The introduction of dynamic covalent bonds into the structure of epoxy resins can improve the degradation performance of the materials.But to a certain extent,it will affect the insulating properties of the resin,and ...The introduction of dynamic covalent bonds into the structure of epoxy resins can improve the degradation performance of the materials.But to a certain extent,it will affect the insulating properties of the resin,and how to balance the insulating properties and degradation performance has become an urgent problem.In this paper,the effects of different catalysts on the thermal-force-electrical properties of sorbitolbased resins were systematically investigated based on the dynamic ester bonding to construct the resin crosslinking network,and the biobased sorbitol glycidyl ether was used as the resin matrix.The experiments show that the resin system catalyzed by triethanolamine(TEOA)exhibits excellent comprehensive performance,which combines good thermal stability and mechanical properties with excellent electrical properties(breakdown field strength of 44.21 k V/mm and dielectric loss factor of 0.29%).In addition,chemical degradation tests were conducted on the resin systems with different catalysts,and the experiments showed that the produced resins could be degraded in benzyl alcohol and exhibited good degradation performance.This study provides a theoretical basis and technical path for the development of new bio-based electrical insulating materials with both high insulation and degradation properties,which is conducive to the popularization and application of bio-based resins in the field of electrical equipment.展开更多
The poor degradability and limited recyclability of epoxy resins are key challenges hindering the efficient recycling of ex-service wind turbine blades(EWTBs).Herein,we proposed a selective degradation strategy for di...The poor degradability and limited recyclability of epoxy resins are key challenges hindering the efficient recycling of ex-service wind turbine blades(EWTBs).Herein,we proposed a selective degradation strategy for direct recycling and high-value recovery of epoxy resins by introducing degradable Schiff base groups into the molecular structure and utilizing the resulting oligomers as curing agents.To realize this strategy,a series of Schiff base compounds were synthesized using bio-based vanillin and diamines and subsequently functionalized with epichlorohydrin to yield bio-based epoxy resins.The cured epoxy resins demonstrated remarkable improvements in the mechanical properties of diglycidyl ether of bisphenol-A(DGEBA),with an increases of 44.49%in the tensile strength of 38.55%,bending strength,and impact strength of 71.20%.The introduction of dynamic Schiff base bonds enabled the selective degradation of the vanillin-2,2-bis[4-(4-aminophenoxy)phenyl]propane-based epoxy resin(VBEP)/DGEBA copolymer,producing 84.20% oligomers that can be directly recycled and reused.Replacing 30 wt% of the curing agent with the oligomer increased the tensile strength of the cured sample to 75.40 MPa,surpassing that of the cured DGEBA.Under simulated acid rain and seawater exposure,the copolymer exhibited a service life of 27 years at 40℃,significantly exceeding the currently reported service life of 20 years.This study presents a sustainable strategy for the direct recycling and high-value reuse of epoxy resin,offering a promising solution for EWTBs.展开更多
Glass fibres/epoxy resins composites have been performed as ideal materials to make support instruments for high-energy and nuclear physics experiments. The effects of the 3,-ray irradiation on the fatigue strength, t...Glass fibres/epoxy resins composites have been performed as ideal materials to make support instruments for high-energy and nuclear physics experiments. The effects of the 3,-ray irradiation on the fatigue strength, thermal conductivities and thermal stabilities of the glass fibres/epoxy resins composites were investigated. And a two-parameter fatigue life model was established to predict the fatigue life of the composites. Results revealed that the y-ray irradiation could probably result in the degradation of epoxy resins, but hardly damage to the glass fibres. And the γ-ray irradiation treatment could significantly affect the fatigue strength of the composites at a low-cycle fatigue stage, but seldom influence at a high-cycle fatigue stage. Furthermore, the fabricated glass fibres/epoxy resins composites after the γ-ray irradiation still presented excellent fatigue strength, ideal thermal conductivities, remarkable dimensional and thermal stabilities, which can meet the actual requirements of normal operation for supporting instruments under high-energy and nuclear physics experiments.展开更多
In this work, low-temperature vulcanized, transparent silane modified epoxy resins for LED filament bulb package were prepared. Firstly, transparent silane modified epoxy resins were produced through a controllable so...In this work, low-temperature vulcanized, transparent silane modified epoxy resins for LED filament bulb package were prepared. Firstly, transparent silane modified epoxy resins were produced through a controllable sol-gel method using γ-（2,3-epoxypropoxy）propytrimethoxysilane and dimethyldiethoxylsilane. The features of the reaction were investigated and the products were characterized in detail. Subsequently, various curing agents were explored to prepare transparent silane modified epoxy resins. The silane modified epoxy resins cured by PEA-230 at a fairly low temperature（40 °C/2 h then 60 °C/1 h） exhibited excellent thermal stability with a thermal degradation temperature as high as 316.5 °C and adjustable hardness between 40-60 shore A. The application tests showed the materials obtained were good candidates for LED filament bulb package.展开更多
The synthesis and characterization of hyperbranched polyester （HBP） with different molecular weight are studied. The effect of HBP on the modification of epoxy resins cured with anhydride is mainly discussed. The ch...The synthesis and characterization of hyperbranched polyester （HBP） with different molecular weight are studied. The effect of HBP on the modification of epoxy resins cured with anhydride is mainly discussed. The characteristics of HBP and the morphologies of cured system are determined by nuclear magnetic resonance spectroscopy （NMR）, gel permeation chromatography （GPC） and scanning electron microscope （SEM）. The impact strength of cured system is detected and Fourier transform infrared （FTIR） measurements were used to pursue the curing process. The investigation shows that HBP can improve the toughness by forming copolymer networks between epoxy resins, HBP and anhydride. Moreover, when the molecular weight of HBP is 1342g/mol the toughening effect is the best, and the changes of toughness are small with the increase of molecular weight of HBP to 3500 g/mol.展开更多
By means of ultrasonic attenuation apparatus, the ultrasonic velocity and attenuation ofanhydride-cured epoxy resins (EP)/poly (ethylene oxide) (PEO) blends were measured on thebasis of pulse-echo method. It was found...By means of ultrasonic attenuation apparatus, the ultrasonic velocity and attenuation ofanhydride-cured epoxy resins (EP)/poly (ethylene oxide) (PEO) blends were measured on thebasis of pulse-echo method. It was found that the sonic velocity of the blends decreased as thetemperature increased, but attenuation coefficient increased and possessed a peak value. Largervelocity and smaller attenuation coefficient(α)can be obtained from perfect crosslinking networkstructures of pure DGEBA cured with phthalic anhydride(PA). As for cured DGEBA/PEO blendsystems,sonic velocity decreased as a function of PEO concentration,but attenuation coefficient(α) increased.展开更多
Bisphenol A (BPA) is the primary chemical used in the production of epoxy resins but as of today is not widely available in a bio-based form. BPA is also classified as a substance of very high concern due to its repro...Bisphenol A (BPA) is the primary chemical used in the production of epoxy resins but as of today is not widely available in a bio-based form. BPA is also classified as a substance of very high concern due to its reproductive toxicity and endocrine-disrupting effects. Phlorotannins, a type of polyphenols, offer a promising structural alternative to bisphenol A as a more sustainable option. They are found in high quantities in brown algae, which are already harvested for alginate production. As a result, phlorotannins present an under-researched yet promising marine resource for the chemical industry, particularly in the area of epoxy resin formulation. In this study, a model epoxy resin compound based on phloroglucinol, the simplest phlorotannin, was chosen to explore its reactivity and the thermo-mechanical properties of epoxy resins based thereof. As hardeners well-established systems like isophorone diamine for ambient temperature cure as well as heat-curing anhydrides and dicyandiamide were used. Across all cases, thermosets with glass transition temperatures above 100?C were achieved under cross-linking conditions similar to those used today. One phthalic anhydride derivative yielded a glass transition temperature of 198?C, highlighting the significant potential of these algae-based epoxy resins for industrial uses, such as impregnating resins for fiber-reinforced plastics.展开更多
A high performance thermosetting epoxy resin crosslinkable at room temperature was obtained via directly moulding diglycidyl ether of bisphenol A（DGEBA） and flexibleα,ω-bisamino（n-alkylene）phenyl terminated poly...A high performance thermosetting epoxy resin crosslinkable at room temperature was obtained via directly moulding diglycidyl ether of bisphenol A（DGEBA） and flexibleα,ω-bisamino（n-alkylene）phenyl terminated poly（ethylene glycol）.The influences of the n-alkylene inserted in aminophenyl of flexible amino-terminated polythers（ATPE） on the mechanical properties,fractographs and curing kinetics of the ATPE-DGEBA cured products were studied.The results show that the insertion of n-alkylene group into the aminophenyl group of the ATPE,on one hand,can significantly increase the strain relaxation rate and decrease glass transition temperature of the ATPE-DGEBA cured products,resulting in slight decrease of the Young’s modulus and tensile strength,and significant increase of the toughness and elongation of the ATPE-DGEBA cured products.On the other hand,it can remarkably enhance the reactivity of amine with epoxy,much accelerating the curing rate of the ATPE-DGEBA systems.The activation energy of DGEBA cured by BAPTPE,BAMPTPE and BAEPTPE was 53.1,28.5 and 25.4 kJ·mol;,respectively.The as-obtained ATPE-DGEBA cured products are homogeneous, transparent,and show excellent mechanical properties including tensile strength and toughness.Thus they are promising to have important applications in structure adhesives,casting bulk materials,functional coatings,cryogenic engineering, damping and sound absorbing materials.展开更多
Rubbers have been well accepted for modifying brittle epoxies but rubber modified epoxies usually posses lowered tensile strength though enhanced ductility and fracture resistance. In this work, a polyethylene glycol ...Rubbers have been well accepted for modifying brittle epoxies but rubber modified epoxies usually posses lowered tensile strength though enhanced ductility and fracture resistance. In this work, a polyethylene glycol （PEG-4000） is used to modify diglycidyl ether of bisphenol A/methyltetrahydrophthalic anhydride system for enhancing cryogenic tensile strength, ductility and impact resistance. The results display that the cryogenic tensile strength, ductility （failure strain） and fracture resistance （impact strength） are all enhanced for the modified epoxy system at proper PEG contents. The maximum tensile strength （127.8 MPa） at the cryogenic temperature （77 K） with an improvement of 30.1% is observed for the modified system with the 15 wt% PEG content. The ductility and impact resistance at both room temperature and cryogenic temperature are all improved for the modified epoxy system with proper PEG-4000 contents. These observations are explained by the positron annihilation lifetime spectroscopy results and scanning electron microscopy results. Moreover, the glass transition temperature decreases slightly with increasing PEG content.展开更多
Self-healing polymers based on dynamic crosslinkers have drawn rapidly increasing interest over the last decade.Here,a self-healable epoxy network with exchangeable disulfide bonds was synthesized by polymerizing two ...Self-healing polymers based on dynamic crosslinkers have drawn rapidly increasing interest over the last decade.Here,a self-healable epoxy network with exchangeable disulfide bonds was synthesized by polymerizing two epoxies with an aromatic amine containing a disulfide bond.The bisphenol A diglycidyl ether(DGEBA)and poly(ethylene glycol)diglycidyl ether(DER736)were used as rigid and soft components,respectively.The crosslinking densities of studied polymers decreased with the increasing amount of DER736,resulting in the lower glassy temperature and weaker mechanical strength.The dynamic covalent network character of disulfide bond and its low active energy were also investigated through stress relaxation experiments at various temperatures.The self-healing performance of healable epoxy resins with varied flexibility was measured by tensile tests.The tensile strength of a full-cut sample was restored to 84%(13 MPa)of the initial values(16 MPa)at moderate temperature.Its healed fracture strain was up to 505%.Moreover,the effect of healing time and temperature on the self-healing properties was also studied.A model was proposed to investigate the self-repairing efficiency evolution with healing time,suggesting that hydrogen bonds mainly contributed to the initial sticking or interfacial adhesion while disulfide links and chain interdiffusion assisted time dependent reformation of networks to restore the original mechanical strength.展开更多
To obtain high-efficiency flame retardancy of epoxy resins,a cyclophosphazene derivative tri-(ohenylenediamino)cyclotriphosphazene(3 ACP)was successfully synthesized and used as a curing agent for the thermosetting of...To obtain high-efficiency flame retardancy of epoxy resins,a cyclophosphazene derivative tri-(ohenylenediamino)cyclotriphosphazene(3 ACP)was successfully synthesized and used as a curing agent for the thermosetting of an epoxy resin system.The flame retardant properties,thermal stability,and pyrolysis mechanism of the resultant thermosets were investigated in detail.The experiments indicated that the synthesized thermoset achieved a UL-94 V-0 rate under a vertical burning test as well as a limiting oxygen index(LOI)of 29.2%,which was able to reach V-0 even when a small amount of 3 ACP was incorporated.Scanning electronic microscopic observation demonstrated that the char residue of the thermosets was extremely expanded after the vertical flame test.Thermal analysis showed that the samples had a lower initial decomposition temperature when 3 ACP was introduced into the epoxy resin systems.This indicates that the carbonization ability of the thermosets was significantly improved at elevated temperatures.In addition,the incorporation of 3 ACP can effectively suppress the release of combustible gases during the pyrolysis process,and the decomposition of E-44/DDS-3 ACP curing systems also promotes the formation of polyphosphoramides charred layer in the condensed phase.The investigation on the chemical structures of both the gaseous and condensed phase pyrolysis process confirmed the flame-retardant mechanism of the 3 ACP-cured epoxy resins.Therefore,the nonflammable halogen-free epoxy resin developed in this study has potential applications in electric and electronic fields for environment protection and human health.展开更多
Biphenyl-contained monomer of 1,4-bis[2-（3,4-epoxy cyclohexyl ethyl） dimethylsilyl] biphenyl （BP-SiH-EP） was prepared via hydrosilylation reaction of 1,4-bis（dimethylsilyl） biphenyl （BP-SiH） and 1,2-epoxy-4-vi...Biphenyl-contained monomer of 1,4-bis[2-（3,4-epoxy cyclohexyl ethyl） dimethylsilyl] biphenyl （BP-SiH-EP） was prepared via hydrosilylation reaction of 1,4-bis（dimethylsilyl） biphenyl （BP-SiH） and 1,2-epoxy-4-vinylcyclohexane in the presence of Karstedt＇s catalyst. ^1H-NMR, 13C-NMR and FTIR were used to characterize the structure of the obtained monomer. BP-SiH-EP was then cured by methyl hexahydrophthalic anhydride （MeHHPA） with 1-cyanoethyl-2-ethyl-4- methylimidazole as an accelerator. The polymerization behavior was studied by DSC. The results of DMA measurement demonstrate that the cured BP-SiH-EP/MeHHPA can maintain high storage modulus （〉1 GPa） in a wide range of temperature up to 176 ℃. According to the damping factor curve of DMA, cured BP-SiH-EP/MeHHPA exhibits a high glass transition temperature （Tg） of 192 ℃, which is 20 ℃ higher than that of cured 1,4-bis[2-（3,4-epoxy cyclohexyl ethyl） dimethylsilyl] benzene （DEDSB）/MeHHPA. TGA results show that cured BP-SiH-EP/MeHHPA has good thermal stability （Tso/o = 339 ℃） due to the high heat-resistance of rigid biphenyl group. Moreover, the crosslinking density of cured BP-SiH-EP/MeHHPA should be lower than that of cured DEDSB/MeHHPA estimated from their chemical structures, which conflicts with the calculated results based on the rubber elasticity equation. The inconsistence indicates that the calculated crosslinking densities are not comparable, possibly owing to their differences in the rigidity of polymer chains and intermolecular interaction.展开更多
The integration of high mechanical toughness,impact strength as well as excellent flame-retardant properties toward epoxy resins(EPs)have always been a dilemma.The inadequate overall performance of EPs severely restri...The integration of high mechanical toughness,impact strength as well as excellent flame-retardant properties toward epoxy resins(EPs)have always been a dilemma.The inadequate overall performance of EPs severely restricts their sustainable utilization in engineering aspects over long-term.Herein,a new bio-based agent(diglycidyl ether of magnolol phosphine oxide,referred as DGEMP)derived from magnolol(classified as lignan),extracted from natural plants Magnolia officinalis,was successfully synthesized and further employed as a flameretardant reactive additive to diglycidyl ether of bisphenol A(DGEBA).As demonstration,the composite resin,DGEBA/15DGEMP(15 wt%DGEMP),achieved an Underwriters Laboratories-94 V-0 rating with a high limiting oxygen index(LOI)value(41.5%).In cone calorimeter tests,it showed that heat release and smoke production were effectively inhibited during combustion,wherein the peak heat release rate(PHRR)value of DGEBA/15DGEMP was reduced by 50%compared to neat DGEBA.Additionally,it exhibited a superior tensile strength(82.8 MPa),toughness(5.11MJ/m^(3))and impact strength(36.5 k J/m^(2)),much higher than that of neat DGEBA(49.7 MPa,2.05 MJ/m^(3)and 20.9 k J/m^(2)).Thus,it is highly anticipated that DGEMP imparts significantly improved mechanical and fire-retarded properties to conventional EPs,which holds a great potential to address the pressing challenges in EP thermosets industry.展开更多
A bisphenol A based epoxy was incorporated with a quadruply hydrogen bonded supramolecular polymer as a toughening agent to prepare a composite epoxy resin with higher impact resistance. The supramolecular polymer com...A bisphenol A based epoxy was incorporated with a quadruply hydrogen bonded supramolecular polymer as a toughening agent to prepare a composite epoxy resin with higher impact resistance. The supramolecular polymer comprising poly-（propylene glycol） bis（2-aminopropyl） ether chains and 2-ureido-4[1H]-pyrimidinone moieties（UPy） self-assembled into spherical domains with sizes of 300 nm to 600 nm in diameter by micro phase separation in bulk epoxy matrixes. A significant improvement of 300% in impact resistance of the supramolecular polymer incorporated epoxy resin was obtained when the content of supramolecular polymer was 10 wt%. Tensile tests showed that the mechanical properties of the modified epoxy resin containing the hydrogen-bonded supramolecular polymers are also improved compared with those of the neat epoxy resin.展开更多
This paper discusses the fundamental principle of microwave heating, and based on the advantages of microwave heating, use maleic anhydride as curing agent. The technology of microwave curing E44 epoxy resins is inves...This paper discusses the fundamental principle of microwave heating, and based on the advantages of microwave heating, use maleic anhydride as curing agent. The technology of microwave curing E44 epoxy resins is investigated, the mechanical properties of cured epoxy resin samples in different contents of curing agent by microwave and thermal curing methods are measured respectively, and then some experimental results for which are obtained. At last, this paper analyses why microwave curing can improve mechanical property of epoxy resin.展开更多
To research the relationship between epoxy and fiber inherent property and mechanical properties of composite,we prepared a series of composites using three kinds of high mechanical performance epoxy resins as matrice...To research the relationship between epoxy and fiber inherent property and mechanical properties of composite,we prepared a series of composites using three kinds of high mechanical performance epoxy resins as matrices and reinforced by the same volume fraction(5%)of short carbon and glass fiber.Their mechanical properties were investigated from the perspective of chemical structure and volume shrinkage ratio of epoxy.We analyzed their tensile strength and modulus based on the mixing rule and Halpin-Tsai eq...展开更多
Phenolic hydroxyl-terminated polysiloxanes were incorporated into epoxy resins to reduce the internal stress owing to the mismatch in coefficient of thermal expansion (CTE). Polysiloxane-epoxy resin block copolymers w...Phenolic hydroxyl-terminated polysiloxanes were incorporated into epoxy resins to reduce the internal stress owing to the mismatch in coefficient of thermal expansion (CTE). Polysiloxane-epoxy resin block copolymers were made by a pre-reaction step prior to the curing. In the cured resin, the domain size of the polysiloxane phase depended on the structure of the phenolic hydroxyl-terminated polysiloxane. It was found that the modulus of the cured resin depended largely on the level of the modifier, while the CTE was affected greatly by the structure of the polysiloxane. By means of incorporating a few percent of methylphenylsiloxane unit into the polydimethylsiloxane chain, or by introducing; more compatible end-capping groups, the compounds of more effective low stress modifiers were synthesized.展开更多
The influence of the type of epoxy resins(E-51, F-51)on themechanical properties and mi- crostructure of carboxyl-terminatedbutadiene nitrile rubber(CTBN)toughened epoxy resins investigated bydetermination of adhesive...The influence of the type of epoxy resins(E-51, F-51)on themechanical properties and mi- crostructure of carboxyl-terminatedbutadiene nitrile rubber(CTBN)toughened epoxy resins investigated bydetermination of adhesive strength and toughness as well asobservation of scanning electron microstructure (SEM). The resultsindicate that the adhesive strength of CTBN toughened E-51 system issuperior to CTBN toughened F-51 system. However, CTBN toughened E-51system is inferior to CTBN toughened F-51 system in the toughness.展开更多
Poly(butylene terephthalate)-b-poly(tetramethylene glycol) (PBT-b-PTMG) was used as rheology modifier for the epoxy resin. The segmental copolymer formed spherulites in the epoxy medium. This copolymer was very effect...Poly(butylene terephthalate)-b-poly(tetramethylene glycol) (PBT-b-PTMG) was used as rheology modifier for the epoxy resin. The segmental copolymer formed spherulites in the epoxy medium. This copolymer was very effective in endowing yield stresses to the liquid resin. The PTMG segment brought in a lowering of the dissolution temperature of the spherulites in the epoxy gel. The cured resin with PBT-b-PTMG as modifier was two-phase materials. The rheology modifier improved the mechanical properties of the cured resin as well. The flexible PTMG segments, however, were not in favour of the toughening effect of the modifier. This was attributed to the large domain size of the dispersed phase.展开更多
Nano silica-modified epoxy resins were synthesized by the sol-gel process, The materials have the morphological structure of nano particales dispersed in the epoxy matrix. The dispersed phase formed a physical network...Nano silica-modified epoxy resins were synthesized by the sol-gel process, The materials have the morphological structure of nano particales dispersed in the epoxy matrix. The dispersed phase formed a physical network in the resin and thus influenced the rheological behavior greatly. However, the nano silica did not show a significant influence on the mechanical properties of the cured resins.展开更多
基金financially supported by the National Natural Science Foundation of China(No.52377025)。
文摘The introduction of dynamic covalent bonds into the structure of epoxy resins can improve the degradation performance of the materials.But to a certain extent,it will affect the insulating properties of the resin,and how to balance the insulating properties and degradation performance has become an urgent problem.In this paper,the effects of different catalysts on the thermal-force-electrical properties of sorbitolbased resins were systematically investigated based on the dynamic ester bonding to construct the resin crosslinking network,and the biobased sorbitol glycidyl ether was used as the resin matrix.The experiments show that the resin system catalyzed by triethanolamine(TEOA)exhibits excellent comprehensive performance,which combines good thermal stability and mechanical properties with excellent electrical properties(breakdown field strength of 44.21 k V/mm and dielectric loss factor of 0.29%).In addition,chemical degradation tests were conducted on the resin systems with different catalysts,and the experiments showed that the produced resins could be degraded in benzyl alcohol and exhibited good degradation performance.This study provides a theoretical basis and technical path for the development of new bio-based electrical insulating materials with both high insulation and degradation properties,which is conducive to the popularization and application of bio-based resins in the field of electrical equipment.
基金financially supported by the National Natural Science Foundation of China(No.U23A20691)Innovation Group of National Ethnic Affairs Commission of China(No.MZR20006)+2 种基金Fund for Academic Innovation Teams of SouthCentral Minzu University(No.XTZ24012)Fundamental Research Fund for the Central Universities of South-Central Minzu University(Nos.CZD24001 and CZQ25012)Scientific Research Fund of South-Central Minzu University(No.YZY25007)。
文摘The poor degradability and limited recyclability of epoxy resins are key challenges hindering the efficient recycling of ex-service wind turbine blades(EWTBs).Herein,we proposed a selective degradation strategy for direct recycling and high-value recovery of epoxy resins by introducing degradable Schiff base groups into the molecular structure and utilizing the resulting oligomers as curing agents.To realize this strategy,a series of Schiff base compounds were synthesized using bio-based vanillin and diamines and subsequently functionalized with epichlorohydrin to yield bio-based epoxy resins.The cured epoxy resins demonstrated remarkable improvements in the mechanical properties of diglycidyl ether of bisphenol-A(DGEBA),with an increases of 44.49%in the tensile strength of 38.55%,bending strength,and impact strength of 71.20%.The introduction of dynamic Schiff base bonds enabled the selective degradation of the vanillin-2,2-bis[4-(4-aminophenoxy)phenyl]propane-based epoxy resin(VBEP)/DGEBA copolymer,producing 84.20% oligomers that can be directly recycled and reused.Replacing 30 wt% of the curing agent with the oligomer increased the tensile strength of the cured sample to 75.40 MPa,surpassing that of the cured DGEBA.Under simulated acid rain and seawater exposure,the copolymer exhibited a service life of 27 years at 40℃,significantly exceeding the currently reported service life of 20 years.This study presents a sustainable strategy for the direct recycling and high-value reuse of epoxy resin,offering a promising solution for EWTBs.
基金financially supported by the National Natural Science Foundation of China (No. 51605025)the Major Program of National Key Research and Development Program of China (2016YFC0802905)+2 种基金the Fundamental Research Funds for the Central Universities (FRF-GF-17-B19)the BEPC great reconstruction projectthe Knowledge Innovation Fund of the Chinese Academy of Sciences, U-603 and U-34 (IHEP)
文摘Glass fibres/epoxy resins composites have been performed as ideal materials to make support instruments for high-energy and nuclear physics experiments. The effects of the 3,-ray irradiation on the fatigue strength, thermal conductivities and thermal stabilities of the glass fibres/epoxy resins composites were investigated. And a two-parameter fatigue life model was established to predict the fatigue life of the composites. Results revealed that the y-ray irradiation could probably result in the degradation of epoxy resins, but hardly damage to the glass fibres. And the γ-ray irradiation treatment could significantly affect the fatigue strength of the composites at a low-cycle fatigue stage, but seldom influence at a high-cycle fatigue stage. Furthermore, the fabricated glass fibres/epoxy resins composites after the γ-ray irradiation still presented excellent fatigue strength, ideal thermal conductivities, remarkable dimensional and thermal stabilities, which can meet the actual requirements of normal operation for supporting instruments under high-energy and nuclear physics experiments.
基金financial support from the Zhejiang Provincial Natural Science Foundation of China (No.Y14E030008)the Commonweal Technology Application Research Project of Zhejiang Province (No.2013C31079)
文摘In this work, low-temperature vulcanized, transparent silane modified epoxy resins for LED filament bulb package were prepared. Firstly, transparent silane modified epoxy resins were produced through a controllable sol-gel method using γ-（2,3-epoxypropoxy）propytrimethoxysilane and dimethyldiethoxylsilane. The features of the reaction were investigated and the products were characterized in detail. Subsequently, various curing agents were explored to prepare transparent silane modified epoxy resins. The silane modified epoxy resins cured by PEA-230 at a fairly low temperature（40 °C/2 h then 60 °C/1 h） exhibited excellent thermal stability with a thermal degradation temperature as high as 316.5 °C and adjustable hardness between 40-60 shore A. The application tests showed the materials obtained were good candidates for LED filament bulb package.
文摘The synthesis and characterization of hyperbranched polyester （HBP） with different molecular weight are studied. The effect of HBP on the modification of epoxy resins cured with anhydride is mainly discussed. The characteristics of HBP and the morphologies of cured system are determined by nuclear magnetic resonance spectroscopy （NMR）, gel permeation chromatography （GPC） and scanning electron microscope （SEM）. The impact strength of cured system is detected and Fourier transform infrared （FTIR） measurements were used to pursue the curing process. The investigation shows that HBP can improve the toughness by forming copolymer networks between epoxy resins, HBP and anhydride. Moreover, when the molecular weight of HBP is 1342g/mol the toughening effect is the best, and the changes of toughness are small with the increase of molecular weight of HBP to 3500 g/mol.
文摘By means of ultrasonic attenuation apparatus, the ultrasonic velocity and attenuation ofanhydride-cured epoxy resins (EP)/poly (ethylene oxide) (PEO) blends were measured on thebasis of pulse-echo method. It was found that the sonic velocity of the blends decreased as thetemperature increased, but attenuation coefficient increased and possessed a peak value. Largervelocity and smaller attenuation coefficient(α)can be obtained from perfect crosslinking networkstructures of pure DGEBA cured with phthalic anhydride(PA). As for cured DGEBA/PEO blendsystems,sonic velocity decreased as a function of PEO concentration,but attenuation coefficient(α) increased.
文摘Bisphenol A (BPA) is the primary chemical used in the production of epoxy resins but as of today is not widely available in a bio-based form. BPA is also classified as a substance of very high concern due to its reproductive toxicity and endocrine-disrupting effects. Phlorotannins, a type of polyphenols, offer a promising structural alternative to bisphenol A as a more sustainable option. They are found in high quantities in brown algae, which are already harvested for alginate production. As a result, phlorotannins present an under-researched yet promising marine resource for the chemical industry, particularly in the area of epoxy resin formulation. In this study, a model epoxy resin compound based on phloroglucinol, the simplest phlorotannin, was chosen to explore its reactivity and the thermo-mechanical properties of epoxy resins based thereof. As hardeners well-established systems like isophorone diamine for ambient temperature cure as well as heat-curing anhydrides and dicyandiamide were used. Across all cases, thermosets with glass transition temperatures above 100?C were achieved under cross-linking conditions similar to those used today. One phthalic anhydride derivative yielded a glass transition temperature of 198?C, highlighting the significant potential of these algae-based epoxy resins for industrial uses, such as impregnating resins for fiber-reinforced plastics.
基金supported by the National 863 Plan(No.2006AA03A209)New Century Excellent Talent Plan (No.NECT-05-0660) from Ministry of EducationDefense Basic Research Item(No.D1420061057)
文摘A high performance thermosetting epoxy resin crosslinkable at room temperature was obtained via directly moulding diglycidyl ether of bisphenol A（DGEBA） and flexibleα,ω-bisamino（n-alkylene）phenyl terminated poly（ethylene glycol）.The influences of the n-alkylene inserted in aminophenyl of flexible amino-terminated polythers（ATPE） on the mechanical properties,fractographs and curing kinetics of the ATPE-DGEBA cured products were studied.The results show that the insertion of n-alkylene group into the aminophenyl group of the ATPE,on one hand,can significantly increase the strain relaxation rate and decrease glass transition temperature of the ATPE-DGEBA cured products,resulting in slight decrease of the Young’s modulus and tensile strength,and significant increase of the toughness and elongation of the ATPE-DGEBA cured products.On the other hand,it can remarkably enhance the reactivity of amine with epoxy,much accelerating the curing rate of the ATPE-DGEBA systems.The activation energy of DGEBA cured by BAPTPE,BAMPTPE and BAEPTPE was 53.1,28.5 and 25.4 kJ·mol;,respectively.The as-obtained ATPE-DGEBA cured products are homogeneous, transparent,and show excellent mechanical properties including tensile strength and toughness.Thus they are promising to have important applications in structure adhesives,casting bulk materials,functional coatings,cryogenic engineering, damping and sound absorbing materials.
基金support of the National Natural Science Foundation of China(Nos. 51073169,10972216 and 11002141)
文摘Rubbers have been well accepted for modifying brittle epoxies but rubber modified epoxies usually posses lowered tensile strength though enhanced ductility and fracture resistance. In this work, a polyethylene glycol （PEG-4000） is used to modify diglycidyl ether of bisphenol A/methyltetrahydrophthalic anhydride system for enhancing cryogenic tensile strength, ductility and impact resistance. The results display that the cryogenic tensile strength, ductility （failure strain） and fracture resistance （impact strength） are all enhanced for the modified epoxy system at proper PEG contents. The maximum tensile strength （127.8 MPa） at the cryogenic temperature （77 K） with an improvement of 30.1% is observed for the modified system with the 15 wt% PEG content. The ductility and impact resistance at both room temperature and cryogenic temperature are all improved for the modified epoxy system with proper PEG-4000 contents. These observations are explained by the positron annihilation lifetime spectroscopy results and scanning electron microscopy results. Moreover, the glass transition temperature decreases slightly with increasing PEG content.
基金the Natural Science Foundation of Jiangxi Education Department(No.GJJ170680)the National Natural Science Foundation of China(Nos.51963010,21867011,and 51563011).
文摘Self-healing polymers based on dynamic crosslinkers have drawn rapidly increasing interest over the last decade.Here,a self-healable epoxy network with exchangeable disulfide bonds was synthesized by polymerizing two epoxies with an aromatic amine containing a disulfide bond.The bisphenol A diglycidyl ether(DGEBA)and poly(ethylene glycol)diglycidyl ether(DER736)were used as rigid and soft components,respectively.The crosslinking densities of studied polymers decreased with the increasing amount of DER736,resulting in the lower glassy temperature and weaker mechanical strength.The dynamic covalent network character of disulfide bond and its low active energy were also investigated through stress relaxation experiments at various temperatures.The self-healing performance of healable epoxy resins with varied flexibility was measured by tensile tests.The tensile strength of a full-cut sample was restored to 84%(13 MPa)of the initial values(16 MPa)at moderate temperature.Its healed fracture strain was up to 505%.Moreover,the effect of healing time and temperature on the self-healing properties was also studied.A model was proposed to investigate the self-repairing efficiency evolution with healing time,suggesting that hydrogen bonds mainly contributed to the initial sticking or interfacial adhesion while disulfide links and chain interdiffusion assisted time dependent reformation of networks to restore the original mechanical strength.
基金financially supported by the National Natural Science Foundation of China(No.51773010)the Fundamental Research Funds for the Central Universities(No.XK1802-2)。
文摘To obtain high-efficiency flame retardancy of epoxy resins,a cyclophosphazene derivative tri-(ohenylenediamino)cyclotriphosphazene(3 ACP)was successfully synthesized and used as a curing agent for the thermosetting of an epoxy resin system.The flame retardant properties,thermal stability,and pyrolysis mechanism of the resultant thermosets were investigated in detail.The experiments indicated that the synthesized thermoset achieved a UL-94 V-0 rate under a vertical burning test as well as a limiting oxygen index(LOI)of 29.2%,which was able to reach V-0 even when a small amount of 3 ACP was incorporated.Scanning electronic microscopic observation demonstrated that the char residue of the thermosets was extremely expanded after the vertical flame test.Thermal analysis showed that the samples had a lower initial decomposition temperature when 3 ACP was introduced into the epoxy resin systems.This indicates that the carbonization ability of the thermosets was significantly improved at elevated temperatures.In addition,the incorporation of 3 ACP can effectively suppress the release of combustible gases during the pyrolysis process,and the decomposition of E-44/DDS-3 ACP curing systems also promotes the formation of polyphosphoramides charred layer in the condensed phase.The investigation on the chemical structures of both the gaseous and condensed phase pyrolysis process confirmed the flame-retardant mechanism of the 3 ACP-cured epoxy resins.Therefore,the nonflammable halogen-free epoxy resin developed in this study has potential applications in electric and electronic fields for environment protection and human health.
基金financially supported by the National Natural Science Foundation of China(Nos.51403039 and 21476072)the Natural Science Foundation of Shanghai(No.13ZR1451300)
文摘Biphenyl-contained monomer of 1,4-bis[2-（3,4-epoxy cyclohexyl ethyl） dimethylsilyl] biphenyl （BP-SiH-EP） was prepared via hydrosilylation reaction of 1,4-bis（dimethylsilyl） biphenyl （BP-SiH） and 1,2-epoxy-4-vinylcyclohexane in the presence of Karstedt＇s catalyst. ^1H-NMR, 13C-NMR and FTIR were used to characterize the structure of the obtained monomer. BP-SiH-EP was then cured by methyl hexahydrophthalic anhydride （MeHHPA） with 1-cyanoethyl-2-ethyl-4- methylimidazole as an accelerator. The polymerization behavior was studied by DSC. The results of DMA measurement demonstrate that the cured BP-SiH-EP/MeHHPA can maintain high storage modulus （〉1 GPa） in a wide range of temperature up to 176 ℃. According to the damping factor curve of DMA, cured BP-SiH-EP/MeHHPA exhibits a high glass transition temperature （Tg） of 192 ℃, which is 20 ℃ higher than that of cured 1,4-bis[2-（3,4-epoxy cyclohexyl ethyl） dimethylsilyl] benzene （DEDSB）/MeHHPA. TGA results show that cured BP-SiH-EP/MeHHPA has good thermal stability （Tso/o = 339 ℃） due to the high heat-resistance of rigid biphenyl group. Moreover, the crosslinking density of cured BP-SiH-EP/MeHHPA should be lower than that of cured DEDSB/MeHHPA estimated from their chemical structures, which conflicts with the calculated results based on the rubber elasticity equation. The inconsistence indicates that the calculated crosslinking densities are not comparable, possibly owing to their differences in the rigidity of polymer chains and intermolecular interaction.
基金Anhui Provincial Natural Science Foundation for Distinguished Young Scholar(No.2008085J26)Natural Science Foundation in University of Anhui Province(Nos.KJ2021ZD0119 and 2022AH040251)+3 种基金China Scholarship Council(No.202008340021)Start-up Fund for Distinguished Scholars in Hefei University(No.20RC37)Anhui Provincial Natural Science Foundation(No.2108085QB47)Research Grants Council of the Hong Kong Special Administrative Region(No.City U 11208617)。
文摘The integration of high mechanical toughness,impact strength as well as excellent flame-retardant properties toward epoxy resins(EPs)have always been a dilemma.The inadequate overall performance of EPs severely restricts their sustainable utilization in engineering aspects over long-term.Herein,a new bio-based agent(diglycidyl ether of magnolol phosphine oxide,referred as DGEMP)derived from magnolol(classified as lignan),extracted from natural plants Magnolia officinalis,was successfully synthesized and further employed as a flameretardant reactive additive to diglycidyl ether of bisphenol A(DGEBA).As demonstration,the composite resin,DGEBA/15DGEMP(15 wt%DGEMP),achieved an Underwriters Laboratories-94 V-0 rating with a high limiting oxygen index(LOI)value(41.5%).In cone calorimeter tests,it showed that heat release and smoke production were effectively inhibited during combustion,wherein the peak heat release rate(PHRR)value of DGEBA/15DGEMP was reduced by 50%compared to neat DGEBA.Additionally,it exhibited a superior tensile strength(82.8 MPa),toughness(5.11MJ/m^(3))and impact strength(36.5 k J/m^(2)),much higher than that of neat DGEBA(49.7 MPa,2.05 MJ/m^(3)and 20.9 k J/m^(2)).Thus,it is highly anticipated that DGEMP imparts significantly improved mechanical and fire-retarded properties to conventional EPs,which holds a great potential to address the pressing challenges in EP thermosets industry.
文摘A bisphenol A based epoxy was incorporated with a quadruply hydrogen bonded supramolecular polymer as a toughening agent to prepare a composite epoxy resin with higher impact resistance. The supramolecular polymer comprising poly-（propylene glycol） bis（2-aminopropyl） ether chains and 2-ureido-4[1H]-pyrimidinone moieties（UPy） self-assembled into spherical domains with sizes of 300 nm to 600 nm in diameter by micro phase separation in bulk epoxy matrixes. A significant improvement of 300% in impact resistance of the supramolecular polymer incorporated epoxy resin was obtained when the content of supramolecular polymer was 10 wt%. Tensile tests showed that the mechanical properties of the modified epoxy resin containing the hydrogen-bonded supramolecular polymers are also improved compared with those of the neat epoxy resin.
基金The research was supported by the open fund from the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing(SKJ-9805)
文摘This paper discusses the fundamental principle of microwave heating, and based on the advantages of microwave heating, use maleic anhydride as curing agent. The technology of microwave curing E44 epoxy resins is investigated, the mechanical properties of cured epoxy resin samples in different contents of curing agent by microwave and thermal curing methods are measured respectively, and then some experimental results for which are obtained. At last, this paper analyses why microwave curing can improve mechanical property of epoxy resin.
文摘To research the relationship between epoxy and fiber inherent property and mechanical properties of composite,we prepared a series of composites using three kinds of high mechanical performance epoxy resins as matrices and reinforced by the same volume fraction(5%)of short carbon and glass fiber.Their mechanical properties were investigated from the perspective of chemical structure and volume shrinkage ratio of epoxy.We analyzed their tensile strength and modulus based on the mixing rule and Halpin-Tsai eq...
文摘Phenolic hydroxyl-terminated polysiloxanes were incorporated into epoxy resins to reduce the internal stress owing to the mismatch in coefficient of thermal expansion (CTE). Polysiloxane-epoxy resin block copolymers were made by a pre-reaction step prior to the curing. In the cured resin, the domain size of the polysiloxane phase depended on the structure of the phenolic hydroxyl-terminated polysiloxane. It was found that the modulus of the cured resin depended largely on the level of the modifier, while the CTE was affected greatly by the structure of the polysiloxane. By means of incorporating a few percent of methylphenylsiloxane unit into the polydimethylsiloxane chain, or by introducing; more compatible end-capping groups, the compounds of more effective low stress modifiers were synthesized.
基金This project was supported by Open Foundation of State Key Lab. of Advanced Technology for Materials Synthesis and Process-ing.
文摘The influence of the type of epoxy resins(E-51, F-51)on themechanical properties and mi- crostructure of carboxyl-terminatedbutadiene nitrile rubber(CTBN)toughened epoxy resins investigated bydetermination of adhesive strength and toughness as well asobservation of scanning electron microstructure (SEM). The resultsindicate that the adhesive strength of CTBN toughened E-51 system issuperior to CTBN toughened F-51 system. However, CTBN toughened E-51system is inferior to CTBN toughened F-51 system in the toughness.
基金The project is supported by Ford-China Research and Development Fund.
文摘Poly(butylene terephthalate)-b-poly(tetramethylene glycol) (PBT-b-PTMG) was used as rheology modifier for the epoxy resin. The segmental copolymer formed spherulites in the epoxy medium. This copolymer was very effective in endowing yield stresses to the liquid resin. The PTMG segment brought in a lowering of the dissolution temperature of the spherulites in the epoxy gel. The cured resin with PBT-b-PTMG as modifier was two-phase materials. The rheology modifier improved the mechanical properties of the cured resin as well. The flexible PTMG segments, however, were not in favour of the toughening effect of the modifier. This was attributed to the large domain size of the dispersed phase.
基金This work was supported by the Ford-China Research and Development Fund (No.9415311).
文摘Nano silica-modified epoxy resins were synthesized by the sol-gel process, The materials have the morphological structure of nano particales dispersed in the epoxy matrix. The dispersed phase formed a physical network in the resin and thus influenced the rheological behavior greatly. However, the nano silica did not show a significant influence on the mechanical properties of the cured resins.
