•Aromatic bismaleimides and aliphatic bismaleimides were prepared.•Aliphatic bismaleimides have lower activation energy.•Aromatic bismaleimides possess superior thermal stability and lower dielectric ...loss.•Aliphatic bismaleimides exhibit lower dielectric constant and low water absorption.
In this paper, three aromatic bismaleimides (BMI-70, BMI-DE and BMI-80) and two aliphatic bismaleimides (BMI-DDA and BMI-C36) were synthesized. The structures were characterized using nuclear magnetic resonance (NMR) spectra and Fourier transform infrared (FT-IR) spectra. Their polymerization behaviors were discussed by non-isothermal differential scanning calorimetry (DSC). The thermal and dielectric properties of the poly(bismaleimide) were investigated using thermogravimetric analysis (TGA), dynamic thermo-mechanical analysis (DMA), and an impedance analyzer. The results indicate that the aliphatic bismaleimides exhibit lower apparent activation energies and dielectric properties, with BMI-DDA displaying an average activation energy of 105.5 kJ mol−1 and the dielectric constant of P(BMI-C36) is 2.558 @ 10 MHz. The aromatic polybismaleimides possessed better thermal stability, among which, the 5 % thermal decomposition temperature (Td,5) of P(BMI-70) was 513.5 °C, and the residual carbon rate at 800 °C was 44.6 %. In additional, water absorption was studied and their saturated water absorption was less than 4 %.
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With increasing development of chip and circuit integration, the requirements regarding the viscosity, activity, and thermomechanical properties of underfill are becoming increasingly stringent. ...However, common low-viscosity resins are often obtained with poor thermal and thermomechanical properties. In this study, natural renewable pyrogallol was used as a raw material and preparedto prepare a high-performance polyphenol epoxy resin monomer named E3PG (pyrogallol triglycidyl ether) through employing a combination of epichlorohydrin and olefin epoxidation methods for the first time. At 25°C, the viscosity of E3PG was only 210 cps, indicating excellent processability. Compared with traditional epoxy resin (E51), E3PG has a lower activation energy, and more importantly, exhibits excellent thermomechanical properties after curing; its glass transition temperature (Tg) reaches 164°C, and its storage modulus (E′) reaches 3500 MPa at 25°C. In this study, an epoxy resin monomer with excellent properties was successfully prepared using renewable polyphenols as raw materials, providing a unique and novel approach for the synthesis of epoxy resin monomers.
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•High purity of pyrogallol triglycidyl ether (E3PG) was successfully prepared.•E3PG exhibits higher curing activity than traditional resin (E51).•E3PG has a very low viscosity of 210 cps at 25°C.•The curing kinetic equations were visualized and α-T-t were drawn.•The Tg of E3PG/MeTHPA cured was as high as 164°C.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The design, synthesis, and characterization of a novel epoxy monomer, CP-EP, which consists of nontoxic eugenol and nonflammable cyclotriphosphazene has been carried out in this work. Chemical ...structure of CP-EP was confirmed by nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). Using 4,4′-diaminodiphenylmethane + diethyltoluenediamine (DDM + DETDA), succinic anhydride (SA), or methylhexahydrophthalic anhydride (MeHHPA) as curing agent, three cyclotriphosphazene-based thermosets (CPTs) were produced, and non-isothermal curing behaviors were investigated by using dynamic differential scanning calorimetry. In comparison to the bisphenol-A epoxy resin, CPTs exhibit higher glass transition temperature, enhanced tensile/flexural strengths, and significantly improved nonflammability. UL-94 rating and limiting oxygen index (LOI) for CPTs were V-0 and 28% respectively. These observations suggest an effective approach for the preparation of a halogen-free epoxy thermosetting system. This approach may be used for the generation of high-performance fire-safe epoxy thermosets. Both environment and human health can benefit from the use of such materials.
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•A novel phosphazene epoxy monomer (CP-EP) is efficient and controlled synthesized.•Investigation of thermal curing kinetics of CP-EP indicate its high reactivity.•All cyclotriphosphazene-based thermosets (CPTs) showed excellent nonflammability.•Comparing to E44 thermosets, CPTs show higher mechanical and thermal properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•The contribution of boron (PBPS) to the curing kinetics of epoxy resin is systematically revealed for the first time.•PBPS reduces the reaction induction time and accelerates the ...non-catalytic stage of the epoxy-amine system.•The improved curing behavior endows EP with excellent thermal stability and mechanical properties.
The curing kinetics of epoxy resin (EP) play an important role in optimizing the final properties of the resin, such as thermal stability, flame retardancy and mechanical properties, etc. However, full understanding of the curing kinetic remains a formidable challenge due to the progressively crosslinked structure and the multi-stage exothermic curing reactions. In this study, a hyperbranched polysiloxane (PBPS) with a Si-O-B backbone, containing reactive hydroxyl and epoxy end groups, is synthesized to facilitate the amine curing of EP. For the first time, the contribution of boron to the curing kinetics of epoxy resin is systematically revealed. The Kamal-Sourour model and the Arrhenius four-parameter model, having good fittings to rheology data, successfully describe the isothermal and non-isothermal curing kinetics of the epoxy-amine system loaded with PBPS, respectively. Acting as a Lewis acid, the boron in PBPS coordinates with epoxy groups, efficiently reducing the induction time of curing of the epoxy-amine system. The reaction rate of the non-catalytic stage is increased with reduced activation energy. Meanwhile, a gentle autocatalytic curing stage is achieved with PBPS. The effect of PBPS on the initial viscosity of EP leads to an increase in the activation energy of the viscous flow stage of the non-isothermal process. The curing behavior determines the final properties of EP. The combined effect of improved curing conditions, which endow EP with high crosslink density, and the flexible segments of PBPS exhibit excellent toughening effects. PBPS cavities can in situ form filament structures, thereby reinforcing and toughening the EP. This systematic study fills the knowledge gap regarding the mechanism of hyperbranched polysiloxane participating in the curing of epoxy resin and its influence on the final properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Most composites require a certain amount of pressure to cure, therefore, it is crucial to comprehend the effect of pressure on the curing reaction. Nonetheless, the majority of studies on curing ...reaction focus on isothermal or non-isothermal DSC measurements at ambient pressure. Using a high-pressure differential calorimetry scanner (Netzsch DSC 204HP), the curing process of a bisphenol A diglycidyl ether system is studied in order to evaluate the influence of curing pressure. The results indicate a competitive relationship between the effect of heating rate and pressure on the reaction rate, with the influence of heating rate being stronger. The reaction follows the autocatalytic model, and the average activation energy EP and pre-exponential factor AP decrease as the pressure increases. The obtained kinetics are used to simulate the process of forming composite laminates. When the thickness of laminates exceeds 18 mm, the maximum difference of the temperature and curing degree between ambient pressure and 2 MPa pressure is 20.65 °C and 0.161, respectively, indicating that the simulation results of thick composites are affected by whether the curing pressure is considered in kinetics.
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•The effects of pressure and temperature on reaction rate compete.•Epoxy curing kinetics are obtained and verified at different pressures.•Effects of kinetic models with varied pressures on simulation are obtained.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Pyrogallol was used to lower the curing temperature of a fully bio-based benzoxazine.•The exothermal peak temperature of benzoxazine greatly decreased with pyrogallol.•The apparent activation energy ...of benzoxazine was reduced with pyrogallol.•Detailed thermal curing kinetics of benzoxazine/pyrogallol was studied.
In this work, the effect of pyrogallol which served as a phenolic nucleophile on the ring-opening polymerization and curing kinetics of the eugenol/stearylamine-based benzoxazine (E-s) was examined with phenol as a contrast. The differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) results revealed that pyrogallol demonstrated higher ability to promote the ring-opening polymerization of E-s compared to phenol. The exothermal peak temperature of E-s was reduced from 254 °C to 168 °C with the addition of pyrogallol. Moreover, the curing kinetics of the E-s and pyrogallol mixture (E-s/py) were studied with Kissinger, Ozawa, Flynn-Wall-Ozawa and Friedman methods. The results indicated that the apparent activation energies (Ea) of E-s decreased with the addition of pyrogallol. In addition, the polymerization process of E-s/py followed the autocatalytic kinetic model based on Friedman method.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Curing kinetics of flame retardant composite based on benzoxazine and MCC is studied.•Differential scanning calorimetry was used to examine the curing kinetics.•Activation energy, pre-exponential ...factor and kinetic model were determined.•A catalytic behavior is noticed for the curing of the resin supplemented with MCC.
A comprehensive investigation into the curing kinetics of composites based on bisphenol A aniline benzoxazine resin (BA-a) and microcrystalline cellulose (MCC) modified by phosphorylation (MCC-pH), was conducted in this study. For this purpose, differential scanning calorimetry (DSC) analysis, at different heating rates, was used to examine the curing process. The kinetic parameters as a function of conversion were determined using isoconversional approaches, i.e., iterative Kissinger-Akahira-Sunose (it-KAS), Trache-Abdelaziz-Siwani methodology (TAS), and Vyazovkin methodology. The incorporation of MCC-pH reduced considerably the curing temperatures, indicating their catalytic effect. A combination of isoconversional methods and multi-step kinetic fitting was done to elucidate the effect of adding MCC-pH on BA-a curing. The reported data exhibited the enhanced reactivity of the composite systems, which was associated with the acceleration of the regular polymerization reaction. The possible pathway of the polymerization in the presence of phosphorylated cellulose was also discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this paper, a polyether-ether-ketone (PEEK)/epoxy composite was prepared by using PEEK microparticles as the reinforcement. The nonisothermal differential scanning calorimetry (DSC) test was used ...to evaluate the curing reaction of PEEK/epoxy resin system. The curing kinetics of this system were examined utilizing nonisothermal kinetic analyses (Kissinger and Ozawa), isoconversional methods (Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose) and an autocatalytic reaction model. During these analyses, the kinetic parameters and models were obtained, the curing behavior of PEEK/epoxy resin system under dynamic conditions was predicted. The results show that isoconversional methods can adequately interpret the curing behavior of PEEK/epoxy resin system and that the theoretical DSC curves calculated by the autocatalytic reaction model are in good agreement with experimental data. Furthermore, the tensile elongation at break, tensile strength, flexural strength, compression strength and compression modulus increased by 81.6%, 33.66%, 36.53%, 10.98% and 15.14%, respectively, when PEEK microparticles were added in epoxy resin composites.
•The PEEK/epoxy composites were prepared by using thermoplastic PEEK microparticles as reinforcement.•The nonisothermal DSC test was used to evaluate the curing reaction of the PEEK/epoxy resin system.•Varies methods were applied to obtain the curing kinetics parameters and the kinetic model was built.•The curing behavior of the PEEK/epoxy resin system under dynamic conditions was predicted.•The obtained PEEK/epoxy composites presented better tensile, flexural and compression properties than pure epoxy resin.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
To prepare epoxy resins (EP) with flame retardancy and remolding capability, novel amine curing agents (DDPM and DDPS), which incorporate phosphonates and bis-Schiff bases, were used to replace DDM ...partially or completely for EP curing. Curing kinetics based on a dual-parameter autocatalytic model showed that DDPM and DDPS had higher reactivity of than DDM. EP/DDPM and EP/DDPS vitrimers demonstrated excellent flame retardancy and remolding capability (up to 60.8%). EP/DDPS with disulfide bonds could not effectively improve the dynamic bond exchange. The molecular weight, dynamic bond stability, and viscosity were analyzed to investigate the underlying mechanisms. This study endows the dynamic properties of EP using novel curing agents and achieves flame-retardant and sustainable epoxy thermosets.
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•DDPM and DDPS were amino-epoxy curing agents containing phosphonates and Schiff base.•The dynamic bonds in DDPM and DDPS showed autocatalytic effects.•EP/DDPM and EP/DDPS showed flame retardancy and remolding capability.•Compared to EP/DDPM, EP/DDPS contains disulfide bonds that could not effectively improve dynamic bond exchange.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Lignin-based epoxy resins cured with aromatic and aliphatic amine curing agents.•Curing behavior was monitored by using DSC and evaluated by isoconversional models.•The mechanism of curing process ...was influence by the type of curing agents.•The thermal stability of epoxy resins depended on the type of curing agents and lignins.
Lignin-based epoxy resins were synthesized by reacting de-polymerized organosolv lignin (DOL) or de-polymerized Kraft lignin (DKL) with epichlorohydrin under an alkaline condition in the presence of a phase transfer catalyst. The synthesized lignin-based epoxy resins were cured with 4,4′-diaminodiphenyl methane (DDM, an aromatic amine) and diethylenetriamine (DETA, an aliphatic amine) to generate a 3-dimentional cross-linked structure. The effects of curing agents on the curing process were investigated by non-isothermal differential scanning calorimetry (DSC). The dependency of activation energy of the curing reaction on the extent of curing (conversion) was determined in this study by model-free kinetics based on the DSC results. In addition, it was found that the thermal stability of the cured lignin-based epoxy resins was also influenced by the type of curing agents and the types of lignin used in the synthesis of the bio-based epoxy resins.
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