Morphologies and mechanical properties of polyethersulfone modified epoxy blends through multifunctional epoxy composition

Thermoplastic polyethersulfone (PES) modified multifunctional tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) and triglycidyl para‐aminophenol (TGAP) epoxy prepolymers cured with 4,4′‐diaminodiphenylsulfone (44DDS) were prepared using a continuous reactor method and their reaction‐induced phase separated morphologies and mechanical properties were measured and correlated with chemical compositions. ¹H nuclear magnetic resonance (¹H NMR) and near‐infrared spectroscopy (NIR) were used to quantify the chemical network formation. Atomic force microscopy (AFM) with nanomechanical mapping was employed to resolve the nanoscale phase‐separated morphologies. The extent of phase separation in cured networks and resultant domain sizes were determined to be controllable depending upon the multifunctional epoxy compositions. The results obtained from mechanical studies further indicated that tensile modulus was not largely affected by multifunctional epoxy compositions while fracture toughness increased with increase of TGAP content. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44775.     

反应性聚碳酸酯/环氧树脂体系的形态与增韧性能

将胺化聚碳酸酯（a-PC)和环氧树脂（EP)以一定的比例混合,加热到120－160℃后加入熔化的二氨基二苯基甲烷,可制备固化的胺化聚碳酸酯增韧环氧树脂,结果表明,EP与a-PC形成了网络结构,且当a-PC质量分数为10％时,试样断裂韧性最大。     

Effect of prereaction on curing of elastomer-modified epoxy resins

Three multifunctional epoxy resins novolac epoxy (EPN), triglycidyl para-aminophenol (TGPAP), and tetraglycidyl diaminodiphenylmethane (TGDDM) were modified with a carboxy-terminated acrylate-based liquid elastomer (PnBA). The effect of prereaction of the epoxy groups in the resin and carboxyl group in the elastomer on curing parameters, such as the cure reaction conversions; processing parameters, such as gel times and vetrification times; initial cure temperatures, and activation energy values were evaluated. Fourier transform infrared spectrometry (FTIR), dynamic mechanical spectrometry (DMS), and differential scanning calorimetry (DSC) were used for the study. The results indicated that while the cure reactions were slightly retarded in the presence of elastomer, they were slightly accelerated when certain prereaction catalysts were used. The gel times and vitrification times decreased due to the prereaction. The physical properties such as fracture toughness and modulus of neat resin castings and flexural strength properties of carbon cloth-reinforced laminates were evaluated. Results indicated that the toughness property increased and the modulus decreased with elastomer addition. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1751–1757, 1997     

Morphologies and properties of cured epoxy/brominated‐phenoxy blends

Morphologies of cured epoxy/brominated‐phenoxy blends were observed by scanning transmission electron microscopy (STEM) and energy dispersive X‐ray fluorescence spectroscopy (EDX). When brominated‐phenoxy content was 30 wt %, cocontinuous phase structures between cured epoxy and brominated‐phenoxy were found. Since every loss tangent (tan δ) curve as a function of temperature on dynamic mechanical analysis (DMA) showed 2 peaks at 128°C and 155°C respectively, cured epoxy phases and brominated‐phenoxy phases were incompatible together and T_gs of cured epoxy phases were not decreased. Tensile strength and tensile elongation of the cured blends were increased together. T‐peel adhesion strength and the lap‐shear adhesion strength were also increased together. These phenomena could be due to the cocontinuous structures consisted by the rigid cured epoxy phases of thermosets and ductile the brominated‐phenoxy phases of thermoplastics. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1702–1713, 2007     

石墨烯改性对环氧树脂/碳纤维复丝拉伸性能的影响

采用直接分散法和上浆剂法分别制备了环氧树脂/碳纤维复丝,通过红外光谱、分光光度法等分析方法对处理的石墨烯的表面官能团及表面形貌进行表征,借助扫描电子显微镜对碳纤维表面进行微观形貌观察,研究了石墨烯改性对环氧树脂/碳纤维复丝界面性能的影响。结果表明:石墨烯表面成功地接枝了硅烷偶联剂KH-560;接枝硅烷偶联剂KH-560的石墨烯的环氧树脂/碳纤维复丝的拉伸性能优于未经改性的石墨烯的复丝;上浆法制得的环氧树脂/碳纤维复丝的拉伸性能优于分散法制得的复丝的拉伸性能;上浆剂法制备的石墨烯改性的环氧树脂/碳纤维复丝的断裂强力比未经过改性的未上浆的复丝的提高了48.6%,拉伸强度提高了30.4%,断裂伸长率提高了90.9%。     

Elastomer modification of epoxy based film adhesives: adhesive and mechanical properties

Three approaches were employed to improve the flow and sandwich bonding properties of a nylon-carrier supported film adhesive based on carboxyl terminated butadiene acrylonitrile (CTBN)-modified novolac epoxy resin. These included the addition of a commercial acrylate flow modifier, replacement of novolac epoxy partly with solid diglycidyl ether of bisphenol A (DGEBA) resins, and replacement of CTBN partly with an epoxy functional acrylate terpolymer (EPOBAN). Adhesive properties such as lap shear strength (LSS), T-peel strength (TPS) and flatwise tensile strength (FTS) on honeycomb core bonded sandwich specimens were evaluated using aluminium adherends. The addition of the flow modifier in low concentrations enhanced the flexibility of the system and resulted in a marginal increase in LSS, TPS and FTS. Replacing novolac epoxy partly with solid DGEBA resulted in a less brittle system with enhanced LSS and TPS, but with reduced FTS due to the decreased flow characteristics. A substantial increase in FTS was observed when CTBN was partly replaced with EPOBAN. The introduction of EPOBAN resulted in good flow and fillet properties and the optimum FTS was obtained for the composition based on 25/75 CTBN/EPOBAN ratio. Mechanical properties of selected systems were also studied in addition to adhesive properties.     

Synthesis and properties of urethane elastomer-modified epoxy resin having hydroxymethyl group

Synthesis and properties of urethane elastomer-modified epoxy resins were studied. The urethane elastomer-modified epoxy resins were synthesized by the reaction of a 4-cresol type epoxy compound having hydroxymethyl groups (EPCDA) with isocyanate prepolymer. The structure was identified by IR, ¹H NMR and GPC. These epoxy resins (EPCDATDI) were mixed with a commercial epoxy resin (DGEBA) in various ratios. The mixed epoxy resins were cured with a mixture of 4,4′-diaminodiphenylmethane and 3-phenylenediamine (molar ratio 6:4) as a hardener. The curing behaviour of these epoxy resins was studied by DSC. The higher the concentration of EPCDATDI, the higher the onset temperature and the smaller the rate constant (k) of the exothermic cure reaction were. It was considered that the ratio of hydroxymethyl group to epoxide group was very small and the molecular weight of EPCDATDI was large. Therefore, the accelerating effect of the hydroxymethyl group on the epoxide–amine reaction was cancelled by the retardant effect of increased molecular weight and viscosity, and decreased molecular motion. Toughness was estimated by Izod impact strength and fracture toughness (K_1C). On addition of 10 wt% EPCDATDI with low molecular weight (M?_n 6710, estimated by GPC using polystyrene standard samples), Izod impact strength and K_1C increased by 70% and 60%, respectively, compared with unmodified epoxy resin. Glass transition temperatures (T_g) for the cured epoxy resins mixed with EPCDATDI measured by dynamic mechanical spectrometry were the same as those of unmodified epoxy resin. The storage modulus (E′) at room temperature decreased with increasing concentration of EPCDATDI. Toughness and dynamic mechnical behaviour of cured epoxy resin systems were studied based on the morphology.     

Morphologies and properties of polycarbonate/polyethylene in situ microfibrillar composites prepared through multistage stretching extrusion

The sheets of polycarbonate (PC)/polyethylene (PE) in situ microfibrillar composites are successfully prepared directly through multistage stretching extrusion with an assembly of laminating‐multiplying elements (LMEs) instead of the secondary processing. The morphological development of the PC dispersed phase in PE matrix with increasing the number of LMEs during multistage stretching extrusion investigated by scanning electron microscope shows that core‐skin structure of the microfibrillar PC/PE composites during multistage stretching extrusion with 4 LMEs is weakened, and the diameter of the PC microfibrils is relatively more uniform, indicating that the shear field in LMEs greatly affects the morphology of PC dispersed phase in PE matrix. The tensile, crystalline, melting, orientation and rheological behavior of the PC/PE microfibrillar composites are also investigated. The results show that the PC microfibrils are helpful to increase complex viscosity and yield stress of the PE/PC composites. In addition, it is found that the glass transition temperature of PC in PE matrix reduced with increasing the number of LMEs during dynamic rheological testing. It is coincided with the results of DSC analysis of the PC/PE composites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40108.     

Preparation,morphology, and properties of silane‐modified MWCNT/epoxy composites

Both epoxy resin and acid‐modified multiwall carbon nanotube (MWCNT) were treated with 3‐isocyanatopropyltriethoxysilane (IPTES). Scanning electron microscopy (SEM) and transmission electronic microscope (TEM) images of the MWCNT/epoxy composites have been investigated. Tensile strength of cured silane‐modified MWCNT (1.0 wt %)/epoxy composites increased 41% comparing to the neat epoxy. Young's modulus of cured silane‐modified MWCNT (0.8 wt %)/epoxy composites increased 52%. Flexural strength of cured silane‐modified MWCNT (1.0 wt %)/epoxy composites increased 145% comparing to neat epoxy. Flexural modulus of cured silane‐modified MWCNT (0.8 wt %)/epoxy composites increased 31%. Surface and volume electrical resistance of MWCNT/epoxy composites were decreased with IPTES‐MWCNT content by 2 orders and 6 orders of magnitude, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mechanical and morphological properties of carbon fiber reinforced–modified epoxy composites

Epoxy, prepared through aminomethyl 3,5,5‐trimethylcyclohexylamine hardening of diglycidylether of bisphenol‐A (DGEBA) prepolymer, toughened with polycarbonate (PC) in different proportions, and reinforced with carbon fiber, was investigated by differential scanning calorimetry, tensile and interlaminar shear strength testing, and scanning electron microscopy (SEM). A single glass transition temperature was found in all compositions of the epoxy/PC blend system. The tensile properties of the blend were found to be better than that of the pure epoxy matrix. They increased with PC content up to 10%, beyond which they decreased. The influence of carbon fiber orientation on the mechanical properties of the composites was studied, where the fiber content was kept constant at 68 wt %. Composites with 45° fiber orientation were found to have very weak mechanical properties, and the mechanical properties of the blend matrix composites were found to be better than those of the pure epoxy matrix composites. The fracture and surface morphologies of the composite samples were characterized by SEM. Good bonding was observed between the fiber and matrix for the blend matrix composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3529–3536, 2006     

Morphologies and properties of epoxy resin/layered silicate–silica nanocomposites

A new nanofiller containing layered organo‐modified montmorillonite (oMMT) and spherical silica (SiO₂) was prepared by an in situ deposition method and coupling agent modification. Fourier transform infrared spectrometry, X‐ray diffraction and transmission electron microscopy show that there are interactions between oMMT and SiO₂, and the spherical SiO₂ particles are self‐assembled on the edge of oMMT layers, forming a novel layered–spherical nanostructure. An epoxy resin (EP)/oMMT–SiO₂ nanocomposite was obtained by adding oMMT–SiO₂ to EP matrix. Morphologies and mechanical and thermal properties of the new ternary nanocomposite were investigated. For purposes of comparison, the corresponding binary nanocomposites, i.e., EP modified with either oMMT or SiO₂, were also tested. The results for the mechanical properties show that oMMT obviously improves the strength of EP, and SiO₂ enhances the toughness of EP, but oMMT–SiO₂ exhibits a synergistic effect on toughening and reinforcing of EP. The toughening and reinforcing mechanism is explained by scanning electron microscopy. In addition, the thermal resistance of EP/oMMT–SiO₂ is better than that of EP/SiO₂, but it is worse than that of EP/oMMT. Copyright © 2006 Society of Chemical Industry     

Effect of external electric field on morphologies and properties of the cured epoxy and epoxy/acrylate systems

In this article, the influences of the external electric field exerted to the curing epoxy and epoxy/acrylate systems on their cured microstructures and macroscopic performances were investigated by means of morphological investigation and some characteristic analyses. Epoxy and epoxy/acrylate (an interpenetrating polymer network) systems were subjected to the action of the alternating electric field during the curing process. The changes in the nanolamellae microstructure in the cured epoxy and the nanoellipsoid microstructure in the cured epoxy/acrylate systems resulting from the electric field treatment were observed using atomic force microscopy. Dynamic mechanical analysis showed that the external electric field treatment made the low and high relaxation peaks shift to the lower and higher temperatures, respectively. Thermogravimetric analysis implied that the curing reactions of the epoxy systems with the aid of the external electric field resulted in some negative influences on their thermal stability. The dielectric measurements demonstrated that the electrical properties of the epoxy system for vacuum pressure impregnation insulation of the high-voltage electric machines could be much improved with the aid of the external electric field. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The curing reaction and physical properties of DGEBA/DETA epoxy resin blended with propyl ester phosphazene

The influences of different amounts of propyl ester phosphazene (FR) on the curing kinetics and physical properties of diglycidyl ether of bisphenol A (DGEBA) epoxy prepolymer cured with diethylenetriamine (DETA) were investigated with DSC, SEM, DMA, and tensile testing. The results revealed that FR could be a catalyst or a diluent depending on the FR content. In addition, the blending systems were partially miscible. The tensile strength and modulus of blends decreased with increasing amounts of FR, but the elongation increased with increasing FR. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 229–237, 1999     

Laboratory investigation of the properties of asphalt modified with epoxy resin

Epoxy asphalts were prepared by mixing styrene–butadiene–styrene (SBS) modified asphalt with epoxy resin. The curing process and morphology of epoxy asphalts were characterized by infrared spectroscopy and fluorescent microscope, respectively. The effects of epoxy resin contents, ratio of curing agent to epoxy resin and curing temperature on properties of epoxy asphalt were investigated. Results indicated that epoxy resin and epoxy asphalt showed similar curing efficiency. Epoxy asphalts can be cured at 120 or 60°C and its viscosity at 120°C can meet the demands of asphalt mixture mixing and paving. The chemical reaction of epoxy resin in epoxy asphalt is slow and reaction occurs not only with the curing agent but also carboxylic acid in epoxy asphalt. The microstructure of epoxy asphalt transforms from the dispersed structure to networks structure with epoxy resin content increasing and phase transition starts when 30 wt % epoxy resin present in asphalt. The softening point and tensile strength of epoxy asphalt increased with epoxy resin contents increasing. The softening point and tensile strength of epoxy asphalt were markedly improved when epoxy resin content was more than 30 wt %, which is attributed to formation of continuous structure of epoxy resin. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polyether and polyester polyol based glycidyl-terminated polyurethane modified epoxy resins: Mechanical properties and morphology

A glycidyl-terminated polyurethane prepolymer was synthesized and used to enhance the properties of epoxy resins. Some properties of glycidyl-terminated PU/epoxy with polyether based (PPG) and polyester based (PBA) glycidyl-terminated PU were investigated in this research. The polyether based glycidyl-terminated PU(PPG) modified epoxy resin proved to be superior to conventional epoxy resins in improved impact strength and fracture energy, but not tensile strength, tensile modulus, flexural strength and flexural modulus. On the other hand, the polyester based glycidyl-terminated PU(PBA) modified epoxy resin had increased mechanical properties while showing slight variation of impact strength and fracture energy. Different mechanisms for this behaviour are advanced in this paper.     

Morphologies and properties of polyblends: 1. Blends of poly(methylmethacrylate) and a chlorine-containing polycarbonate

The morphologies and dynamic mechanical properties of blends of poly(methylmethacrylate) and a chlorine-containing polycarbonate, cast from dichloromethane solutions, have been studied. The results are discussed in terms of a phase diagram which has been determined for the system. It is demonstrated that the blends do not have equilibrium morphologies, which are virtually impossible to attain: nevertheless, their properties and morphologies can be related to the phase diagram and sample histories. Apparently anomolous variations in miscibility with composition are shown to be a consequence of an assymetric phase diagram and preferential solubility of polycarbonate in poly(methylmethacrylate).     

Effect of reactive compatibilisation on the phase morphology and tensile properties of PA12/PP blends

Both uncompatibilized and compatibilized blends based on polyamide 12 (PA12) and isotactic polypropylene (PP) were prepared in a Brabender Plastograph®. The compatibiliser used was maleic anhydride functionalized polypropylene (PP‐g‐MA). Phase morphology of the blends was inspected in scanning electron microscope (SEM) on cryogenically fractured etched surfaces of the specimens. PA12/PP blends possessed a nonuniform and unstable morphology owing to the incompatibility between their constituents. Addition of compatibiliser improved the interfacial characteristics of the blends by retarding the rate of coalescence. So, the phase morphology became more fine, uniform, and stable. Tensile properties of both uncompatibilized and compatibilized blends were measured as a function of blend composition and compatibiliser concentration. Uncompatibilized blends displayed inferior mechanical properties to compatibilized ones; especially for those containing 40–60 wt % of PP. Reactive compatibilisation of blends was found to be efficient and improved the tensile strength of the blends considerably. Addition of PP‐g‐MA improved the interfacial adhesion, decreased the interfacial tension, and thereby, enhanced the tensile strength by 85%. Finally, various models were adopted to describe the tensile strength of the blends. The experimental data exhibited a reasonably good fit with Nielsen's first power law model. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Mechanical and morphological properties of polycarbonate and montmorillonite filled epoxy hybrid composites

This work investigates the effect of polycarbonate (PC) and montmorillonite (MMT) content on the properties and morphology of epoxy resin (EP). Izod impact strength (IS), flexural strength and critical stress intensity factor (K_C) were estimated as function of modifiers content. The values of IS and K_C parameters increased by respectively 150% and 90% with the addition of 5 wt % PC. Hybrid compositions containing 1 wt % MMT and 5 wt % PC exhibited the best mechanical properties. Indeed, the addition of 1 wt % MMT to EP modified with 5 wt % PC caused enhancement of IS values by 100% in comparison with neat EP. SEM micrographs revealed that the enhancement mechanism of mechanical properties might be due to extensive yielding of EP associated with the formation of stratified elongated structures. Moreover, differential scanning calorimetry analysis revealed that the addition of nanoclay to EP resulted in a decrease of the glass transition temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fracture properties of epoxy/poly(styrene‐co‐allylalcohol) blends

The epoxy/polystyrene system is characterized by a poor adhesion between the constituent phases, which determines its mechanical properties. The adhesion can be improved via blends based on epoxy resin and random copolymers, poly(styrene‐co‐allylalcohol) (PS‐co‐PA). In this work, the influence of PS‐co‐PA content and the good adhesion between the phases on the tensile properties and the fracture toughness achieved through instrumented Charpy tests have been investigated. The tensile strength and the deformation at break showed an increase in the PS‐co‐PA content while the Young's modulus remained the same. The tensile fracture surfaces revealed that the improvement of these magnitudes was mainly due to a crack deflection mechanism. Also, the fracture toughness of the blends was superior to that of the pure epoxy resin. The main operating toughening mechanism was crack deflection. The fractographic analysis showed that ～ 80% of the particles were broken, and the crack tended to divert from its original path through the broken PS‐co‐PA particles. The remaining particles were detached from the epoxy resin, and the holes left suffered plastic deformation. Analytical models were used to predict successfully the toughness due to these mechanisms. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Thermomechanical and morphological properties of epoxy blends with hyperbranched polyester: Effect of the pseudo‐generation number

The thermomechanical and morphological properties of some epoxy blends modified with hyperbranched polymers are reported. The effects of pseudo‐generation numbers, from the second to the fourth, were studied. All the hyperbranched polymers used had ? OH end groups. The blends were thoroughly characterized in both the unreacted and cured states. The unreacted blends, characterized by parallel plate rheometry and hot stage microscopy, revealed that pseudo‐generation number can have a profound effect both on the reactivity and the phase separation behavior. Analysis of the cured samples was carried out through scanning electron microscopy, dynamic mechanical tests, and fracture mechanics. The results supported some findings obtained from the analysis of the unreacted blends; and dynamic mechanical analysis helped shed more light on the phase separation behavior. Pseudo‐generation number also influenced the glass transitions of the blends. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010