, we report on the effect of curing agents on the miscibility, morphology, thermomechanical properties, and surface hydrophobicity of diglycidyl ether of bisphenol A (DGEBA)/poly(e-caprolactone) (PCL) blends. Two curing agents, 4,4′-diamino diphenylsulfone (DDS) and 4,4′-diamino diphenylmethane (DDM), were used. Studies revealed that the epoxy/PCL/DDM system was completely miscible due to the intermolecular hydrogen bonding interactions between carbonyl groups of PCL and hydroxyl groups of epoxy resin. On the other hand, the epoxy/PCL/DDS system exhibited phase separated matrix/droplet type morphology, primarily due to the intramolecular hydrogen bonding interactions within the epoxy phase between sulfonyl groups of DDS and hydroxyl groups generated during epoxy–DDS reaction. The storage modulus of the epoxy/PCL/DDM system was greater than that of the epoxy/PCL/DDS system, and the dependence of modulus on PCL content was more pronounced in the former. Moreover, the epoxy/PCL/DDM system exhibi...

Dielectric Properties of Polyether Sulfone/Bismaleimide Resin Composite Based on Nanolumina Modified by Super-Critical Ethanol

Nano-alumina was chemically modified with super-critical ethanol enabling a surface active coating. Modified nano-alumina was incorporated in polymer blends based on thermoplastic polyether sulfone and thermosetting bismaleimide resin to produce novel nanocomposites designated as SCE-Al2O3/PES-MBAE. In the SCE-Al2O3/PES-MBAE nano-composites, the matrix was originally formed from 4,4′-diamino diphenyl methane bismaleimide (MBMI) using the diluents of 3,3′-diallyl bisphenol A (BBA) and bisphenol-A diallyl ether (BBE), while polyether sulfone (PES) was used as toughening agent along with super-critically modified nano-alumina (SCE-Al2O3) as filler material. The content of SCE-Al2O3 was varied from 0 wt.% to 6 wt.%. The nano-composites were characterized for their morphological, spectroscopic and dielectric properties. Fourier transform infrared spectroscopy (FT-IR) indicated that ethanol molecules had adhered to the surface of the nano-Al2O3 in super-critical state. A reaction between MBMI and allyl compound occurred and SCE-Al2O3 was doped into the polymer matrix. Volume resistivity of the composite initially increased and then decreased. The modification due to SCE-Al2O3 could overcome the undesirable impact of PES by using a bare minimum level of SCE-Al2O3. The dielectric constant (e) and dielectric loss (tan δ) as in the case of volume resistivity were initially increased and then decreased with the content of SCE-Al2O3 in the composite. The dielectric constant, dielectric loss and dielectric strength of SCE-Al2O3 (4 wt.%)/PES (5 wt.%)-MBAE nano-composite were 3.53 (100 Hz), 1.52 × 10−3 (100 Hz) and 15.66 kV/mm, respectively, which indicated that the dielectric properties of the composite fulfilled the basic requirements of electrical and insulating material. It was evident from the morphological analysis that the SCE-Al2O3 was evenly dispersed at the nanoscale; for example, the size of SCE-Al2O3 in SCE-Al2O3 (4 wt.%)/PES (5 wt.%)-MBAE measured less than 50 nm.

The effect of 10-(2,5-dihydroxyphenyl)-9, 10-dihydro-9-oxa-10-phosphaphenanthrene- 10-oxide on liquid oxygen compatibility and cryogenic mechanical properties of epoxy resins

In the present study, 10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (ODOPB) was chemically incorporated into bisphenol A epoxy resin (EP) to improve liquid oxygen compatibility of the EP. Fourier transform infrared (FTIR) spectroscopy verified that ODOPB was successfully introduced into the molecular chain of bisphenol A EP. Thermogravimetric analysis confirmed that the ODOPB-modified EPs exhibited much better thermal stability than the pristine ones during the whole decomposition process under oxygen atmosphere. The 4,4′-diaminodiphenyl sulfone (DDS)-cured resins showed higher initial degradation temperature, and the 4,4′-diaminodiphenyl methane (DDM)-cured resins demonstrated better thermal stability at high temperature. The results of limited oxygen index measurements indicated that the modified EPs also possessed much improved flame retardancy. Furthermore, the enhanced liquid oxygen compatibility of the modified EPs characterized by the liquid oxygen impact test implied that improving thermal stability and flame retardancy of EPs was beneficial to enhance their liquid oxygen compatibility. X-ray photoelectron spectroscopy results demonstrated that the DDS-cured modified EPs had much higher reactivity with liquid oxygen compared to the DDM-cured ones. Mechanical performance tests indicated that the introduction of ODOPB could simultaneously improve the tensile properties and fracture toughness of the EPs at cryogenic temperature. Summarily, it can be considered that the ODOPB-modified EPs have the application prospect in the fabrication of the composite liquid oxygen tanks.