Mechanical properties of epoxy networks based on DGEBA and aliphatic amines

The mechanical properties of epoxy networks based on diglycidyl ether of bisphenol A epoxy resin cured with various linear aliphatic amines, such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and cyclic amines such as 1‐(2‐aminoethyl)piperazine and isophorone diamine, were studied. General characteristics such as T_g, density, and packing density, were determined and related to the structure and funcionality of the curing agent. Dynamic mechanical spectra were used to study both the α and β relaxations. Tensile and the flexural tests were used to determine the Young's and flexural modulus, and fracture strength all in the glassy state. Furthermore, linear elastic fracture mechanics was used to determine K_IC. As a rule, isophorone diamine network presented the higher tensile and flexure modulus while 1‐(2‐aminoethyl)piperazine gave the highest toughness properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Mechanical properties of blocked polyurethane/epoxy interpenetrating polymer networks

The mechanical properties of blocked polyurethane(PU)/epoxy interpenetrating polymer networks (IPNs) were studied by means of their static and damping properties. The studies of static mechanical properties of IPNs are based on tensile properties, flexural properties, hardness, and impact method. Results show that the tensile strength, flexural strength, tensile modulus, flexural modulus, and hardness of IPNs decreased with increase in blocked PU content. The impact strength of IPNs increased with increase in blocked PU content. It shows that the tensile strength, flexural strength, tensile modulus, and flexural modulus of IPNs increased with filler (CaCO₃) content to a maximum value at 5, 10, 20, and 25 phr, respectively, and then decreased. The higher the filler content, the greater the hardness of IPNs and the lower the notched Izod impact strength of IPNs. The glass transition temperatures (T_g) of IPNs were shifted inwardly compared with those of blocked PU and epoxy, which indicated that the blocked PU/epoxy IPNs showed excellent compatibility. Meanwhile, the T_g was shifted to a higher temperature with increasing filler (CaCO₃) content. The dynamic storage modulus (E′) of IPNs increased with increase in epoxy and filler content. The higher the blocked PU content, the greater the swelling ratio of IPNs and the lower the density of IPNs. The higher the filler (CaCO₃) content, the greater the density of IPNs, and the lower the swelling ratio of IPNs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1826–1832, 2006     

Amphiphilic networks. XI. Mechanical properties and morphology

The bulk properties of two types of amphiphilic networks, poly(2-hydroxyethyl methacrylate)-l-polyisobutylene (PHEMA-l-PIB, H-network) and poly(N,N-dimethylacrylamide)-l-polyisobutylene (PDMAAm-l-PIB, A-network), have been investigated. Tensile strengths decreased considerably by swelling, and the decrease was more severe by swelling in water than in n-heptane. Elongations increased by swelling in water; however, the change was not consistent upon swelling in n-heptane. The hardness of dry networks decreased with increasing PIB content, while for wet networks it was similar to dry networks containing 85 wt % PIB. Small-angle X-ray scattering showed that average interdomain spacings decreased with increasing PIB content. According to dynamic mechanical thermal analysis (DMTA) the glass transition temperatures (T_g) of the respective hydrophobic and hydrophilic components shift toward each other with increasing PIB content. A “liquid-liquid transition” (T_ll) above the T_g of the hydrophilic component was apparent by DMTA, but could not be found by differential scanning calorimetry (DSC). © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 901–910, 1997     

Lignin Epoxy Composites: Preparation,Morphology, and Mechanical Properties

A novel route to lignin epoxy composites is developed through covalent incorporation of depolymerized lignin epoxide into amine‐cured epoxy matrix. The partially depolymerized lignin is first epoxidized with epichlorohydrin and the resultant depolymerized lignin epoxide shows decreased solubility in common organic solvents. When dispersed in epoxy matrix and cured, the depolymerized lignin epoxide is integrated into epoxy networks in the form of submicron aggregates. The resulting lignin epoxy composites show improved mechanical properties compared with neat epoxy. At a loading content of 1.0 wt% of degraded lignin epoxide, the Young's modulus and the critical stress intensity factor (K_IC) of the composite increase by 10% and 25%, respectively, in comparison with those of neat epoxy, while the glass transition temperature is little changed. This method presents a promising way to convert wasteful lignin to an alternative epoxy monomer and effective additive in epoxy composites.

     

Physical and Mechanical Interfacial Properties of Epoxy Copolymers Initiated by Latent Thermal Catalysts

Summary: The epoxy copolymers containing sulfone groups, diglycidyl ether of bisphenol‐A – Bisphenol‐S (DGEBA‐S) were synthesized by a hot‐melt method. The thermal properties of the epoxy systems initiated by two cationic latent catalysts, i.e., N‐benzylpyrazinium hexafluoroantimonate (BPH) and N‐benzylquinoxalinium hexafluoroantimonate (BQH), were investigated by using a dynamic DSC, DMA, and TGA. The mechanical properties were measured by single‐edge‐notched (SEN) beam fracture toughness tests. As a result, the thermal stability and mechanical interfacial properties of the DGEBA‐S/catalyst system were found to be higher than those of the DGEBA/catalyst. This was probably due to the fact that the introduction of sulfone groups with a polar nature to the main chain of the epoxy resins led to an improvement of thermal stability and toughness of the cured epoxy copolymers.

Conversion of the epoxy/catalyst systems as a function of curing temperature.     

Mechanical and Morphological Behavior of Bismaleimide-Modified Soy-Based Epoxy Matrices

This study is concerned with the preparation and mechanical characterization of bio-based polymers from renewable resources. Epoxidized soybean oil at various concentrations is cured with an amine curing agent. The prepared matrices have been chemically modified with three types of bismaleimides, namely N, N′-bismaleimido-4, 4′-diphenyl methane (BMI-1), 1,3-bis(maleimido)benzene(BMI-2) and 3,3′-bis(maleimido phenyl)phenyl phosphineoxide (BMI-3). The crosslinked matrices thus developed were characterized for their mechanical properties such as tensile strength, tensile modulus, flexural strength, flexural modulus, and impact strength. The incorporation of bismaleimides in the soy-based matrices significantly enhances the mechanical properties. The morphological behavior of matrices is also studied using a scanning electron microscope. The results indicate that the bismaleimide-modified soy-based epoxy resin at appropriate concentration holds great potential as a replacement for petroleum-based materials in engineering applications.     

Gas and water transport properties of epoxy–amine networks: Influence of crosslink density

The gas and water transport properties were studied on seven epoxy–amine networks that differ by their di/mono epoxy composition and their cure cycle. The characteristic parameters of transport M_∞ and D were determined in each case, and they show that the solubility and diffusion coefficients are influenced by their composition. The solubility increases with the extend of cure and with the decrease of dangling chains, and in both cases the evolution of the diffusivity is inverse. The variations of the solubility and diffusivity have been discussed as a function of two parameters: polar groups and unrelaxed holes of the glassy networks. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2058–2066, 2001     

一种高温环氧树脂的工艺及力学性能

对比研究了国产MERICAN 3768和国外CYCOM 890 RTM两种高温环氧树脂的工艺性和力学性能。同时选取典型航空结构,采用双轴向碳纤维织物和真空灌注工艺制备了对比零件。结果表明,国产MERICAN 3768树脂的浸润性、流变固化特性和力学性能均与国外CYCOM 890 RTM树脂相当,均具有优异的工艺性和力学性能,与纤维匹配性好,满足航空应用对树脂的要求。     

Infusion of SiC Nanoparticles Into SC‐15 Epoxy: An Investigation of Thermal and Mechanical Response

Summary: In the present investigation we have developed a novel technique to synthesize nanocomposite materials consisting of SC‐15 epoxy resin and silicon carbide (β‐SiC) nanoparticles. A high intensity ultrasonic liquid processor was used to obtain a homogeneous molecular mixture of epoxy resin and β‐SiC nanoparticles. In this study, we have prepared three different samples containing 0.5, 1, and 1.5% of β‐SiC nanoparticles by weight of the epoxy resin. In parallel, control samples were also made following identical procedures without the infusion of nanoparticles. Test samples were characterized by TGA, DSC and three‐point bend flexural tests to evaluate thermal and mechanical properties. The results indicate that 1 wt.‐% loading derives the maximum improvement in both thermal and mechanical properties when compared to the neat system. The dispersion of nanoparticles and morphological changes were studied by field emission scanning electron microscopy (FE‐SEM) and high resolution transmission electron microscopy (TEM). These results demonstrate that the nanoparticles are spherical in shape (≈30 nm sizes) and are uniformly dispersed over the entire volume of the resin.

FE‐SEM micrograph of the plasma etched 1 wt.‐% SiC‐epoxy system.     

The Mechanical Properties and Chemical Resistance of Short Glass-Fiber-Reinforced Epoxy Composites

ABSTRACT

Epoxy–short glass fiber composites were prepared by directly blending two-pack system of Araldite (CY-230) and hardner (HY-951) with short glass fibers. The short glass fiber content was varied from 2% to 10% by weight of the total matrix. These composites were then characterized for morphology using scanning electron microscopy, mechanical properties, that is, tensile and flexural properties and resistance toward various chemicals. The epoxy-glass fiber composites showed improved tensile and flexural properties but increased dispersion among the properties with increasing fiber content. Several reasons to explain these effects in terms of reinforcing mechanisms were discussed. These composites were stable in most chemicals but were completely destroyed in concentrated sulfuric acid, nitric acid, and pyridine.     

Effect of Bio-Based Cobalt Alginate on the Fire Safety and Mechanical Properties for Epoxy Resin

There is a growing demand to develop epoxy resins (EP) with smoke suppression as well as satisfactory flame retardancy. Herein, bio-based cobalt alginate is successfully fabricated and incorporated into EP to prepare EP/Cobalt Alginate composites with better fire safety performance. The addition of cobalt alginate reduces the thermal-decomposition rate, temperature at maximum weight-loss rate of EP, whereas obviously improves the thermal stabilities at a higher temperature range. Furthermore, the addition of cobalt alginate substantially reduces the fire hazard of EP, resulting in 56.2% reduction in peak heat release rate, as well as 17.8% and 56.3% reduction in total smoke production and peak smoke production rate, respectively, compared with EP matrix. Moreover, the presence of cobalt alginate increases smoke-suppressant properties, according to the smoke density test. Additionally, the incorporation of cobalt alginate has no obviously destructive effect on the mechanical properties of EP, while EP/Cobalt Alginate-3 exhibits a 27.0% improvement in impact strength. In prospective, this study may provide a significant method for producing eco-friendly flame retardant EP.     

Physico‐Mechanical and Antibacterial Properties of Pine Gum/Epoxy Composites with/without Silver Nanoparticles

Silver nanoparticles/polymer composite (Ag‐NPs/PC) may eventually be biodegradable, sustainable, or burned without production of lethal by‐products and can be utilized as packaging and biomedical device applications. Nanoparticles engaged in pine gum (resin and rosin) are preserved for months without any significant effect on particle size and distribution. This paper focuses on the pine gum/epoxy composites with and without silver nanoparticles fabricated by a hand lay‐up technique. Silver nanoparticles are fixed at 0.37% and pine gum varies from 2 to 24% by weight to acquire the best mechanical and wear properties. The result indicates that Ag‐NPs with pine gum (23.7 wt% resin &13.3 wt% rosin) has the best tensile and impact strength reaching a gain of 51.34% and 53.68% simultaneously. Hardness is noted most extreme 17.92% at Ag‐NPs sample (7.4 wt% resin and 3.7 wt% rosin) and wear resist behavior is best noted with neat pine gum/epoxy composite. The antibacterial assay of the Ag‐NPs is done against Escherichia coli and noted that the zone of inhibition is found to be 1.6 cm as compared to inhibition of 0.4 cm for pine gum reaching an advance of 75%. The various arrangements are enhanced and sited on the basis of TOPSIS technique.     

Flame Retardancy and Mechanical Properties of Bio‐Based Furan Epoxy Resins with High Crosslink Density

This work outlines an interesting approach to bioepoxy resins from sustainable 2,5‐bis((oxiran‐2‐ylmethoxy)methyl)furan (BOF). The 3,3′‐diamino diphenyl‐sulfone (33DDS) and 4,4′‐diamino diphenyl‐sulfone (44DDS) are employed as hardeners. For comparison, petro‐based networks from diglycidyl ether of bisphenol A (DGEBA) are developed as well. The systematic analyses suggest that the BOF/DDS networks show higher crosslink densities and mechanical properties than DGEBA/DDS thermosets. Remarkably, an attractive multilayer tubular microstructure is fabricated in the BOF/44DDS thermosets, and it greatly enhances the mechanical performance. Apart from that, BOF/DDS composites exhibit excellent flame retardancy. Especially, for BOF/44DDS, the self‐extinguishment happens in 7 s. The fire retardant mechanism confirms that a low heat release rate and heat release capacity as well as a compact char layer occur in the pyrolysis of BOF/DDS. Thus, the BOF/DDS exhibits superior performance over its DGEBA counterparts and meets a wide variety of requirements in engineering.     

Using PA11 and 12 as curing agents for epoxy networks: Influence of reactivity on miscibility and properties

The Rilsan PA11 prepolymer was evaluated as a curing agent of a diepoxy prepolymer (DGEBA). The miscibility, the glass transition temperature, and the melting of the blend were studied as a function of time at 200°C. A gelation phenomenon was evidenced by dynamic mechanical analysis and the gel time was determined at 200°C. The participation of amide groups to the reaction process at this temperature was confirmed by the study of the PA12 Orgasol®/DGEBA system and a reaction mechanism was elucidated by the study of a model system composed of ethylacetamide/phenyl glycidyl ether. The mechanical properties of DGEBA/Rilsan networks cured 7 h at 200°C were evaluated and indicate very high Young's modulus and critical stress intensity factor. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 857–865, 2000     

Silica aerogel/epoxy nanocomposites: Mechanical,vibrational, and morphological properties

The present study was an attempt to examine the effects that adding silica aerogel (SA) nanoparticles to epoxy would exert on its mechanical, vibrational, and morphological properties. Neat epoxy was consecutively combined with 1, 2, and 4 wt% of SA nanoparticles. A number of tests of mechanical properties were then performed on the samples, including tests of tensile, bending, compressive, dynamic mechanical thermal, hardness, and Izod impact. Vibration and water uptake tests were also conducted on the samples. The highest modulus and strength values were found in the nanocomposite sample with 4 wt% of SA, and the highest toughness and elongation values were detected in the sample with 1 wt% of SA. Furthermore, adding the SA nanoparticles to the epoxy improved the energy absorption and hardness of the epoxy matrix. The findings from the tests of dynamic mechanical thermal and vibration properties demonstrated that, with an increase in the nanoparticles content in the samples, the values of storage modulus and natural frequency increased while the values of tan δ and damping ratios decreased. A comparison between the values of natural frequency from the vibration test and the values from the Euler–Bernoulli beam theory showed a good agreement between the theoretical and experimental results.     

Mechanical properties of an epoxy resin toughened by polyester

The epoxy resins were toughened by 4–24 phr polyester with average molecular weight 1.9×10⁴ g/mol in this investigation. The mechanical properties were examined and dynamic mechanics analyses were performed for the epoxy resins before and after the modification. The toughening mechanism of polyester to epoxy resin is discussed in light of the scanning electronic microscopy observation of the fracture surfaces. The results showed that the impact strength and tensile strength of the modified epoxy resin were remarkably greater than those of the unmodified cured epoxy resin. The most suitable composition for the modified epoxy resin was the addition of 16 phr polyester, which led to 138 and 46% increments in the impact strength and the tensile strength, respectively. And the mechanical properties depended greatly on the congregating state of polyester added. The polyester dispersing in the epoxy matrix was amorphous when its addition was less than or equal to 12 phr, and was sphere crystals when the addition was over 16 phr. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3384–3389, 2003     

New Epoxy Resins Containing Hard-soft Segments: Synthesis, Characterization and Modification Studies for High Performance Applications

We have attempted two methods to improve the properties of the epoxy materials for high performance applications. Solventless reactions of epoxy backbones tailored with hard-soft segments were adopted to improve the toughness. This was followed by curing of epoxy groups with cyanate to enhance the properties of epoxy formulations. We have reported here the synthesis of new epoxy resins having hard-soft segments based on aromatic and aliphatic backbones. An attempt was made at the modification and characterization of TGDDM/DDS (Tetraglycidyl 4,4^′′-diaminodiphenyl methane/diaminodiphenyl sulphone) system with new epoxides and 4-dicyanato diphenyl-2,2^′-propane (DCDPP). Thus, new epoxides of 1,4-, 1,5- and 1,6-methylene groups with terephthalate/isophthalate backbones were synthesized and the intermediates were characterized by FT-IR, ¹H/¹³C-NMR spectroscopic methods. The synthesized epoxides were used to modify the TGDDM/DDS/DCDPP. The neat cast laminates were made and characterized for their physical and mechanical properties. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mechanical and Anticorrosive Properties of Graphene/Epoxy Resin Composites Coating Prepared by in-Situ Method

The graphene nanosheets-based epoxy resin coating (0, 0.1, 0.4 and 0.7 wt %) was prepared by a situ-synthesis method. The effect of polyvinylpyrrolidone/reduced graphene oxide (PVP-rGO) on mechanical and thermal properties of epoxy resin coating was investigated using nanoindentation technique and thermogravimetric analysis, respectively. A significant enhancement (ca. 213% and 73 °C) in the Young modulus and thermal stability of epoxy resin coating was obtained at a loading of 0.7 wt %, respectively. Furthermore, the erosion resistance of graphene nanosheets-based epoxy resin coating was investigated by electrochemical measurement. The results showed also that the Rrcco (ca. 0.3 mm/year) of graphene nanosheets-based epoxy resin coating was far lower than neat epoxy resin (1.3 mm/year). Thus, this approach provides a novel route for improving erosion resistance and mechanical-thermal stability of polymers coating, which is expected to be used in mechanical-thermal-corrosion coupling environments.     

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.     

Mechanical properties of poly(ether-ether-ketone) for engineering applications

An outline of the characteristics of PEEK and the versatility of its compositional forms (micro and macro composites) are given to illustrate its wide potential for success in engineering applications. Although it is necessary to have particular tabulations of mechanical properties for engineering design, these are seldom available and consequently it is argued that an understanding of stiffness, toughness and strength properties are required to fully exploit available manufacturer's data and thus develop the full potential of PEEK and its composites. Stiffness characteristics are considered in terms of a modulus function which is dependent on time under load and temperature. In its composite forms, whether reinforced with short or continuous fibres, stiffness anistropy can be both considerable and complex, but some empirical ground-rules are apparent. For continuous fibre composites even in the form of complex lay-ups, it is also possible to attempt some stiffness prediction from certain pseudo-elastic constants. Toughness of PEEK and its composites is described in terms of both comparative and intrinsic properties. Instrumented falling weight impact data, particularly as a function of temperature enable some insight into ductile-brittle transitions for the unreinforced material, but crack initiation and crack propagation processes for the various fibre reinforced forms. Intrinsic toughness is described in terms of linear elastic fracture mechanics theory. Strength properties are described for static and dynamic loading configurations. In particular, PEEK and its composites are evaluated for increasing test severities for strength characteristics; stress concentration, loading form and test temperature are considered.