固化体系对环氧树脂耐高温性能的影响

针对覆铜板的耐高温要求,分别使用胺类固化剂4,4′-二氨基二苯砜(DDS)、4,4′-二氨基二苯醚(DDE)和乙二胺(EDA)固化改性双酚A型环氧树脂,研制适用于耐高温覆铜板的环氧树脂固化物。用示差扫描量热法(DSC)研究其固化过程,讨论了固化剂用量、固化剂种类及固化温度等因素对固化物玻璃化转变温度(Tg)的影响。实验结果表明,固化物耐热性最好的配比不是化学计量,而是偏离化学计量,在理论用量的基础上适当增加固化剂用量,可有效地提高固化产物的玻璃化温度Tg值;使用芳香胺类固化剂固化双酚A型环氧树脂,其固化产物有较高的玻璃化温度,可以满足覆铜板耐高温的要求。     

先进复合材料基体树脂的增韧研究

通过4种聚醚酰亚胺(PEI)PID、PIM、PIP和PIB改性3种热固性树脂(环氧、氰酸酯以及双马来酰亚胺树脂)的研究,讨论了PEI结构、用量、分子质量以及固化剂用量等因素对改性体系的相结构以及力学性能的影响,结果表明控制相结构是增韧基体树脂的关键因素,对基体树脂增韧的研究有指导意义。对不同的热固性树脂体系需采用不同的结构、配方和固化工艺。PIP改性环氧体系呈现的双连续相结构,PEI改性双马来酰亚胺体系,PEI质量分数为5%时呈现了PIM分散粒子相结构,PEI质量分数为10%时呈现了双连续相结构而PEI质量分数大于15%时呈现了相反转结构,PIP分子质量为18 000或20 000时呈现了双连续相结构,而对于PIP改性氰酸酯体系高PIP分子质量较低的呈现双连续相结构,该体系在120℃固化6 h呈现相反转结构,而150℃或180℃固化形成双连续相结构,双连续相结构增韧效果明显。     

双酚A型环氧树脂/芳香胺固化体系的固化动力学研究

分别以4,4‘-二氨基二苯甲烷（DDM）和4,4‘-二氨基二苯砜（DDS）为固化剂，采用非等温差示扫描量热法（DSC）研究了E-44和E-51两种双酚A型环氧树脂的固化反应动力学。收集与分析了在25～350℃范围内分别以5、10、15、20℃/min的升温速率进行固化的反应参数，然后采用Starink法计算得到不同环氧固化体系的表观活化能。同时，借助各固化体系的动态流变性能，分析了双酚A型环氧树脂/芳香胺固化体系的固化反应机理，并选用双参数自催化模型计算了各固化体系的反应速率方程。研究结果表明：当环氧固化体系的固化剂不同时，采用DDM作为固化剂的环氧固化体系（E-44/DDM、E-51/DDM），其表观活化能均低于添加DDS固化剂的环氧体系；选用同种固化剂（DDM或DDS）时，E-51树脂体系的表观活化能均低于E-44树脂固化体系。反应速率方程结果显示，该双参数自催化模型与实际试验结果的吻合性良好，可用于描述双酚A型环氧树脂/芳香胺固化体系的固化历程。     

四溴双酚A环氧树脂/二氨基二苯砜固化过程的研究

用高分子材料动态力学谱仪 (TBA)、示差扫描量热仪 (DSC)等方法研究了二氨基二苯砜 (DDS)固化四溴双酚A环氧树脂 (TBBPAER)的固化过程 ,讨论了固化时间、固化剂用量及固化剂的种类等因素对固化物玻璃化转变温度 (Tg)的影响。实验结果表明 ,随着固化时间的延长 ,固化产物的玻璃化转变温度逐渐升高 ,并且在固化初始阶段为一个值 ,到固化中间阶段变为两个值 ,最后到固化末期又为一个值 ,显示出固化产物的结构有所不同 ;适当增加固化剂的用量未超过理论用量的 2 0 %之前 ,可有效地提高固化产物的玻璃化转变温度Tg值 ;选择不同的固化剂 ,可获得具有不同玻璃化转变温度Tg值的固化产物。     

双环戊二烯酚型环氧树脂的固化反应研究

研究了ＤＣＰＤ酚环氧树脂与酸酐及胺类固化剂的固化反应活性。通过ＤＳＣ热分析方法表征了ＤＣＰＤ酚环氧树脂与甲基六氢苯酐（ＭeHHPA)及４,４′－二氨基二苯甲烷（ＤＤＭ）的固化反应过程,测定了反应热焓,并分析了固化温度、时间及固化剂结构等对ＤＣＰＤ酚环氧树脂凝胶时间及固化度的影响,探讨了温度、时间对ＤＣＰＤ酚环氧树脂固化反应活性的影响。     

新型耐热环氧单体的合成及性质研究

报道了一种含萘芳香酯型环氧单体二（4-（2,3-环氧丙氧基）苯甲酸）．2,7-萘4,4-二酯（P4）的合成及性质研究。利用FT-IR、1HNMR、质谱等分析测试方法对P4目标化合物的结构进行了表征。并用4,4．二氨基二苯基砜（DDS）和4,4-二氨基二苯基甲烷（DDM）两种芳香二胺固化剂对P4进行非等温固化研究。由结果可知,DDM／P4的固化峰温度为140℃,DDS／P4的固化峰温度为210℃,DDM能显著降低P4的固化温度。最后,通过对P4／DDM和环氧E20／DDM这两种固化物的热失重研究表明P4／DDM固化物具有较高的热稳定性。     

常温固化自乳化型水性环氧固化剂的制备及性能研究

以聚乙二醇、环氧树脂E20、间苯二甲胺（MXDA）为原料、过硫酸钾为催化剂，合成了一种非离子型常温固化自乳化型水性环氧固化剂。系统优化了反应温度、时间、催化剂用量以及原料配比对固化剂性能的影响，利用红外光谱对固化剂进行结构表征，测试了基于该固化剂乳化固化环氧树脂E44所得涂层的性能。结果表明：当过硫酸钾用量占环氧树脂和聚乙二醇总量的0.75%、n（环氧树脂）∶n（聚乙二醇）∶n(MXDA)=1∶1∶4，反应温度为180℃、时间为4 h时，所得涂膜的机械性能、耐腐蚀性能优异。     

粘度调节剂对制备环氧树脂微球的影响

研究粘度调节剂对环氧树脂/二氨基二苯基砜/聚醚酰亚胺(EP/DDS/PEI)共混物相结构及制备EP微球的影响。结果表明,共混物中加入粘度调节剂后,固化过程中共混体系的粘度明显降低,随着粘度调节剂用量的增加,EP分散相尺寸逐渐增大,制得的EP微球粒径及粒径分布指数逐渐增大。EP微球的红外光谱显示粘度调节剂对EP微球的成分和相结构没有明显影响。     

碱催化2步法制备SiO2/环氧树脂杂化材料的研究

以氨水为催化剂,以二氨基二苯砜(DDS)为固化剂,采用2步法制备二氧化硅/环氧树脂(SiO2/环氧树脂)杂化材料.分析了正硅酸乙酯(TEOS)用量对SiO2/环氧树脂杂化材料化学结构、力学性能和热性能的影响.结果表明,TEOS的加入没有改变固化物的化学结构.拉伸和弯曲模量均随TEOS用量增加先增加后降低,当TEOS质量...     

丁烯二醇基环氧树脂的合成及其性能研究

以丁烯二醇为原料，采用固碱法，配合相转移催化剂，与环氧氯丙烷反应，合成一种脂肪族且含双键的环氧树脂。采用红外光谱、核磁共振氢谱、盐酸-丙酮法滴定对产物结构进行表征。将树脂与4,4’-二氨基二苯基甲烷（DDM）固化后，研究树脂-固化剂的比例对固化物力学性能的影响。通过差示扫描量热仪测定固化物的玻璃化转变温度。通过溶胀法测定固化物的交联密度参数。结果表明：树脂-固化剂比例为1.0∶1.5时，固化物性质偏向塑料，具有较大的强度与较小的韧性。树脂-固化剂比例为1.0∶2.5时，固化物具有较好的韧性与适中的强度，性质偏向较硬的橡胶。     

Morphology effect on water sorption behavior in a thermoplastic modified epoxy resin system

Water sorption behavior in polyetherimide (PEI) modified diglycidyl ether bisphenol-A/4,4′-diaminodiphenyl sulfone (DGEBA/DDS) systems was investigated by gravimetric analysis, positron annihilation lifetime spectroscopy and scanning electron microscopy. The equilibrium water uptake showed strong composition-dependent, which suggested that hydrophilic groups rather than free volume were more significant in determining ultimate water sorption. While besides the number of hydrophilic groups and fractional free volume, morphology induced by phase separation was another key factor that decided the value of diffusion coefficient, which was chiefly responsible for the anomalous diffusion behavior observed at the beginning of co-continuous phase. In addition, morphology not only had the function of decreasing fractional free volume, but also changed the number of hydrophilic groups in epoxy rich regions, which obviously distinguished water sorption behavior in the blends from that in single component systems.     

Phase separation and rheological behavior during curing of an epoxy resin modified with syndiotactic polystyrene

The phase separation and crystallization processes occurring in a semicrystalline thermoplastic‐(epoxy/amine) system were studied by using dynamic oscillatory rheometry and differential scanning calorimetry (DSC). Moreover, a transmission optical microscope (TOM) equipped with a hot stage was used to get a direct representation of the obtained morphologies at different times during the phase separation and crystallization processes. The morphology of the cured samples was additionally studied by atomic force microscopy (AFM). The selected thermoset system was diglicydylether of bisphenol‐A (DGEBA) cured with 4,4′‐methylene bis (3‐chloro‐2,6‐diethylaniline) (MCDEA) and modified with syndiotactic polystyrene (sPS). In the initially miscible semicrystalline thermoplastic/thermoset system, phase separation is induced by the curing reaction (reaction‐induced phase separation [RIPS]) and by crystallization of the thermoplastic (crystallization induced phase separation [CIPS]). Both phenomena take place almost at the same curing time and both have strong influence on the morphology of cured samples. POLYM. ENG. SCI. 45:303–313, 2005. © 2005 Society of Plastics Engineers.     

Morphology profiles generated by temperature gradient in PMMA modified epoxy system

A diglycidyl ether of bisphenol‐A (DGEBA) epoxy resin was modified with 15 wt% of poly(methylmethacrylate) (PMMA) and cured with a stoichiometric amount of 4,4′‐diamino diphenyl methane (DDM). The reactive mixture was cured in a heated mold with different gradients of temperature. Temperature profiles in the mold were imposed by generation of a heat flux from the base, supported on a hot plate, and the top, cooled with water; they were measured along the mold. Depending on the thermal history in each position of the mold, the competition between the phase‐separation process and reaction kinetics produces opaque or transparent zones. Phase separation can also occur in the postcure process while the gelation does not take place before. Therefore, a thermoset plate with gradient of morphology and properties was obtained. Mass fractions of PMMA dissolved in the matrix were calculated with the Fox equation from glass transition temperatures measured along the mold. They were related to morphologies developed during curing. The superposition of the phase diagrams with the conversion‐temperature trajectories during cure permitted an explanation of the morphology gradients generated.     

Morphology profiles obtained by reaction‐induced phase separation in epoxy/polysulfone/poly(ether imide) systems

The reaction‐induced phase separation in epoxy/aromatic diamine formulations simultaneously modified with two immiscible thermoplastics (TPs), poly(ether imide) (PEI) and polysulfone (PSF), has been studied. The epoxy monomer was based on the diglycidyl ether of bisphenol A (DGEBA) and the aromatic diamine was 4,4′‐methylenebis(3‐chloro 2,6‐diethylaniline) (MCDEA). Phase‐separation conversions are reported for various PSF/PEI proportions for blends containing 10 wt% total TP. On the basis of phase‐separation results, a conversion–composition phase diagram at 200 °C was compiled. This diagram was used to design particular cure cycles in order to generate different morphologies during the phase‐separation process. It was found that, depending on the PSF/PEI ratio employed, a particulate or a morphology characterized by a distribution of irregular PEI‐rich domains dispersed in an epoxy‐rich phase was obtained for initially miscible blends. Scanning electron microscopy (SEM) characterization revealed that the PEI‐rich phase exhibits a phase‐inverted structure and the epoxy‐rich matrix presents a bimodal size distribution of TP‐rich particles. For PSF/PEI ratios near the miscibility limit, slight temperature change result in morphology profiles. Copyright © 2005 Society of Chemical Industry     

Organically modified layered-silicates facilitate the formation of interconnected structure in the reaction-induced phase separation of epoxy/thermoplastic hybrid nanocomposite

We incorporated organic modified layered silicates (OLS) into the mixture of epoxy and poly(ether imide) (PEI) to obtain a ternary hybrid nanocomposite and investigated its reaction-induced phase separation behavior. We found that OLS had dramatic impact to the phase separation process and the final phase morphology. The onset of phase separation and the gelation or vitrification time were greatly brought forward and the periodic distance of phase-separated structure was reduced when OLS was incorporated. Phase separation of the unfilled specimens was greatly suppressed at temperatures higher than 190 °C, and no etch hole of PEI-rich phase could be observed in the SEM images. An interconnected, or bicontinuous morphology could only be observed at cure temperatures lower than 140 °C. On the contrary, the OLS-filled hybrid nanocomposites carried out obvious phase separation at cure temperatures ranging from 120 to 220 °C. Even at cure temperatures higher than 190 °C, the hybrid nanocomposites had an interconnected phase-separated microstructure. These phenomena were related to the preferential wettability, chemical reaction of OLS with epoxy oligomer and the enhanced viscosity of the mixture.     

Modeling of Multi-Autocatalytic Cure Reactions of An Epoxy/Amine Terminated Polyetherimide/NMA System

Summary Amine terminated polyetherimide (ATPEI) as a modifier for epoxy resin was synthesized, then blended with a diglycidyl ether bisphenol A (DGEBA)/nadic methyl anhydride (NMA)/catalyst. A study on cure kinetics and morphology was conducted for a blend of a DGEBA/NMA/Catalyst/ATPEI (5phr) system. In the curing process, two major reactions were observed. Each reaction was identified, and a novel model equation for the cure kinetics is suggested.     

Polyetherimide-modified epoxy networks: Influence of cure conditions on morphology and mechanical properties

The morphologies and mechanical properties of thermoplastic-modified epoxy networks generated through the reaction-induced phase separation procedure were studied as a function of isothermal cure conditions. The selected model system was diglycidyl ether of bisphenol A cured with 4,4′-methylenebis [3-chloro,2,6-diethylaniline] in the presence of a nonfunctionalized polyetherimide. Appropriate precuring and postcuring schedules were selected. The precure temperature had a strong effect on final morphologies because it affected the viscosity of the system at the cloud point and the extent of the separation process. The morphologies generated are discussed in connection with phase separation mechanisms. The ratio of the height of the loss peaks corresponding to each phase was an appropriate parameter to qualitatively predict the shape of morphology and to determine if the system was phase-inverted or not. The fracture toughness, K_Ic was significantly improved only when bicontinuous or inverted structures were generated, resulting from the plastic drawing of the thermoplastic-rich phase. Before phase inversion, K_Ic was hardly higher than that of the neat matrix due to poor interfacial adhesion. Nevertheless, the thermoplastic-rich particles constitute obstacles to the propagation of the crack and contribute to the toughening of the material, measured through impact resistance measurements. The observation of fracture surfaces revealed the occurrence of microcracking and crack-pinning. Strain recovery experiments showed that particle-induced shear yielding of the matrix was present as well. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2433–2445, 1997     

Dielectric properties and their dependence of polyetherimide/bismaleimide blends for high performance copper clad laminates

Developing high performance matrix for High Performance Copper Clad Laminates (HPCCLs) has been a fascinating focus in the micro-electric industry since the beginning of this century. This article presents the first report on investigating the dielectric properties of a blend system (PEI/BD) based on polyetherimide (PEI) and o,o′-diallyl bisphenol A (DBA) modified 4,4′-bismaleimidodiphenyl methane (BDM), and discussing the dependence of dielectric properties on morphology, frequency and absorbed water. Results show that the morphology of the blend changes from a dispersed phase to completely co-continuous phase and perfect phase inversion, successively, as the content of PEI in the blend is increased. The dielectric properties of the PEI/BD system are not only frequency-dependent, but also morphology-dependent and moisture-dependent. The very good water resistance and extremely stable dielectric properties suggest that PEI/BD blends have great potential to be the matrices for fabricating HPCCLs and other advanced composites.     

Phase separation time/temperature dependence of thermoplastics-modified thermosetting systems

The cure-induced phase separation processes of various thermoplastics(TP)-modified thermosetting systems which show upper critical solution temperature (UCST) or lower critical solution temperature (LCST) were studied with emphasis on the temperature dependency of the phase separation time and its potential application in the cure time-temperature processing window. We found that the phase separation time/temperature relationship follows the simple Arrhenius equation. The cure-induced phase separation activation energy E_a(ps) generated from the linear fitting of the Arrhenius equation is irrelevant to the detection means of phase separation time. We also found that E_a(ps) is insensitive to TP content, TP molecular weight and curing rate, but it changes with the cure reaction kinetics and the chemical environment of the systems. With the established phase separation time-temperature dependence relation, we can easily establish the whole cure time-temperature transformation (TTT) diagram with morphology information which is a useful map for the TP/TS composites processing industry.     

Effect of reinforcing glass fibers on morphology and properties of thermoplastic modified epoxy-aromatic diamine matrix

A usual way to improve the fracture toughness of thermosetting polymers consists of using an initially miscible thermoplastic that phase separates at a particular conversion, depending on composition and reaction temperature. This work deals with the effect of glass reinforcing fibers on the morphologies of polyetherimide and aminografted polyetherimide toughened epoxy-diamine systems. The presence of fibers in these systems does not affect the phase separation process, but the final morphology changes in the case where polyetherimide (PEI) is used as an additive. Furthermore, the use of aminografted PEI does not change the previously observed morphology. In terms of mechanical properties, the use of fibers leads to a great improvement in the fracture energy, indicating that good adhesion between fiber and matrix is also achieved. Polym. Compos. 25:368–374, 2004. © 2004 Society of Plastics Engineers.