环氧树脂/聚砜共混体系相结构的调控研究——环氧预聚物分子量的影响

研究了不同分子量的环氧预聚物对双酚A型双官能团环氧树脂 /聚砜 (PSF) /固化剂 (二氨基二苯基砜 ,DDS)体系相分离结构的影响 .通过红外光谱 (FTIR)和动态热机械分析 (TMA)对反应转化率、玻璃化温度以及固化温度的关系的研究 ,表明环氧预聚物分子量较小时 ,凝胶点和玻璃化是影响相结构的关键因素 ;环氧分子量较大时 ,环氧扩链后粘度的变化则成为抑制相分离的重要因素 .电子显微镜 (SEM)结果表明改变环氧预聚物分子量可以达到调控相结构的目的 ,随着预聚物分子量的增大 ,体系的微区尺寸减小 .     

热塑性聚醚酰亚胺改性四官能度环氧树脂的相分离研究──固化剂用量的影响

以DSC、TRLS和SEM等方法研究了固化剂DDS用量对苯端基聚醚酰亚胺(P-PEI)改性4,4'-二氨基二苯甲烷四缩水甘油环氧树脂(TGDDM)体系的固化速率及相结构的影响.结果表明,20phrP-PEI改性环氧体系在150℃固化时,随DDS量增加,固化反应速率增大,相分离时间提前,形成了不同的相结构,解释了DDS量对粘接剪切强度的影响.     

Chemically induced phase separation in the preparation of porous epoxy monolith

A methodology for preparing porous epoxy monolith via chemically induced phase separation was proposed. The starting system was a mixture of an epoxy precursor, diglycidyl ether of bisphenol‐A (DGEBA), a curing agent, 4,4′‐diaminodiphenylmethane (DDM), and a thermoplastic polymer, polypropylene carbonate (PPC). As DGEBA was cured with DDM, the system became phase‐separated having PPC particles dispersed in epoxy matrix. After PPC particles were removed by thermal degradation, a porous structure was obtained. The phase separation mechanism was determined by the initial composition and illustrated by a pseudophase diagram. The pore size increased with increasing the concentration of PPC and raising the curing temperature. The intermediate and final morphologies of the system were studied using optical and scanning electron microscopy, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Fracture toughening of epoxy matrices with blends of resins of different molecular weights and other modifiers

The microstructure and fracture behavior of epoxy mixtures containing two monomers of different molecular weights were studied. The variation of the fracture toughness by the addition of other modifiers was also investigated. Several amounts of high‐molecular‐weight diglycidyl ether of bisphenol A (DGEBA) oligomer were added to a nearly pure DGEBA monomer. The mixtures were cured with an aromatic amine, showing phase separation after curing. The curing behavior of the epoxy mixtures was investigated with thermal measurements. A significant enhancement of the fracture toughness was accompanied by slight increases in both the rigidity and strength of the mixtures that corresponded to the content of the high‐molecular‐weight epoxy resin. Dynamic mechanical and atomic force microscopy measurements indicated that the generated two‐phase morphology was a function of the content of the epoxy resin added. The influence of the addition of an oligomer or a thermoplastic on the morphologies and mechanical properties of both epoxy‐containing mixtures was also investigated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3920–3933, 2004     

The influence of polyetherimide on gelation and phase separation in epoxy systems

In the process of curing under thermostatic conditions, the time dependence of active and reactive components of the dielectric permittivity of epoxy amine compositions that contain a thermoplastic substance is studied in a wide range of electrical frequencies. The times of gelation and vitrification are calculated from the dielectric data and the onset of the phase separation is identified. The curing behavior established by dielectric spectroscopy is confirmed by viscometry and optical microscopy. During the phase separation, the morphology of the precipitating phase differs between samples depending on the chemical nature of the curing agent.     

热塑性聚醚酰亚胺改性四官能度环氧树脂的相分离研究Ⅳ.聚醚酰亚胺用量的影响

研究了不同用量新型苯端基聚醚酰亚胺（Ｐ－ＰＥＩ）对其改性４,４’－二氨基二苯甲烷四缩水甘油醚环氧树脂（ＴＧＤＤＭ）／４,４’－二氨基二苯砜（ＤＤＳ）体系的固化速率及相结构的影响。结果表明,随着ＰＥＩ用量的增加,固化反应速率增大,形成了不同的相结构。解释了ＰＥＩ用量对粘接剪切强度的影响。     

Effect of cellulose nanofiber on the dynamically asymmetric phase separation in epoxy/polysulfone blends

Significant effect of cellulose nanofibers (CNFs) on cure‐induced phase separation in dynamically asymmetric system is reported. An epoxy/polysulfone blends with typical layered structure formation was chosen as the polymer matrix, and morphology evolution and rheological behavior of systems with different nano‐size fiber loadings upon curing reaction were investigated using optical microscopy and rheological measurement. CNF distributed uniformly in the polymer matrix and had good interaction with polymer chains. Curing reaction of epoxy was promoted by CNF, making the system gel and phase separate earlier. Meanwhile, system viscosity was increased with CNF addition, and the movement of polymer chains and component diffusion were constrained, as a result, the structure evolution process was slowed down. The CNF altered the final morphologies, resulting in refined structures with smaller characteristic length scales or even completely change the morphologies from the layered structures to a bicontinuous structure when the CNF concentration reached to a relatively high level. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1357–1366     

Phase behavior and morphology in epoxy resin/poly(L-lactide) blends. Comparison with epoxy resin/poly(L,D-lactide) blends

Thermoset/thermoplastic blends were prepared with epoxy–aromatic diamine mixtures and poly(L-lactide) (PLLA), as semicrystalline thermoplastic, in concentrations ranging from 4 to 25 wt.%. In some cases, poly(L,D-lactide) (PDLLA), an amorphous thermoplastic, was used instead for comparative purposes. Diglycidyl ether of bisphenol-A (DGEBA) was employed as epoxy resin and 4,4′-diaminodiphenylmethane (DDM) as curing agent. Phase behavior and morphology were studied during curing at 140 °C. Initially, all blends were homogeneous; however, the curing reaction of the epoxy resin caused a liquid–liquid phase separation. A co-continuous morphology was formed at the beginning of the phase separation in all the considered blend compositions. Blends evolved to a particle/matrix structure or to a phase-inverted structure depending on the initial blend composition. At 140 °C, crystallization only occurred in blends with 16 and 25 wt.% PLLA. This crystallization originates changes in the surface of the epoxy-rich droplets developed with the phase separation.     

Morphology and interphase formation in epoxy/PMMA/glass fiber composites: effect of the molecular weight of the PMMA

In this work ternary composites based on an epoxy thermoset modified with a thermoplastic polymer and reinforced with glass fibers were prepared. The aim of this study is to analyze the influence of the molecular weight of the thermoplastic polymer on the final morphologies. To obtain tailor made interphases four poly(methylmethacrylate), PMMA, which differ in their molecular weight (34,000, 65,000, 76,000 and 360,000 g/mol) were chosen to modify the epoxy resin. The amount of PMMA in the composites was fixed to 5 wt.%. Neat polymer matrices (epoxy-PMMA without fibers) were also prepared for comparison. To study all systems dynamic mechanical analysis (DMA), atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used. Although all the systems showed the typical phase separation in the epoxy/PMMA blend, DMA experiments revealed a new phase with more restricted mobility when the glass fibers are present. The amount of this phase increases as molecular weight of PMMA does. The morphologies as well as the fracture surface in the immediate surroundings of the fibers were found to be different from those observed further away from the surface of the fiber, suggesting therefore that, in this case, different fracture mechanism operates. These observations allow us to conclude that an interphase with specific properties is formed. This interphase is based on a polymer or a polymer blend (epoxy-PMMA) enriched in the component with lower mobility.     

非等温法研究TGDDM/DDS体系固化反应动力学

采用DSC对4,4′-四缩水甘油基二氨基二苯基甲烷(TGDDM)和3,3′-二氨基二苯基砜(DDS)体系的固化反应动力学进行了研究.分别通过n级反应法和Malek的最大概然机理函数法确定了固化反应机理函数,求解了固化反应动力学参数,得到了固化反应动力学模型.结果表明,通过Kissinger,Crane方法求解动力学参数所得到的n级反应模型与实验值差别较大;而采用Malek方法判别机理,表明该固化反应按照自催化反应机理进行,实验得到的DSC曲线与模型计算所得到的曲线吻合的较好,所确立的模型在5~20K/min的升温速率下能较好地描述TGDDM/DDS体系的固化反应过程,并为工艺参数的选择和工艺窗口的优化提供了理论依据.     

Improving the impact property and heat‐resistance of PLA/PC blends through coupling molecular chains at the interface

The influences of both the molecular structure and the melt viscosity differences between Poly(lactic acid) (PLA) and polycarbonate (PC) on the interpenetration of molecular chains at the interface were investigated by comparing the dynamic mechanical properties and morphologies of the as‐prepared PLA/PC solution‐casting blends with those of their corresponding annealed (180°C, 8 h) samples or PLA/PC melt blends. Additionally, two chain extenders containing epoxy groups (ADR and TGDDM) were used to improve the interfacial strength. Subsequently, the interpenetration of PLA and PC molecular chains at the interface was also surveyed. Finally, the effects of the morphology formed by after adding ADR or TGDDM on the impact property, and heat resistance were discussed. The results showed that there was no interpenetration of molecular chains at the interface in PLA/PC melt blends because of the serious hindrance of the molecular structure and the melt viscosity differences. Although the interfacial strength achieved significant increase after adding ADR or TGDDM, the increase of the interfacial strength should be caused by the connection of ADR or TGDDM molecules with PLA and PC molecules at the interface through chemical bonds rather than the entanglements of PLA and PC molecular chains because of no interpenetration of PLA and PC molecular chains at the interface. Thus, the morphology formed after adding ADR or TGDDM is still the type of complete phase separation, which may be the most suitable morphology for achieving high impact and heat resistance PLA/PC blends because these two properties strongly depend on the crystallinity of PLA phase. Copyright © 2015 John Wiley & Sons, Ltd.     

聚醚酰亚胺改性TGDDM环氧树脂的相分离研究

合成了不同化学结构的聚醚酰亚胺(PEI)并用于4,4′-二氨基二苯甲烷四缩水甘油醚(TGDDM)环氧树脂的增韧改性,以DSC,TRLS和SEM等方法研究了体系相分离过程中相容性和熔融粘度对相分离过程和结构的影响,对固化反应诱导相分离中相结构的控制提出初步的看法.     

Influence of substituents on the kinetics of epoxy/aromatic diamine resin systems

Eleven different epoxy/diamine systems, including tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM), triglycidyl p‐aminophenol (TGAP), and diglycidyl ether of bisphenol A (DGEBA) with 4,4′‐diaminodiphenylsulfone (DDS), diethyltoluenediamine (DETDA), dimethylthiotoluenediamine (DMTDA), and meta‐phenylenediamine (m‐PDA), were studied with near‐infrared spectroscopy at different temperatures. The reactivities of the epoxies were determined and found to be in the following order when reacted with the same amine: DGEBA > TGAP > TGDDM. When the primary amine was reacted with the same epoxy, the order was DETDA > DDS > DMTDA; for the secondary amine, the order was DETDA > DMTDA > DDS. The relative reaction rates of the secondary amine to the primary amine were compared and discussed in terms of the structural differences and the corresponding substitution effect. It was concluded that the increase in the secondary amine reactivity of DETDA and DMTDA was caused by the deconjugation of the benzene‐ring π electrons from the lone pair on the N atom. The overall order of the secondary amine relative reactivity was DMTDA > DETDA > DDS for the same epoxy and TGDDM > TGAP > DGEBA for the same amine. The m‐PDA systems had no significant positive or negative substitution effects. Molecular orbital calculations were performed, and the results showed the most significant deconjugation effect in the secondary amine of DETDA. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3143–3156, 2004     

Thermal and mechanical properties of a dendritic hydroxyl‐functional hyperbranched polymer and tetrafunctional epoxy resin blends

Blends of a tetrafunctional epoxy resin, tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM), and a hydroxyl‐functionalized hyperbranched polymer (HBP), aliphatic hyperbranched polyester Boltorn H40, were prepared using 3,3′‐diaminodiphenyl sulfone (DDS) as curing agent. The phase behavior and morphology of the DDS‐cured epoxy/HBP blends with HBP content up to 30 phr were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The phase behavior and morphology of the DDS‐cured epoxy/HBP blends were observed to be dependent on the blend composition. Blends with HBP content from 10 to 30 phr, show a particulate morphology where discrete HBP‐rich particles are dispersed in the continuous cured epoxy‐rich matrix. The cured blends with 15 and 20 phr exhibit a bimodal particle size distribution whereas the cured blend with 30 phr HBP demonstrates a monomodal particle size distribution. Mechanical measurements show that at a concentration range of 0–30 phr addition, the HBP is able to almost double the fracture toughness of the unmodified TGDDM epoxy resin. FTIR displays the formation of hydrogen bonding between the epoxy network and the HBP modifier. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 417–424, 2010     

Research of Silica Particles Dispersion in Polymer Matrix Under Acoustic Levitation

Series of resins consisting different amount of silica particles with different sizes and surface properties were prepared as suspended samples under an acoustic levitator. The resulting composites after curing under irradiation have been investigated. Fracture surface morphologies of the resins were compared to those with same composition prepared in a normal gravity field via scanning electron microscopy. The results showed that except for such factors like particle sizes, surface properties, particles concentration, and monomer viscosity, the microgravity state produced by acoustic levitation could also be an element that affects silica particles dispersion in the resins.     

Studies on the effect of different levels of toughener and flame retardants on thermal stability of epoxy resin

A thermoplastic toughener, polyether sulphone (PES) and a number of different types of flame retardants were blended in different ratios with a commercial epoxy resin triglycidyl-p-aminophenol (TGAP) and 4,4-diamino diphenyl sulphone (DDS) a curing agent. The effect of type and levels of flame retardants (FR) and the toughening agent on the curing, thermal decomposition and char oxidation behaviour of the epoxy resin was studied by the simultaneous differential thermal analysis and thermogravimetric techniques. It was observed that the toughener slightly increases the curing temperature (by up to 20 °C) but had minimal effect on the decomposition temperature of the resin. Flame retardants, however affected all stages depending upon the type of flame retardant used. The curing peak for samples containing tougher and flame retardants although slightly changed depending upon the type of FR, was not more than ± 20 °C compared to that of samples containing toughener only. All flame retardants lowered the decomposition temperature of the epoxy resin. Phosphorus- and nitrogen-containing flame retardants reduced the char oxidation leading to more residual char, whereas halogen- containing flame retardants had less effect on this stage.     

Epoxy/poly(benzyl methacrylate) blends: miscibility, phase separation on curing and morphology

Diglycidyl ether of bisfenol-A (DGEBA)/polybenzyl methacrylate (PBzMA) blends cured with 4,4’-diaminodiphenylmethane (DDM) were studied. Miscibility, phase separation, cure kinetics and morphology were investigated through differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Non-reactive DGEBA/PBzMA blends are miscible over the whole composition range. The addition of PBzMA to the reactive (DGEBA+DDM) mixture slows down the curing rate, although the reaction mechanism remains autocatalytic. On curing, initially miscible (DGEBA+DDM)/PBzMA blends phase separate, arising two glass transition temperatures that correspond to a PBzMA-rich phase and to epoxy network. Cured epoxy/PBzMA blends present different morphologies as a function of the PBzMA content.     

E-beam curing of epoxy-based blends in order to produce high-performance composites

In this work, blends of a difunctional epoxy monomer and a thermoplastic toughening agent are E-beam irradiated at two different dose rates and two different total absorbed doses. The influence of the processing conditions on the thermal properties and on the morphology of the obtained matrices has been investigated. In particular, it is shown how the increase of the dose rate causes an increase of the temperature during irradiation, thus inducing a simultaneous thermal and radiation curing. On the contrary, at low-dose rate the system mainly undergoes to radiation curing, thus making the cured material very sensible to a post-irradiation thermal treatment with a significant improvement of the thermal properties.     

Curing reaction characteristics and phase behaviors of biphenol type epoxy resins with phenol novolac resins

Diglycidyl ether of 4,4′-dihydroxybiphenol (BPDGE) is a liquid crystalline epoxy. The biphenyl epoxy (diglycidyl ether of 3,3′,5,5′-tetramethyl-4,4′-biphenyl, TMBPDGE) has found great applications in plastic encapsulated semiconductor packaging. Phenol novolac (PN) was used as curing agent. The reaction kinetics of BPDGE/PN and TMBPDGE/PN systems in the presence of triphenylphosphine (TPP) were characterized by an isoconversional method under dynamic conditions using differential scanning calorimetry (DSC) measurements. The results showed that the curing of epoxy resins involves different reaction stages and the values of activation energy are dependent on the degree of conversion. The effects of curing temperature on their phase structure have been investigated with polarized optical microscopy and Wide-angle X-ray diffraction. With proper curing process, BPDGE showed a nematic phase when cured with PN.     

Visualization of the morphology at the interphase of glass fibre reinforced epoxy-thermoplastic polymer composites

This work deals with the effect that the use of glass fibres has on the morphology developed by a thermoplastic polymer modified epoxy. In particular, three surface modifications of the glass fibres were studied: calcinations desizing, activation with hydrochloric acid and coating with 3-aminopropyltriethoxy silane. As the epoxy polymer, a model system based on the full reaction of DGEBA and 2-methyl-1,5-diaminopentane was used. As the modifiers of the epoxy thermoset, two thermoplastic polymers were used: poly(methylmethacrylate) and polystyrene. The morphologies were examined either in the polymer bulk or at the interfaces by means of scanning electron microscopy and atomic force microscopy. After a thoroughly examination of the samples it was found that the thermoplastic polymers preferentially accumulate at the interfaces of these materials when activated and silanized glass fibres are used. These results might be attributed to a gradual phase separation process due to stoichiometric gradients which, on the other hand, seems to be conditioned by the nature of glass fibres surface.