扩链脲改性环氧树脂E-51/双氰双胺(dicy)体系的固化行为

反应活性;扩链脲改性环氧树脂E-51/双氰双胺(dicy)体系的固化行为     

含聚醚间隔链的扩链脲改性环氧树脂/双氰双胺固化体系性能研究

合成了一系列含不同分子量聚环氧丙烷 (PPG)柔性间隔链的扩链脲 ,系统考察了扩链脲改性环氧树脂E 5 1/双氰双胺 (dicy)固化体系的固化反应活性、动态力学行为、冲击性能和断裂面形态结构 ,并对体系的冲击性能、形态结构与动态力学行为之间的关系进行了探讨 .结果表明 ,改性体系固化反应活性明显提高 ,固化反应表观活化能降低 ,固化反应峰顶温度从 190℃降低至 14 0℃ ,固化反应的表观活化能由 14 5 5kJ/mol降至 70～ 80kJ mol;改性体系冲击强度明显提高 ,其中所含PPG柔性链分子量为 10 0 0的扩链脲改性的E 5 1/dicy体系冲击强度较未改性的E 5 1/dicy体系提高了 8倍 ,其冲击试样断裂面的形态具有明显的韧性断裂特征 ,微观两相网络结构的存在导致了改性体系冲击强度显著提高     

咪唑封端聚氨酯予聚体改性环氧树脂E-51/双氰双胺固化体系性能研究

以聚丙二醇PPG10 0 0、甲苯二异氰酸酯 (TDI)、咪唑为原料 ,合成了咪唑封端的聚氨酯予聚体 ,简称扩链脲TIEU .利用DSC、粘弹谱仪、冲击试验机及扫描电镜 (SEM)等手段对TIEU改性的环氧树脂E 5 1/双氰双胺(dicy)固化体系的反应活性、动态力学行为、冲击性能、断裂面形态结构进行了系统研究 .实验结果表明 ,改性后的E 5 1 dicy体系反应活性明显提高 ,固化反应的表观活化能由未改性体系的 131kJ mol降至 75～ 80kJ mol.与咪唑促进体系比较结果显示 ,两种固化反应的促进机制具有一定的差异 .另外与未改性体系相比 ,经过改性的环氧树脂体系冲击强度提高 2～ 3倍 ,而玻璃化温度和模量基本不变 ,冲击断面呈韧性断裂     

DSC分析及原位FT-IR法对聚合物接枝碳纳米管/环氧树脂固化体系的固化反应的研究

合成了一种扩链脲修饰的多壁碳纳米管(MWCNT-PEG-TU),差示扫描量热分析(DSC)结果表明,MWCNT-PEG-TU可明显提高E-51环氧树脂/双氰双胺(DICY)固化体系的固化反应活性。利用原位傅里叶变换红外光谱(in situ FT-IR)法研究了MWCNT-PEG-TU/E-51环氧树脂/DICY固化体系的等温固化动力学,该固化体系在不同温度下的dα/dt与α的关系曲线较好地符合Kamal自催化反应模型。     

含刚性链节和脲端基聚醚增韧剂改性环氧树脂的研究—反应活性及力学 …

合成了一系列既含环氧丙烷聚醚柔性间隔基，又含刚性介晶结构单元的端脲基活性改性剂，并对其改性环氧树脂Ｅ－５１／双氰双胺体系的固化反应活性，改性剂含量对增韧体系动态力学性能及冲击性能的影响进行了研究。     

一种新型液晶环氧树脂的合成表征与固化研究

首次合成了一种不对称联苯和芳香酯型液晶环氧树脂4"-环氧丙氧基苯甲酸-4-环氧丙氧基联苯-4'-酯(EBEPC),利用FT-IR、1H NMR、DSC和POM对其结构和性能进行了表征.结果表明,EBEPC在190℃时可形成明显的向列相液晶.对其同普通固化剂DDM体系的固化反应过程、固化动力学进行了研究,与普通环氧树脂E-51/DDM体系比较,液晶环氧树脂EBEPC体系具有较低的固化反应温度,且表观话化能Ea(54.5kJ/mol)较E-51/DDM体系(60.7kJ/mol)低,EBEPC体系具有更高的反应活性.     

含刚性链节和脲端基聚醚增韧剂改性环氧树脂的研究———反应活性及力学性能

合成了一系列既含环氧丙烷聚醚（ＰＰＧ）柔性间隔基、又含刚性介晶结构单元的端脲基活性改性剂（ＬＣＥＵＰＰＧ），并对其改性环氧树脂Ｅ ５１／双氰双胺（Ｅ ５１／ｄｉｃｙ）体系的固化反应活性、改性剂含量对增韧体系动态力学性能及冲击性能的影响进行了研究．结果表明：ＬＣＥＵＰＰＧ的加入对固化体系具有明显的增韧作用，冲击强度提高了３～７倍；其对Ｅ ５１／ｄｉｃｙ固化反应具有明显的促进作用，可使固化反应表观活化能（Ｅａ）降低５０～７０ＫＪ／ｍｏｌ、固化温度降低３０～４０℃；体系的玻璃化转变温度（Ｔｇ）略有下降，但模量基本不降低或略有升高；β 转变向低温方向移动．     

1-己基-3-甲基咪唑四氯化铁盐固化环氧树脂E-51的反应特性

采用差示扫描(DSC)量热分析法研究了1-己基-3-甲基咪唑四氯化铁离子液体([C₆mim]FeCl₄)与双酚A型环氧树脂E-51的固化反应。结果显示,由于[C₆mim]FeCl₄包含多级胺基结构,因此可以作为E-51的高温固化剂使用,其与E-51的反应包含两个阶段:第一个阶段的反应放热峰峰顶温度约在120 ℃,第二个阶段的反应放热峰峰顶温度会随着[C₆mim]FeCl₄用量的增加而发生变化。当[C₆mim]FeCl₄与混合胺复配成新型固化剂时,二者产生明显的协同效应。通过恒温DSC实验发现,复配体系与E-51的固化反应可以在室温下发生,表现为在30 ℃固化反应放热峰峰顶放热时间为5 min左右,且随着恒温固化反应温度的提高,峰顶放热峰时间会缩短。非等温动力学结果显示:复配体系与E-51的反应活化能为979 J/mol,仅是混合胺体系的17%左右。反应级数为0.5表明这一固化反应是无规反应。     

含介晶结构单元的反应性增韧剂改性环氧树脂研究──Ⅱ.材料断裂面形态结构的研究

该文合成了一种既含聚醚柔性链又含介晶结构单元的环氧树脂改性剂LCEU（PEG），用其改性环氧树脂／双氰双胺（E－51／dicy）固化体系，对改性体系的动态力学行为和冲击性能作了研究，用扫描电子显微镜（SEM）对试样断裂面的形态结构进行了观察，并探讨了体系的形态结构与动态力学行为、冲击性能之间的关系。结果表明改性体系断裂时产生大量应力条纹，断裂面呈微观两相网络结构，为韧性断裂。     

聚酯型扩链脲改性环氧树脂E-51/DDS体系反应活性研究

提高二氨基二苯砜(DDS)固化环氧树脂体系的反应活性,降低反应温度、提高反应速率,具有重要的研究意义和实用价值.本研究以聚酯(PEGA1000,2000,PNGA1000,2000)、甲苯-2,4-二异氰酸酯(TDI)、二甲胺为原料合成了含有聚酯型柔性间隔基的扩链脲U-PEGA1000,2000,U-PNGA1000,2000,用其改性环氧树脂E-51/DDS体系,采用DSC系统考察了改性体系的固化反应活性.结果表明,改性体系固化反应活性明显提高,固化反应表现活化能降低,固化反应峰顶温度从230℃降至170℃,固化反应的表观活化能由67.74kJ/mol降至47.80kJ/mol.     

聚醚扩链脲增韧环氧树脂体系的冲击性能及其断裂面形态结构

聚醚扩链脲增韧环氧树脂体系的冲击性能及其断裂面形态结构     

功能基化介晶高聚物增韧环氧树脂性能研究——材料断裂面形态结构与力学性能的关系

在系统研究含介晶基团的高聚物ＬＣＥＵＰＰＧ增韧环氧树脂Ｅ ５１／双氰双胺（ｄｉｃｙ）固化体系固化反应活性、反应机制、动态力学行为及冲击性能的基础上,以扫描电镜（ＳＥＭ）为手段,对材料断裂面的形态结构进行了研究,并对体系的形态结构与动态力学行为、冲击性能之间的关系进行了探讨．结果表明,改性后材料断裂面的形态均呈微观两相网络结构,明显不同于未改性体系,正是由于两相网络结构的存在,导致了改性体系的冲击强度大幅度提高．     

In situ monitoring by DSC and modeling of curing of vinyl polysiloxanes in layered silicate nanocomposites

The study of curing mechanism and the related kinetics in montmorillonite/vinyl-terminated polysiloxane nanocomposites was carried out. Commercially unmodified montmorillonite, as well as two different types of organically modified products, under the trade names: Nanofil 116, Cloisite 20A and Cloisite 30B, respectively, was used as the reinforcing nanofillers. The vulcanization reaction was followed by isothermal and non-isothermal differential scanning calorimetry analysis. The Cloisite 20A/PDMS systems showed increased reaction rate at the early stages of cross-linking, followed by a retardation of the rate and extension of curing time, with respect to the pure PDMS. On the other hand, Cloisite 30B decreases the curing rate of PDMS during the whole process, whereas a significant increase in this parameter was recorded in the case of unmodified clay/PDMS nanocomposites. This diversity of the effect of various types of fillers was attributed to physicochemical interactions between the cross-linking system and organoclay particles mainly due to their surface chemistry. In an attempt to further evaluate the obtained results, it was found that the autocatalytic model shows good fitting with the experimental data.     

Properties of methyltetrahydrophthalic anhydride‐cured epoxy resin modified with MITU

Methylimidazole‐terminated chain‐extended urea (MITU) containing polypropylene oxide spacer was synthesized and employed to modify epoxies composed of a diglycidyl ether of bisphenol‐A (E‐51) and methyltetrahydrophthalic anhydride (MTHPA). The curing behavior, viscoelastic property, impact response, and fracture surface morphology of the curing systems were systematically investigated. Differential scanning calorimeter (DSC) analysis reveals that the curing reactivity of the epoxy system is greatly enhanced with the addition of MITU. From the dynamic mechanical analysis, besides the low‐temperature β relaxation, shoulder at higher temperature side appears for the MITU‐modified systems. Meanwhile, the addition of MITU leads to the increase of loss factor (tan δ) over the temperature range of 0–75°C. Impact tests show that the modifier can be effective in toughening the epoxy resin at relatively low loading, and the scanning electron microscope (SEM) images of the fracture surface for the modified systems display signs of ductility. Copyright © 2008 John Wiley & Sons, Ltd.     

Intercalated clay nanocomposites: Morphology,mechanics, and fracture behavior

Intercalated nanocomposites of modified montmorillonite clays in a glassy epoxy were prepared by crosslinking with commercially available aliphatic diamine curing agents. These materials are shown to have improved Young's modulus but corresponding reductions in ultimate strength and strain to failure. The results were consistent with most particulate‐filled systems. The macroscopic compressive behavior was unchanged, although the failure mechanisms in compression varied from the unmodified samples. The fracture toughness of these materials was investigated and improvements in toughness values of 100% over unmodified resin were demonstrated. The fracture‐surface topology was examined using scanning electron and tapping‐mode atomic force microscopies and shown to be related to the clay morphology of the system. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1137–1146, 2001     

Cellulosic diamines as reaction-incorporated fillers in epoxy composites

Cellulosic fillers have been chemically modified by attaching pendant primary amine groups (diamino propane). The modified cellulose fillers were used for curing an epoxy resin (diglycidyl ether of bisphenol A). Gel times thus obtained are much less than systems containing unmodified cellulose. The advantages from the use of such modified organic fillers are discussed. Our investigations could encourage greater utilization of renewable lignocellulosic materials as reactionincorporated fillers for polymer composites.NCL Communication No. 4908.     

Curing of dicyanate ester/epoxy copolymers modified with polysiloxane and butadiene-acrylonitrile rubbers

The cyanate ester (CE) and epoxy (EP) resins were cured together at various mass compositions. The curing behavior of CE and CE/EP systems was studied by means of differential scanning calorimetry (DSC) in non-isothermal conditions. The DSC measurements indicated that the curing reactions were dependent on the stoichiometric ratio of the mixtures and showed the dilution effect of the EP resin in the cyclotrimerization of the catalyzed CE resin. The CE and CE/EP (70/30) systems were modified using reactive liquid butadiene-acrylonitrile copolymer (ETBN) and polysiloxane core?Cshell (PS) elastomer. The influence of ETBN and PS on the curing process and glass transition temperature (T _g) of CE/EP systems was determined. The impact resistance characteristics of the completely cured systems indicated the influence of the modifiers and the EP content in the mixtures on its impact resistance.