bisphenol-A Type Epoxy Research Articles

A study on sisal fiber-reinforced benzoxazine/epoxy copolymer based on diamine-based benzoxazine

A diamine-based benzoxazine monomer has been synthesized via the Mannich condensation reaction of ethylenediamine, phenol and formaldehyde. The effect of solvent was investigated. The chemical structure and thermal properties of the diamine-based benzoxazine were characterized by FT-IR, NMR, DSC and TGA. Sisal fibers are incorporated in a mixture of benzoxazine and bisphenol-A type epoxy resins to form a unidirectionally reinforced composite. The effects of varying fiber contents and matrix composition on the mechanical properties of the composites are studied.

Encapsulated white-light CdSe nanocrystals as nanophosphors for solid-state lighting

White-light emitting ultra-small CdSe nanocrystals present exciting possibilities in the area of solid-state lighting technology. In this work, thirteen dissimilar polymers were examined as potential encapsulants for these single-sized nanocrystals. Films of the encased nanocrystals were characterized in terms of nanocrystal aggregation and changes to the nanocrystals' natural emission. The Hildebrand and Hansen solubility parameters of each encapsulant were found to be correlated to the quality of nanocrystal encapsulation achieved. Encapsulants with cyclosiloxane or bisphenol-A type epoxy structures caused extensive aggregation of the nanocrystals at low loading levels (<0.5% w/w) due to the solubility difference between the polymer structure and the nanocrystals' ligands. Of the encapsulants tested, the most robust, color stable, and homogenous encapsulation was obtained using a biphenylperfluorocyclobutyl polymer. In this polymer, nanocrystal loading levels up to 18% w/w were achieved. White-light emitting CdSe nanocrystals encapsulated in the biphenylperfluorocyclobutyl polymer were coated on various UV-LEDs creating a white light source with chromaticity coordinates of (0.324, 0.322) and a high color-rendering index of 93.

Preparation, morphology, mechanical and electrical properties of TiO2 coated multiwalled carbon nanotube/epoxy composites

A titanium oxide (TiO 2 )-coated multiwalled carbon nanotube (MWCNT)/epoxy composite was prepared by coating MWCNTs with a layer of TiO 2 and then modified with 3-(aminopropyl)triethoxysilane (APTES). The TiO 2 -coated MWCNTs and APTES-modified TiO 2 -coated MWCNTs (AT-MWCNTs) were analyzed by X-ray photoelectron spectroscopy. The AT-MWCNTs were added to the diglycidyl ether of bisphenol A-type epoxy to fabricate silane-grafted TiO 2 -coated MWCNT/epoxy composites. The amine functional groups on the AT-MWCNT surface react with the epoxy, improving the adhesion between the MWCNTs and epoxy. The morphological properties have been studied by TEM and SEM. The mechanical properties of the AT-MWCNT/epoxy composites dramatically exceeded that of the unmodified MWCNT/epoxy. However, since the MWCNTs were isolated by the TiO 2 , the volume electrical resistivity of the AT-MWCNT/epoxy composite exceeded that of the unmodified MWCNT/epoxy composites for a given amount of MWCNT added.

Morphology, dynamic mechanical and thermal studies on poly(styrene-co-acrylonitrile) modified epoxy resin/glass fibre composites

Poly(styrene-co-acrylonitrile) (SAN) was used to modify diglycidyl ether of bisphenol-A (DGEBA) type epoxy resin cured with diamino diphenyl sulfone (DDS) and the modified epoxy resin was used as the matrix for fibre reinforced composites (FRPs) in order to get improved mechanical and thermal properties. E-glass fibre was used as the fibre reinforcement. The morphology, dynamic mechanical and thermal characteristics of the systems were analyzed. Morphological analysis revealed heterogeneous dispersed morphology. There was good adhesion between the matrix polymer and the glass fibre. The dynamic moduli, mechanical loss and damping behaviour as a function of temperature of the systems were studied using dynamic mechanical analysis (DMA). DMA studies showed that DDS cured epoxy resin/SAN/glass fibre composite systems have two Tgs corresponding to epoxy rich and SAN rich phases. The effect of thermoplastic modification and fibre loading on the dynamic mechanical properties of the composites were also analyzed. Thermogravimetric analysis (TGA) revealed the superior thermal stability of composite system.

Determination of interface properties from experiments on the fragmentation process in single-fiber composites

This paper attempts to quantify the fracture properties (strength and toughness) of the fiber–matrix interface in composites, using the fragmentation process and debonding growth for HI-Nicalon™ SiC single-fiber and T300 carbon single-fiber epoxy (Bisphenol-A type epoxy resin with triethylenetetramine (TETA) as curing agent) composite systems. This method is based on the numerical modeling for the microscopic damage and fragmentation process in single-fiber composite (SFC) tests, with a cohesive zone model (CZM). For the HI-Nicalon™ SiC single-fiber epoxy composite in which the major damage near a fiber break is interfacial debonding, interface properties were reasonably determined as ( T II,max, G IIc) = (75 MPa, 200 J/m 2). In contrast, for T300 carbon single-fiber epoxy composite, we could not determine unique interfacial properties, since the variation of the cohesive parameters hardly affects the microscopic damage process due to the transition to the damage pattern dominated by matrix cracking.

Effect of composing particles of two sizes on mechanical properties of spherical silica-particulate-reinforced epoxy composites

The correlation between compositions using particles of different two sizes and mechanical properties was studied experimentally. Spherical silica particles of 0.24 and 1.56 μm in diameter were compounded into a bisphenol A-type epoxy matrix at composition ratios ranging from 0 to 1.0 with a constant volume fraction, 0.30. Although varying the composition ratio of two-particle did not significantly affect the bending elastic modulus, the bending strength and fracture toughness were strongly dependent on the particle composition. The composition effect of different particle sizes on fracture toughness was clarified to have a difference from the one on bending strength, although elastic modulus varied according to volume fraction of particles.

Morphology and contact angle studies of poly(styrene-co-acrylonitrile) modified epoxy resin blends and their glass fibre reinforced composites

In this study, the surface characteristics of blends and composites of epoxy resin were investigated. Poly(styrene- co-acylonitrile) (SAN) was used to modify diglycidyl ether of bisphenol-A (DGEBA) type epoxy resin cured with diamino diphenyl sulfone (DDS) and the modified epoxy resin was used as the matrix for fibre reinforced composites (FRP's). E-glass fibre was used as the fibre reinforcement. The scanning electron micrographs of the fractured surfaces of the blends and composites were analyzed. Morphological analysis revealed different morphologies such as dispersed, cocontinuous and phase-inverted structures for the blends. Contact angle studies were carried out using water and methylene iodide at room temperature. The solid surface energy was calculated using harmonic mean equations. Blending of epoxy resin increases its contact angle. The surface free energy, work of adhesion, interfacial free energy, spreading coefficient and Girifalco-Good's interaction parameter were changed significantly in the case of blends and composites. The incorporation of thermoplastic and glass fibre reduces the wetting and hydrophilicity of epoxy resin.

Enhancement of the Protectiveness of Epoxy Coatings with Surface-Modified Nano-Titanium Particles

Nano-Ti particles with grain sizes of 56 nm similar to 128 nm were modified by inoculating an organic amine functional group onto their surface using a two-step process. These modified nano-Ti particles were dispersed into the bisphenol A-type epoxy resin and then cured with polyamide to form a coating on the metal substrates. The results of differential scanning calorimetry (DSC) and x-ray photoelectron spectroscopy (XPS) showed that the organic aminefunctional group on the surface of nano-Ti particles could enhance the interfacial interaction between the particles and epoxy resin. The results of electrochemical impedance spectroscopy (EIS) showed that the protection performances of the epoxy coatings dispersed with modified nano-Ti particles were further improved in comparison to coatings with unmodified ones.

Effect of Particle Size on Fracture Toughness of Spherical-Silica Particle Filled Epoxy Composites

We investigated the particle size effects on the fracture toughness of epoxy resin composites reinforced with spherical-silica particles. The silica particles had different mean particle diameters of between 1.56 and 0.24µm and were filled with bisphenol A-type epoxy resin under different mixture ratios of small and large particles and a constant volume fraction for all particles of 0.30. As the content with the added smaller particle increased, the viscosity of each composite before curing remarkably increased. We conducted the single edge notched bending test (SENB) to measure the mode I fracture toughness of each composite. The fracture surface with the small particle content exhibited more rough areas than the surface with larger particles. The fracture toughness increased below the small particle content of 0.8 and saturated above it. Therefore, near the small particle content of 0.8, the composite had a relatively low viscosity and a high fracture toughness.

Studies on thermal and morphological characteristics of siloxane containing epoxy resins cured by microwave radiation

Microwave radiation was performed on a diglycidyl ether of a bisphenol-A type epoxy monomer with an aliphatic polyamino-curing agent. The ratio of epoxy monomer to curing agent was taken as 2. Two different molecular weights of silicone acrylates were used in various ratios for the modification of the system. The mechanical characterisation and hardness measurements of these samples were performed. As the siloxane content in the epoxy resin system was increased, Young’s modulus and hardness decreased. Further, the strength at Fmax, toughness and percentage elongation showed a maximum of about 10% for one kind of PDMS containing epoxy system. Thermal characterisations of the samples were determined with a thermogravimetric analyzer. The decomposition of the samples was a two-stage process with maximum weight loss rates in between 320 to 400°C or 330 to 430°C°C, depending on the molecular weights of PDMS modifier. The SEM photographs of the cold-fractured samples were taken. As the siloxane content in the epoxy resins was increased, the fractured surfaces became rougher and showed more irregular stripes in the matrix.

Nanostructures, Semicrytalline Morphology, and Nanoscale Confinement Effect on the Crystallization Kinetics in Self-Organized Block Copolymer/Thermoset Blends

This work reports the first instance of self-organized thermoset blends containing diblock copolymers with a crystallizable thermoset-immiscible block. Nanostructured thermoset blends of bisphenol A-type epoxy resin (ER) and a low-molecular-weight (Mn = 1400) amphiphilic polyethylene-block-poly(ethylene oxide) (EEO) symmetric diblock copolymer were prepared using 4,4‘-methylenedianiline (MDA) as curing agent and were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), and differential scanning calorimetry (DSC). All the MDA-cured ER/EEO blends do not show macroscopic phase separation but exhibit microstructures. The ER selectively mixes with the epoxy-miscible PEO block in the EEO diblock copolymer whereas the crystallizable PE blocks that are immiscible with ER form separate microdomains at nanoscales in the blends. The PE crystals with size on nanoscales are formed and restricted within the individual spherical micelles in the nanostructured ER/EEO blends with EEO content up to 30 wt %. The spherical micelles are highly aggregated in the blends containing 40 and 50 wt % EEO. The PE dentritic crystallites exist in the blend containing 50 wt % EEO whereas the blends with even higher EEO content are completely volume-filled with PE spherulites. The semicrystalline microphase-separated lamellae in the symmetric EEO diblock copolymer are swollen in the blend with decreasing EEO content, followed by a structural transition to aggregated spherical micellar phase morphology and, eventually, spherical micellar phase morphology at the lowest EEO contents. Three morphological regimes are identified, corresponding precisely to the three regimes of crystallization kinetics of the PE blocks. The nanoscale confinement effect on the crystallization kinetics in nanostructured thermoset blends is revealed for the first time. This new phenomenon is explained on the basis of homogeneous nucleation controlled crystallization within nanoscale confined environments in the block copolymer/thermoset blends.

Evolution of residual-inplane stress during adhesive curing and recuring in chip-on-board packages

The residual stress induced in assembly is a common concern in electronic packaging, especially for those chips sensitive to residual stress. On chip-on-board (COB) packages, bisphenol A-type epoxy adhesive is applied to attach the chip to the substrate board. Silicon piezoresistive sensors are used to record residual stresses and stress evolution during adhesive curing. After 20-days storage in air at room temperature after curing, the residual stresses accumulate significantly in the recuring process, and after additional curing, the residual stress stabilizes at a relatively low level. Thermal analysis of the adhesive was performed to identify the incomplete cure of the adhesive after the first curing process.

Epoxy resins possessing flame retardant elements from silicon incorporated epoxy compounds cured with phosphorus or nitrogen containing curing agents

New silicon-containing epoxy compounds were obtained by reacting a bisphenol-A type epoxy and an o-cresol–formaldehyde novolac type epoxy with diphenylsilandiol and triphenylsilanol, respectively. The reactions were performed with tin(II) chloride as a catalyst at 140–170 °C. With various feeding ratios of reactants, the epoxy compounds contained various silicon contents. The thermal stability and the flame retardant property of the cured epoxy resins were improved with this incorporation of silicon. Synergistic effects of phosphorus/silicon and nitrogen/silicon on enhancing limited oxygen index values were also observed for the epoxy resins from the silicon-containing epoxy compounds cured with phosphorus- and melamine-containing agents.

Phase Behavior, Crystallization, and Hierarchical Nanostructures in Self-Organized Thermoset Blends of Epoxy Resin and Amphiphilic Poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) Triblock Copolymers

Nanostructured thermoset blends of bisphenol A-type epoxy resin (ER) and amphiphilic poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO−PPO−PEO) triblock copolymers were successfully prepared. Two samples of PEO−PPO−PEO triblock copolymer with different ethylene oxide (EO) contents, denoted as EO30 with 30 wt % EO content and EO80 with 80 wt % EO content, were used to form the self-organized thermoset blends of varying compositions using 4,4‘-methylenedianiline (MDA) as curing agent. The phase behavior, crystallization, and morphology were investigated by differential scanning calorimetry (DSC), transmission electron microscopy (TEM), atomic force microscopy (AFM), and small-angle X-ray scattering (SAXS). It was found that macroscopic phase separation took place in the MDA-cured ER/EO30 blends containing 60−80 wt % EO30 triblock copolymer. The MDA-cured ER/EO30 blends with EO30 content up to 50 wt % do not show macroscopic phase separation but exhibit nanostructures on the order of 10−30 nm as revealed by both the TEM and SAXS studies. The AFM study further shows that the ER/EO30 blend at some composition displays structural inhomogeneity at two different nanoscales and is hierarchically nanostructured. The spherical PPO domains with an average size of about 10 nm are uniformly dispersed in the 80/20 ER/EO30 blend; meanwhile, a structural inhomogeneity on the order of 50−200 nm is observed. The ER/EO80 blends are not macroscopically phase-separated over the entire composition range because of the much higher PEO content of the EO80 triblock copolymer. However, the ER/EO80 blends show composition-dependent nanostructures on the order of 10−100 nm. The 80/20 ER/EO80 blend displays hierarchical structures at two different nanoscales, i.e., a bicontinuous microphase structure on the order of about 100 nm and spherical domains of 10−20 nm in diameter uniformly dispersed in both the continuous microphases. The blends with 60 wt % and higher EO80 content are completely volume-filled with spherulites. Bundles of PEO lamellae with spacing of 20−30 nm interwoven with a microphase structure on the order of about 100 nm are revealed by AFM study for the 30/70 ER/EO80 blend.

Network chain orientation in the toughening process of the elastomer modified mesogenic epoxy resin

A biphenol-type epoxy resin, which has a mesogenic group in the backbone moiety, was modified with a reactive elastomer (CTBN). Toughness of the epoxy resin was significantly increased with the addition of the CTBN elastomer compared with that of the bisphenol-A type epoxy resin. It was clearly observed by SEM that a large plastic deformation occurred near the crack-tip in the biphenol-type epoxy resin modified with CTBN. The arrangement of the network chains in the plastic deformation region was quantitatively studied by polarized microscopic FT-IR technique, which was related to the toughening mechanism of the elastomer modified epoxy resin.

Epoxy Resin Particles, 3. Particle Formation of Epoxy Resin in Aqueous Emulsion State

A Bisphenol A-type epoxy resin is readily emulsified in aqueous medium with an ethylene oxide adduct to a Friedel-Crafts reaction product of styrene and 4-(4-cumyl)phenol as emulsifier. The resultant epoxy resin emulsion is reacted with amine-type hardeners to obtain epoxy resin particles that are fully cross-linked. The size and size distribution of the resultant particles are almost comparable to those of the primarily formed emulsion particles which are determined by the amount of emulsifier, mixing temperature and speed. The average diameter of the finally obtained particles ranges from 0.5 to 22 μm depending on the reaction conditions. The particles hardened with 1,2-diaminoethane (DEA) have a spherical form with homogeneous surface, whereas the particles hardened with N,N ′-bis(2-aminoethyl)-1,2-diaminoethane (TTA) have a shrunk appearance with rough surface. These particles can readily be isolated from the dispersion without causing the solvent-derived pollution for environment.

Epoxy Resin Particles, 3. Particle Formation of Epoxy Resin in Aqueous Emulsion State

A Bisphenol A-type epoxy resin is readily emulsified in aqueous medium with an ethylene oxide adduct to a Friedel-Crafts reaction product of styrene and 4-(4-cumyl)phenol as emulsifier. The resultant epoxy resin emulsion is reacted with amine-type hardeners to obtain epoxy resin particles that are fully cross-linked. The size and size distribution of the resultant particles are almost comparable to those of the primarily formed emulsion particles which are determined by the amount of emulsifier, mixing temperature and speed. The average diameter of the finally obtained particles ranges from 0.5 to 22 μm depending on the reaction conditions. The particles hardened with 1,2-diaminoethane (DEA) have a spherical form with homogeneous surface, whereas the particles hardened with N,N ′-bis(2-aminoethyl)-1,2-diaminoethane (TTA) have a shrunk appearance with rough surface. These particles can readily be isolated from the dispersion without causing the solvent-derived pollution for environment.

Miscibility, crystallization and real-time small-angle X-ray scattering investigation of the semicrystalline morphology in thermosetting polymer blends

The results of the study of a completely miscible thermosetting polymer blend containing a crystallizable component are reported. Blends of poly(ϵ-caprolactone) (PCL) and bisphenol-A-type epoxy resin (ER) cured with 4,4′-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA) were prepared and compared with blends of PCL with uncured bisphenol A-type epoxy resin, i.e. diglycidylether of bisphenol A (DGEBA). The miscibility, crystallization behavior and spherulitic morphology of both uncured DGEBA/PCL blends and MCDEA-cured ER/PCL blends were investigated by differential scanning calorimetry (DSC), optical microscopy, and Fourier-transform infrared (FTIR) spectroscopy. It was found that PCL is completely miscible with both DGEBA and MCDEA-cured ER in the melt and in the amorphous state over the entire composition range, as shown by the existence of a single composition-dependent glass transition temperature (Tg). The overall crystallization rate and crystallinity of PCL in the MCDEA-cured ER/PCL blends decrease much more rapidly with increasing amorphous content than those of the DGEBA/PCL blends. The spherulitic morphology of PCL in both the uncured and the cured blends is characteristic of miscible crystalline/amorphous blends, and the PCL spherulites in these blends are always completely volume-filling. The miscibility of the uncured DGEBA/PCL blends is considered to be due predominately to the entropic contribution, whereas that of the cured ER/PCL blends is due to the enthalpic contribution. FTIR investigations indicated hydrogen bonding interaction between the hydroxyl groups of MCDEA-cured ER and the carbonyl groups of PCL in the cured system, which is an important driving force for the miscibility of the cured ER/PCL blends. Real-time small-angle X-ray scattering (SAXS) experiments revealed that the amorphous cured ER segregated interlamellarly during the crystallization process of PCL, which is considered to result from the low chain mobility of the cured ER in the ER/PCL blends. On the basis of the SAXS results, a model describing the semicrystalline morphology of MCDEA-cured ER/PCL blends is proposed. The amorphous fraction of PCL, the branched ER chains and imperfect ER network are located between PCL lamellae in the crystallized blend.

Bonding properties of epoxy resin containing mesogenic group

A liquid crystalline epoxy resin with a mesogenic group was synthesized and its adhesive bonding properties are compared to that of the bisphenol-A type epoxy resin. The bonding strength of the former resin system was higher than that of the latter. This suggested that the high bonding strength of the liquid crystalline epoxy system was due to the large deformation of this system along the stress direction. Bonding strength of all the cured systems had a maximum peak during curing, due to the increase in the internal stress which occurred during the curing shrinkage of the epoxy resins. To decrease the internal stress, we cured the epoxy resin with an excess amount of curing agents. Bonding strength of the system with the added excess amount of curing agent showed a higher value than that for the system with an equivalent amount of curing agent. It was considered that the high bonding strength of the former system was due to the low internal stress in this system.

Synthesis of a novel epoxy resin containing diphenylether moiety and thermal properties of its cured polymer with phenol novolac

A new type of epoxy resin containing 4,4′-diphenylether moiety in the backbone (2) was synthesized, and was confirmed by gel permeation chromatography, infrared spectroscopy, and 1H nuclear magnetic resonance spectroscopy. In addition, in order to evaluate the influence of 4,4′-diphenylether moiety in the structure, epoxy resins having 4,4′-biphenylene moiety (4) and having 1,4-phenylene moiety (6) in place of 4,4′-diphenylether moiety were synthesized. The cured polymer obtained through the curing reaction between the new diphenylether-containing epoxy resin and phenol novolac was used for making a comparison of its thermal and physical properties with those obtained from 4, 6, and bisphenol-A (4,4′-isopropylidenediphenol) type epoxy resin. The cured polymer obtained from 2 showed markedly higher anaerobic char yield at 700°C of 44.0 wt %, higher fracture toughness, and higher mechanical strength and modulus. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3687–3693, 1999