非等温DSC法研究甲壳型液晶PBPCS改性环氧树脂的固化动力学

采用非等温DSC法对聚乙烯基对苯二甲酸二(对丁氧基苯酚)酯(PBPCS)/环氧树脂/甲基四氢苯酐固化体系的固化反应热行为以及固化动力学进行了研究,分别利用Kissinger和Ozawa动力学模型计算得到各体系固化反应的表观活化能,利用Crane模型计算出固化反应级数,得出了适于该树脂体系固化反应过程的动力学方程.结果表明该体系固化反应按照一级反应进行,PBPCS的加入不改变环氧树脂的固化机理,甲壳型液晶高分子PBPCS可以用于环氧树脂的改性研究.通过固化体系的DSC分析确定了体系固化工艺为90℃/2h→120℃/2h→140℃/1.5h,为聚乙烯基对苯二甲酸二(对丁氧基苯酚)酯/环氧树脂/甲基四氢苯酐体系的固化、性能测试和应用提供了理论依据,也为甲壳型液晶高分子改性环氧树脂的研究提供一定理论基础.     

酸酐固化环氧树脂/蒙脱土复合材料的等温固化动力学

用等温差示扫描量热法(DSC)研究了酸酐固化环氧树脂/蒙脱土复合材料的等温固化过程，考察了未处理的蒙脱土(MMT)和有机蒙脱土(OMMT)对环氧树脂固化动力学的影响. 实验表明， 环氧树脂的固化过程包含自催化机理，加入蒙脱土没有改变固化反应机理. 用Kamal方程对该体系的固化过程进行拟合，得到反应级数m、n，反应速率常数k1、k2，总反应级数(m + n)在2.4～3.0之间. MMT的加入使环氧树脂体系的k1、k2有所降低，而OMMT的加入对体系的k1、k2影响较为复杂，加入蒙脱土对环氧树脂固化体系的活化能影响较小.     

几种聚醚胺改性蒙脱土对环氧树脂固化过程的影响

首先制备了五种聚醚胺改性蒙脱土(MMT), 并将这五种聚醚胺改性蒙脱土加入到双酚A 型环氧树脂E51 和聚醚胺D400体系中, 采用差示扫描量热法(DSC)考察了五种聚醚胺改性MMT对环氧树脂升温固化进程的影响. 随后, 优选一种EP/MMT 混合体系即EP/D400-T500-MMT 混合体系, 系统地研究了该体系与纯环氧树脂体系在130, 140, 150 及160 ℃等几个温度下的等温固化过程, 考察了等温固化时间对固化度和固化度变化速率的影响以及固化度与固化度变化速率之间的关系, 并利用Kamal 模型进行拟合计算了固化动力学参数. 研究结果表明, 与纯环氧树脂相比, 几种聚醚胺改性MMT 的固化放热峰均向高温迁移, 同时聚醚胺D400 协同插层MMT 降低了高分子量聚醚胺插层MMT 所导致的环氧树脂DSC 曲线的畸变情况; EP/D400-T500-MMT 混合体系和纯环氧体系的等温固化反应过程符合Kamal 模型;在相同的固化温度下, EP/D400-T5000-MMT 混合体系的反应速率常数k₁ 和k₂ 值以及反应级数m 均比纯EP 体系小, 而反应级数n 以及总反应级数m+n 值比纯EP 体系大, 表明两种聚醚胺协同插层的改性蒙脱土D400-T5000-MMT 的加入降低了环氧体系固化反应速率. 另外, EP/D400-T5000-MMT 混合体系的活化能E_a1 和E_a2 与纯EP 体系的相比也略有升高.     

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。     

树枝形大分子/环氧树脂体系固化反应动力学研究

用示差扫描量热仪(DSC)对树枝形大分子PAMAM/双酚-A型环氧树脂体系的固化反应动力学过程进行了分析。通过Kissinger法求得体系固化反应的表观活化能ΔE为59.78kJ/mol,通过Crane法求得体系的固化反应级数n=0.91,并计算出了反应速率常数k和不同升温速率下的频率因子A。根据动态DSC数据确定体系合适的固化反应温度为80~90℃,后固化温度为140℃。     

高性能环氧树脂/碳纳米管复合物的热分析研究

用差示扫描量热仪(DSC)、热失重分析仪(TGA)和动态力学热分析仪(DMTA)研究了多壁碳纳米管(MWNTs)/高性能4,4′-二氨基二苯甲烷四缩水甘油环氧树脂(TGDDM)/4,4′-二氨基二苯基砜(DDS)复合物的热性能.Kissinger和Flynn-Wall-Ozawa的非等温固化动力学研究发现,随着MWNTs含量的增加,复合物固化反应的活化能先减小后增大.TGA研究表明,MWNTs的添加对环氧树脂热稳定性影响很小.碳纳米管填充到TGDDM/DDS体系后,复合物的储存模量随着MWNTs含量的增加而增大,而玻璃化温度却随之减小.     

升温与等温法非模型动力学研究环氧树脂固化反应

基于DSC数据,采用以Vyazovkin积分法为基础的升温法非模型动力学和等温法非模型动力学对双酚A型环氧树脂E51/4,4′-二氨基二苯基砜(DDS)体系及多官能度环氧树脂AG80/DDS体系的固化过程进行了研究,并结合玻璃化转变温度的变化和原位红外测试技术,对比分析了升温与等温条件下的固化反应规律.结果表明,与传统的模型拟合法相比,非模型动力学更适合定量预测树脂固化反应过程,并能为固化过程中反应机理变化的研究提供重要依据;等温法非模型动力学能够更好地预测两种树脂体系在不同恒温条件下的固化反应历程,并且升温法与等温法非模型动力学所得到的反应活化能-固化度之间的变化关系不同,表明不同温度条件下树脂的反应机理不同,这与升温和恒温条件下玻璃化效应及环氧官能团的变化规律相吻合.     

耐热芴型环氧树脂的非等温固化动力学

合成了9,9’-二[4-(2,3环氧丙氧基)苯基]芴,并以4,4’-二氨基二苯砜胺为固化剂,用非等温DSC法研究了其固化动力学,用Flynn-Wall-Ozawa法和Friedman法确定了固化动力学参数,用动力学模拟推测了固化机理函数,并用TGA法对等温固化树脂的耐热性进行了表征。结果表明:双酚芴环氧固化反应的表观活化能约63.86 kJ/mol,扩散因子为3.80×104s-1,反应级数为1.57;固化反应为枝状成核的自催化反应;等温固化后的环氧树脂于400℃开始分解,700℃时残碳率为41.73%。     

环氧树脂/氧化石墨纳米复合物的等温固化行为研究

用示差扫描分析仪(DSC)研究了氧化石墨(GO)对N,N,N',N'-四缩水甘油基-4,4'-二氨基二苯基甲烷环氧树脂(TGDDM)/4,4'-二氨基二苯基砜(DDS)体系的等温固化反应的影响,用X射线光电子能谱仪(XPS)和傅里叶变换红外光谱仪(FTIR)研究了GO上存在的官能团及其对TGDDM/DDS体系固化行为的影响,用热失重分析仪(TGA)研究了天然石墨和GO的热力学稳定性.XPS、FTIR和TGA结果表明,GO上存在的大量羟基、羧基、环氧基等官能团能够影响环氧树脂的固化行为.DSC研究发现,环氧树脂/氧化石墨纳米复合物的固化反应属于自催化类型,随着GO含量的增加,达到最大反应速率的时间不断减小,初始反应速率不断增大,这说明GO对环氧树脂的固化反应有促进作用.Kamal模型计算得到的结果表明,随着GO含量的增加自催化反应初期阶段表观活化能E1先减小再增大,而自催化反应结束后表观活化能E2略微减小.经Kamal模型扩散控制函数修正后,整个固化过程中拟合得到的结果与实验数据相当吻合.以上结果说明,少量的GO对TGDDM/DDS体系的固化反应起着催化作用.     

C=C修饰的胆酸功能单体的非等温固化动力学研究

采用非等温DSC法分别对3,7,12–三甲基丙烯酰基胆酸甲酯(CAME3MA)和2-甲基丙烯酰氧基-3,7,12-三甲基丙烯酰基胆酸乙酯(CAGE4MA)的固化反应进行了研究,并与2-甲基丙烯酰氧基-3-甲基丙烯酰基胆酸乙酯(CAGE2MA)固化体系进行了比较。结果显示,3个体系有相似的非等温固化曲线,但是相同升温速率的峰顶温度不同,C=C数量越多,放热峰温度越高。用Kissinger法处理非等温DSC数据,3个体系的Ea和lnA值有差别,变化趋势均为CAGE2MA>CAGE4MA>CAME3MA。由于CAGE2MA容易形成分子间氢键,因此它反应所需的活化能也比后两者大;CAME3MA的分子间作用力稍小于CAGE4MA,因此前者的固化反应活化能也比后者略低。     

Effect of Non-Woven Carbon Nanofiber Mat Presence on Cure Kinetics of Epoxy Nanocomposites

Summary : An investigation was carried out into the cure kinetics of carbon nanofiber (CNF) mat-epoxy nanocomposites, composed of bisphenol-A based epoxy resin and diethylene triamine as a curing agent. It was observed that the rate of cure reaction for CNF mat-epoxy nanocomposites was higher than that for neat epoxy resin at low curing temperatures and the presence of the CNF mat produced the maximum influence at a certain curing temperature and time. At high curing temperature and long curing times, the effect of CNF mat on the cure rate was insignificant. The CNF mat-epoxy composite exhibited somewhat lower value of activation energy than that of the neat epoxy system at the beginning of the curing stage. The weight fraction of CNF mat also affected the cure reaction of epoxy nanocomposites at the same curing temperature. As the amount of CNF mat increased, the cure rate was higher at the same cure time. However, at high CNF mat loading, the cure reaction was retarded since the amount of epoxy and hardener decreased dramatically at high CNF contents together with the hindering effect of the CNF mat on the diffusion of epoxy resin and the curing agent, leading to lower crosslinking efficiency. Although the curing efficiency of epoxy nanocomposites dropped at high CNF mat content, the glass transition temperature (T_g) was still high due to the ultra-high strength of the CNF mat. The cure kinetics of CNF mat-epoxy nanocomposites was in good agreement with Kamal's model.     

基于松香酸酐的环氧树脂体系固化动力学及TTT图绘制

研制了基于松香酸酐固化剂的生物质环氧树脂体系,采用全动态DSC法研究了树脂体系的固化反应动力学,通过半经验的唯象模型拟合得到了固化反应参数,活化能Ea为59.68 kJ/g,指前因子A0为1.28×1015s-1,反应级数n为2.483,由此建立了体系固化温度/时间/固化度间的关系;采用恒温DSC及DMA方法测试玻璃化转变温度,应用DiBenedetto经验方程拟合得到了玻璃化转变温度与固化度间的关系.应用锥板旋转黏度计测试了树脂体系不同温度下的凝胶时间,通过线性回归分析得到了凝胶时间与温度之间的关系.由唯象模型和DiBenedetto方程分别计算得到凝胶时的固化度为0.386,玻璃化转变温度为26.22°C.由上述工作绘制了基于松香酸酐生物质树脂体系的TTT(time-temperature-transition diagram)固化图,可确定树脂体系在不同温度任意时间下的状态.     

Pulsed NMR study of the curing process of epoxy resin

To analyze a curing process of epoxy resin in terms of molecular motion, we adapted a pulsed NMR method. Three kinds of (1)H spin-spin relaxation times (T(2L) (long), T(2S) (short) and T(2M) (intermediate)) were estimated from observed solid echo train signals as the curing process proceeded. A short T(2S) value below 20 micros suggests the existence of a motion-restricted chain, that is, cured elements of resin, and its fraction, P(S), sigmoidally increased with the curing time. On the other hand, the fraction of T(2L), P(L), decreased with the reaction time reciprocally against P(S), suggesting the disappearance of highly mobile molecules raised from pre-cured resin. The spin-lattice relaxation time, T(1), was also measured to check another aspect of molecular motion in the process. T(1) of the mixed epoxy resin and curing agent gradually increased just after mixing both of them. This corresponds to an increment of a less-mobile fraction, of which the correction time is more than 10(-6) s, and also means that the occurrence of a network structure whose mobility is strongly restricted by chemically bonded bridges between the epoxy resin and curing agent. The time courses of these parameters coincided with those of IR peaks pertinent to the curing reaction. Therefore, pulsed NMR is a useful tool to monitor the hardening process of epoxy resin in real time non-distractively in terms of the molecular motion of protons.     

Thermal and physical properties of flame-retardant epoxy resins containing 2-(6-oxido-6H-dibenz〈c,e〉〈1,2〉oxaphosphorin-6-yl)-1,4-naphthalenediol and cured with dicyanate ester

2-(6-oxido-6H-dibenz(c,e)(1,2)oxaphosphorin-6-yl)-1,4-naphthalenediol (DOPONQ) was prepared by the addition reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) with 1,4-naphthoquinone. The phosphorus-containing diol (DOPONQ) was used as a reactive flame retardant by an advancement reaction with the diglycidyl ether of bisphenol-A epoxy (DGEBA) resin at various stoichiometric ratios. DOPONQ-containing advanced epoxy was separately cured with various dicyanate esters to form flame-retardant epoxy/cyanate ester systems. The effect of the phosphorus content and dicyanate ester structure on the curing characteristic, glass transition temperature, dimensional stability, thermal stability, flame retardancy, and dielectric property was studied and compared with that of the control advanced bisphenol-A epoxy system. The DOPONQ-containing epoxy/cyanate ester systems exhibited higher glass transition temperatures as well as better thermal dimensional and thermal degradation stabilities. The flame retardancy of the phosphorus-containing epoxy/dicyanate ester system increased with the phosphorus content, and a UL-94 V-0 rating could be achieved with a phosphorus content as low as 2.1%.     

Effects of novel polyhedral oligomeric silsesquioxane containing hydroxyl group and epoxy group on the dicyclopentadiene bisphenol dicyanate ester composites

Two types of novel Polyhedral Oligomeric Silsesquioxanes respectively containing hydroxyl group and epoxy group (P-POSS and E-POSS) were achieved and evaluated. The structure had been characterized by IR spectra and NMR spectra. Dicyclopentadiene bisphenol dicyanate ester (DCPDCE) composites were then prepared using P-POSS and E-POSS respectively. Their effect on the curing kinetics, dielectric, mechanical, flame-retardant and thermal properties and water absorption of the resulting composites were investigated. The results suggested that the addition of modified POSS could facilitate the curing reaction of DCPDCE. Besides, the DCPDCE composites containing modified POSS exhibited excellent flame-retardant property over pure DCPDCE resin. Adding only a little amount as small as 1.5 wt% P-POSS or 2.5 wt% E-POSS could change the UL-94V of DCPDCE resin from V-2 to V-0. The composite with P-POSS exhibited better flame-retardant and thermal properties than the composite with E-POSS. However, composite filled with E-POSS presented better dielectric property and lower water absorption.     

活性酯固化邻甲酚环氧树脂反应机理的研究

采用交叉反应研究在促进剂2-甲基咪唑存在下活性酯固化邻甲酚环氧树脂的反 应机理，用傅立叶转换红外（FTIR）原位测量技术，NMR，气-质联用（GC-MS）等 手段研究了模型化合物的反应动力学，并提出了其反应机理。结果表明，在促进剂 2-甲基咪唑存在下活性酯固化邻甲酚环氧树脂的反应是通过分子内机理进行的。     

Kinetics studies on the accelerated curing of liquid crystalline epoxy resin/multiwalled carbon nanotube nanocomposites

A new class of nanocomposite has been fabricated from liquid crystalline (LC) epoxy resin of 4,4′‐bis(2,3‐epoxypropoxy) biphenyl (BP), 4,4′‐diamino‐diphenyl sulfone (DDS), and multiwalled carbon nanotubes (CNTs). The surface of the CNTs was functionalized by LC epoxy resin (ef‐CNT). The ef‐CNT can be blended well with the BP that is further cured with an equivalent of DDS to form nanocomposite. We have studied the curing kinetics of this nanocomposite using isothermal and nonisothermal differential scanning calorimetry (DSC). The dependence of the conversion on time can fit into the autocatalytic model before the vitrification, and then it becomes diffusion control process. The reaction rate increases and the activation energy decreases with increasing concentration of the ef‐CNT. At 10 wt % of ef‐CNT, the activation energy of nanocomposite curing is lowered by about 20% when compared with the neat BP/DDS resin. If the ef‐CNT was replaced by thermal‐insulating TiO₂ nanorods on the same weight basis, the decrease of activation energy was not observed. The result indicates the accelerating effect on the nanocomposite was raised from the high‐thermal conductivity of CNT and aligned LC epoxy resin. However, at ef‐CNT concentration higher than 2 wt %, the accelerating effect of ef‐CNTs also antedates the vitrification and turns the reaction to diffusion control driven. As the molecular motions are limited, the degree of cure is lowered. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

电子束固化环氧树脂的物理特征及其分析

分析了环氧树脂电子束辐射固化的物理特征 ,电子束辐射固化过程受活性中心扩散控制 ,整个固化区域由片层状结构组成 .与电子能量沉积分布相对应 ,环氧树脂辐射固化度的最高值是在一定深度而不是在辐射表面出现 .对电子束辐射环氧树脂体系的固化过程进行了模型解释 ,固化区域大小主要由电子的能量传递范围和浓度决定 ,反应活性中心的扩散作用影响较弱     

Influence of T31 content on combustion and thermal degradation behaviors on flame-retardant epoxy composites

To study the influence of the T31 content on the combustion properties and thermal degradation behaviors of flame-retardant epoxy composites, a series of flame-retardant epoxy composites were prepared using E-44 epoxy resin as matrix, T31 curing agent as curing agent, and intumescent flame retardant (IFR, based on phosphorus acid, melamine, and pentaerythritol) as flame retardant. The influence of T31 content on combustion behaviors and thermal degradation properties of the flame-retardant epoxy composites were studied using cone calorimeter test (CCT) and thermal-gravimetric analysis (TG), respectively. The cone calorimeter test results indicate that the decrease of T31 can significantly decrease the HRR, THR, SPR, and enhance the char residue of the epoxy composites. EP-4 with 7.0 wt% T31 shows the lowest HRR, SPR and the highest char residue. Furthermore, the TG results indicate that the EP-4 has the highest char residue among all the epoxy composites.