Improvement of tensile properties and toughness of an epoxy resin by nanozirconium-dioxide reinforcement

Zirconium dioxide (ZrO₂) nanoparticles were systematically added as reinforcement to a diglycidyl ether of bisphenol A (DGEBA)-based epoxy resin. A series of composites with varying amounts of nanoparticles was prepared and their morphology and mechanical properties were studied. The obtained nanocomposites were characterized by tensile tests, dynamic mechanical thermal analysis, and fracture toughness (K_IC) investigations; by standardized methods, to define the influence of the nanoparticle content on their mechanical and thermal properties. The morphological analysis of the composites shows that nanoparticles form small clusters, which are uniformly distributed into the matrix bulk. The tensile modulus (E) and the K_IC of the epoxy matrix increase at rising zirconia content. Improvements of more than 37% on modulus and 100% on K_IC were reached by the nanocomposite containing 10 vol.-% ZrO₂ with respect to the neat epoxy (E_o = 3.1 GPa, K_ICo = 0.74 MPam^0.5). The presence of nanoparticles produces also an increment on glass transition temperature (T _g). The epoxy resin added with 8 vol.-% ZrO₂ records a T _g approximately 8% higher than the unmodified matrix (T _go = 100.3 °C).     

Excellent flexural properties of aminimide-cured epoxy resin as a matrix for mica-dispersed polymer composites

The flexural behaviour of mica-dispersed epoxy resin composites has been examined. The flexural strength and flexural modulus have been determined as a function of the volume fraction of mica flakes (V _f) for both aminimide-cured epoxy resin matrix and a conventional epoxy resin reference matrix. On the basis of microscopic observation of fractured surfaces, the effect of improving the particle-matrix interface has been analysed using the modulus reduction factor (MRF) in a modified form. It is found that there is a steady increase in the flexural modulus with the volume fraction of mica flake for the aminimide-cured epoxy resin matrix. In contrast, the increase in flexural modulus levels off at a high content of filler for the reference samples. It is noteworthy that the intact mica flakes without surface treatment exhibit a substantial reinforcing effect on the flexural strength in the case of aminimide-cured epoxy resin composites. A further surprise is the difference among the curing agents used. The reference epoxy resins behave just like conventional matrix resins, exhibiting 30 to 40% reduction in the flexural strength when a small fraction of mica is added. These superior properties of the matrix resin for the composites are ascribed to the characteristics of aminimide-cured epoxy resins such as hardness, toughness, and excellent adhesivity.     

Impact-modified epoxy resin with glassy second component

A resorcinol-based epoxy resin was modified by incorporating a glassy second component. The mixture showed a heterogeneous morphology with two clearly defined phases, one phase rich in oligomer, the other phase composed mainly of resorcinol epoxy resin. The fracture toughness measured asG _1c andK _1c values showed an increase from 174J m^–2 and 0.89 MN m^–1.5 S in pure epoxy resin to 431 J m^–2 and 1.36 MN m^–1.5 in 30% oligomer modified resins. The scanning electron micrographs showed that the oligomer-rich phase exhibited ductile failure behaviour and formed the dispersed phase at low concentrations while it was the continuous matrix when the concentration was 30%. Optical observations on the failure mode of thin films of the oligomer-modified epoxy resin showed the existence of both inter face failure and considerable distortion in both phase.     

Mechanical properties of polyethersulfone modified epoxy/3,3′-<Emphasis Type="Italic">bis</Emphasis> (maleimidophenyl)phenylphosphine oxide (BMI) intercrosslinked matrices

Novel intercrosslinked networks of polyethersulfone modified epoxy-3,3′-bis(maleimidophenyl) phenylphosphine oxide matrix systems are developed. The polyethersulfone modification of epoxy resin is carried out by using tetramethyl ammonium hydroxide (TMAH) as a catalyst. The polyethersulfone modified epoxy systems are further modified with 4–12% 3,3′-bis(maleimidophenyl) phenylphosphine oxide and cured by using diaminodiphenylmethane. Tensile, flexural, impact properties and dynamic mechanical analysis (DMA) are carried out to assess the mechanical behaviour of the prepared neat resin castings. Mechanical studies indicate that the introduction of polyethersulfone into these epoxy resins improves the toughness without any reduction in the stress-strain values. But, the incorporation of bismaleimide (BMI) into the epoxy resin improves the stress-strain properties with a lowering of the toughness. The introduction of both polyethersulfone and bismaleimide into the epoxy resin influences the mechanical properties according to their content percentages.     

Cryogenic mechanical behaviors of carbon nanotube reinforced composites based on modified epoxy by poly(ethersulfone)

Cryogenic mechanical properties are important parameters for epoxy resins used in cryogenic engineering areas. In this study, multi-walled carbon nanotubes (MWCNTs) were employed to reinforce diglycidyl ether of bisphenol F (DGBEF)/diethyl toluene diamine (DETD) epoxy system modified by poly(ethersulfone) (PES) for enhancing the cryogenic mechanical properties. The epoxy system was properly modified by PES in our previous work and the optimized formulation of the epoxy system was reinforced by MWCNTs in the present work. The results show that the tensile strength and Young’s modulus at 77 K were enhanced by 57.9% and 10.1%, respectively. The reported decrease in the previous work of the Young’s modulus of the modified epoxy system due to the introduction of flexible PES is offset by the increase of the modulus due to the introduction of MWCNTs. Meanwhile, the fracture toughness (K_IC) at 77 K was improved by about 13.5% compared to that of the PES modified epoxy matrix when the 0.5 wt.% MWCNT content was introduced. These interesting results imply that the simultaneous usage of PES and MWCNTs in a brittle epoxy resin is a promising approach for efficiently modifying and reinforcing epoxy resins for cryogenic engineering applications.     

Optimum mixing ratio of epoxy for glass fiber reinforced composites with high thermal stability

The optimum condition of glass fiber/epoxy composites was investigated according to mixing ratio of two epoxy matrices. Novolac type epoxy and isocyanate modified epoxy were used as composites matrix. Based on chemical composition of mixing matrix, optimum mixing ratio of epoxy resins was obtained through FT-IR instrument. In order to investigate thermal stability and interface of epoxy resin, glass transition temperature was observed by DSC instrument, and static contact angle was measured by reflecting microscope. Change of IR peak and T_g was conformed according to different epoxy mixing ratios. After fabrication of glass fiber/epoxy composites, tensile, compression, and flexural properties were tested by UTM by room and high temperature. The composites exhibited best mechanical properties when epoxy mixing ratio was 1:1.     

Effects of 3D structure of silsesquioxane moieties on the thermal and optical properties of transparent epoxy/silsesquioxane hybrid materials

Transparent and colorless epoxy/silsesquioxane (SQ) hybrids were prepared by modifying bisphenol-A epoxy resin with two SQ type epoxy resins having different 3D structures, that is, double-decker SQ and cage SQ type epoxy resins. To compare these two hybrids, the cured resin modified with the imperfect ladder SQ epoxy resin was also prepared. The effects of the 3D-structure of the SQ moieties on the thermomechanical, optical and dielectric properties of the cured epoxy/SQ hybrids were investigated. Thus, the refractive index and dielectric constant of the hybrids significantly decreased with an increase in the contents of the SQ moieties. This is due to the introduction of Si atoms with a low atomic polarity and large intermolecular space that was estimated from the difference between the volume of the space surrounded by “Connolly surface” and the van der Waals volume of the SQ moieties. The glass transition temperature, T _g, also decreased with the introduction of the SQ moieties, due to the increase in the intermolecular space. Thus, it was concluded that the performance of the epoxy/SQ hybrids depends not only on the SiO_3/2 content, but also on the 3D structure of the SQ moieties.     

聚磷酸铵-三聚氰胺-三嗪成炭剂协同阻燃改性环氧树脂及玻璃纤维增强树脂复合材料

采用聚磷酸铵(APP)与不同比例三聚氰胺(MA)和三嗪成炭剂(CFA)复配对环氧树脂进行阻燃改性。系统研究了不同配比阻燃剂(总量保持40wt%)的加入对环氧树脂流变特性、固化行为、热机械性能、力学性能及阻燃性能的影响。将优化后的阻燃改性环氧树脂用于制备玻璃纤维增强环氧树脂复合材料(GFRC),对并其力学和阻燃性能进行了研究。结果表明,APP单独与MA或CFA复配改性环氧树脂并未表现出明显的协同阻燃效应,但它们组成的三元复配阻燃体系(30wt%APP-5wt%MA-5wt%CFA)具有良好的协同阻燃效应。相比未改性环氧树脂,APP-MA-CFA改性环氧树脂的极限氧指数(LOI)由18.0%提高到了50.2%,热释放峰值速率(PHRR)下降了84%,总热释放量(THR)下降了78%。树脂基体中加入阻燃剂后,GFRC的力学性能有所下降,尤其是层间剪切强度。同样地,基于APP-MA-CFA复配改性环氧树脂的GFRC表现出最佳阻燃性能,相比未改性的GFRC,其LOI值由22.8%提高到了66.0%,PHRR由354 kW/m2下降到93 kW/m2,THR由49.3 MJ/m2下降到22.8 MJ/m2。      

扩链增韧环氧树脂水分散乳液的制备及性能

采用聚丙二醇对高相对分子量环氧树脂E-20进行扩链增韧,即而丙烯酸类极性单体进行自由基接枝共聚合,制备了增韧改性的环氧树脂水分散乳液。利用ZETA电位分析仪、差示扫描量热法和热重分析等对其乳液的粒径与分布、稀释行为,改性树脂的玻璃化转变温度、耐热性能及力学性能进行了测定与分析。结果表明,水分散乳液粒径随着改性树脂中羧基中和程度的增加而减小,其稀释行为与溶剂分散体系明显不同;当作为固化涂膜材料时,比较改性环氧树脂与未改性树脂,其柔韧性和耐热性能均有显著提高。     

ZrW2O8-doped epoxy as low thermal expansion insulating materials for superconducting feeder system

Epoxy resin insulating materials used in superconducting feeder system of fusion device are required to be low thermal expansion coefficient (TEC). In this paper, negative thermal expansion (NTE) material ZrW₂O₈ filled epoxy resins were fabricated. To improve the dispersion of fillers in epoxy matrix, plasma polymerization was performed on the surface of ZrW₂O₈ powders. Transmission electron microscope (TEM) and surface wettability analysis were performed before and after the surface modification of ZrW₂O₈ powders. The TEC of ZrW₂O₈/epoxy composites were measured from 77 K to room temperature. The results show the doping of ZrW₂O₈ can significantly reduce the TEC of epoxy resins. The sedimentation rate of ZrW₂O₈ before and after modified in epoxy was compared by density measurement. It can be seen that the ZrW₂O₈ surface modified by plasma polymerization can enhance its dispersion properties in epoxy matrix.     

Preparation and film formation mechanism of an environmental-friendly polyester/epoxy ester coil coating primer

In this investigation, we have prepared an environmental-friendly waterborne coil coating primer. Waterborne saturated polyester resin and waterborne epoxy ester resin were selected as the binder resins, and methylated melamine resin and waterborne blocked isocyanate were selected as crosslinking resins. ZnMoO₄, Zn₃(PO₄)₂, Zn₃Al(PO₄)₃, and AlH₂P₃O₁₀ were selected as the anti-corrosion pigments, and modified nano-TiO₂ particles and other fillers were also employed to further enhance the primer performance. It was found that when polyester/epoxy ester equals to 7/3; binder resins/curing agent equals to 5/1; pigments/binder resin is in range of 1.4–1.6; additives of each is in amount of 0.5 wt.%–1.5 wt.%, the obtained primer has ideal properties, such as T-bend performance and qualified adhesion, and the salt spray resistance test can reach 360 h with the primer film thickness in range of 6 μm–7 μm after baking at 224 °C for 45 s. As to the coil coating primer film formation mechanism, Fourier transform infrared spectrum analysis indicates that both the amino resin and blocked isocyanate may react with the binder resin, and such chemical reactions can make them crosslinked to form a stereo-network film, giving birth to a good overall performance of the obtained primer.     

The cryogenic thermal expansion and mechanical properties of plasma modified ZrW2O8 reinforced epoxy

In this article, epoxy resin reinforced by negative thermal expansion material, ZrW₂O₈, was fabricated. The surface modification of ZrW₂O₈ particles was performed via plasma enhanced chemical vapor deposition (PECVD) process. As a result, a thin film was uniformly deposited on the surfaces of the ZrW₂O₈ particles, leading to an improvement of compatibility and dispersion of ZrW₂O₈ fillers inside epoxy matrix. Moreover, the coefficients of thermal expansion (CTEs) of the composite material containing 0-40 vol.% fillers were studied under cryogenic temperatures. The results showed a significant reduction in thermal expansion with increasing ZrW₂O₈ content. The cryogenic mechanical properties of ZrW₂O₈/epoxy composites were also investigated, showing the properties were improved by adding ZrW₂O₈ to certain content. In addition, the mechanical strength and modulus of the composite were observed significantly higher at cryogenic temperature than that at room temperature because of the thermal shrink effect and the frozen epoxy matrix.     

Polymer resins with epoxy end groups obtained from hydrocarbon pyrolysis C9 fraction

Polymer resins with epoxy groups (PREGs) are synthesized by radical copolymerization of hydrocarbon pyrolysis C₉ fraction using 1,2-epoxy-3-tert-butylperoxypropane as the initiator or by copolymerization of the ED-20 epoxy resin modified by tert-butyl hydroperoxide. The effect of the initiator nature and quantity, temperature and reaction time on the yield and characteristic of PREGs are examined. The structure of synthesized products is established by chemical methods and IR spectroscopy. The structurization of ED-22 epoxy resin is studied in the presence of polyethylenamine using 10 and 25 mass% of PREG.     

A COMPARATIVE STUDY OF THE PREPARATION AND CHARACTERIZATION OF AROMATIC AND ALIPHATIC BISMALEIMIDES TO PRODUCE MODIFIED SILICONIZED EPOXY INTERCROSSLINKED MATRICES FOR ENGINEERING APPLICATIONS

A novel hybrid intercrosslinked network of hydroxyl-terminated polydimethylsiloxane modified epoxy and bismaleimides [N,N'-bismaleimido-4,4'-diphenylmethane and 1,6-bis(maleimido)hexane] matrix systems were developed. Epoxy resin was modified with 5, 10, and 15% (wt%) of hydroxyl-terminated polydimethylsiloxane using γ-aminopropyltriethoxysilane as crosslinking agent and dibutyltindilaurate as catalyst. The reaction between hydroxyl-terminated polydimethylsiloxane and epoxy resin was confirmed by IR spectral studies. The siliconized epoxy systems were further modified with 5, 10, and 15% (wt%) of both aromatic and aliphatic bismaleimides separately. The castings and E-glass fiber-reinforced composites prepared were characterized for their mechanical properties. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) of the matrix samples were also performed to determine the glass transition temperature (T_g) and thermal degradation temperature of the hybrid intercrosslinked systems. Data obtained from mechanical studies and thermal characterization indicate that the introduction of siloxane into epoxy resin improves the toughness and thermal stability, with reduction in strength and modulus values. The incorporation of aromatic bismaleimide into epoxy resin improved both tensile strength and thermal properties, whereas it was observed that the incorporation up to 5% of aliphatic bismaleimide into epoxy resin decreased the stress-strain value and above 5% increased the strength properties. However, the introduction of both aromatic and aliphatic bismaleimides (aromatic and aliphatic) into siliconized epoxy resin influenced both mechanical and thermal properties according to the percentage content.     

Mechanism of radiation-induced degradation in mechanical properties of polymer matrix composites

Four kinds of polymer matrix composites (filler, E-glass or carbon fibre cloth; matrix, epoxy or polyimide resin) and pure epoxy and polyimide resins were irradiated with ⁶⁰Co -rays or 2 MeV electrons at room temperature. Mechanical tests were then carried out at 77 K and at room temperature. Following irradiation, the Young's (tensile) modulus of these composites and pure resins remains practically unchanged even at 170 MGy for both test temperatures. The ultimate strength, however, decreases appreciably with increasing dose. The dose dependence of the composite strength depends not only on the combination of fibre and matrix in the composite but also on the test temperature. A relationship is found between the composite ultimate strain and the matrix ultimate strain, thus indicating that the dose dependence of the composite strength is virtually determined by a change in the matrix ultimate strain due to irradiation. Based on this finding, we propose a mechanism of radiation-induced degradation of a polymer matrix composite in order to explain the dose dependence of the composite strength measured at 77 K and at room temperature.     

改性F-51/E-51环氧树脂水乳液研究

多官能度环氧树脂F-51与适量二乙醇胺反应,再与乙酸成盐得到一种水性环氧树脂,该树脂保留了较多的环氧基团,与胺类固化剂配合,可作为涂料或复合材料基体。此外,该改性树脂对其它环氧树脂有良好的乳化能力,用适量E-51环氧树脂与之混合,通过相转变法制备的水乳液稳定性好,固化膜综合性能良好,吸水率与溶剂型环氧体系相当。     

Characterization of transverse tensile, interlaminar shear and interlaminate fracture in CF/EP laminates with 10 wt% and 20 wt% silica nanoparticles in matrix resins

The transverse tensile properties, interlaminar shear strength (ILSS) and mode I and mode II interlaminar fracture toughness of carbon fibre/epoxy (CF/EP) laminates with 10 wt% and 20 wt% silica nanoparticles in matrix were investigated, and the influences of silica nanoparticle on those properties of CF/EP laminates were characterized. The transverse tensile properties and mode I interlaminar fracture toughness (G_IC) increased with an increase in nanosilica concentration in the matrix resins. However, ILSS and the mode II interlaminar fracture toughness (G_IIC) decreased with increasing nanosilica concentration, especially for the higher nanosilica concentration (20 wt%). The reduced G_IIC value is attributed to two main competing mechanisms; one is the formation of zipper-like pattern associated with matrix microcracks aligned 45° ahead of the crack tip, while the other is the shear failure of matrix. The ratio of G_IIC/G_IC decreased with the concentration of silica nanoparticles, comparable with similar CF/EP laminates with dispersed CNTs in matrix. Fractographic studies showed that interfacial failure between carbon fibre and epoxy resin occurred in the neat epoxy laminate, whereas a combination of interfacial failure and matrix failure occurred in the nanosilica-modified epoxy laminates, especially those with a higher nanosilica concentration (20 wt%).     

用液态含环氧基丙烯酸酯低聚物改性环氧树脂

采用溶液聚合法合成了以丙烯酸丁酯为主链的液态含环氧基丙烯酸酯低聚物,并用其对环氧树脂进行增韧改性.讨论甲基丙烯酸环氧丙酯以及低聚物用量对改性环氧树脂力学性能的影响,并研究了改性环氧树脂的微观形态和耐热性能.结果表明:当低聚物用量为10%(质量分数),丙烯酸丁酯和甲基丙烯酸环氧丙酯的质量比为80∶20时,改性环氧树脂的拉伸强度和冲击强度比纯环氧树脂提高6.7%和219.1%,同时体系的耐热性能基本不下降;改性环氧树脂呈两相结构,随低聚物用量增加橡胶粒子粒径尺寸增大;且Tg先升高后降低.     

Mechanical properties of high strength and high toughness metallic filament composites with epoxy and poly(ether ether ketone) matrices

High strength and high toughness metallic filament was produced by glass-coated melt spinning. The mechanical properties of the composite consisting of the filaments uniaxially aligned in brittle epoxy resin, ductile epoxy resin with plasticizer and poly(ether ether ketone) matrices were investigated. It was found that the Young's modulus (E _c) and tensile strength (,_cu) of the composite consisting of uncoated filaments in brittle epoxy matrix were higher than those predicted by a linear function of the filament content (Vf), and the filaments fractured tightly in contact with the matrix. On the other hand, no improvement of the mechanical properties of the composite consisting of glass-coated filaments in brittle epoxy matrix was detected, due to the weak interfacial force between metallic filaments and the coating glass. The composite consisting of filaments in a ductile matrix was a high toughness material with a long range of plasticity deformation, and the experimental values ofE _c and _cu against V_f agreed with the simple law of mixtures.     

Thermal expansion and swelling of cured epoxy resin used in graphite/epoxy composite materials

This paper presents results of experiments in which the thermal expansion and swelling behaviour of an epoxy resin system and two graphite/epoxy composite systems exposed to water were measured. It was found that the cured epoxy resin swells by an amount slightly less than the volume of the absorbed water and that the swelling efficiency of the water varies with the moisture content of the polymer. Additionally, the thermal expansion of cured epoxy resin that is saturated with water is observed to be more than twice that of dry resin. Results also indicate that cured resin that is saturated with 7.1% water at 95° C will rapidly increase in moisture content to 8.5% when placed in 1° C water. The mechanism for this phenomenon, termed reverse thermal effect, is described in terms of a slightly modified free-volume theory in conjunction with the theory of polar molecule interaction. Nearly identical behaviour was observed in two graphite/epoxy composite systems, thus establishing that this behaviour may be common to all cured epoxy resins.