Rheological and mechanical properties of percolated cyanate ester nanocomposites

The rheological properties and mechanical properties of percolated cyanate ester monomer/layered silicate mixtures are reported. A number of different cation exchanged montmorillonites were examined in an effort to achieve maximal montmorillonite delamination. The dispersion throughout the cyanate ester of a montmorillonite with phenylated ammonium cations (2MBHT MMT) results in the formation of a percolated network. The rheology of this percolated network undergoes a viscous liquid to elastic solid transition at 4 wt% montmorillonite. The percolation of the montmorillonite in the cyanate ester results in a significant improvement in crack resistance (80%) without a sacrifice of flexural strength.     

氰酸酯树脂及其胶粘剂

介绍了高性能氰酸酯树脂的品种、主要性能、商业产品和氰酸酯树脂固化反应的原理和特点;评述了氰酸酯树脂与环氧树脂、双马来酰亚胺树脂和热塑性树脂共混体系的物理－机械性能。     

氰酸酯树脂及其胶粘剂（续）

５　改性氰酸酯树脂氰酸酯树脂与其他热固性树脂相比虽然具有较好的韧性,但如作为结构用复合材料和胶粘剂的基体,仍然较脆。与其他热固性树脂的增韧相似,它可采用热塑性塑料（ＴＰ）和橡胶增韧。这类增韧改性氰酸酯树脂许多已商品化。另一类是氰酸酯分别与环氧、ＢＭＩ共混改性,以达到取长补短的目的。这２种共混树脂也已商品化。５．１　ＴＰ增韧氰酸酯氰酸酯树脂可与许多无定形的ＴＰ共混。固化后形成半互穿网络（Ｓｅｍｉ－ＩＰＮ）［１５,１６］。所用ＴＰ主要有：聚砜（ＰＳＵ）、聚醚砜（ＰＥＳ）、聚醚砜亚胺（ＰＥＩ）和聚碳酸…     

氰酸酯树脂改性研究进展

综述了氰酸酯树脂(CER)改性的概况,重点讨论和分析了以聚醚、聚酯、线型聚氨酯、交联聚氨酯及原位聚合改性的CER,这些改性的CER均能形成各种互穿聚合物网络(IPN)结构。CER的改性可进一步改善其性能和拓宽其应用领域。     

氰酸酯改性双马来酰亚胺耐高温胶粘剂

研制了一种氰酸酯改性双马来酰亚胺耐高温胶粘剂,探讨了双官能度氰酸酯与双马来酰亚胺的共聚机理,得出两者并非各自聚合形成互穿网络结构,而是发生共聚形成新的化合物的结论。该胶工艺性良好, 对钢、铝等材料具有良好的粘接性能,耐高温老化性能优良。热失重(TG)分析表明,该胶热失重起始温度为 355．85℃,热分析和性能测试结果表明该胶可以在230℃长期工作。     

氰酸酯树脂改性的研究进展

简要介绍了氰酸酯的缺陷,并综述了用各种方法对氰酸酯树脂改性的研究进展,包括热固性树脂改性(环氧树脂改性和双马来酰亚胺树脂改性)、热塑性树脂改性、橡胶弹性体改性、互穿网络聚合物改性以及物理改性法。     

Cure reactions in the blend of cyanate ester with maleimide

Cure reactions of a bismaleimide (4,4′-bismaleimidodiphenylmethane, BMI) associated with a liquid aromatic dicyanate ester (1,1′-bis(4-cyanatophenyl)ethane, BEDCy) and with a powder type aromatic dicyanate ester (bisphenol A dicyanate, BADCy) were investigated by in situ FTIR and DSC dynamic scanning. In non-catalyzed blend systems, co-reactions between dicyanate ester and bismaleimide always occur, and hence the formation of pyrimidine and/or pyridine structures take place. Pyrimidine structures always predominate. Probable reaction paths were also proposed for various formulations of hybrid blends. In addition, N-phenylmaleimide (MI) and p-phenyl-phenylcyanate (S-Cy) were utilized as model compounds and mixed via a melting method and a solution method to explore the corresponding cure reactions by means of FTIR, DSC and NMR. ¹³C NMR spectra of the model compounds demonstrated the formation of linkages of sym-triazine rings, pyrimidine structures, pyridine structures and dioxazine structures. The reaction mechanism or linkage structures produced in the model compound system studied may be somewhat different from those of the real system due to a diffusion effect in real systems or to the different activation energy in both systems.     

氰酸酯树脂/八(γ-氯丙基)多面体低聚倍半硅氧烷复合材料

采用八(γ-氯丙基)多面体低聚倍半硅氧烷(T8)改性氰酸酯树脂(CE)制备了系列CE/T8复合材料。研究了复合材料的冲击性能、动态热力学性能、热稳定性能以及断面形貌。结果表明:T8的加入能明显提高复合材料的冲击性能,当加入10%的T8时,复合材料的冲击强度较纯CE提高了12.29 kJ/m2;复合材料在高温阶段(大于500℃)的热稳定性与纯CE相比有一定提高,有助于改善CE的阻燃性能;T8的加入使复合材料的玻璃化转变温度和储能模量均有所降低。     

中温固化氰酸酯树脂发泡胶膜研制

通过加入自制潜伏性促进剂,降低了氰酸酯发泡胶的固化温度,实现了在130~135℃固化。通过加入耐热性工程塑料、环氧树脂、偶氮发泡剂、导热填料制备出具有良好的发泡状态、较低放热温度和较高粘接性能的氰酸酯发泡胶膜。发泡胶膜在-55℃至180℃的范围内具有较高的管剪切强度,在膨胀比为3.20时,室温和180℃管剪切强度分别为10.5MPa和5.9MPa。发泡胶具有较好的耐热老化和耐湿热老化、耐介质和耐空间环境性能,在室温下具有良好的贮存期。     

改性氰酸酯载体胶膜的研究

以酚醛型氰酸酯树脂为主体树脂,以乙酰丙酮铝／二烯丙基双酚A为混合催化剂,以酚酞基聚芳醚砜为增韧剂,以纳米级气相二氧化硅为流动控制剂制备了一种耐高温氰酸酯载体胶膜。实验结果表明：2‰乙酰丙酮铝与5％二烯丙基双酚A构成的催化体系对氰酸酯产生了较好的催化作用,其DSC曲线的峰温从269.2℃降到了181．7℃,经177℃×4h固化后异氰酸酯红外特征峰完全消失,其固化产物三嗪环红外特征峰明显加强;15phr酚酞基聚芳醚砜和2phr气相二氧化硅改性剂的使用不仅改善了胶黏剂成膜性和流动性,而且获得了耐热性和韧性的统一,其室温剪切强度为21．8MPa,250℃和300％剪切强度分别达到了16．47MPa和11．34MPa,其滚筒剥离强度达到了38．3N·m／m,其玻璃化转变温度和5％热失重温度分别达到了279．4℃和423．7℃。     

Properties and structure of cyanate ester/polysulfone/organoclay nanocomposites

In this paper, a cyanate ester (CE) matrix has been modified with polysulfone and an organic montmorillonite (Nanofil 919). The blend was thermally cured in presence of copper acetylcetonate and nonylphenol. The morphology of the cured materials was investigated by wide angle X-ray, scanning and transmission electron microscopy techniques. An intercalate structure of silicate platelets in the cyanate matrix has been obtained. Furthermore, results of thermogravimetric analysis (TGA) suggest that CE/PSF/Nanofil 919 nanocomposites have higher thermal stability than the neat resin, increasing the onset decomposition temperature. Flexural strength distributions of modified and neat cyanate matrices were obtained by testing the materials in three-point bending. The results were analyzed within the framework of Weibull statistics. The flexural behavior of the resins demonstrated to be sensitive to the intrinsic flaw distribution. The modified system displayed higher fracture toughness and impact strength compared to pure CE. Dynamic mechanical analysis (DMA) studies confirmed that the PSF modified matrix developed a two-phase morphology consisting of spherical PSF dispersed in a thermoset matrix.     

改性氰酸酯纤维缠绕工艺研究

本文采用环氧树脂改性氰酸酯树脂,研究出适用于纤维湿法缠绕的低粘度并具有较高耐热性能的改性树脂体系。通过试验研究确定了树脂体系的纤维湿法缠绕工艺,对改性树脂与碳纤维复合材料的力学性能进行了研究,并进行了标准容器爆破试验。研究结果表明：改性氰酸酯树脂体系的粘度小（420mPa·S,25℃）,并具有较长使用期（30小时以上）,完全适用于湿法缠绕工艺。使用改性氰酸酯体系缠绕的标准容器,其纤维方向复合材料性能相当于环氧树脂体系缠绕的容器,并且具有较高的玻璃化转变温度（Tg=232℃）,与现有的环氧树脂体系相比,玻璃化转变温度提高了30％～40％。     

氰酸酯树脂的改性研究

本文介绍了目前氰酸酯（CE）树脂的几种改性方法,包括热固性树脂、热塑性树脂、橡胶弹性体、晶须及含不饱和双键的化合物等改性方法,其中主要阐述了环氧树脂（EP）和双马来酰亚胺树脂（BMI）改性氰酸酯树脂（CE）的反应机理及共聚体系的性能,指出了上述各种增韧改性方法的优缺点,并展望了了氰酸酯树脂的研究发展前景。     

Synthesis and properties of a liquid oligomeric cyanate ester resin

A multiple aromatic ether-containing cyanate ester resin system with high thermal stability and superb processability has been developed. The oligomeric monomer was prepared via a hydroxyl-terminated intermediate synthesized from a modified Ullmann synthesis with bisphenol A and 1,3-dibromobenzene in the presence of potassium carbonate and a catalytic amount of a copper (I) complex in N,N-dimethylformamide. The hydroxyl-terminated intermediate was end-capped with the cyanate moiety by reaction with cyanogen bromide and triethylamine in dry acetone resulting in a resinous material at ambient temperatures. The thermo-oxidative and water absorption properties were determined for the new cyanate ester polymer as well as its flexural strength, flexural modulus and Rockwell hardness. Mechanical tests were also conducted on the commercially available 2,2′-bis(4-cyanatophenyl)isopropylidene cyanate ester resin to investigate the effect of introducing an oligomeric spacer between the terminal end groups on the properties of the material.     

Reinforced Cyanate Ester Resins with Carbon Nanotubes: Surface Modification,Reaction Activity and Mechanical Properties Analyses

The reinforcement and toughness of cyanate ester (CE) resins with multiwalls carbon nanotubes (MW-CNTs) were investigated in this paper. Based on the surface modification of MW-CNTs, the reaction activity of CE resins, desperation of MW-CNTs, mechanical properties and thermal properties of MW-CNTs/CE composites were addressed. TEM and XRD analyses demonstrate that the MW-CNTs with regular arrangement and perfect crystals structures can be achieved after the treatments with pyrolysis and dense HNO₃/H₂SO₄ acids oxidation. The reaction activity of CE systems with MW-CNTs is increased with the incorporation of carbon nanotubes. The mechanical analysis, dynamic mechanical analysis (DMA), and thermal gravimetric analysis (TGA) indicate that the addition of MW-CNTs can enhance both impact strength and flexural strength of cured CE resins without decreasing their thermal stability. The storage module for the MW-CNTs/CE composites is much higher than that of the pure CE sample in a wide temperature range. After aging in boiling distilled water, the water absorption of is less than that of CE resins.     

Mechanisms of moisture absorption by cyanate ester modified epoxy resin matrices: the clustering of water molecules

One of the important factors, which determine the concentration of moisture that a polymer will absorb, is the effect of non-random mixing whereby water-clustering is said to occur. The Flory-Huggins theory cannot predict the isotherms observed for highly polar polymers since the theory assumes complete random mixing. The complementary model of Brown [Brown GL. In: Rowland SP, editor. Water in polymers. Washington, DC: American Chemical Society; 1980. p. 441. [1]] considers the moisture distribution in polar polymers, consists of components associated with random mixing (Flory-Huggins theory) and clustering of the water molecules. Moisture sorption isotherms of cyanate ester/epoxy blends at different relative humidities have been analysed by the clustering theory of Brown [Brown GL. In: Rowland SP, editor. Water in polymers. Washington, DC: American Chemical Society; 1980. p. 441. [1]] and the dual mode sorption theory of Zimm [Zimm BH. J Chem Phys 1953;21:934. [2]]. Clustering was found to occur in cyanate ester/epoxy blends conditioned at relative humidities of 40% and higher. The Cluster size indicates that the majority of the absorbed water in a cured cyanate ester/epoxy blend was not clustered but present in monomeric form through hydrogen bonding to polar sites. It is postulated that the phenomenon of thermal spiking enhanced moisture absorption can be explained by an equilibrium between cluster formation and declustering associated with network relaxation at the spike-temperature.     

Multivariate analysis of spectra of cyanate ester/bismaleimide blends and correlations with properties

A multivariate approach to the analysis of cured resin blends comprising cyanate ester and bismaleimides is reported. An analysis of samples subjected to accelerated ageing tests by immersion in water at temperatures up to 70 °C shows that simple near infrared spectroscopic measurements on virgin materials can predict dynamic mechanical thermal analysis results, and provide correlations with thermogravimetric analysis. This suggests a rapid screening method for a range of materials, perhaps in conjunction with a combinatorial approach to advanced composites manufacture.     

Studies on a dicyanate containing four phenylene rings and polycyanurate blends. 2. Application of mathematical models to the catalysed polymerization process

Selected blends of bis-4-(4-cyanatophenoxy)phenyl sulphone with a commercial dicyanate, 2,2-bis(4-cyanatophenyl)propane are analysed using differential scanning calorimetry (DCS) to examine the processes of the aluminium-catalysed thermal polymerisation. Kinetic treatment of these data show that the kinetics of the formation of the bis-4-(4-cyanatophenoxy)phenyl sulphone homopolymer were fitted with just two processes, but three processes were required for the 2,2-bis(4-cyanatophenyl)propane homopolymer, for which a more complex thermogram was obtained. When considering the polymerisation kinetics of binary blends of the monomers it was necessary to select the minimum number of kinetic parameters to obtain the best fits to the data. The binary blends generally show trends in the data that reflect the monomer composition. The parameters derived from two kinetic methods are broadly in agreement; the kinetic treatment of the thermal data for 2,2-bis(4-cyanatophenyl)propane monomer suggests the presence of at least one impurity and this is supported by spectroscopic and chromatographic analyses. The latter was not observed for bis-4-(4-cyanatophenoxy)phenyl sulphone, a monomer found to be of a higher purity by chromatography. From the kinetic analysis of the thermal data (from dynamic DSC), the mathematical model predicts that, following an isothermal cure regime at 450 K, bis-4-(4-cyanatophenoxy)phenyl sulphone should reach a conversion of 90% after ca. 33 min. The empirical data for this isothermal experiment show that bis-4-(4-cyanatophenoxy)phenyl sulphone reaches a conversion of 73% after 33 min and 87% after 2 h at 450 K.     

Moisture absorption by cyanate ester modified epoxy resin matrices. Part I. Effect of spiking parameters

The moisture absorption of cyanate ester modified epoxy resin matrices has been studied under thermal spiking conditions. Enhanced moisture absorption has been observed at spike-temperatures above 120 °C. The results of the desorption studies on both control specimens and the spiked specimens showed that some of the water molecules remained entrained in the polymer. It is postulated that this water could be associated with that which is hydrogen bonded or from the hydrolysis of isolated residual cyanate ester groups because the concentration of entrained water remains constant at spike-temperatures below 180 °C. Above 180 °C a thermally activated process, leading to chain scission as indicated by a reduced recoverability of the glass transition temperature (T_g) on drying.On isothermal resorption, the moisture concentration was found to be similar to that achieved through thermal spiking, showing that the entrained water at the lower spike-temperatures can also be achieved under mild conditions. The T_g is reversibly recovered to within 5 °C, which indicates a degree of relaxation rather than degradation. The moisture diffusion coefficient estimated from the resorption curves is lower than those estimated from the absorption and desorption curves. The isothermal resorption diffusion coefficient also decreased with increasing spike temperature. It is proposed that thermal spiking induced a relaxation of the network but as the spike-temperature approaches the transition region of the wet polymer, further hydrolytically induced relaxation events become feasible.     

环氧树脂/氰酸酯树脂体系的改性研究

为增加环氧树脂/氰酸酯树脂体系(EP/CE)的韧性,向EP/CE树脂体系中引入第三组分——双酚A(BPA)。采用傅里叶转换红外光谱、差式扫描量热仪研究了BPA对EP/CE固化温度与固化机理的影响,测定了固化物的力学性能和耐湿热性。结果表明,BPA的加入改变了EP/CE树脂体系固化历程,引起EP/CE树脂体系固化温度明显下降。BPA在EP/CE树脂体系内可形成大量的—C—O—C—键,与EP/CE树脂体系形成互穿网络,提高了EP/CE的韧性。随着体系中BPA含量的增加,其力学性能提高,吸水率有所下降。当CE∶EP∶BPA质量比为7∶3∶0.75时,其拉伸强度提高27.3%,冲击强度提高34.7%,吸湿率降为1.2%。