Effect of Functionalized Magnetite Nanoparticles and Diaminoxanthone on the Curing,Thermal Degradation Kinetic and Corrosion Property of Diglycidyl Ether of Bisphenol A-Based Epoxy Resin

To prepare a high-performance epoxy resin with excellent thermal, chemical and corrosion stability, diaminoxanthone（DAX） was used to cure diglycidylether of bisphenol-A（DGEBA）-based epoxy resin and blend of DGEBA with functionalized Fe3O4 nanoparticles. Kinetic parameters of curing and thermal degradation of epoxy resin systems were estimated by differential scanning calorimetry（DSC） and thermogravimetric analysis（TGA）, respectively. The 10% weight loss temperature has been increased from 340 °C to 366 °C and there was an increase in the char yield from 32.6% to 45.3% for the above systems. The corrosion performance of epoxy coated carbon steel was examined by potentiodynamic polarization, along with immersion test in 1.0 mol/L HCl solution. The results showed that epoxy resins cured with DAX had low tendency to corrosion. In addition, the cured epoxy resin containing 10% Fe3O4 had higher anticorrosion activity than bare DGEBA system. The results showed that functionalized Fe3O4 nanoparticles enhanced char formation and improved the thermal stability as well as anticorrosion activity of the resin.     

PHASE STRUCTURE AND PROPERTIES OF EPOXY RESIN MODIFIED BY POLYSILOXANE BEARING PENDANT AMINO GROUPS

Polysiloxane-modified epoxy resins were prepared through the reaction of epoxy resin with polydimethylsiloxanesbearing pendant N-(β-aminoethyl)-γ-aminopropyl groups. The morphology and properties of the cured epoxy resins modifiedby the polysiloxanes were investigated. It was found that the phase structure and properties of the cured epoxy resins dependmainly on the amino group content in the polydimethylsiloxane and the level of the modifier. The change of phase structurein the cured epoxy resin systems was responsible for the dramatic change in their mechanical and surface properties.     

EPOXY RESINS TOUGHENED WITH CARBOXYL TERMINATED POLYETHERS

Carboxyl terminated polyethers, the adducts of hydroxyl terminated polytetrahydrofuran and maleic anhydride, were used as toughener for epoxy resins. The morphology of the toughened resins was investigated by means of turbidity measurement, dynamic mechanical testing and scanning electron microscope observation. It turned out that the molecular weight and the carboxyl content of the polyether and the cure conditions are important factors, which affect the particle size of the polyether-rich domains and, in turn, the mechanical properties of the cured resin. Carboxyl terminated polytetrahydrofurans have a low glass transition temperature, and in appropriate amount they do not affect the thermal resistance of the resin. These advantages make them preferable as toughener for epoxy resins.     

SYNTHESIS OF A NEW SILICONE-CONTAINING BISMALEIMIDE COPOLYMER RESIN

A copolymer of bismaleimide-diallylbisphenol A-diphenylsilandiol was synthesized andthe copolymerization was studied by using N-phenylmaleimide, bisphenol A and diphenyl-silandiol as model compounds. The copolymer could be well cured around 200℃, andthe cured resins had good thermal stability In the range of 170-210℃, a higher curingtemperature was favorable to obtain more thermal stable resin by reducing the content ofdiphenylsilandiol cyclo-homopolymer in resin which would spoil its thermal stability     

A novel epoxy methacrylate resin containing phthalazinone moiety for UV coatings

A novel phthalazinone modified epoxy acrylate resin for the high temperature resistant ultravioet (UV) curable coating was synthesized. The methacrylated epoxy resins obtained were utilized to UV radiation curing by taking 2.5% (wt%) of photoinitiator in combination with 20% (wt%) of diluent, and generated the interpenetraring polymer networks. The cured film had good thermal and chemical stability.     

MODIFICATION OF EPOXY RESIN WITH POLYSILOXANE BEARING PENDANT QUATERNARY AMMONIUM GROUPS

Polysiloxane bearing pendant quaternary ammonium groups (PSI) was used to modify the surface properties ofepoxy resins. In the cured resin, PSI formed the dispersed phase. Remarkable enrichment and gradient distribution ofpolysiloxane on the surface region of the epoxy resins were demonstrated by XPS analysis. The composition and propertiesof the surface of PSI-modified epoxy resin, which is in contact with the mold, are dependent on the material of the mold.Through the incorporation of PSI, epoxy resins with low surface energy and low friction coefficient were obtained.Polysiloxane with lower ionic group content shows a higher degree of enrichment on the resin surface and leads to a highercontact angle against water, while the polysiloxane having optimum compatibility with the epoxy resin shows a greater effectin reducing the static friction coefficient of the resin against glass.     

Curing kinetics and thermal stability of epoxy blends containing phosphorous-oxirane with aromatic amide-amine as curing agents

This article describes the synthesis of a series of aromatic amide-amines and their potential use as epoxy hardeners. These amines were synthesized by the reaction of L-phenylalanine（PA） with diamines of different structures i.e.1,4- phenylene diamine（PD）,1,5-diamino naphthalene（N）,4,4’-（9-fluorenyllidene）-dianiline（F）,4,4’-diaminodiphenyl sulphide （DS） and 3,4’-oxydianiline（O） in a stoichiometric ratio（1:1）.Structural characterization of synthesized amide-amines was done with the help of elemental analysis and spectroscopic techniques viz.FT-IR,¹H-NMR and ¹³C-NMR.An epoxy blend was prepared by mixing tris（glycidyloxy） phosphine oxide（TGPO） with conventional epoxy i.e.diglycidyl ether of bisphenol-A（DGEBA） in an equivalent ratio of 2:3 to incorporate phosphorous into the main chain.The curing kinetics of the epoxy blend with synthesized aromatic amide-amines was investigated by non-isothermal DSC technique using multiple heating rate method（5,10,15 and 20 K/min.）.The activation energies were determined by fitting the experimental data into Kissinger and Ozawa kinetic models.The activation energies obtained through Ozawa method were slightly higher than those of Kissinger method but were comparable.However,both the energies were found to be dependent on the structure of amines.The thermal stability and weight loss behavior of isothermally cured thermosets were also investigated using thermogravimetric analysis（TGA） in nitrogen atmosphere.All the samples showed improved thermal stability in terms of char yield than using only amines as hardeners.     

乙酰丙酮金属络合物对酸酐固化环氧树脂体系潜伏性促进作用的研究

A transition metal acetylacetone was studied as latent accelerator in the curing of anhydride cured epoxy resin by DSC, TEA, and rotation viscometer technique. The results reveal that the metal acetylacetone serves as an latent accelerator for anhydride curable epoxy resin system, and the rate of curing is found to increase with enhanced concentrations of the metal chelate. The system provides very fast gel time at 160-180℃ and combined with very good storage stability (> two months). Curing kinetic studies reveal that the overall suring process follows first order kinetics. The electrical,mechanical and thermal properties of cured com-pound of epoxy resin system catalyzed by the M_T(acac)_n and BDMA accelerator and cured by anhydride was also studied and compared in this paper.     

Preparation and Characterization of DGEBA/EPN Epoxy Blends with Improved Fracture Toughness

The physical and mechanical properties of blends composed of two kinds of epoxy resins of different numbers of functional groups and chemical structure were studied.One of the resins was a bifunctional epoxy resin based on diglycidyl ether ofbisphenol A and the other resin was a multifunctional epoxy novolac resin.Attempt was made to establish a correlation between the structure and the final properties of cured epoxy samples.The blend samples containing high fraction of multifunctional epoxy resin showed higher solvent resistance and lower flexural modulus compared with the blends containing high fraction of bifunctional epoxy resin.The epoxy blends showed significantly higher ductility under bending test than the neat epoxy samples.The compressive modulus and strength increased with increasing of multifunctional epoxy in the samples,probably due to enhanced cross-link density and molecular weight.Morphological analysis revealed the presence of inhomogeneous sub-micrometer structures in all samples.The epoxy blends exhibited significantly higher fracture toughness (by 23％ at most) compared with the neat samples.The improvement of the fracture toughness was attributed to the stick-slip mechanism for crack growth and activation of shear yielding and plastic deformation around the crack growth trajectories for samples with higher content of bifunctional epoxy resin as evidenced by fractography study.     

Characterization and thermal stability of PMR polyimides using 7-oxa-bicyclo[2,2,1]hept-5-ene-2, 3-dicarboxylic anhydride as end caps

An anhydride monomer containing ether oxide bridge,7-oxa-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic anhydride (ONA),was successfully synthesized by Diels-Alder reaction of furan and maleic anhydride.The ONA was also studied as an end-cap for the polymerization of monomer reactant(PMR) type polyimides.Three molecular weight levels of the ONA end-capped PMR resins were evaluated.The effects of process conditions of these novel PMR resins on thermal and mechanical properties were investigated.It was demonstrated that the imidized prepolymers using the end-cap have good processability,and the cured polyimide specimens exhibited good thermal stability.The initial decomposition temperature, T_d(ca.580℃) and glass transition temperature,T_g(330℃) of the novel resin(PI-20),prepared under optimum process conditions,compare favorably with the T_d(ca.620℃) and T_g(ca.348℃) of the state-of-the-art resin(PI’-20),respectively.     

含芳基噻唑基团环氧树脂材料的制备及热性能

制备了一种含芳基噻唑基团热稳定环氧树脂材料(TDABZ),通过傅里叶变换红外光谱(FTIR)对其结构进行了表征,采用热重分析-微熵热重分析(TGA-DTG)计算了TDABZ的热分解动力学参数,利用热重分析(TGA)和动态热机械分析(DMTA)探讨了TDABZ的耐热性能。 结果表明,TDABZ通过TGDDM结构中的环氧基团与混合固化剂(DDS和2-ABZ)结构中的活泼氢反应,在较低的温度下就能完全交联固化。 通过Kissinger和Ozawa方法求得TDABZ的热分解活化能分别为205.5和221.9 kJ/mol。 TDABZ固化物具有优异的耐热性能,双悬臂梁法测得的玻璃化转变温度(T_g)达到242.3 ℃,在N₂气气氛下失重5%对应的温度(T_d5)为340.2 ℃,最大失重速率对应的温度(T_dmax)为395.5 ℃,600 ℃的质量保留率为24.1%,显著提高了环氧树脂的热稳定性能,拓宽了其应用领域。     

Thermal and flame retardant properties of epoxy resin cured by a novel phosphorus-containing 4,4′-bisphenol novolac curing agent

A novel flame retardant curing agent for epoxy resin (EP), i.e., a DOPO (9,10-dihydro-9-oxa-10-phosphaphenan-threne-10-oxide)-containing 4,4'-bisphenol novolac (BIP-DOPO) was synthesized and characterized by Fourier transform infrared (FTIR), ¹H NMR, ³¹P NMR spectroscopy, and gel permeation chromatography. The epoxy resin cured by BIP-DOPO itself or its mixture with a commonly used bisphenol A-formaldehyde novolac resin (NPEH720) was prepared. The flame retardancy of the cured EP thermosets were studied by limiting oxygen index (LOI), UL 94 and cone calorimeter test (CCT), and the thermal properties by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results show that the cured epoxy resin EPNP/BI/3/1, which contains 2.2% phosphorus, possesses a value of 26.2% and achieves the UL 94 V-0 rating. The data from cone calorimeter test demonstrated that the peak release rate, average heat release rate, total heat release decline sharply for the flame retarded epoxy resins, compared with those of pure ones. DSC results show that the glass-transition temperatures of cured epoxy resins decrease with increasing phosphorus content. TGA indicates that the incorporation of BIP-DOPO promotes the decomposition of epoxy resin matrix ahead of time and leads to higher char yield. The surface morphological structures of the char residues reveal that the introduction of BIP-DOPO benefits to the formation of a continuous and solid char layer on the epoxy resin material surface during combustion.     

含硅磷杂化物环氧树脂固化物性能研究

首先用γ-环氧丙氧基三甲氧基硅烷(KH-560)和亚磷酸二乙酯(DEP)反应的中间产物进行水解缩合反应,合成了一种含磷低聚硅氧烷杂化物.并用FTIR,NMR,GPC对其结构及分子量进行了表征.然后将含磷低聚硅氧烷引入到双酚A环氧树脂(E-54)制备硅磷杂化物环氧树脂的固化物.对这种含硅磷杂化物环氧树脂固化物的性能研究发现其极限氧指数为23～29,DSC分析结果玻璃化转变温度(Tg)可以达到204℃,失重5%的温度(Td)5%比纯E-54提高近20℃.该固化物具有阻燃性能,同时具有较好的热性能。     

Preparation,flame retardancy,and thermal degradation of epoxy thermosets modified with phosphorous/nitrogen‐containing glycidyl derivative

Phosphorus/nitrogen‐containing advanced epoxy resins were obtained by chain‐extension of the diglycidyl ether of bisphenol‐A epoxy (DGEBA) resin with phosphorus‐modified triglycidyl isocyanurate (TGICP). The structure of TGICP was characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). Differential scanning calorimetry revealed that the EP/TGICP composites possessed higher glass transition temperatures than that of phosphorus free EP. The thermal stability and flame retardant properties of the epoxy resin/TGICP systems were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), and vertical burning test (UL‐94) test. When the TGICP content was 10 wt%, the LOI value of epoxy resin system was as high as 35.0% and it can obtain the V‐0 grade in UL‐94 protocol. From microscale combustion calorimetry (MCC) measurement, it was found that the addition of TGICP reduced the value of peak heat release rate and total heat release. The thermal degradation process of EP and EP/TGICP composite was monitored by real time FTIR. Moreover, scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS) were used to explore the morphology and chemical components of the char residues. Copyright © 2010 John Wiley & Sons, Ltd.     

Epoxy-modified, unsaturated polyester hybrid networks

Hybrid polymer networks (HPNs) based on unsaturated polyester resin (UPR) and epoxy resins were synthesized by reactive blending. The epoxy resins used were epoxidised phenolic novolac (EPN), epoxidised cresol novolac (ECN) and diglycidyl ether of bisphenol A (DGEBA). Epoxy novolacs were prepared by glycidylation of the novolacs using epichlorohydrin. The physical, mechanical, and thermal properties of the cured blends were compared with those of the control resin. Epoxy resins show good miscibility and compatibility with the UPR resin on blending and the co-cured resin showed substantial improvement in the toughness and impact resistance. Considerable enhancement of tensile strength and toughness are noticed at very low loading of EPN. Thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) were employed to study the thermal properties of the toughened resin. The EPN/UPR blends showed substantial improvement in thermal stability as evident from TGA and damping data. The fracture behaviour was corroborated by scanning electron microscopy (SEM). The performance of EPN is found to be superior to other epoxy resins.     

Flame retardant epoxy polymers based on all phosphorus-containing components

A phosphorus-containing epoxy resin, bis(3-t-butyl-4-glycidyloxyphenyl-2,4-di-t-butylphenyl)resorcinol diphosphate, was synthesized and subsequently cured with non-phosphorus containing amines, and/or novel phosphorus-containing aromatic or polyoxyalkylene amines. Chemical structures of these materials were characterized with FTIR, NMR, elemental analysis, and amine titration. The introduction of soft -P-O- linkage, polyoxyalkyene, or hard aromatic group into the backbones of the synthesized phosphorus-containing amines provides epoxy polymers with high phosphorus contents and tailored flexibility. Thermal analysis of differential scanning calorimeter and thermal gravimetric analysis (TGA) reveals that these resulted epoxy polymers possess moderate T_gs and thermal stability. Furthermore, high char yields in TGA analysis and high limited oxygen index values indicate that these phosphorus-containing epoxy polymers possess excellent flame retardant properties.     

A flame-retardant epoxy resin based on a reactive phosphorus-containing monomer of DODPP and its thermal and flame-retardant properties

A flame-retardant epoxy resin (EP) was synthesized based on a novel reactive phosphorus-containing monomer, 4-[(5,5-dimethyl-2-oxide-1,3,2-dioxaphosphorinan-4-yl)oxy]-phenol (DODPP), and its structures were characterized by FTIR, ¹H NMR and ³¹P NMR spectra. The DODPP-EP₃/LWPA (low molecular weight polyamide), which contains 2.5% phosphorus, can reach UL-94 V-0 rating and a limiting oxygen index (LOI) value of 30.2%. The thermal properties and burning behaviours of cured epoxy resins were investigated by differential scanning calorimeter (DSC), thermogravimetry (TG), LOI, UL-94 tests and cone calorimetry. The morphologies of residues of cured epoxy resins were investigated by scanning electron microscopy (SEM). DSC shows that the glass-transition temperatures of cured epoxy resins decrease with increasing phosphorus content. TGA shows that the onset decomposition temperatures and the maximum-rate decomposition temperatures decrease, while char yields increase, with the increase of phosphorus content. The data from the cone calorimeter tests give the evidence that heat release rate (HRR), peak heat release rate (PHRR), average heat release rate (Av-HRR), average mass loss rate (Av-MLR) and the fire growth rate index (FIGRA) decrease significantly for DODPP-EP₃/LWPA. SEM shows that the DODPP-EP₃/LWPA forms lacunaris and compact charred layers which inhibit the transmission of heat during combustion.     

Synthesis and thermal characterization of phosphorus containing siliconized epoxy resins

Siliconized epoxy matrix resin was developed by reacting diglycidyl ethers of bisphenol A (DGEBA) type epoxy resin with hydroxyl terminated polydimethylsiloxane (silicone) modifier, using γ-aminopropyltriethoxysilane crosslinker and dibutyltindilaurate catalyst. The siliconized epoxy resin was cured with 4, 4-diaminodiphenylmethane (DDM), 1,6-hexanediamine (HDA), and bis (4-aminophenyl) phenylphosphate (BAPP). The BAPP cured epoxy and siliconized epoxy resins exhibit better flame-retardant behaviour than DDM and HDA cured resins. The thermal stability and flame-retardant property of the cured epoxy resins were studied by thermal gravimetric analysis (TGA) and limiting oxygen index (LOI). The glass transition temperatures (T_g) were measured by differential scanning calorimetry (DSC) and the surface morphology was studied by scanning electron microscopy (SEM). The heat deflection temperature (HDT) and moisture absorption studies were carried out as per standard testing procedure. The thermal stability and flame-retardant properties of the cured epoxy resins were improved by the incorporation of both silicone and phosphorus moieties. The synergistic effect of silicone and phosphorus enhanced the limiting oxygen index values, which was observed for siliconized epoxy resins cured with phosphorus containing diamine compound.     

Preparation of Poly(phosphoric acid piperazine) and Its Application as an Effective Flame Retardant for Epoxy Resin

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,13C and 31p 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 5wt％ 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.