基于多重动态共价键的环氧类玻璃网络的制备与性能

以三羟甲基丙烷三缩水甘油醚(TTE)为基体, 2,2′-(1,4-亚苯基)-双[4-硫醇1,3,2-二氧杂戊烷](BDB)和3,3-二硫代二丙酸(DTDPA)为交联剂, 通过环氧-巯基“点击”反应和环氧-羧酸酯化反应, 制备了基于多重动态共价键(硼酸酯键、 二硫键和酯键)的环氧类玻璃网络. 利用红外光谱和拉曼光谱对其结构进行了表征, 结果表明, 环氧类玻璃中不仅存在硼酸酯键、 二硫键和酯键, 还存在可逆氢键, 并且大量氢键的存在能提高环氧类玻璃的交联度. 对所得环氧网络的热稳定性、 热机械性能和力学性能进行了测试, 并对基于多重动态共价键环氧网络进行了自修复、 焊接、 形状记忆和再加工能力测试. 结果表明, 在80 ℃下可实现网络的完全自修复、 再加工与焊接, 且焊接后样品的力学性能(拉伸强度)恢复率在80%以上, 具有优异的功能性.     

聚氨酯/环氧树脂互穿网络硬质泡沫塑料反应过程和微观结构

聚氨酯／环氧树脂互穿网络(PU／EPIPN)硬泡中异氰酸根的消耗速度较纯PU硬泡高，是由于环氧树脂的固化荆同时也是异氰酸根反应的催化荆。而PU／EP IPN硬泡中环氧基的反应速度和反应程度均较纯EP网络低，归因于互穿网络对基团扩散的阻碍。在互穿网络硬泡形成过程中，存在环氧开环中所新产生的羟基与异氰酸根的反应、大分子多元醇中羟基与环氧基的反应以及异氰酸根与环氧基形成嗯唑烷酮的反应三种形成网络间的化学键的途径。同时由于PU／EPIPN硬泡高度的交联，使得IPN硬泡中两个网络具有良好的相容性。动态力学性能表明所有IPN样品都只有一个玻璃化温度。透射电镜表明IPN样品无明显的相界面。     

AFM substantiation of the fracture behavior and mechanical properties of sol–gel derived silica packed epoxy networks

Silica packed epoxy networks are prepared in two steps via in situ, solvent free sol–gel processing of tetraethoxysilane in liquid epoxy monomer and curing the mixture with a flexible diamine afterwards. The influence of filler content and processing conditions on the mechanical properties and the fracture behavior is studied by means of the static mechanical analysis and AFM characterization of the pristine and the fractured polymer surfaces, and a mechanism to enhance polymer strength and toughness is proposed. The in–situ evolution and packing of silica nanostructures into epoxy networks influences the overall morphology and performance of polymers under high stress. It is found that smaller silica domains distributed at the molecular level cause efficient crack distribution by absorbing energy and thus improve the strength and toughness of silica packed epoxy polymers.     

化学结构变化对刚棒状环氧树脂相行为和热力学性能的影响

用线性酚醛树脂(PN)和4-氨基苯基氨基砜(SAA)作为固化剂, 与刚性棒状环氧树脂联苯环氧(DGEBP)、四甲基联苯环氧(DGETMBP)和传统双酚A环氧树脂(DGEBA)分别进行固化. 研究了固化剂和环氧树脂化学结构的改变对热固网络相行为和热力学性能的影响. 结果表明, 刚性环氧网络比传统的DGEBA具有更好的热力学性能. DGEBP可形成不同类型的取向网络, 而取向态的类型也直接影响了热固网络的热力学性能. 用扫描电镜(SEM)观察不同网络体系的断裂面结构, 发现取向的刚性棒状环氧网络的断裂面呈韧性断裂, 而其它无定形环氧网络则呈典型的脆性断裂.     

Novel Epoxy Resins Derived from Biomass Components

Biomass has received considerable attention because it is renewable and offers the prospect of circulation of carbon in the ecological system. The concept “Biorefinery” has been developed rapidly in order to establish sustainable industries. Recently, new types of epoxy resins with polyester chains, which can be derived from saccharides, lignin and glycerol, have been investigated. In the above studies, the relationship between chemical structure and physical properties was investigated. In the present review, the features of the preparation system and the action of biomass components in epoxy resin polymer networks are described. The glass transition temperatures of the epoxy resins increased with increasing content of biomass components in epoxy resin polymer networks. Thermal decomposition temperatures were almost constant regardless of the content of biomass components contents in epoxy resins. Mass residue at 500 °C increased with increasing contents of biomass components in epoxy resins. It was found that the thermal properties can be controlled by changing the contents of biomass components.     

An investigation of the interconnection between topological characteristics of physical and chemical networks of anhydride adamantane-containing epoxy polymers

The interconnection between topological characteristics of chemical and physical networks of adamantane-containing epoxy polymers of anhydride curing is studied. It is shown that the introduction of adamantane fragments into the network of an epoxy polymer by different methods affects the glass-transition point and stress-strain properties. The changes in polymer properties depending on the concentration of modifying agents are analyzed during comparison of the frequency parameters of the networks of chemical bonds and engagements within a cluster model of the structure of the polymer amorphous state.     

Kinetic features of the formation of poly(epoxy isocyanurate) networks

A new method is developed for the synthesis of branched and network polymers that give rise to poly(epoxy isocyanurate) matrices during thermal curing. Matrix polymers are prepared on the basis of polyethers (poly(propylene glycol) or poly(tetramethylene glycol)), diisocyanate, and an epoxy oligomer. The chemistry of formation of networks is studied by NMR and IR spectroscopy. Formation of structures with different topologies is analyzed, and optimum conditions for the formation of gradient networks that are complex structural organizations are ascertained. It is shown that, during microphase separation of a three-component system whose components differ appreciably in surface energy and other parameters, the composition of microphases may be estimated. Optimum conditions of the curing process that provide formation of the perfect structure of networks are found, and their chemical structure is investigated.     

Effect of coal on the rheological and mechanical properties of epoxy matrix

An experimental study was conducted to investigate the effect of coal used as a new type of filler in epoxy networks. For this purpose two series of epoxy composites with different coal weight fraction were studied and their thermo-mechanical properties were characterized. The work demonstrated that coal-filled epoxy networks show a typical behavior of a particulate filled material and follows the theoretical models already used.     

Morphology and dielectric properties of an epoxy network modified by end‐functionalized liquid polybutadiene

Epoxy resin networks modified with different functionalized liquid polybutadiene were characterized by scanning electron microscopy, atomic force microscopy (AFM), and dielectric thermal analysis techniques. Different morphologies were observed for these different systems, which were attributed to different interaction degrees between the components. Hydroxyl‐terminated polybutadiene (HTPB) and carboxyl‐ terminated polybutadiene (CTPB) resulted in epoxy networks with two‐phase morphology that differed in rubber particle size. The use of isocyanate‐terminated polybutadiene (NCOTPB) resulted in transparent thermoset material, whose rubber domains were in the nanoscale dimension, only detected by the AFM technique. The different morphological aspects in these epoxy systems also affected the dielectric properties. The epoxy–HTPB network exhibited two low temperature relaxation peaks corresponding to two different phases present in the system, whereas the epoxy–CTPB or epoxy–NCOTPB systems, whose rubber particles are well adhered to the epoxy matrix by chemical bonds, displayed only one single low temperature relaxation peak. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4053–4062, 2004     

Formation of fibril structures in polymerizable, rod-coil-oligomer-modified epoxy networks

This paper describes the in situ preparation of fibrils in epoxy networks in which the fibril-like structures are cured polymerizable rod-coil oligomers. The epoxy-terminated alpha,omega-modified PEO oligomers, which are ABA rod-coil-rod oligomers with a poly(ethylene oxide) coil unit and two aromatic azomethine liquid-crystalline rod units, were synthesized and then further blended with an epoxy precursor. Uniform nanoscale columnar structures were observed in the neat rod-coil oligomers as well as in the crosslinked liquid-crystalline state. During the curing of the blends, the supramolecular nanoscale columnar structures of the rod-coil oligomers are transformed into polymeric fibrils where the epoxy functional end groups have co-reacted with epoxy precursors to form a crosslinked network.     

Bio‐based epoxy vitrimers: Reprocessibility,controllable shape memory,and degradability

The research activities in the development of recyclable and reprocessable covalently crosslinked networks, and the construction of polymers from renewable resources are both stemmed from the economical and environmental problems associated with traditional thermosets. However, there is little effort in combination of these two attractive strategies in material designs. This article reported a bio‐based vitrimer constructed from isosorbide‐derived epoxy and aromatic diamines containing disulfide bonds. The resulted dynamic epoxy resins showed comparable thermomechanical properties as compared to similar epoxy networks cured by traditional curing agent. Rheological tests demonstrated the fast stress relaxation of the dynamic network due to the rapid metathesis of disulfide bonds at temperature higher than glass transition temperature. This feature permitted the recycling and reprocessing of the fragmented samples for several times by hot press. The dynamic epoxy resins also exhibited shape‐memory effect, and it is demonstrated that the shape recovery ratio could be readily adjusted by controlling the stress relaxation in the temporary state at programming temperature. Moreover, the degradability of the dynamic epoxy resins in alkaline aqueous solution was also demonstrated. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1790–1799     

环氧树脂/氨酯丙烯酸酯树脂互穿聚合物网络生成动力学研究

用ＦＴＩＲ跟踪研究了由不同分子量聚氧化丙烯（ＰＰＯ）合成的氨酯丙烯酸酯树脂（ＵＡＲ）／环氧树脂（ｅｐｏｘｙ）同步互穿网络（ＳＩＮ）的生成动力学．结果表明,在聚合反应初期（转化率＜０４）环氧基和不饱和双键的转化率均和反应时间呈近似线性关系,聚合反应主要由单体的扩散控制;由不同分子量ＵＡＲ合成的ｅｐｏｘｙ／ＵＡＲＳＩＮ的生成动力学有较大差异,与ＳＩＮ形成过程中的形态发展有关．通过不同用量的ＡＩＢＮ,可以调节ＵＡＲ网络的形成速度,导致ＳＩＮ中两个网络的生成顺序发生改变．     

Graft interpenetrating polymer networks composed of epoxy resin and urethane acrylate resin

For enhancing the interpenetratoin and/or compatibility of the simultaneous interpenetrating networks (SINs) composed of epoxy resin (epoxy) and urethane acrylate resin (UAR), the graft epoxy consisting of different lengths of poly(oxypropylene) (PO) side chains were synthesized and characterized. It was found that the graft epoxy composed of short PO side chains [MW 480, epoxy-g-PO(480)] showed a compatible system while if consisting of longer PO grafts [MW 950, epoxy-g-PO(950)] exhibited a partial microphase separation morphology. DSC measurements as well as the SEM or TEM observation indicated that the interpenetration between the two phases for epoxy/UAR SINs including epoxy-g-PO(480) was improved appreciably due to the excellent miscibility between the PO grafts and PO segments existing in the graft epoxy and the UAR network, respectively. In this case, for SIN(80/20) containing 10 wt % of epoxy-g-PO(480) the tensile strength increases by a factor of 2.70 compared with that of pure epoxy network. However, the improvement of interpenetration and/or compatibility between the two networks as well as the mechanical properties for SINs composed of epoxy-g-PO(950) are limited resulting in the partial microphase separation of epoxy-g-PO(950) network's own self. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3568–3574, 1999     

聚硫橡胶和环氧树脂互穿网络和共聚网络

本文以丙烯酸酯封端的聚硫橡胶，环氧封端的聚硫橡胶分别同双酚环氧树脂合成互穿网络和共聚网络，并研究了它们的相结构和性能。结果表明，所有样品都具有低温柔性和良好的力学性。     

Toughness Properties of Lightly Crosslinked Epoxies Using Block Copolymers

Summary: In this work is discussed an alternative approach to the toughening of epoxy networks by the addition of acrylic block copolymers, composed of rigid and rubbery blocks. Once the reaction is completed, the initial self-assembly of block copolymers in epoxy thermoset precursors produces rubbery domains: depending on the block copolymer structure and composition, these domains are of the micrometer or the nanometer size. Nanostructures are obtained when the rigid block is a random copolymer of methylmethacrylate and N,N-dimethylacrylamide. The rubbery domains prevent rapid crack propagation and the highest toughness is obtained with filament-like microparticles or wormlike micelles.     

Revealing defects hampering the formation of epoxy networks with extremely high thermal properties: Theory and experiments

We present a combined experimental and theoretical investigation of thermal properties of cycloaliphatic epoxy networks. The networks are prepared from 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate ERL-4221 as a monomer and 4-methylhexahydrophthalic anhydride as a curing agent and their glass transition temperature T_g is evaluated by dynamic mechanical and thermal mechanical analyses as well as by differential scanning calorimetry. It is found that the cured epoxy networks have high T_g values reaching 233–238 °C. The method of anharmonic oscillators is first proposed to simulate the effect of network structure on the thermal properties. It suggests that further increase of T_g values is not attained because of the formation of intramolecular cyclic structures. Studies of model reaction by mass-spectrometry confirm the formation of such structures at curing.     

Metal-catalyzed transesterification for healing and assembling of thermosets

Catalytic control of bond exchange reactions enables healing of cross-linked polymer materials under a wide range of conditions. The healing capability at high temperatures is demonstrated for epoxy-acid and epoxy-anhydride thermoset networks in the presence of transesterification catalysts. At lower temperatures, the exchange reactions are very sluggish, and the materials have properties of classical epoxy thermosets. Studies of model molecules confirmed that the healing kinetics is controlled by the transesterification reaction rate. The possibility of varying the catalyst concentration brings control and flexibility of welding and assembling of epoxy thermosets that do not exist for thermoplastics.     

Nanoscale confinement effects on the relaxation dynamics in networks of diglycidyl ether of bisphenol-A and low-molecular-weight poly(ethylene oxide)

Thermoplastic poly(ethylene oxide) (PEO) (Mw(PEO) approximately 4000) has been used to prepare thermosetting nanocomposites incorporating diglycidyl ether of bisphenol A (DGEBA) epoxy oligomer. Blends with various PEO/DGEBA weight ratios were cured using stoichiometric portions of 4,4'-diaminodiphenylmethane. The resulting semi-interpenetrating polymer networks were studied by several techniques. Nanoscale confinement effects, thermal (glass transition, melting and crystallization temperatures) and structural features of our materials are similar to those for networks with much higher Mw(PEO) and different curing agents; however, the polyether crystallization onset occurs in our case at a lower PEO concentration; shorter PEO chains organize themselves more easily into crystalline domains. Very low estimates of the k parameter of the Gordon-Taylor equation, used to fit the compositional dependences of the dielectric and calorimetric glass transition temperatures, and a strong plasticization of the motion of the glyceryl segments (beta-relaxation) in the epoxy resin were observed. These illustrate an intensified weakening in the strength of the intermolecular interactions in the modified networks, as compared to the high strength of the self-association of hydroxyls in the neat resin. The significance of hydrogen-bonding interactions between the components for obtaining structurally homogeneous thermoset-i-thermoplastic networks is discussed.     

聚丙烯酸酯/环氧树脂互穿网络聚合物的研究Ⅲ.橡胶态弹性模量和互穿缠结

采用一步法（Ｓｉｍｕｌｔａｎｅｏｕｓｌｙ）合成了双组分的聚丙烯酸酯／环氧树脂互穿网络聚合物（ＩＰＮｓ）．选择预溶胀方法制备了聚丙烯酸酯和环氧树脂两种组分网络．测定了各种组分比的ＩＰＮ和不同溶胀度下的组分网络的动态力学性能，从橡胶态弹性理论出发讨论了ＩＰＮ和预溶胀网络之间在橡胶态弹性模量上的关系，并据此指出互穿缠结增加了网络的有效“交联密度”，因此，它对ＩＰＮ的橡胶态弹性模量有较大的贡献．密度测量的结果也提供了另一方面的证据