Thermosets are indispensable to our daily life,but their crosslinked structures make them unable to be processed by the melt processing like thermoplastics,which greatly limits their shape designs and applications.Her...Thermosets are indispensable to our daily life,but their crosslinked structures make them unable to be processed by the melt processing like thermoplastics,which greatly limits their shape designs and applications.Herein,we address this challenge via an in situ self-growing strategy,i.e.utilizing the dynamic imidazole-urea moiety to suck up and integrate epoxy into the materials and making the thermoplastics grow in situ into thermosets.With this strategy,thermosets can be readily processed via hot-melt extrusion molding,including melt spinning and fused deposition modeling 3D printing.More importantly,this strategy simultaneously integrates the flexibility of polyurethane and the robustness of epoxy resin into the resulting thermosets,yielding a mechanical-reinforcing effect to make the material not only strong but also tough(toughness:99.3 MJ·m^(-3),tensile strength:38.8 MPa).Moreover,the crosslinking density and modulus of the as-prepared thermosets(from 34.1 MPa to613.7 MPa)can be readily tuned on demand by changing the growth index.Furthermore,these thermosets exhibited excellent thermal stability and chemical resistance.展开更多
Epoxy resin is widely used in electronic packaging due to its exceptional performance,particularly the low-temperature curable thiol/epoxy system,which effectively minimizes thermal damage to sensitive electronic comp...Epoxy resin is widely used in electronic packaging due to its exceptional performance,particularly the low-temperature curable thiol/epoxy system,which effectively minimizes thermal damage to sensitive electronic components.However,the majority of commercial thiol curing agents contain hydrolysable ester bonds and lack rigid structures,which induces most of thiol/epoxy systems still suffering from unsatisfactory heat resistance and hygrothermal resistance,significantly hindering their application in electronic packaging.In this study,we synthesized a tetrafunctional thiol compound,bis[3-(3-sulfanylpropyl)-4-(3-sulfanylpropoxy)phenyl]sulfone(TMBPS)with rigid and ester-free structures to replace traditional commercial thiol curing agents,pentaerythritol tetra(3-mercaptopropionate)(PETMP).Compared to the PETMP/epoxy system,the TMBPS/epoxy system exhibited superior comprehensive properties.The rigid structures of bisphenol S-type tetrathiol enhanced the heat resistance and mechanical properties of TMBPS/epoxy resin cured products,outperforming those of PETMP/epoxy resin cured products.Notably,the glass transition temperature of TMBPS/epoxy resin cured products was 74.2℃which was 11.8°C higher than that of PETMP cured products.Moreover,the ester-free structure in TMBPS contributed to its enhanced resistance to chemicals and hygrothermal conditions.After undergoing 1000 h of hightemperature and high-humidity aging,the tensile strength and adhesion strength of TMBPS-cured products were 73.33 MPa and 3.39 MPa,respectively exceeding 100%and 40%of their initial values,while PETMP-cured products exhibited a complete loss of both tensile strength and adhesion strength.This study provides a strategy for obtaining thermosetting polymers that can be cured at low temperatures and exhibit excellent comprehensive properties.展开更多
Quest for bio-based halogen-free green flame retardant has attracted many concerns in recent years.Herein a reactive functional flame retardant containing phosphorus VDP is synthesized from vanillin,9,10-dihydro-9-oxa...Quest for bio-based halogen-free green flame retardant has attracted many concerns in recent years.Herein a reactive functional flame retardant containing phosphorus VDP is synthesized from vanillin,9,10-dihydro-9-oxa-10-phosphophene-10-oxide(DOPO)and phenol via a facile way.VDP is characterized with^(1)H NMR,^(31)P NMR,FTIR and Time of Flight Mass Spectrometry,and used as a new reactive flame retardant for bisphenol epoxy thermosets.Thermogravimetry analysis shows that when the VDP loading is only 0.5P%(based on phosphorus content),the residue increases from 14.2%to 21.1%at 750℃ in N_(2)compare with neat DGEBA.Correspondingly,the limit oxygen index increased to 29.6%,and flame retardancy reaches UL-94 V0 grade.Micro combustion calorimetry(MCC)and cone calorimetry analyses demonstrate that VDP can significantly lower flammability of the epoxy thermoset.With only 0.5P%of VDP,the heat release rate,total heat release rate and smoke production are reduced markedly.At the same time,the mechanical properties of the modified epoxy thermosets are also improved.The impact strength increases by 34%and the flexural strength increased by 23%,with 1.5P%of VDP.In short,VDP not only improves the flame retardancy,but also improves the mechanical properties of the epoxy thermosets.展开更多
A series of Diels-Alder reaction cross-linked thermosets with recyclability and healability were prepared from furan-containing aromatic polyamide and bismaleimides with different chemical structures.The structures of...A series of Diels-Alder reaction cross-linked thermosets with recyclability and healability were prepared from furan-containing aromatic polyamide and bismaleimides with different chemical structures.The structures of synthesized bismaleimides were confirmed by 1 H nuclear magnetic resonance(1 H-NMR)spectroscopy;their reversible cross-linking with the furanic polyamide was further detected by 1 H-NMR technique and sol-gel transition behavior.The dynamic mechanical analysis and tensile test revealed the variable thermal and mechanical properties of thermosets cross-linked by different bismaleimides and with different molar ratios of maleimide group to furan group(Ima/fur).The tensile test also demonstrated that the better recyclability and solvent-assisted healability of thermosets cross-linked could be achieved by more flexible bismaleimides.This work is expected to provide valuable information for design of recyclable and healable high-performance thermosets with desired properties.展开更多
Two kinds of difunctionalized isosorbide derivatives containing norbornene groups were designed and synthesized by a facile one-step reaction under mild conditions.~1H NMR spectroscopy confirmed the chemical compositi...Two kinds of difunctionalized isosorbide derivatives containing norbornene groups were designed and synthesized by a facile one-step reaction under mild conditions.~1H NMR spectroscopy confirmed the chemical composition and differential scanning calorimetry（DSC） revealed the distinct curing behaviors between conventional petroleum-based dicyclopentadiene（DCPD） and synthesized renewable isosorbided-based monomer（ISN）. In contrast to DCPD, ISN was low viscous liquid at room temperature and had even higher reactivity to perform ring-opening metathesis polymerization（ROMP） in the presence of Grubbs＇ catalyst. Due to the presence of flexible and elastic Si–C long chains, the cured poly（ISN） thermosets not only had good mechanical properties but also exhibited much higher storage modulus at the rubbery state in comparison with traditional poly（DCPD）.展开更多
The development of efficient green flame retardants is an important way to realize more sustainable epoxy thermosets and downstream materials.In this work,a monoepoxide is synthesized through O-glycidylation of eugeno...The development of efficient green flame retardants is an important way to realize more sustainable epoxy thermosets and downstream materials.In this work,a monoepoxide is synthesized through O-glycidylation of eugenol,and then reacted with DOPO(9,10-dihydro-9-oxa-10-phosphophenanthrene-10-oxide)to obtain a new bio-based flame retardant,DOPO-GE.DOPO-GE is blended with a bisphenol A epoxy prepolymer exhibiting good compatibility and DDS(4,4′-diaminodiphenylsulfone)is used as the curing agent to afford epoxy thermosets.Although DOPO-GE leads to the reduced glass transition temperature of the thermosets,the storage modulus increases considerably.The DOPO-GE-modified thermosets exhibit the high thermal stability with the onset thermal decomposition temperature in nitrogen and air exceeding 300℃.When the phosphorus content in the thermoset is 1.0%,the residual yield of the thermosets at 750℃ in nitrogen increases from 13.9%to 30.6%,due to the increased charring ability.More interestingly,when the phosphorus content is only 0.5%,the limiting oxygen index is as high as 30.3%with UL94 V0 achieved.Cone calorimeter results reveals the significantly decreased heat release rate,total heat release,mass loss and total smoke production.Furthermore,DOPO-GE can notably improve the flexural strength,flexural modulus and fracture toughness,whereas the shear and impact strength are reduced to varied extents.In short,DOPO-GE can be obtained via a facile way,and shows the good flame-retardant effect on the epoxy thermosets with an application potential.展开更多
In this work,apigenin was chosen as a raw material to synthesize a novel epoxy monomer(DGEA),while the bio-based epoxy resin was further obtained after curing with 4,4’-diaminodiphenylmethane(DDM).The control samples...In this work,apigenin was chosen as a raw material to synthesize a novel epoxy monomer(DGEA),while the bio-based epoxy resin was further obtained after curing with 4,4’-diaminodiphenylmethane(DDM).The control samples were prepared by curing diglycidyl ether of bisphenol A(DGEBA)with DDM.The non-isothermal differential scanning calorimeter(DSC)method was utilized to further investigate the curing behavior and curing kinetics of the DGEA/DDM system.Despite no flame retardant active elements,the DGEA/DDM thermoset still exhibited exceptional anti-flammability.Specifically,the DGEA/DDM thermoset reached a V-0 rating in the UL-94 test and owned a high limiting oxygen index(LOI)value of 37.0%,while DGEBA/DDM resins were consumed completely in the vertical combustion test with a low LOI of 23.0%.Furthermore,the microscale combustion calorimetry(MCC)results manifested that compared with DGEBA/DDM resins,both PHRR and THR values of the DGEA/DDM resins were dropped by 84.0%and 57.6%,respectively.Additionally,the DGEA/DDM resin also presented higher storage modulus and tensile strength compared with DGEBA/DDM one.Particularly,in contrast with that of the cured DGEBA/DDM one(156℃),the DGEA/DDM thermoset displayed an extremely high glass transition temperature(232℃).This study breaks new ground on how to produce biobased monomers with aromatic structures and achieve high-performance thermosetting polymers.展开更多
The use of CO_(2) as monomer to synthesize polymer materials is an important and potential applications topic from the viewpoint of green and sustainable chemistry.A new kind of CO_(2)-based polyurea(PUa)was synthesiz...The use of CO_(2) as monomer to synthesize polymer materials is an important and potential applications topic from the viewpoint of green and sustainable chemistry.A new kind of CO_(2)-based polyurea(PUa)was synthesized by polycondensation of CO_(2) with 4,7,10-trioxa-1,13-tridecanediamine and tris(2-aminoethyl)amine(TAEA).TAEA was used as cross-link reagent.The mechanical properties of PUa were significantly improved by inserted the crosslink agent of TAEA.The formed slight cross-linked PUa exhibited excellent mechanical properties with tensile strength of 26.8 MPa,elongation at break of 34%and Young’s modulus of 351 MPa.Moreover,it could be remolded for 3 times without obvious change in the mechanical properties,which are ascribed to the hydrogen bonding interaction among the main chains and the slight cross-linked structure.In addition,the synthesized CO_(2)-based PUa is of outstanding thermal performance with an initial decomposition temperature above 300℃,besides it is tolerance for a variety of organic solvents.展开更多
Recently developed low fluorine containing polymers are advanced materials which confer advantageous properties to surfaces at a lower cost than conventional fluoropolymers (like PTFE), and are also more easily proces...Recently developed low fluorine containing polymers are advanced materials which confer advantageous properties to surfaces at a lower cost than conventional fluoropolymers (like PTFE), and are also more easily processable. Fluoropolymer surfaces are characterized by a low surface energy, high oleo and hydrophobicity, low coefficients of friction, among many other properties. This makes them desired materials in microelectronics, antifogging, antifouling and medical applications, to name a few. Fluorinated compounds are not easily coupled with macromolecules or common organic systems, and great efforts are made to compatibilize fluorinated species with hydrocarbon polymers. In this work, two chemical routes were explored in order to incorporate perfluorinated alkyl chains in an epoxy-amine based thermoset. On one side, a perfluoroalkyl thiolated molecule was used as a stabilizing ligand for silver nanoparticles, which were incorporated in the matrix polymer. On the other hand, fluorinated chains containing epoxy functionalities, were used as the matrix modifier. In the first case, fluorinated chains covering the nanoparticles, were mixed with the matrix, while in the second case, the fluoroalkyl chains were chemically linked to the network. Fluorine migration to the air—polymer interface was confirmed by X-Ray photoelectron spectroscopy (XPS). The materials hydrophobicity was then studied in terms of their contact angle with water (CA), as a function of the surface composition and the topography. Scanning electron microscopy (SEM) and atomic force microscopy (AFM), operated in moderate and light tapping modes, were used to morphologically describe the surfaces. An exhaustive surface analysis was made in order to explain the different hydrophobicity grades found.展开更多
Two kinds of rosin derivatives, （2-hydroxy-3-（methacryloyloxy）propyl 7-isopropyl-1,4a-dimethyl-1,2,3,4,4a,4b,5,6,10,10a- decahydrophenanthrene-1-carboxylate） （HMPIDDC） and （（（7-isopropyl-1,4a-dimethyl-1,2,3,4...Two kinds of rosin derivatives, （2-hydroxy-3-（methacryloyloxy）propyl 7-isopropyl-1,4a-dimethyl-1,2,3,4,4a,4b,5,6,10,10a- decahydrophenanthrene-1-carboxylate） （HMPIDDC） and （（（7-isopropyl-1,4a-dimethyl-1,2,3,4,4a,9,10,10a-octahydrophenan- thren-1-yl）methyl）azanediyl）bis（2-hydroxypropane-3,1-diyl）bis（2-methylacrylate） （IDOMAHM） were synthesized under mild and easy to implement conditions. The two derivatives were employed as the rigid monomers to copolymerize with acrylated epoxidized soybean oil （AESO）, as so to improve the performance of the cured resins. The chemical structures of HMPIDDC and IDOMAHM were confirmed by nuclear magnetic resonance （NMR） and Fourier Transform Infrared （FT-IR） before copolymerization. The curing behaviors of pristine AESO, AESO/HMPIDDC blend, and AESO/IDOMAHM blend were monitored by differential scanning calorimetry （DSC）. Moreover, the thermal and mechanical properties of the cured resins were evaluated by universal mechanical testing, dynamic mechanical analysis （DMA） and thermogravimetric analysis （TGA）. The results demonstrated that after the introduction of HMPIDDC and IDOMAHM, the glass transition temperature and mechanical properties of the copolymerized resin were significantly increased. In one word, HMPIDDC and IDOMAHM showed dramatic potential to be used as bio-based compounds to improve the properties of soybean-oil based thermosets.展开更多
In this study,epoxidized soybean oil(ESO)and ricinoleic acid(RA)were used to synthesize polyol esters,designated ESO-RA(ER)resin.The esters were further crosslinked with 4,4-diphenylmethane diisocyanate(PMDI)to create...In this study,epoxidized soybean oil(ESO)and ricinoleic acid(RA)were used to synthesize polyol esters,designated ESO-RA(ER)resin.The esters were further crosslinked with 4,4-diphenylmethane diisocyanate(PMDI)to create a biodegradable flame-retardant thermoset foam,referred to as ESO-RA-PMDI(ERP)foam,using water as a foaming agent.Additionally,flame retardants such as triethyl phosphate(TEP)and expanded graphite(EG)have been combined for foam preparation without the need for catalysts or foaming agents.The study findings showed that the incorporation of TEP and EG diminished the pulverization ratio while augmenting the compressive strength and shore hardness.Furthermore,the ERP foam exhibited exceptional flame retardant characteristics,as evidenced by a reported limiting oxygen index(LOI)value of 30.6vol%.A peak heat release rate of 97.12 kW/m^(2)was reported during the fire test.Significantly,a low peak smoke production rate(pSPR)of 0.026m^(2)/s and a total smoke production(TSP)of 0.62 m^(2)were achieved.In addition,ERP foam exhibited exceptional ultraviolet(UV)resistance,thermal insulation,and biodegradability.After 60 days of exposure to Penicillium sp.,foam containing both TEP and EG exhibited a mass loss of 9.39%,indicating that the incorporation of flame retardants did not negatively impact its biodegradability.展开更多
It is of great significance to design epoxy coatings with superior antibacterial properties and high adhesive properties, as well as excellent processing, superior durability, and high transparency. However, it is sti...It is of great significance to design epoxy coatings with superior antibacterial properties and high adhesive properties, as well as excellent processing, superior durability, and high transparency. However, it is still a challenge because of the common complex design and synthesis. Herein, the bio-based monomer protocatechuic acid(PCA) was used as raw material, the catechol structure with high bonding and antibacterial properties was introduced into the flexible alkane segment of ethylene glycol diglycidyl ether(EGDE) through an efficient, and green method, and it was cured with isophorone diamine(IPDA) to prepare corresponding thermosets. The cured resins exhibited excellent allaround qualities, particularly in bonding and antibacterial. When 30% PCA was added to pure epoxy resin, the adhesion between substrate and coating increased from 4.40 MPa to 13.60 MPa and the antibacterial rate of coating against E. coli and S. aureus could approach 100%. All of this is due to the fact that the catechol structure present in PCA has the ability to interact with various substrates and alter the permeability of bacterial cell membranes. The architecture of this method offers a fresh approach to dealing with the issues of challenging raw material selection and complex synthesis techniques.展开更多
Chemical degradation of diglycidyl ether of bisphenol A（DGEBA） epoxy resin cured with an aliphatic amine in supercritical 1-propanol was investigated under different reaction temperature and time. The combination of...Chemical degradation of diglycidyl ether of bisphenol A（DGEBA） epoxy resin cured with an aliphatic amine in supercritical 1-propanol was investigated under different reaction temperature and time. The combination of GC-MS and LC-MS proved that the epoxy resin was decomposed to five main products including phenol, 4-isopropylphenol, 4-isopropenylphenol, bisphenol A, and 4,4’-（cyclopropane-1,1-diyl）diphenol. The 13C-NMR results verified the chemical structures of the degradation products. The change of the products′ yield with time was evaluated by an effective means of HPLC. In addition, the GPC analysis confirmed the formation of soluble low molecular weight clusters during the degradation reaction. A possible free-radical reaction mechanism was proposed for chemical depolymerization of the epoxy resin in supercritical 1-propanol. After the homolytic cleavage of the aromatic ether linkages, the resulting bisphenol A biradical either produced 4,4’-（cyclopropane-1,1-diyl）diphenol after intramolecular rearrangement or generated bisphenol A after capturing hydrogen from 1-propanol.展开更多
Nanocomposites from nanoscale silica particles（NS）,diglycidylether of bisphenol-A based epoxy（DGEBA）,and 3,5-diamino-N-（4-（quinolin-8-yloxy） phenyl） benzamide（DQPB） as curing agent were obtained from direct ...Nanocomposites from nanoscale silica particles（NS）,diglycidylether of bisphenol-A based epoxy（DGEBA）,and 3,5-diamino-N-（4-（quinolin-8-yloxy） phenyl） benzamide（DQPB） as curing agent were obtained from direct blending of these materials.The effect of nanosilica（NS） particles as catalyst on the cure reaction of DGEBA/DQPB system was studied by using non-isothermal DSC technique.The activation energy（E_a） was obtained by using Kissinger and Ozawa equations. The E_a value of curing of DGEBA/DQPB/10%NS system showed a decrease of about 10 kJ/mol indicating the catalytic effect of NS particles on the cure reaction.The E_a values of thermal degradation of the cured samples of both systems were 148 kJ/mol and 160 kJ/mol,respectively.The addition of 10%of NS to the curing mixture did not have much effect on the initial decomposition temperature（T_i） but increased the char residues from 20%to 28%at 650℃.展开更多
A phosphorus-nitrogen containing flame retardant additive of poly（phosphoric acid piperazine）, defined as PPAP, was synthesized by the salt-forming reaction between anhydrous piperazine and phosphoric acid, and the ...A phosphorus-nitrogen containing flame retardant additive of poly（phosphoric acid piperazine）, defined as PPAP, was synthesized by the salt-forming reaction between anhydrous piperazine and phosphoric acid, and the dehydration polymerization under heating in nitrogen atmosphere. Its chemical structure was well characterized by Fourier transform infrared（FTIR） spectroscopy, ^（13）C and ^（31）P solid-state nuclear magnetic resonance measurements. The synthesized PPAP and curing agent m-phenylenediamine were blended into epoxy resin（EP） to prepare flame retardant EP thermosets. The effects of PPAP on the fire retardancy and thermal degradation behavior of cured EP/PPAP composites were investigated by limiting oxygen index（LOI）, vertical burning（UL-94）, thermogravimetric analysis/infrared spectrometry（TG-IR） and cone calorimeter tests. The morphologies and chemical compositions of char residues for cured epoxy resin were investigated by scanning electron microscopy（SEM） and X-ray photoelectron spectroscopy（XPS）, respectively. The results demonstrated that the flame retardant EP thermosets successfully passed UL-94 V-0 flammability rating and the LOI value was as high as 30.8% when incorporating 5 wt% PPAP into the EP thermosets. The TGA results indicated that the synthesized PPAP flame retardant additive possessed high thermal stability and excellent charring capability. Meanwhile, the incorporation of PPAP stimulated the epoxy resin matrix to decompose and charring ahead of time due to its catalytic decomposition effect, which led to a higher char yield at high temperature. The morphological structures and the analysis results of XPS for char residues of EP thermosets revealed that the introduction of PPAP benefited the formation of a sufficient, more compact and homogeneous char layer containing phosphorus-nitrogen flame retardant elements on the material surface during combustion. The formed char layer with high quality effectively prevented the heat transmission and diffusion, limited the production of combustible gases, and inhibited the emission of smoke, leading to the reduction of heat and smoke release.展开更多
Polymers are indispensable to humans in different applications due to their ease of manufacturing and overall performance.However,after a material lifetime,there is a large amount of polymer-based waste,which greatly ...Polymers are indispensable to humans in different applications due to their ease of manufacturing and overall performance.However,after a material lifetime,there is a large amount of polymer-based waste,which greatly contributes to the loss of valuable resources and environmental pollution.Thermoplastics may be readily recycled,but because of their flammability,large amounts of flame retardant(FR)ad-ditives are required for many applications.This results in a significant volume of FR polymeric wastes too,particularly halogenated plastics,which are subject to severe recycling regulations.In general,ther-moplastics containing FRs are raising concerns,as their effective recycling is strongly influenced by the chemical composition,additive content,and physicochemical characteristics of the waste stream.The recycling of FR thermosets is even more challenging due to their crosslinked and cured nature,which makes them resistant to melting and reprocessing.In many cases,traditional mechanical recycling meth-ods,such as grinding and melting,are not applicable to thermosetting polymers.Current recycling meth-ods do not always consider the recovery of the thermosetting/thermoplastic matrix and the presence of toxic FRs in the polymer network.Sorting and solvent washing treatment are important steps,which are usually performed before recycling the FR polymeric waste to reduce contamination in the following steps.展开更多
A novel boron-containing monomer,(4-(3,4-dicyanophenoxy)phenyl)boronic acid(BPhPN)was synthesized and used to promote the curing process of phthalonitrile monomer 1,3-bis(3,4-dicyanophenoxy)benzene(MPN).Differential s...A novel boron-containing monomer,(4-(3,4-dicyanophenoxy)phenyl)boronic acid(BPhPN)was synthesized and used to promote the curing process of phthalonitrile monomer 1,3-bis(3,4-dicyanophenoxy)benzene(MPN).Differential scanning calorimetry and rheological analysis were used to study the curing behaviors of BPhPN/MPN(namely B-MPN),and results suggested that B-MPN systems have better processibility.FTIR spectra and solid-state 13C-NMR exhibited triazine and isoindoline have been formed in the curing process.Boron-containing Lewis acid curing mechanism was preliminarily speculated and verified by two model compounds with different boron chemical environments.The thermogravimetric analysis and dynamic mechanical analysis demonstrated that the cured B-MPN polymers showed excellent thermal stability and heat resistance,which were comparable with conventional catalytic systems for phthalonitrile resins.This study not only presented a novel curing system for phthalonitrile resins,but also shed light on future design of high temperature thermosets.展开更多
Due to their extraordinary durability and thermal stability,Epoxy Resin Thermosets(ERTs)are essential in various industries.However,their poor recyclability leads to unacceptable environmental pollution.In this study,...Due to their extraordinary durability and thermal stability,Epoxy Resin Thermosets(ERTs)are essential in various industries.However,their poor recyclability leads to unacceptable environmental pollution.In this study,Wu et al.successfully synthesized a completely bio-based ERT using lignocellulose-derived building blocks which exhibit outstanding thermal and mechanical properties.Remarkably,these bio-materials degrade via methanolysis without the need of any catalyst,presenting a smart and cost-effective recycling strategy.Furthermore,this approach could be employed for fabricating reusable composites comprising glass fiber and plant fiber,thereby expanding its applications in sustainable transportation,coatings,paints or biomedical devices.展开更多
Stiffened thermosetting composite panels were fabricated with co-curing processing.In the co-curing processing,the temperature distribution in the composite panels was nonuniform.An investigation into the threedimensi...Stiffened thermosetting composite panels were fabricated with co-curing processing.In the co-curing processing,the temperature distribution in the composite panels was nonuniform.An investigation into the threedimensional cure simulation of T-shape stiffened thermosetting composite panels was presented.Flexible tools and locating tools were considered in the cure simulation.Temperature distribution in the composites was predicted as a function of the autoclave temperature history.A nonlinear transient heat transfer finite element model was developed to simulate the curing process of stiffened thermosetting composite panels.And a simulation example was presented to demonstrate the use of the present finite element procedure for analyzing composite curing process.The glass/polyester structure was investigated to provide insight into the nonuniform cure process and the effect of flexible tools and locating tools on temperature distribution.Temperature gradient in the intersection between the skin and the flange was shown to be strongly dependent on the structure of the flexible tools and the thickness of the skin.展开更多
The morphological structure of various epoxies toughened with a special amorphous thermoplastic PEK-C and their carbon fiber composites were studied by using SEM. For both cases, phase separation and inversion took pl...The morphological structure of various epoxies toughened with a special amorphous thermoplastic PEK-C and their carbon fiber composites were studied by using SEM. For both cases, phase separation and inversion took place to form fine epoxy-rich globules dispersing in the PEK-C matrix, in which the epoxy-rich phase had the absolutely higher volume fraction. The phase structure and the interfacial properties were also studied by means of FTIR, DSC, and DMTA as well. An accompanying mechanical determination revealed that an improved toughness was achieved both in the blend casts and in the carbon fiber composites. A composite structural model was hence suggested.展开更多
基金financially supported by the Natural Science Foundation of Zhejiang Province(No.LQ24B040004)。
文摘Thermosets are indispensable to our daily life,but their crosslinked structures make them unable to be processed by the melt processing like thermoplastics,which greatly limits their shape designs and applications.Herein,we address this challenge via an in situ self-growing strategy,i.e.utilizing the dynamic imidazole-urea moiety to suck up and integrate epoxy into the materials and making the thermoplastics grow in situ into thermosets.With this strategy,thermosets can be readily processed via hot-melt extrusion molding,including melt spinning and fused deposition modeling 3D printing.More importantly,this strategy simultaneously integrates the flexibility of polyurethane and the robustness of epoxy resin into the resulting thermosets,yielding a mechanical-reinforcing effect to make the material not only strong but also tough(toughness:99.3 MJ·m^(-3),tensile strength:38.8 MPa).Moreover,the crosslinking density and modulus of the as-prepared thermosets(from 34.1 MPa to613.7 MPa)can be readily tuned on demand by changing the growth index.Furthermore,these thermosets exhibited excellent thermal stability and chemical resistance.
基金the support of the Science and Technology Commission of Shanghai Municipality(STCSM,No.20dz1203600)the Experimental Center of Materials Science and Engineering in Tongji University。
文摘Epoxy resin is widely used in electronic packaging due to its exceptional performance,particularly the low-temperature curable thiol/epoxy system,which effectively minimizes thermal damage to sensitive electronic components.However,the majority of commercial thiol curing agents contain hydrolysable ester bonds and lack rigid structures,which induces most of thiol/epoxy systems still suffering from unsatisfactory heat resistance and hygrothermal resistance,significantly hindering their application in electronic packaging.In this study,we synthesized a tetrafunctional thiol compound,bis[3-(3-sulfanylpropyl)-4-(3-sulfanylpropoxy)phenyl]sulfone(TMBPS)with rigid and ester-free structures to replace traditional commercial thiol curing agents,pentaerythritol tetra(3-mercaptopropionate)(PETMP).Compared to the PETMP/epoxy system,the TMBPS/epoxy system exhibited superior comprehensive properties.The rigid structures of bisphenol S-type tetrathiol enhanced the heat resistance and mechanical properties of TMBPS/epoxy resin cured products,outperforming those of PETMP/epoxy resin cured products.Notably,the glass transition temperature of TMBPS/epoxy resin cured products was 74.2℃which was 11.8°C higher than that of PETMP cured products.Moreover,the ester-free structure in TMBPS contributed to its enhanced resistance to chemicals and hygrothermal conditions.After undergoing 1000 h of hightemperature and high-humidity aging,the tensile strength and adhesion strength of TMBPS-cured products were 73.33 MPa and 3.39 MPa,respectively exceeding 100%and 40%of their initial values,while PETMP-cured products exhibited a complete loss of both tensile strength and adhesion strength.This study provides a strategy for obtaining thermosetting polymers that can be cured at low temperatures and exhibit excellent comprehensive properties.
基金This work is supported by the National Natural Science Foundation of China(NSFC)under the agreements of 21875131 and 21773150The Natural Science Basic Research Plan in Shaanxi Province of China(2020JM-283)the Fundamental Research Funds for the Central Universities(GK202003044 and GK201902014)are also acknowledged for partial support。
文摘Quest for bio-based halogen-free green flame retardant has attracted many concerns in recent years.Herein a reactive functional flame retardant containing phosphorus VDP is synthesized from vanillin,9,10-dihydro-9-oxa-10-phosphophene-10-oxide(DOPO)and phenol via a facile way.VDP is characterized with^(1)H NMR,^(31)P NMR,FTIR and Time of Flight Mass Spectrometry,and used as a new reactive flame retardant for bisphenol epoxy thermosets.Thermogravimetry analysis shows that when the VDP loading is only 0.5P%(based on phosphorus content),the residue increases from 14.2%to 21.1%at 750℃ in N_(2)compare with neat DGEBA.Correspondingly,the limit oxygen index increased to 29.6%,and flame retardancy reaches UL-94 V0 grade.Micro combustion calorimetry(MCC)and cone calorimetry analyses demonstrate that VDP can significantly lower flammability of the epoxy thermoset.With only 0.5P%of VDP,the heat release rate,total heat release rate and smoke production are reduced markedly.At the same time,the mechanical properties of the modified epoxy thermosets are also improved.The impact strength increases by 34%and the flexural strength increased by 23%,with 1.5P%of VDP.In short,VDP not only improves the flame retardancy,but also improves the mechanical properties of the epoxy thermosets.
基金financially supported by the National Natural Science Foundation of China (No. 51473031)the Natural Science Foundation of Shanghai (No. 17ZR1401100)the doctoral innovation foundation (No. CUSF-DH-D-2017037)
文摘A series of Diels-Alder reaction cross-linked thermosets with recyclability and healability were prepared from furan-containing aromatic polyamide and bismaleimides with different chemical structures.The structures of synthesized bismaleimides were confirmed by 1 H nuclear magnetic resonance(1 H-NMR)spectroscopy;their reversible cross-linking with the furanic polyamide was further detected by 1 H-NMR technique and sol-gel transition behavior.The dynamic mechanical analysis and tensile test revealed the variable thermal and mechanical properties of thermosets cross-linked by different bismaleimides and with different molar ratios of maleimide group to furan group(Ima/fur).The tensile test also demonstrated that the better recyclability and solvent-assisted healability of thermosets cross-linked could be achieved by more flexible bismaleimides.This work is expected to provide valuable information for design of recyclable and healable high-performance thermosets with desired properties.
基金National Natural Science Foundation of China (No. 51503181)Foundation of Educational Committee of Zhejiang Province of China (No. Y201225071)Ningbo Natural Science Foundation of China (Nos. 2013A610135, 2015A610092, 2015A610100) for financial support
文摘Two kinds of difunctionalized isosorbide derivatives containing norbornene groups were designed and synthesized by a facile one-step reaction under mild conditions.~1H NMR spectroscopy confirmed the chemical composition and differential scanning calorimetry（DSC） revealed the distinct curing behaviors between conventional petroleum-based dicyclopentadiene（DCPD） and synthesized renewable isosorbided-based monomer（ISN）. In contrast to DCPD, ISN was low viscous liquid at room temperature and had even higher reactivity to perform ring-opening metathesis polymerization（ROMP） in the presence of Grubbs＇ catalyst. Due to the presence of flexible and elastic Si–C long chains, the cured poly（ISN） thermosets not only had good mechanical properties but also exhibited much higher storage modulus at the rubbery state in comparison with traditional poly（DCPD）.
基金The authors acknowledge the support from the National Natural Science Foundation of China(21875131 and 21773150)the Natural Science Basic Research Plan in Shaanxi Province of China(2020JM-283)the Fundamental Research Funds for the Central Universities(GK202003044 and GK201902014).
文摘The development of efficient green flame retardants is an important way to realize more sustainable epoxy thermosets and downstream materials.In this work,a monoepoxide is synthesized through O-glycidylation of eugenol,and then reacted with DOPO(9,10-dihydro-9-oxa-10-phosphophenanthrene-10-oxide)to obtain a new bio-based flame retardant,DOPO-GE.DOPO-GE is blended with a bisphenol A epoxy prepolymer exhibiting good compatibility and DDS(4,4′-diaminodiphenylsulfone)is used as the curing agent to afford epoxy thermosets.Although DOPO-GE leads to the reduced glass transition temperature of the thermosets,the storage modulus increases considerably.The DOPO-GE-modified thermosets exhibit the high thermal stability with the onset thermal decomposition temperature in nitrogen and air exceeding 300℃.When the phosphorus content in the thermoset is 1.0%,the residual yield of the thermosets at 750℃ in nitrogen increases from 13.9%to 30.6%,due to the increased charring ability.More interestingly,when the phosphorus content is only 0.5%,the limiting oxygen index is as high as 30.3%with UL94 V0 achieved.Cone calorimeter results reveals the significantly decreased heat release rate,total heat release,mass loss and total smoke production.Furthermore,DOPO-GE can notably improve the flexural strength,flexural modulus and fracture toughness,whereas the shear and impact strength are reduced to varied extents.In short,DOPO-GE can be obtained via a facile way,and shows the good flame-retardant effect on the epoxy thermosets with an application potential.
基金financially supported by the National Natural Science Foundation of China(Nos.22075265 and 22050410269)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2021459)。
文摘In this work,apigenin was chosen as a raw material to synthesize a novel epoxy monomer(DGEA),while the bio-based epoxy resin was further obtained after curing with 4,4’-diaminodiphenylmethane(DDM).The control samples were prepared by curing diglycidyl ether of bisphenol A(DGEBA)with DDM.The non-isothermal differential scanning calorimeter(DSC)method was utilized to further investigate the curing behavior and curing kinetics of the DGEA/DDM system.Despite no flame retardant active elements,the DGEA/DDM thermoset still exhibited exceptional anti-flammability.Specifically,the DGEA/DDM thermoset reached a V-0 rating in the UL-94 test and owned a high limiting oxygen index(LOI)value of 37.0%,while DGEBA/DDM resins were consumed completely in the vertical combustion test with a low LOI of 23.0%.Furthermore,the microscale combustion calorimetry(MCC)results manifested that compared with DGEBA/DDM resins,both PHRR and THR values of the DGEA/DDM resins were dropped by 84.0%and 57.6%,respectively.Additionally,the DGEA/DDM resin also presented higher storage modulus and tensile strength compared with DGEBA/DDM one.Particularly,in contrast with that of the cured DGEBA/DDM one(156℃),the DGEA/DDM thermoset displayed an extremely high glass transition temperature(232℃).This study breaks new ground on how to produce biobased monomers with aromatic structures and achieve high-performance thermosetting polymers.
文摘The use of CO_(2) as monomer to synthesize polymer materials is an important and potential applications topic from the viewpoint of green and sustainable chemistry.A new kind of CO_(2)-based polyurea(PUa)was synthesized by polycondensation of CO_(2) with 4,7,10-trioxa-1,13-tridecanediamine and tris(2-aminoethyl)amine(TAEA).TAEA was used as cross-link reagent.The mechanical properties of PUa were significantly improved by inserted the crosslink agent of TAEA.The formed slight cross-linked PUa exhibited excellent mechanical properties with tensile strength of 26.8 MPa,elongation at break of 34%and Young’s modulus of 351 MPa.Moreover,it could be remolded for 3 times without obvious change in the mechanical properties,which are ascribed to the hydrogen bonding interaction among the main chains and the slight cross-linked structure.In addition,the synthesized CO_(2)-based PUa is of outstanding thermal performance with an initial decomposition temperature above 300℃,besides it is tolerance for a variety of organic solvents.
文摘Recently developed low fluorine containing polymers are advanced materials which confer advantageous properties to surfaces at a lower cost than conventional fluoropolymers (like PTFE), and are also more easily processable. Fluoropolymer surfaces are characterized by a low surface energy, high oleo and hydrophobicity, low coefficients of friction, among many other properties. This makes them desired materials in microelectronics, antifogging, antifouling and medical applications, to name a few. Fluorinated compounds are not easily coupled with macromolecules or common organic systems, and great efforts are made to compatibilize fluorinated species with hydrocarbon polymers. In this work, two chemical routes were explored in order to incorporate perfluorinated alkyl chains in an epoxy-amine based thermoset. On one side, a perfluoroalkyl thiolated molecule was used as a stabilizing ligand for silver nanoparticles, which were incorporated in the matrix polymer. On the other hand, fluorinated chains containing epoxy functionalities, were used as the matrix modifier. In the first case, fluorinated chains covering the nanoparticles, were mixed with the matrix, while in the second case, the fluoroalkyl chains were chemically linked to the network. Fluorine migration to the air—polymer interface was confirmed by X-Ray photoelectron spectroscopy (XPS). The materials hydrophobicity was then studied in terms of their contact angle with water (CA), as a function of the surface composition and the topography. Scanning electron microscopy (SEM) and atomic force microscopy (AFM), operated in moderate and light tapping modes, were used to morphologically describe the surfaces. An exhaustive surface analysis was made in order to explain the different hydrophobicity grades found.
基金supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2012229)Natural Sciences Foundation of Ningbo City(Grant No.2014A610110)+1 种基金Research Project of Technology Application for Public Welfare of Zhejiang Province(Grant No.2014C31143)National Natural Science Foundation of China(Grant Nos.51373194,51203176)
文摘Two kinds of rosin derivatives, （2-hydroxy-3-（methacryloyloxy）propyl 7-isopropyl-1,4a-dimethyl-1,2,3,4,4a,4b,5,6,10,10a- decahydrophenanthrene-1-carboxylate） （HMPIDDC） and （（（7-isopropyl-1,4a-dimethyl-1,2,3,4,4a,9,10,10a-octahydrophenan- thren-1-yl）methyl）azanediyl）bis（2-hydroxypropane-3,1-diyl）bis（2-methylacrylate） （IDOMAHM） were synthesized under mild and easy to implement conditions. The two derivatives were employed as the rigid monomers to copolymerize with acrylated epoxidized soybean oil （AESO）, as so to improve the performance of the cured resins. The chemical structures of HMPIDDC and IDOMAHM were confirmed by nuclear magnetic resonance （NMR） and Fourier Transform Infrared （FT-IR） before copolymerization. The curing behaviors of pristine AESO, AESO/HMPIDDC blend, and AESO/IDOMAHM blend were monitored by differential scanning calorimetry （DSC）. Moreover, the thermal and mechanical properties of the cured resins were evaluated by universal mechanical testing, dynamic mechanical analysis （DMA） and thermogravimetric analysis （TGA）. The results demonstrated that after the introduction of HMPIDDC and IDOMAHM, the glass transition temperature and mechanical properties of the copolymerized resin were significantly increased. In one word, HMPIDDC and IDOMAHM showed dramatic potential to be used as bio-based compounds to improve the properties of soybean-oil based thermosets.
基金financially supported by the National Natural Science Foundation of China(No.32460363)Yunnan Province Agricultural Joint Key Foundation(No.202401BD070001-029)+3 种基金as well as the Yunnan Provincial Youth top talent project(No.YNWR-QNBJ-2020-166)Foreign Expert Workstation(No.202305 AF150006)111 project(No.D21027)Yunnan Province Natural Science Key Foundation(No.202301AS070043)。
文摘In this study,epoxidized soybean oil(ESO)and ricinoleic acid(RA)were used to synthesize polyol esters,designated ESO-RA(ER)resin.The esters were further crosslinked with 4,4-diphenylmethane diisocyanate(PMDI)to create a biodegradable flame-retardant thermoset foam,referred to as ESO-RA-PMDI(ERP)foam,using water as a foaming agent.Additionally,flame retardants such as triethyl phosphate(TEP)and expanded graphite(EG)have been combined for foam preparation without the need for catalysts or foaming agents.The study findings showed that the incorporation of TEP and EG diminished the pulverization ratio while augmenting the compressive strength and shore hardness.Furthermore,the ERP foam exhibited exceptional flame retardant characteristics,as evidenced by a reported limiting oxygen index(LOI)value of 30.6vol%.A peak heat release rate of 97.12 kW/m^(2)was reported during the fire test.Significantly,a low peak smoke production rate(pSPR)of 0.026m^(2)/s and a total smoke production(TSP)of 0.62 m^(2)were achieved.In addition,ERP foam exhibited exceptional ultraviolet(UV)resistance,thermal insulation,and biodegradability.After 60 days of exposure to Penicillium sp.,foam containing both TEP and EG exhibited a mass loss of 9.39%,indicating that the incorporation of flame retardants did not negatively impact its biodegradability.
基金financially supported by the National Natural Science Foundation of China (Nos.U1909220 and 52003283)Science and Technology Innovation 2025 Major Project of Ningbo (Nos.2021Z092, 2022Z111 and 2022Z160)+1 种基金Defense Industrial Technology Development Program (No.JCKY2021513B001)the Research Project of Technology Application for Public Welfare of Ningbo City (No.202002N3122)。
文摘It is of great significance to design epoxy coatings with superior antibacterial properties and high adhesive properties, as well as excellent processing, superior durability, and high transparency. However, it is still a challenge because of the common complex design and synthesis. Herein, the bio-based monomer protocatechuic acid(PCA) was used as raw material, the catechol structure with high bonding and antibacterial properties was introduced into the flexible alkane segment of ethylene glycol diglycidyl ether(EGDE) through an efficient, and green method, and it was cured with isophorone diamine(IPDA) to prepare corresponding thermosets. The cured resins exhibited excellent allaround qualities, particularly in bonding and antibacterial. When 30% PCA was added to pure epoxy resin, the adhesion between substrate and coating increased from 4.40 MPa to 13.60 MPa and the antibacterial rate of coating against E. coli and S. aureus could approach 100%. All of this is due to the fact that the catechol structure present in PCA has the ability to interact with various substrates and alter the permeability of bacterial cell membranes. The architecture of this method offers a fresh approach to dealing with the issues of challenging raw material selection and complex synthesis techniques.
基金supported by the National Natural Science Foundation of China(No.51103174)Foundation for Young Talents in Institute of Coal Chemistry,Chinese Academy of Sciences(2011SQNRC12 Y1SC6L1781)
文摘Chemical degradation of diglycidyl ether of bisphenol A（DGEBA） epoxy resin cured with an aliphatic amine in supercritical 1-propanol was investigated under different reaction temperature and time. The combination of GC-MS and LC-MS proved that the epoxy resin was decomposed to five main products including phenol, 4-isopropylphenol, 4-isopropenylphenol, bisphenol A, and 4,4’-（cyclopropane-1,1-diyl）diphenol. The 13C-NMR results verified the chemical structures of the degradation products. The change of the products′ yield with time was evaluated by an effective means of HPLC. In addition, the GPC analysis confirmed the formation of soluble low molecular weight clusters during the degradation reaction. A possible free-radical reaction mechanism was proposed for chemical depolymerization of the epoxy resin in supercritical 1-propanol. After the homolytic cleavage of the aromatic ether linkages, the resulting bisphenol A biradical either produced 4,4’-（cyclopropane-1,1-diyl）diphenol after intramolecular rearrangement or generated bisphenol A after capturing hydrogen from 1-propanol.
文摘Nanocomposites from nanoscale silica particles（NS）,diglycidylether of bisphenol-A based epoxy（DGEBA）,and 3,5-diamino-N-（4-（quinolin-8-yloxy） phenyl） benzamide（DQPB） as curing agent were obtained from direct blending of these materials.The effect of nanosilica（NS） particles as catalyst on the cure reaction of DGEBA/DQPB system was studied by using non-isothermal DSC technique.The activation energy（E_a） was obtained by using Kissinger and Ozawa equations. The E_a value of curing of DGEBA/DQPB/10%NS system showed a decrease of about 10 kJ/mol indicating the catalytic effect of NS particles on the cure reaction.The E_a values of thermal degradation of the cured samples of both systems were 148 kJ/mol and 160 kJ/mol,respectively.The addition of 10%of NS to the curing mixture did not have much effect on the initial decomposition temperature（T_i） but increased the char residues from 20%to 28%at 650℃.
基金financially supported by the Fundamental Research Funds for the Central Universities (No.2572014EB06-02)National Natural Science Foundation of China (No.51673035)Heilongjiang Major Research Projects (No.GA15A101)
文摘A phosphorus-nitrogen containing flame retardant additive of poly（phosphoric acid piperazine）, defined as PPAP, was synthesized by the salt-forming reaction between anhydrous piperazine and phosphoric acid, and the dehydration polymerization under heating in nitrogen atmosphere. Its chemical structure was well characterized by Fourier transform infrared（FTIR） spectroscopy, ^（13）C and ^（31）P solid-state nuclear magnetic resonance measurements. The synthesized PPAP and curing agent m-phenylenediamine were blended into epoxy resin（EP） to prepare flame retardant EP thermosets. The effects of PPAP on the fire retardancy and thermal degradation behavior of cured EP/PPAP composites were investigated by limiting oxygen index（LOI）, vertical burning（UL-94）, thermogravimetric analysis/infrared spectrometry（TG-IR） and cone calorimeter tests. The morphologies and chemical compositions of char residues for cured epoxy resin were investigated by scanning electron microscopy（SEM） and X-ray photoelectron spectroscopy（XPS）, respectively. The results demonstrated that the flame retardant EP thermosets successfully passed UL-94 V-0 flammability rating and the LOI value was as high as 30.8% when incorporating 5 wt% PPAP into the EP thermosets. The TGA results indicated that the synthesized PPAP flame retardant additive possessed high thermal stability and excellent charring capability. Meanwhile, the incorporation of PPAP stimulated the epoxy resin matrix to decompose and charring ahead of time due to its catalytic decomposition effect, which led to a higher char yield at high temperature. The morphological structures and the analysis results of XPS for char residues of EP thermosets revealed that the introduction of PPAP benefited the formation of a sufficient, more compact and homogeneous char layer containing phosphorus-nitrogen flame retardant elements on the material surface during combustion. The formed char layer with high quality effectively prevented the heat transmission and diffusion, limited the production of combustible gases, and inhibited the emission of smoke, leading to the reduction of heat and smoke release.
基金the Italian Ministry of Ed-ucation and Research,PON R&I 2014-2020-Asse IV“Istruzione e ricerca per il recupero-REACT-EU”-Azione IV.6-“Contratti di ricerca su tematiche Green”,for the financial support concerning his employment contractThe work was partially supported by funds from the Zuercher Stiftung fuer Textilforshung(Winterthur,Switzerland).
文摘Polymers are indispensable to humans in different applications due to their ease of manufacturing and overall performance.However,after a material lifetime,there is a large amount of polymer-based waste,which greatly contributes to the loss of valuable resources and environmental pollution.Thermoplastics may be readily recycled,but because of their flammability,large amounts of flame retardant(FR)ad-ditives are required for many applications.This results in a significant volume of FR polymeric wastes too,particularly halogenated plastics,which are subject to severe recycling regulations.In general,ther-moplastics containing FRs are raising concerns,as their effective recycling is strongly influenced by the chemical composition,additive content,and physicochemical characteristics of the waste stream.The recycling of FR thermosets is even more challenging due to their crosslinked and cured nature,which makes them resistant to melting and reprocessing.In many cases,traditional mechanical recycling meth-ods,such as grinding and melting,are not applicable to thermosetting polymers.Current recycling meth-ods do not always consider the recovery of the thermosetting/thermoplastic matrix and the presence of toxic FRs in the polymer network.Sorting and solvent washing treatment are important steps,which are usually performed before recycling the FR polymeric waste to reduce contamination in the following steps.
基金financially supported by the National Natural Science Foundation of China(Nos.51803059,51873215 and 52003272)Beijing Natural Science Foundation of China(No.2204101)the Youth Innovation Promotion Association of CAS(No.2017047)。
文摘A novel boron-containing monomer,(4-(3,4-dicyanophenoxy)phenyl)boronic acid(BPhPN)was synthesized and used to promote the curing process of phthalonitrile monomer 1,3-bis(3,4-dicyanophenoxy)benzene(MPN).Differential scanning calorimetry and rheological analysis were used to study the curing behaviors of BPhPN/MPN(namely B-MPN),and results suggested that B-MPN systems have better processibility.FTIR spectra and solid-state 13C-NMR exhibited triazine and isoindoline have been formed in the curing process.Boron-containing Lewis acid curing mechanism was preliminarily speculated and verified by two model compounds with different boron chemical environments.The thermogravimetric analysis and dynamic mechanical analysis demonstrated that the cured B-MPN polymers showed excellent thermal stability and heat resistance,which were comparable with conventional catalytic systems for phthalonitrile resins.This study not only presented a novel curing system for phthalonitrile resins,but also shed light on future design of high temperature thermosets.
基金the foundational support by the Fundamental Research Funds for the Central Universities(BLX202132)the foundational support by the Beijing Youth Talent Funding Program-Visiting program for young foreign scholars(Q2023043)IIT(BHU)Varanasi.
文摘Due to their extraordinary durability and thermal stability,Epoxy Resin Thermosets(ERTs)are essential in various industries.However,their poor recyclability leads to unacceptable environmental pollution.In this study,Wu et al.successfully synthesized a completely bio-based ERT using lignocellulose-derived building blocks which exhibit outstanding thermal and mechanical properties.Remarkably,these bio-materials degrade via methanolysis without the need of any catalyst,presenting a smart and cost-effective recycling strategy.Furthermore,this approach could be employed for fabricating reusable composites comprising glass fiber and plant fiber,thereby expanding its applications in sustainable transportation,coatings,paints or biomedical devices.
文摘Stiffened thermosetting composite panels were fabricated with co-curing processing.In the co-curing processing,the temperature distribution in the composite panels was nonuniform.An investigation into the threedimensional cure simulation of T-shape stiffened thermosetting composite panels was presented.Flexible tools and locating tools were considered in the cure simulation.Temperature distribution in the composites was predicted as a function of the autoclave temperature history.A nonlinear transient heat transfer finite element model was developed to simulate the curing process of stiffened thermosetting composite panels.And a simulation example was presented to demonstrate the use of the present finite element procedure for analyzing composite curing process.The glass/polyester structure was investigated to provide insight into the nonuniform cure process and the effect of flexible tools and locating tools on temperature distribution.Temperature gradient in the intersection between the skin and the flange was shown to be strongly dependent on the structure of the flexible tools and the thickness of the skin.
文摘The morphological structure of various epoxies toughened with a special amorphous thermoplastic PEK-C and their carbon fiber composites were studied by using SEM. For both cases, phase separation and inversion took place to form fine epoxy-rich globules dispersing in the PEK-C matrix, in which the epoxy-rich phase had the absolutely higher volume fraction. The phase structure and the interfacial properties were also studied by means of FTIR, DSC, and DMTA as well. An accompanying mechanical determination revealed that an improved toughness was achieved both in the blend casts and in the carbon fiber composites. A composite structural model was hence suggested.
