环氧树脂灌封料的固化动力学及固化工艺

采用流变学手段、非等温差示扫描量热法和原位升温傅里叶变换红外光谱法研究了2种环氧树脂灌封料的固化动力学,并对其固化工艺进行设计与验证。采用Kissinger和Flynn-Wall-Ozawa方程计算得到2种灌封料的平均表观活化能分别为70.76 kJ/mol和61.61 kJ/mol。根据DSC非等温曲线外推法获得体系的理论固化温度及时间,并依此得到的固化物与原始条件制备的固化物进行力学性能对比,发现影响固化工艺设计的关键因素是温度和时间。研究结果可为环氧树脂灌封料的固化工艺条件设计及实际应用提供理论参考。     

固化度与固化收缩对非对称复合材料 层合板固化变形的影响

采用三维有限元方法研究复合材料非对称层合板在热载荷和固化收缩载荷下的固化变形情况, 建立了材料力学特性、 固化体积收缩量和温度与固化度之间的函数关系, 考察了层合板变形曲率与温度和固化度之间的关系。数值计算结果表明: 非对称层合板变形曲率与固化终止时固化度有密切关系; 固化变形主要发生在降温阶段; 固化收缩对层合板变形曲率影响很小, 主要发生在第二个保温平台的前半段。      

紫外光固化导电胶的制备及固化动力学机制

为研究紫外光固化导电胶的性能及固化机制,以银包铜粉、环氧丙烯酸树脂为原料制备固化胶,采用刮涂法将浆料涂覆到载玻片上,置于紫外光下固化获得导电涂层。对试样的微观结构、力学和电学性能进行表征,对固化体系的热行为及固化反应动力学机理进行了研究,并利用Kissinger和Grane模型计算固化反应的活化能和反应级数。研究结果表明:光辐射下导电胶层可快速固化;当填料含量为70wt%时,浆料达最低电阻率1.122mΩ·cm;填料含量75wt%时剪切值最大为57.4MPa;活性稀释剂含量为35wt%时,浆料具有最佳的固化速度和网联结构;固化反应过程中表观活化能为15.17kJ/mol,固化工艺为172.3℃→302.05℃→369.35℃,为一级固化反应;浆料在200℃以下具有较好的抗氧化性能。     

呋喃树脂固化体系及其固化机理研究进展

呋喃树脂是重要的粘合剂之一,呋喃树脂的使用性能除了和呋喃树脂本身的性能有关外,还与呋喃树脂固化剂体系有很大的关系。主要介绍了国内外呋喃树脂固化剂体系的研究进展,总结归纳了各种固化剂的优缺点,并对它们的固化性能作了对比。从这些对比中可以得出结论,在生产实践中,固化剂的使用必须根据生产条件和要求进行合理选择,以期发挥出各固化剂自身的优点,降低生产和使用成本。同时,还介绍了酸催化下呋喃树脂的固化机理的研究进展,并展望了呋喃树脂固化剂的发展方向。     

3221中温固化环氧树脂体系的固化反应

采用DSC方法研究了不同固化体系对3221环氧树脂固化体系固化反应的影响,探讨了反应机理,分析了双氰胺及双氰胺 取代脲作为固化剂的反应动力学,预测了氰胺 取代脲固化体系的固化工艺参数,并加以验证。结果表明,采用双氰胺 取代脲的复合固化体系能使3221体系的表观活化能Ea比单独使用双氰胺时降低58 kJ/m o l,前者固化温度比后者降低50℃左右,并能使反应缓和。     

紫外光固化导电胶基体固化动力学分析

紫外光固化导电胶作为新型电子连接材料,具有环保、节能等优点。导电胶中基体胶的固化性能是影响导电胶使用可靠性的重要因素。利用实时红外分析研究环氧树脂基体胶的固化过程和固化过程的动力学特征。研究表明基体胶的固化是通过体系中-C=C-双键的互联来实现,随固化反应的进行,双键的相对浓度降低。光引发剂的添加量影响体系的固化速度和固化程度,光引发剂的添加量存在阈值Cmax。     

环氧树脂固化过程两种固化机理的渡越

采用傅立叶转换红外光谱法（FT－IR）对四溴双酚A环氧树脂／二氨基二苯砜（TBBKPAER／DDS）固化体系在不同温度下的固化过程进行了研究。结果表明，反应条件从低温改变到高温，固化体系固化过程的反应机理是由自催化反应机理过渡到n级反应机理的，中间有一渡越过程。     

水性紫外光固化聚氨酯丙烯酸酯的干燥与固化过程

采用聚氨酯丙烯酸酯为研究对象,分别对水溶性、水乳液型紫外光(UV)固化树脂的干燥和固化规律进行研究,考察了树脂分子结构、干燥固化条件等因素对干燥和固化的影响。通过对涂膜红外干燥过程的研究,发现红外辐射可以将UV固化聚氨酯丙烯酸酯乳液的干燥时间降至30 s左右。对涂膜固化过程的研究表明,固化条件、分子结构和添加物对固化时间都有重要影响,选择合适的条件,固化时间可以缩短至5 s以内。     

GFRP厚板制件固化过程固化度分布

采用真空导入模塑工艺(VIMP) 制备了85 mm 厚玻璃纤维增强环氧树脂层合板, 单面刚性模具加热固化, 沿铺层厚度方向设置热电偶, 进行了实时固化温度监测, 发现固化时厚度方向存在明显的温度差异。通过DSC方法得到等温环氧树脂固化度-时间实验数据, 建立了基于自催化反应模型的等温固化反应动力学方程, 模型计算值和实验值符合良好; 提出了时间离散分步计算法, 对非等温固化条件下, 厚度方向的固化度分布进行了计算。结果表明: 固化过程中厚度方向固化度存在差异, 短时间的后固化可以消除此差异。该方法可以模拟出由温度差异导致的固化度的不均匀分布, 用于指导优化固化工艺。      

电子束固化环氧树脂的物理过程及固化厚度的分析

对环氧树脂电子束辐射固化的物理过程进行了分析,研究了辐射剂量、引发剂用量、树脂分子量及其分布,以及化学结构对固化厚度的影响。研究结果显示,环氧树脂体系在电子束辐射后形成围绕入射中心均匀扩展的固化区域,随着辐射剂量的提高,树脂辐射固化厚度的增加幅度变小。引发剂用量增加,辐射固化厚度呈现一种先上升后下降的趋势。提高辐射剂量,树脂分子量对固化厚度的影响减小,固化厚度的增加幅度与树脂的分子量分散性成反比。对于分子量相近而结构不同的环氧树脂,酚醛型环氧树脂在低辐射剂量下的固化区域较大,双酚A型环氧树脂的固化厚度随辐射剂量提高有较大幅度增加,脂环族环氧树脂的固化区域相对较小。     

固化条件对热塑增韧环氧树脂的固化动力学和相分离的影响EI

采用砂型和金属型两种不同铸造方法对铸态、固溶态和时效态ZL210A合金性能及断口形貌的影响进行研究.结果表明:对ZL210A铸造合金而言,金属型铸造方法优于砂型铸造方法,其常规力学性能σb,σ0.2和δ5均高于砂型铸造,从断口形貌上看,试样断口形貌均呈现典型的穿晶断裂,且韧窝较深.其中,金属型固溶态试样的断口韧窝最为明显,呈现出较好的韧性.     

Study on thermoplastic-modified multifunctional epoxies: Influence of heating rate on cure behaviour and phase separation

The effect of heating rate on the cure behaviour and phase separation of thermoplastic-modified epoxy systems was investigated. Polyethersulphone (PES) modified multifunctional epoxies, triglycidyl-aminophenol (TGAP) and tetraglycidyldiaminodiphenylmethane (TGDDM), as well T300/914 prepreg were used. It was shown that heating rate had a significant influence on the cure kinetics and phase structures of investigated systems. Greater heating rate causes higher epoxy conversion. The domain size of the macrophases formed from phase separation increases with the increase of heating rate. A more complete phase separation is achieved by fast heated thermoplastic-modified epoxy blends.     

Designing of epoxy resin systems for cryogenic use

The mechanical and thermal properties of several types of epoxy systems were designed based on the chemical structure, network structure and morphology aiming at cryogenic application. In this research di-epoxies or multifunctional epoxies were cured by several kinds of hardeners such as anhydride, amine or phenol and were blended with polycarbonate, carboxyl-terminated butadiene acrylonitrile copolymer or phenoxy. The mechanical properties and thermal properties of these cured epoxies were measured at room and liquid nitrogen temperature. It was found that the two-dimensional network structured linear polymer shows high performance even at cryogenic temperature. It was concluded that the controls of the structures are very important to optimize epoxy systems for cryogenic application.     

Thermodynamically reversible and irreversible control on morphology of multiphase systems

Morphology and properties of polymer alloys can be controlled by thermodynamically reversible (structure freeze-in) or irreversible (structure lock-in) processes via simultaneously manipulating miscibility, mechanisms of phase separation, glass transition (structural relaxation), and cure kinetics of polymer systems. Using phase diagrams consisting of binodal and spinodal curves, the morphology of epoxy/carboxyl-terminated butadiene acrylonitrile copolymer (CTBN) systems can be controlled by the mechanism of nucleation and growth or by spinodal decomposition. We have found that the particle size of the rubber reinforcement in epoxies is affected by the mechanisms of phase separation. Phase separation by nucleation and growth gives larger rubber particles than the corresponding phase separation by spinodal decomposition. This contrast in the morphology development is the consequence of controlling phase separation through chemorheological behaviour. Modification of the phase separation kinetics in epoxy/CTBN systems was extremely effective at altering both morphology and properties of these alloys. This technique offers a means to shift the glass transition temperature of the rubber-rich phase while leaving the glass transition temperature of the epoxy-rich phase intact. Such control over morphology is the key to ultimately controlling material properties.     

混合比及后处理对混合环氧/热塑性树脂复相体系动态力学特征的影响

以热塑性树脂(TP)/双酚A二缩水甘油醚(DGEBA)及二苯基甲烷四缩水甘油胺(TGMDA)混合环氧树脂的复相体系为基础,采用动态力学分析手段研究了在相同热塑性树脂含量的条件下,混合比例对混合环氧/热塑性树脂的动态力学性能中tanδ曲线的特征峰位置、峰形等的影响,以及在经高温后处理后曲线特征峰的变化.结合树脂断口分析,结果显示:混合环氧在固化反应过程中对热塑性树脂的高粘度高阻碍性的响应是不同的,tanδ曲线上的主峰主要由TP的转变构成而次级峰则主要由DGEBA环氧固化物的转变构成.高温后处理使树脂体系有利于分相及固化网络的完善.在复相体系中,连续相主要由TP及TGMDA环氧固化网络构成,DGEBA环氧主要存在于分散相中.     

Epoxy resin/liquid natural rubber system: secondary phase separation and its impact on mechanical properties

An investigation was carried out to explore the morphology and mechanical properties of diglycidyl ether of bisphenol A epoxy resin (DGEBA) with liquid natural rubber possessing hydroxyl functionality (HLNR). Though modification of epoxies by synthetic rubber has been extensively studied not much attention has been paid to liquid natural rubber. Photo depolymerisation of natural rubber enables us to synthesise low molecular weight oligomers by varying the experimental parameters. Epoxy resin was cured using nadic methyl anhydride as hardener in presence of N,N-dimethyl benzyl amine accelerator. Hydroxylated natural rubber of different concentrations is used as modifier for epoxy resin. The addition of such chemically modified liquid rubber to an anhydride hardener–epoxy resin mixture has given rise to the formation of a two-phase microstructure in the cured systems, consisting of spherical particles of liquid natural rubber strongly bonded to the surrounding matrix, there by providing the required mechanism for toughness enhancement. Subinclusions of epoxy resin were present in the elastomer domains as secondary particles (particle in particle morphology) as evidenced from the SEM (scanning electron micrograph) photomicrographs. The origin of the so-called secondary phase separation is due to the combined effect of hydrodynamics, viscoelastic effects of rubber phase, diffusion, surface tension, polymerisation reaction and phase separation. In a dynamic asymmetric system, the diffusion of the fast dynamic phase is prevented by the slow dynamic phase, and hence the growth of fast dynamic phase gets retarded due to the slow dynamic phase. In the case of low viscosity blends the growth of fast dynamic phase turns fast and hence diffusion of fast dynamic phase cannot follow geometrical growth and cannot establish local concentration equilibrium and hence double phase separation takes place. The double phase separation is responsible for the enhanced impact and toughness behaviour of the blends. The mechanical behaviour of the liquid rubber-modified epoxy resin was evaluated in terms of tensile and flexural properties.     

Morphology, dynamic mechanical and thermal studies on poly(styrene-co-acrylonitrile) modified epoxy resin/glass fibre composites

Poly(styrene-co-acrylonitrile) (SAN) was used to modify diglycidyl ether of bisphenol-A (DGEBA) type epoxy resin cured with diamino diphenyl sulfone (DDS) and the modified epoxy resin was used as the matrix for fibre reinforced composites (FRPs) in order to get improved mechanical and thermal properties. E-glass fibre was used as the fibre reinforcement. The morphology, dynamic mechanical and thermal characteristics of the systems were analyzed. Morphological analysis revealed heterogeneous dispersed morphology. There was good adhesion between the matrix polymer and the glass fibre. The dynamic moduli, mechanical loss and damping behaviour as a function of temperature of the systems were studied using dynamic mechanical analysis (DMA). DMA studies showed that DDS cured epoxy resin/SAN/glass fibre composite systems have two T_gs corresponding to epoxy rich and SAN rich phases. The effect of thermoplastic modification and fibre loading on the dynamic mechanical properties of the composites were also analyzed. Thermogravimetric analysis (TGA) revealed the superior thermal stability of composite system.     

Investigating of polysulfide and epoxy‐polysulfide copolymer curing

Polysulfide can be cured in various methods. In this work, the effect of various oxidative curing agents (manganese dioxide and para quinonedioxime) in presence of curing accelerator (Diphenylguanidine) on mechanical‐dynamical properties and cure time of polysulfide resin (G4) was investigated. Results showed that mentioned oxidative curing agents have no remarkable effect on mechanical properties and cure time. But preferred method is preparation of polysulfide‐epoxy copolymer. This copolymer is a new class of liquid polymer composition containing block copolymers, with alternating blocks of polysulfide and polyepoxide. in different epoxy/polysulfide ratio, the epoxy‐polysulfide copolymer showd different tensile strenght, elongation, hardness, gel time, viscosity and Tg, but epoxy free polysulfide approximately revealed constant mechanical and dynamical properties so that epoxidized polysulfide had excellent mechanical properties and suitable curring times in comparison with those samples which were cured in other methods. FT‐IR spectroscopy, viscometry and GPC were used to verify the formation of epoxy‐polysulfide copolymer. Results obtained from DMTA and SEM showed that phase separation of epoxy resin from the copolymer matrix took place and The glass transition temperature (Tg) of the cured copolymer was between the cured epoxy and polysulfide glass transition temperatures.     

Effects of modified hyperbranched polyester as a curing agent on the morphology and properties of dynamically cured polypropylene/polyurethane blends

The dynamic vulcanization process, usually used for the preparation of thermoplastic elastomers, has been applied to prepare polypropylene (PP)/polyurethane (PU) blends. Boltorn^TM H20 (H20) hyperbranched polyester containing 16 hydroxyl end gropus and pentaerythritol are used as curing agents, respectively, for curing PU oligomer during blending with molten PP. To improve the compatibility of cured PU particles with PP matrix, H20 is partly functionalized with stearic acid. The morphology, mechanical properties, thermal properties and melt flow index (MFI) of the PP/PU blends with different curing agent are investigated. Compared with pentaerythritol, SEM photographs show that H20 partly functionalized with stearic acid effectively reduces the size and size distribution of cured PU particles in PP/PU blends which also is proved by MFI measurement. Consequently, the dynamically cured PP/PU blends with modified H20 have better mechanical properties than those cured with pentaerythritol. The shifts of crystallization peaks to higher temperatures for all PP/PU blends indicate that PU particles in the blends can act as effective nucleating agents. Moreover, due to the smaller size of PU particles PP/PU blends cured with modified H20 have higher crystallization temperatures than those blends cured with pentaerythritol at the same PU content.     

Micro-crack behavior of carbon fiber reinforced thermoplastic modified epoxy composites for cryogenic applications

Three different types of thermoplastics, poly(ether imide) (PEI), polycarbonate (PC), and poly(butylene terephthalate) (PBT) were used to modify epoxy for cryogenic applications. Carbon fiber reinforced thermoplastic modified epoxy composites were also prepared through vacuum-assisted resin transfer molding (RTM). Dynamic mechanical analysis (DMA) shows that the storage moduli of PEI, PC, and PBT modified epoxies are 30%, 21%, and 17% higher than that of the neat epoxy respectively. The impact strength of the modified epoxies at cryogenic temperature increases with increasing thermoplastic content up to 1.5 wt.% and then decreases for further loading (2.0 wt.%). The coefficient of thermal expansion (CTE) values of the PBT, PEI, and PC modified epoxies also decreased by 17.76%, 25.42%, and 30.15%, respectively, as compared with that of the neat epoxy. Optical microscopy image analysis suggests that the presence of PEI and PC in the carbon fiber reinforced epoxy composites can prevent the formation of micro-cracks. Therefore, both the PEI and PC were very effective in preventing micro-crack formation in the composites during thermal cycles at cryogenic condition due to their low CTE values and high impact strength.