Behavior of polyamidoamine dendrimers as curing agents in bis‐phenol A epoxy resin systems

Polyamidoamine (PAMAM) dendrimers with different generations (0–5) were investigated as curing agents in epoxy resin systems. Flory's gelation theory and the Avrami equation were used to predict the cure behavior of epoxy resin/PAMAM/imidazole at various temperatures and PAMAM concentrations. The theoretical prediction is in good agreement with the experimental results obtained from the dynamic torsional vibration method. Copyright © 2004 Society of Chemical Industry     

环氧基POSS/PAMAM杂合材料的制备及性能研究

以3-缩水甘油基氧丙基三甲氧基硅烷(EPTMS)为原料,合成得到了八官能团缩水甘油醚-多面体低聚倍半硅氧烷(简称POSS-EP)。采用4代树型端氨基聚酰胺-胺(PAMAM)作为POSS-EP和双酚A型环氧树脂(DGEBA)共混物的固化剂,制备了5个环氧基POSS/PAMAM杂化材料。通过动态差示扫描量热仪(DSC),研究了环氧和PAMAM的固化反应动力学。通过DSC、热重分析(TGA)、拉力和冲击测试,对环氧基POSS/PAMAM杂化材料的热性能和力学性能进行了研究。结果表明,该环氧基POSS/PAMAM杂化材料具有优良的热性能和力学性能。     

Curing of DGEBA epoxy resin by low generation amino‐group‐terminated dendrimers

Low generation amino‐group‐terminated poly(ester‐amine) dendrimers PEA1.0 (NH₂)₃ and PEA1.5 (NH₂)₈, and poly(amido‐amine) dendrimer PAMAM1.0 (NH₂)₄ were used as diglycidyl ether of bisphenol A (DGEBA) epoxy resin hardeners. Thermal behavior and curing kinetics of dendrimer/DGEBA systems were investigated by means of differential scanning calorimetry (DSC). Compared with ethylene diamine (EDA)/DGEBA system, the dendrimer/DGEBA systems gradually liberated heat in two stages during the curing process, and the total heat liberated was less. Apparent activation energy and curing reaction rate constants for dendrimer and EDA/DGEBA systems were estimated. Thermal stabilities and mechanical properties of cured thermosetting systems were examined as well. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3902–3906, 2006     

树状大分子聚酰胺-胺固化环氧树脂性能研究

采用发散法由乙二胺和丙烯酸甲酯合成了树状聚酰胺-胺(PAMAM).以PAMAM作为环氧树脂(EP)的固化剂,用差示扫描量热法确定其固化工艺及固化物的玻璃化转变温度(T_g),探讨了树状PAMAM用量对固化物力学性能的影响.结果表明,PAMAM与EP的质量比为0.26时,固化物的力学性能最佳,其冲击强度为166.43 kJ/m~2,拉伸强度为43.54 Mpa;明显高于低分子量聚酰胺/EP固化物的冲击强度和拉伸强度.     

PAMAM树状大分子负载和释放阿霉素的耗散粒子动力学模拟

采用耗散粒子动力学模拟方法研究了药物输送载体聚酰胺-胺（PAMAM）树状大分子对抗癌药物阿霉素（DOX）的负载和释放行为。构建了PAMAM树状大分子的粗粒化模型,该模型能准确地重现树状大分子的构象性质。考察了PAMAM树状大分子代数（G）对DOX负载以及pH环境对DOX释放的影响。模拟结果表明,PAMAM树状大分子主要通过疏水作用将DOX包封于内部空腔,G6和G7 PAMAM树状大分子的负载能力较强,因为其孔隙率较高,内部有更多的疏水空腔。在低pH环境下,PAMAM树状大分子结构发生变化,DOX分子能快速地从其中释放,主要原因是PAMAM的伯胺、叔胺和DOX伯胺发生质子化,质子化基团间的静电排斥作用使得PAMAM树状大分子发生溶胀,导致其内部空腔暴露,促进了DOX的释放。本工作可以为基于树状大分子的药物输送体系的设计和优化提供参考。     

环氧树脂改性聚氨酯耐热性能的研究

端异氰酸酯基聚氨酯预聚体与环氧树脂E-51形成了互穿网络,通过热重分析仪(TGA)研究了完全固化后的互穿网络的热分解行为、透射电镜研究了IPN的相分离行为,及拉伸强度、硬度等对其进行了表征。结果表明,经过环氧树脂改性的聚氨酯的耐热性能比纯聚氨酯得到了提高,且力学性能也有所改善,并对其机理进行了阐述。     

端氨基树枝状大分子/环氧树脂体系固化动力学的FTIR研究

用傅立叶变换红外光谱(FTIR)法研究了双酚A二缩水甘油醚环氧树脂(GEBA)用低代端氨基聚(酯-胺)树枝状大分子G1.0(NH2)3、G1.5(NH2)8和聚(胺-酰胺)树枝状大分子PAMAM1.0(NH2)4作为固化剂的等温固化动力学,得到了不同温度下转化率与固化时间及反应速率与固化时间的关系.与小分子固化剂相比,端氨基树枝状大分子作固化剂时环氧基转化率在反应开始时增长得更快,较高代树枝状大分子在高温下固化环氧树脂时尤其如此.在相同温度和时间下,PAMAM1.0(NH2)4/DGEBA、G1.0(NH2)3/DGEBA、G1.5(NH2)8/DGEBA体系的转化率依次增大.进一步估算了3个体系在一定转化率下的固化反应表观活化能.在相同转化率时,用G1.5(NH2)8、PAMAM1.0(NH2)4、G1.0(NH2)3作固化剂的体系表观活化能依次减小.     

不同固化体系对环氧粉末涂料性能的影响

通过非等温示差扫描量热分析(DSC),热重分析(TGA)及物理力学性能测试研究了分别以双氰胺、二氨基二苯基砜、线形酚醛树脂为固化剂,2-甲基咪唑为固化促进剂的环氧树脂体系的固化行为,热稳定性及其粉末涂料性能,并利用外推法求出不同固化体系的理论固化温度。结果表明:双氰胺/2-甲基咪唑体系的综合性能最好,其理论固化温度为142℃,热失重起始分解温度为410℃,冲击强度为50 cm,60°光泽为83,表面电阻为1.33×1012Ω。     

环氧树脂含量对氰酸酯热学性能的影响研究

采用示差扫描量热法(DSC)和热失重分析法(TGA)研究了环氧树脂含量对氰酸酯树脂固化反应特性、热稳定性以及热膨胀系数的影响。结果表明,环氧树脂的加入可有效降低改性体系的固化反应活化能,同时体系的热稳定性和尺寸稳定性有不同程度的削弱。当环氧树脂质量分数达到20%时,改性体系的表观活化能为65.4 kJ/mol,耐热温度指数为174℃,较纯氰酸酯树脂分别降低了25.8%和21.4%。当环氧树脂质量分数达到50%时,改性体系的热膨胀系数为65.3 922×10-6/℃(25～150℃),较纯氰酸酯树脂提高了8.13%。     

Dendritic polyamidoamine-grafted halloysite nanotubes for fabricating toughened epoxy composites

Well-dispersed epoxy resin/halloysite nanotubes composites were prepared by functionalization of the HNTs surfaces using polyamidoamine generation-3 (HNTs-G3.0). A series of modified halloysite nanotubes with different generations of dendritic polyamidoamine (PAMAM) were prepared via a divergent synthetic process by repeating the Michael addition of methyl acrylate to superficial amino groups and the amidation of the resulting esters with ethylenediamine. The products were then characterized by means of FTIR, XPS, XRD and TGA. The results showed that PAMAM polymers are successfully grafted on the surface of HNTs and the grafting percentage of HNTs grafted with polyamidoamine generation-3 (HNTs-G3.0) is 27.21 %. The grafted PAMAM has no effect on the crystalline structure of HNTs. The morphology, interfacial interaction and mechanical properties of epoxy composites were investigated and correlated with the surface functionalization of HNTs. The observations of scanning electronic microscopy and transmission electron microscopy images showed that HNTs-G3.0 exhibited better dispersion than the p-HNTs. The interfacial interaction of the epoxy composites was studied by FTIR and DMA. It was found that dendritic polyamidoamine graft can effectively improve the interfacial interaction of the epoxy composites. With the improvement in particle dispersion and interfacial interaction through polyamidoamine generation-3 grafting, an increase of impact strength and fracture toughness was achieved, accompanied by enhancements of flexural strength and modulus. In particular, the impact strength and fracture toughness (K _IC) of composites with polyamidoamine generation-3 grafted HNTs were about 160 and 20 % higher than the values of functionalization halloysite nanotube system.     

聚苯基甲氧基硅氧烷改性环氧树脂的阻燃性能研究

采用氧指数(LOI),UL-94,热失重(TGA)等手段考察了聚苯基甲氧基硅氧烷(PPMS)改性对环氧树脂(E-20)固化体系阻燃性能的影响.相比未改性环氧体系,当m(E-20)∶m(PPMS)=73∶时,改性环氧体系的LOI由纯E-20环氧树脂的17.5%上升到21.5%;水平火蔓延速率由36.23 mm/min降低到26.60 mm/min;质量损失为5%时的热分解温度由134.7℃上升到163.0℃,750℃时残炭量由0.21%增加到25.79%.此外,还通过红外光谱对燃烧后的残炭结构进行了分析,探讨了相关阻燃机理.     

含磷阻燃剂阻燃环氧树脂热降解动力学

以2-二苯基膦酰基-1,4-苯二酚(DPO-HQ)为阻燃剂制备了阻燃环氧树脂,利用动态热重分析法(TGA)研究了纯环氧树脂(EP)和阻燃环氧树脂(FR-EP)在不同升温速率下的热稳定性,建立了EP和FR-EP体系的动力学模型和非模型动力学(MFK),并对比分析了模型动力学和非模型动力学对于描述EP体系和FR-EP体系的适用性.结果表明:阻燃剂的引入降低了环氧树脂初始降解温度,但增加了残炭率.由Flynn-Wall-Ozawa方法和Coats-Redfern方法建立的模型动力学表征EP和FR-EP体系高温降解过程中误差较大,而非模型动力学能更准确地预测和描述EP和FR-EP体系的高温降解行为.     

固化体系对环氧树脂阻燃性能影响的研究

比较了间苯二胺（m-PDA）、4,4-二氨基二苯甲烷（DDM）、甲基四氢邻苯二甲酸酐（MeTHPA）三种固化剂与双酚A型环氧树脂（E-51）形成的固化体系燃烧性能的差异，研究了DDM、MeTHPA固化体系对聚磷酸铵（AP462）阻燃环氧树脂燃烧性能的影响。结果表明，DDM固化体系与AP462有良好的协同阻燃效果，仅添加质量分数为25％的AP462，EP-AP462-25／DDM体系的氧指数就可达到41．0％。热失重分析指出，协同阻燃与EP／DDM和AP462的热稳定性匹配、相互作用导致成炭量提高有关。     

Cure behavior of epoxy resin/CdS/2,4-EMI nanocomposites investigated by dynamic torsional vibration method (DTVM)

Summary Epoxy resin/CdS nanocomposite was prepared by a novel method and its cure behavior was investigated by the HLX-II Resin Curemeter based on the dynamic torsional vibration method (DTVM). The non-equilibrium thermodynamic fluctuation theory, the Avrami equation and the Flory’s gelation theory have been used to analysis the cure behavior of the composite systems with different CdS and cure agent loadings at various temperatures. The results show that the addition of CdS nanoparticles reduces the gel time t_g, but has little effect on the mechanism of the cure reaction. The theoretical prediction is in good agreement with the experimental results. The Avrami exponent of n decreases a little when the temperature increases.     

Studies on the curing behavior,thermal, and mechanical properties of epoxy resin-co-amine-functionalized lead phthalocyanine

A high performance copolymer was prepared by using epoxy (EP) resin as matrix and 3,10,17,24-tetra-aminoethoxy lead phthalocyanine (APbPc) as additive with dicyandiamide as curing agent. Fourier-transform infrared spectroscopy, dynamic mechanical analysis (DMA), differential scanning calorimetric analysis (DSC), and thermogravimetric analysis (TGA) were used to study the curing behavior, curing kinetics, dynamic mechanical properties, impact and tensile strength, and thermal stability of EP/APbPc blends. The experimental results show that APbPc, as a synergistic curing agent, can effectively reduce the curing temperature of epoxy resin. The curing kinetics of the copolymer was investigated by non-isothermal DSC to determine kinetic data and measurement of the activation energy. DMA, impact, and tensile strength tests proved that phthalocyanine can significantly improve the toughness and stiffness of epoxy resin. Highest values were seen on the 20 wt% loading of APbPc in the copolymers, energy storage modulus, and impact strength increased respectively 388.46 MPa and 3.6 kJ/m², T_g decreased 19.46°C. TGA curves indicated that the cured copolymers also exhibit excellent thermal properties.     

马来海松酸酐的合成及其固化反应特性研究

松香与亲二烯体进行Diels-Alder反应合成了环氧树脂固化剂马来海松酸酐,利用傅里叶红外光谱仪(FT-IR)、热重分析仪(DTA)、拉力机等分析测试手段,对环氧树脂/马来海松酸酐体系固化产物的特性进行了研究。结果表明,环氧树脂/马来海松酸酐固化体系在100℃/2h、120℃/2h、150℃/5h、质量比为1:0.8的条件下可完全固化。固化产物的平均剪切强度17.3MPa,热分解温度可达371.5℃,与甲基四氢苯酐(Me-TH-PA)/环氧固化物相比,分别高3.74MPa,6.1℃。该产物可望在环氧树脂中高温固化领域得到广泛应用。     

环氧树脂/环氧液晶/蒙脱土纳米复合材料研究

采用液晶环氧预聚物(PHQEP)与有机蒙脱土(OMMT)共混改性环氧树脂制备三元共混体系的环氧基复合材料。用X射线衍射法(XRD)测试了有机化蒙脱土在被插层前后片层间距的变化,通过DSC、TGA及SEM等对PHQEP/OMMT增韧改性环氧树脂固化体系的力学性能,热性能及微观相态结构进行了研究。结果表明:当PHQEP质量分数为5%,添加1.5%的有机蒙脱土可以使环氧树脂的冲击强度达到最大值23.43 kJ/m2,比纯环氧树脂提高2倍左右,玻璃化转变温度及5%热分解温度比纯环氧树脂分别高出15℃和27℃。PHQEP与OMMT的加入使纳米复合材料的力学性能和热性能得到明显提高。     

Synthesis and characterization of siliconized epoxy-1,3-bis(maleimido)benzene intercrosslinked matrix materials

Intercrosslinked network of siliconized epoxy-1,3-bis(maleimido)benzene matrix systems have been developed. The siliconization of epoxy resin was carried out by using various percentages of (5-15%) hydroxyl-terminated polydimethylsiloxane (HTPDMS) with γ-aminopropyltriethoxysilane (γ-APS) as crosslinking agent and dibutyltindilaurate as catalyst. The siliconized epoxy systems were further modified with various percentages of (5-15%) 1,3-bis(maleimido)benzene (BMI) and cured by using diaminodiphenylmethane (DDM). The neat resin castings prepared were characterized for their mechanical properties. Mechanical studies indicate that the introduction of siloxane into epoxy resin improves the toughness of epoxy resin with reduction in the values of stress-strain properties whereas, incorporation of bismaleimide into epoxy resin improves stress-strain properties with lowering of toughness. However, the introduction of both siloxane and bismaleimide into epoxy resin influences the mechanical properties according to their percentage content. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and measurement of heat distortion temperature were also carried out to assess the thermal behavior of the matrix samples. DSC thermogram of the BMI modified epoxy systems show unimodel reaction exotherms. The glass transition temperature (T_g), thermal degradation temperature and heat distortion temperature of the cured BMI modified epoxy and siliconized epoxy systems increase with increasing BMI content and this may be due to the homopolymerization of BMI rather than Michael addition reaction. The morphology of the BMI modified epoxy and siliconized epoxy systems were also studied by scanning electron microscopy.     

Preparation and characterization of bismaleimide (N,N′‐bismaleimido‐4,4′‐diphenyl methane)–unsaturated polyester modified epoxy intercrosslinked matrices

An intercrosslinked network of unsaturated polyester–bismaleimide modified epoxy matrix systems was developed. Epoxy systems modified with 10, 20, and 30% (by weight) of unsaturated polyester were made by using epoxy resin and unsaturated polyester with benzoyl peroxide and diaminodiphenylmethane as curing agents. The reaction between unsaturated polyester and epoxy resin was confirmed by IR spectral studies. The unsaturated polyester toughened epoxy systems were further modified with 5, 10, and 15% (by weightt) of bismaleimide (BMI). The matrices, in the form of castings, were characterized for their mechanical properties. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) of the matrix samples were performed to determine the glass transition temperature (T_g) and thermal degradation temperature of the systems, respectively. Mechanical properties, viz: tensile strength, flexural strength, and plain strain fracture toughness of intercrosslinked epoxy systems, were studied by ASTM methods. Data obtained from mechanical and thermal studies indicated that the introduction of unsaturated polyester into epoxy resin improves toughness but with a reduction in glass transition, whereas the incorporation of bismaleimide into epoxy resin improved both mechanical strength and thermal behavior of epoxy resin. The introduction of bismaleimide into unsaturated polyester‐modified epoxy resin altered thermomechanical properties according to their percentage concentration. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2853–2861, 2002     

Evaluation of Thermal Stability and Glass Transition Temperature of Different Aeronautical Polymeric Composites

In this work, the thermal stability of different polymeric composite laminates used in the aeronautical field was investigated by thermogravimetric (TGA) and dynamic mechanical thermal (DMTA) analyses. Four different types of laminates manufactured by combining two epoxy resin systems (F584 and F155) and two different types of carbon fiber fabric reinforcements were examined. The mass losses of the laminates were evaluated by TGA and the glass transition temperatures (T_g) were determined by DMTA. After being conditioned at 80°C and 90% humidity for a period of 8 weeks, the samples were analyzed by DMTA technique to evaluate the influence of the moisture and the elevated temperature on the T_g of the laminates. TGA results showed that the F584 and F155 epoxy systems are thermally stable until 200°C in nitrogen and in air atmospheres. The DMTA results showed the decreasing of T_g after conditioning for both resin systems. Despite the decrease of T_g, the values found are within the acceptable limits for use in aeronautical components.