RTM用环氧树脂体系的固化工艺研究

本文研究了以多官能团环氧树脂及液体酸酐为基体,以叔胺及有机酸盐为促进剂组成的RTM用环氧树脂体系,采用DSC和DMA等方法研究了树脂体系的固化工艺及固化物的性能.结果表明:该树脂体系粘度低,适用期长,适用于RTM工艺;该树脂体系的湿热性能较差,需进一步研究改性.     

真空辅助RTM用环氧树脂成型工艺研究

对环氧树脂LT-5078体系进行了粘度-温度、粘度-时间测试,研究了其粘度特性,通过动态DSC法测定了树脂的固化反应热,并通过外推法得到其特征固化温度和成型工艺条件。实验表明,LT-5078的凝胶温度、固化温度、后处理温度分别为42℃、102℃、185℃,固化工艺为25℃×24 h+120℃×4 h。该树脂25℃时由初始粘度250 mPa.s上升到800 mPa.s所用时间为170 min左右,常温下有较长的低粘度时长,适合真空辅助RTM成型。     

RTM用环氧树脂流变性能与固化性能分析

制备了R2511、R2512两种RTM环氧树脂体系,研究了其工艺性能、固化性能及力学性能,分析表明:两种树脂体系均具有适宜的低粘度操作窗口,R2511树脂体系的最佳工艺区间为40~50℃,R2512树脂体系的最佳工艺区间为常温灌注;R2511树脂体系活化能为72 kJ/mol,R2512树脂体系活化能较低,为62 kJ/mol;R2512树脂体系整体力学性能优于R2511树脂体系;两种树脂适用于不同的温度体系。     

RTM用环氧树脂体系的浸润性及化学流变特性研究

对树脂传递模塑（RTM）用环氧树脂体系对纤维的浸润性能进行了研究,同时在基本的黏度实验基础上,采用双阿仑尼乌斯方程研究了其化学流变特性。结果表明,纤维经丙酮处理后浸润性能提高,RTM环氧树脂浸润纤维变得容易;并通过双阿仑尼乌斯方程建立了RTM环氧树脂体系的化学流变模型,该模型揭示了RTM环氧树脂在35~75 ℃的温度范围内黏度低于800 mPa·s,且低黏度保持时间大于20 min,满足复合材料RTM成型的基本工艺要求。     

RTM工艺用室温可固化环氧树脂体系性能研究

选取了三种低黏度且可以室温固化的环氧树脂体系:QC350A/B,1564/HY3487,EV6620/HVC188,表征了树脂体系的流变性能、室温固化固化度及固化物弯曲性能。结果表明:三种环氧树脂体系在20~50℃有适于树脂传递模塑(RTM)工艺的低黏度操作平台;室温固化2周内固化度可达到90%,可以完成室温固化;室温固化21 d弯曲强度与高温后处理试样相当,弯曲弹性模量优于高温后处理试样,室温固化能够满足使用性能要求。     

航空复合材料RTM工艺用环氧树脂的流变模型

航空高纤维体积含量复合材料树脂传递模塑成型(RTM)工艺要求树脂体系有较低的黏度,因此分别采用双阿累尼乌斯黏度模型和联合工程黏度模型对所配制环氧树脂体系的黏度变化进行预测。结果表明,联合工程黏度模型由于考虑了固化过程中温度变化的累积效应对树脂体系黏度的影响,所以相对于双阿累尼乌斯黏度模型,不管是反应初期还是后期更能准确预测所配制环氧树脂体系黏度的变化。通过联合工程黏度模型确定了该环氧树脂体系的最佳注射温度为35~45℃,该温度范围内树脂的初始黏度大于80mPa·s,且树脂从配制到黏度增加到200m Pa·s的时间大于29min,增加到500mPa·s的时间大于97min,满足航空高纤维体积含量复合材料RTM工艺的充模要求。     

RTM用环氧树脂体系的流变性能研究

研究了RTM用酚醛环氧树脂体系的化学流变行为。采用示差扫描量热分析仪(DSC)考察了树脂体系的固化反应特性,通过流变仪研究了体系黏度与温度及时间的关系。基于树脂体系的化学流变特性,建立双Arrhenius黏度模型。研究表明,在恒温条件下,模型黏度的模拟值与实验结果具有良好的一致性。此模型可描述树脂体系在不同温度条件下的黏度变化趋势,为优化RTM工艺参数和保证产品质量提供了必要的技术基础和理论依据。     

RTM成型用高性能环氧树脂基体的研究

将AG-80和TDE-86以一定比例混合,通过加入自配的低粘度液体固化剂,得到了一种适用于RTM工艺的树脂体系。结果表明,该树脂体系在30℃时的粘度为1081mPa.s,其树脂固化物的拉伸强度为73MPa,弹性模量达到1.36GPa,断裂伸长率为6.3%,弯曲强度为150MPa,弯曲模量为3.12GPa,玻璃化转变温度为191℃,该树脂体系不仅粘度低,还具有优异的力学性能和耐温性,可满足RTM成型工艺对环氧树脂体系的要求。     

真空辅助成型工艺环氧树脂体系化学流变特性研究

通过实验研究了环氧树脂的化学流变特性,分别考察了双阿累尼乌斯黏度模型、工程黏度模型及联合黏度模型在真空辅助成型工艺专用环氧树脂(2511-1A)应用的有效性。通过比较分析发现,联合黏度模型更加准确地反映了该树脂的时间-温度-黏度的变化情况,进而预测了树脂的工艺时间窗口。根据时间-温度的变化关系,建立了非恒温下2511-1A环氧树脂体系的联合黏度模型,预测了在不同升温速率下黏度的变化,预测结果与实验结果较吻合,可进一步应用于热压工艺技术参数的选择。     

APG工艺用环氧树脂体系的固化及流变模型

研究了自动压力凝胶工艺用环氧树脂混合体系在动态升温过程中的固化反应,采用Malek法确定了动力学模型并预测了相应的参数。该体系符合两参数自催化SB模型。用旋转流变仪测定了该体系在动态升温过程中黏度相对于温度的变化曲线,采用WLF和Macosko混合方程描述该体系的化学流变模型,用非线性拟合方法预测了模型中的参数。模型预测与实验数据比较吻合。     

芳基乙炔树脂的固化反应动力学及流变行为研究

通过对芳基乙炔树脂的固化动力学研究确定其适宜的固化工艺。采用DSC和流变分析得到芳基乙炔树脂的特征固化参数及其固化度与温度的关系曲线。结果表明,树脂的起始反应温度为127.1℃,反应峰值温度164.2℃,终止反应温度195.1℃。固化动力学参数为:表观活化能E=190.12kJ/mol,反应级数n=1.87,频率因子A=1.995×1019。芳基乙炔树脂的加压固化温度为110～115℃,其起始固化温度为115℃。固化工艺为:115℃/8h+120℃/8h+140℃/2h+160℃/2h+180℃/2h+200℃/2h+220℃/4h。芳基乙炔树脂凝胶前固化过程由化学反应控制,凝胶后属于扩散控制,因此在凝胶时需延长固化时间。     

Apparent volumetric shrinkage study of RTM6 resin during the curing process and its effect on the residual stresses in a composite

A comprehensive characterization of the volumetric shrinkage of a commercially important aerospace resin (RTM6) during the various stages of the curing process was studied. The apparent volumetric shrinkage, evaluated from density measurements at room temperature, was correlated with the progress of epoxide conversion. During the entire curing process, the apparent volume shrinkage was found to be less than 3% and occurred before vitrification. A slight re‐expansion of the resin, attributed to self‐antiplasticization effects, was observed during postcuring at 180°C. It was concluded that residual stresses were not generated due to chemical cross‐linking during curing but rather from thermal contraction occurring during the cooling stage after cure. A photo‐elastic method was used to characterize residual stresses during cooling in a deliberately engineered resin rich hole of a carbon fiber/RTM6 composite. The residual stress was found to reach approximately 28 MPa, which is in good agreement with the value calculated from the shrinkage and elastic moduli. It is proposed that this simple method can be provide insights useful to the design and materials selection processes by measuring and localizing residual stresses from resin during curing and or thermal cycling. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

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.     

几种RTM用环氧树脂体系研究

为满足RTM工艺对树脂体系低粘度的要求,研究了3种用于制备高性能复合材料主承力构件的环氧树脂体系:CYD-128/IA(脂环族多元胺),TDE-85/TA(脂环族多元酸酐)/DMP-30及双酚F环氧树脂/DT/DP(脂肪族多元胺)。测试了同一体系中不同配比对浇注体力学性能的影响并研究了3种体系的流变行为。结果表明,CYD-128/IA体系中,IA的最佳添加量为22%(质量分数,下同);TDE-85/TA/DMP-30体系中TA最佳用量为110%,DMP-30最佳用量为0.4%;双酚F环氧树脂/DT/DP体系中,单独使用5%DP效果最佳。相同温度下,CYD-128/IA粘度比TDE-85/TA/DMP-30体系大得多,随时间增加粘度上升也较快。双酚F环氧树脂/DT/DP体系粘度特性对配比的依赖性较大。     

Nondestructive rapid and quantitative analysis for the curing process of silicone resin by near-infrared spectra

Reactive group content was a key parameter in polymer curing process. However, the conventional methods to measure the curing were destructive and time consuming. In this article, near-infrared spectra technology had been applied for reactive group analysis of the photothermal curing silicone to achieve rapid nondestructive and quantitative detection. The calibration model was developed about epoxy value and CC double bond value, with determination coefficient (R²) of 0.9631 and 0.9689. Root mean square error of prediction were 0.0179 and 0.0143 by partial least square regression. The optimized calibration model was used to predict the content of epoxy value and CC double bond value in the photothermal curing process, it proved that the silicone resin cured under UV-radiation and heat. This novel method provided a promising approach to analysis the curing mechanism and quality parameters of resin.     

烯丙基酚醛树脂固化行为的研究

利用酚醛树脂与氯丙烯反应,合成出了烯丙基酚醛树脂（APF）,并对其固化过程进行了研究。结果表明,烯丙基酚醛树脂不仅能溶于极性溶剂,还能溶于非极性溶剂,其起始固化温度为180℃,比普通的酚醛树脂高。烯丙基酚醛树脂的固化窗口为44℃,其固化是通过双键的加成反应来实现的,固化后树脂为连续相结构。     

POSS改性BMI树脂固化动力学及固化工艺研究

以双马来酰亚胺(BMI)、二烯丙基双酚A(BA)和七苯基倍半硅氧烷三硅醇(POSS-triol)为原料,采用非等温差示扫描量热(DSC)法研究了BMI/BA/POSS-triol体系的固化反应过程。运用Kissinger极值法、Crane法、Flynn-Wall-Ozawa(FWO)等转化率法和T-β(温度-升温速率)外推法确定了改性树脂体系的固化反应动力学参数和固化工艺参数。结果表明:改性树脂体系的固化反应活化能和反应级数(接近于1)均随POSS-triol用量增加而变化不大,说明POSS-triol的加入并没有明显改变BMI/BA体系的固化反应机理;改性树脂体系的凝胶温度为175.7℃,固化温度为226.9℃,后处理温度为271.7℃。     

Dielectric monitoring of the curing process in cyanoacrylate resin

The cure monitoring of cyanoacrylate resin using a dielectric technique shows that in addition to the usual fast anionic polymerization step, there may be a secondary process involved over longer time scales. Two peaks are distinctly observed in the isothermal curing curves, and from the position of these at various temperatures, the activation energies of 0.4 eV and 0.17 eV could be derived. In cured cyanoacrylate resin, three relaxations were observed, viz., α, β, and γ, occurring at 152°c, 87°c, and 47°c, respectively (for 1 KHz measuring frequency), with activation energies of 1.3 eV, 0.56 eV, and 0.4 eV, respectively. The various results have been explained on the basis of secondary bond formation through the nitrile group, for which some evidence could be obtained from the infrared absorption spectra.