Relationships in a bismaleimide resin system. Part II: Thermomechanical properties

A range of bismaleimide resins of differing network structure was produced both by varying the ratios of N,N′-bismaleimido-4,4′-diphenylmethane (BMI) and methylene dianiline (MDA), and also by the use of different thermal processing cycles. Characterization of the resins by a variety of mechanical, physical, and micrographic techniques showed that properties such as modulus and yield strength varied directly with crosslink density and its associated free volume. Fracture toughness was found to increase as the crosslink density decreased, and microscopic investigation of the resin fracture surfaces identified characteristics which correlated with the resin fracture toughness.     

Cure behavior and properties of an epoxy resin modified with a bismaleimide resin

A bismaleimide (BMI) resin was added to an epoxy system composed of N,N′-tetraglycidyldiaminodiphenyl methane (TGDDM) and diaminodiphenyl methane (DDM). Cure behavior of the BMI modified epoxy resins was studied by a dynamic differential scanning calorimetry (DSC) method. Dynamic DSC thermograms of the BMI modified epoxy resins indicated unimodal reaction exothermic peaks. The overall heat of reaction per unit mass decreased with BMI composition. The residual heat of reactions of the epoxy blends cured at 180°C for 3 h increased with BMI composition. Thermal stability of the epoxy system improved by incorporating BMI resin. Flexural strength and modulus increased with BMI composition.     

新型双马来酰亚胺树脂体系的性能研究

采用扩链改性法制备了由长链BMI-EK[4,4′-双(3-马来酰亚胺基苯氧基)二苯甲酮]、长链BMPP{2,2′-双[4-(4-马来酰亚胺基苯氧基)苯基]丙烷}、DABPA(二烯丙基双酚A)和BDM(N,N-4,4′-二苯甲烷双马来酰亚胺)组成的BMI-MIX(双马来酰亚胺混合体系),其中n(BDM)∶n(BMPP)∶n(BMI-EK)=2∶1∶1、n(混合BMI)∶n(DABPA)=1∶0.87。研究结果表明:BMPP、BMI-EK和BDM具有良好的固化匹配性;BMI-MIX的固化树脂具有优异的力学性能和良好的韧性,其冲击强度(21.87 k J/m2)、临界应力强度因子(KIC)和临界应变能释放率(GIC)比BDM/DABPA体系分别提高了101.7%、38.5%和73.2%,并且前者的玻璃化转变温度(Tg)可达到288℃,而且前者在低于270℃时仍保持良好的力学性能、在低于250℃时储能模量仍未降低。     

Rubber modified epoxy resin. I: Cure kinetics and chemorheology

The curing and vitrification effect during the reaction of ATBN modified epoxy resin was studied through the dynamic differential scanning calorimetry method and a new reaction kinetic equation containing generalized WLF equation was developed to describe the reaction rate at both glassy and rubbery state. An autocatalytic mechanism was found to describe adequately the cure kinetics of the rubber modified epoxy resin and the overall order of reaction was assumed to be 2. The kinetic parameters were determined from the DSC data through the Marquardt's multivariable nonlinear regression method and Runge–Kutta integration technique. The presence of rubber indicated minor effect on the cure kinetics of epoxy resin. The Arrhenius type viscosity function was employed to establish a relationship between viscosity data measured by RMS and chemical conversion calculated from the reaction kinetic equation.     

A new bismaleimide system for resin transfer molding

A new bismaleimide (BMI) resin system, designated 4503A, suitable for resin transfer molding (RTM) has been developed. It is prepared by employing allyl methyl phenol and diallyl bisphenol A as reactive diluents for BMI. The processing properties of 4503A were investigated by time-temperature-viscosity curves, gel characteristics, and differential scanning calorimetry (DSC). Data show that the injection temperature of 4503A prepolymer can be as low as 75°C, while its viscosity is only 0.34Pa · s. In addition, after being maintained at 75°C for 12h, the viscosity is <0.95Pa · s. The cured 4503A resin has a glass transition temperature (T_g) and a heat deflection temperature (HDT) of 266 and 232°C, respectively; properties include tensile strength of 81MPa, flexural strength of 108MPa, and G_1C of 213J/m². Other properties of a composite based on 4503A system and woven glass cloth are also discussed. Regarding short beam shear (SBS) strength, for tests at 150 and 180°C, 80 and 61% of the original room temperature (RT) strength is retained. A similar strength retention (86 and 68%) is noted for flexural properties.     

缠绕用无溶剂低温固化双马来酰亚胺树脂体系

在乙烯基苄基化合物改性双马来酰亚胺树脂体系中添加烯丙基苯酚活性稀释剂,得到了粘度小于1000 mPa·s,加工适用期大于8 h,在150～155℃完成固化与后固化、适用于缠绕成型工艺的树脂体系。增韧改性后,该树脂的玻璃化转变温度达到261℃,拉伸强度和弯曲强度分别为73 MPa和133 MPa。     

烯丙基酚氧树脂/双马来酰亚胺改性树脂的制备及表征

用环氧树脂和二烯丙基双酚A(DP)合成了3种新型烯丙基酚氧树脂,测试了该树脂改性双马来酰亚胺(BMI)树脂体系的力学性能和热性能及黏度特性,探讨了后处理对改性树脂性能的影响。结果表明,改性树脂具有良好的2韧性和耐热性,冲击强度达到了22.31kJ/m,HDT仍有224℃,后处理使得体系耐热性大大提高,韧性略有降低。     

双马来酰亚胺树脂改性研究进展

综述了双马来酰亚胺增韧改性的研究进展,介绍了各种改性方法及其机理.内容包括内扩链新型BMI合成改性、胺类扩链增韧改性、烯丙基系列化合物共聚增韧改性、橡胶共混增韧改性、热塑性树脂共混增韧改性、氰酸酯树脂增韧改性等几个方面.     

An interpenetrated system based on a tetrafunctional epoxy resin and a thermosetting bismaleimide: Structure–properties correlation

The kinetics and mechanism of the curing process of a thermosetting blend formed by tetraglycidyl-4,4′-diaminodiphenyl methane and N,N′-bismaleimido-4,4′-diphenyl methane (BMI) cured in the presence of 4,4′-diaminodiphenyl sulfone, was investigated in detail by Fourier transform infrared spectroscopy. Information on the molecular structure of the network formed upon curing was derived. Dynamic-mechanical measurements on dry samples indicated an interpenetrated polymer network-like structure. Sorption measurements at 70°C showed a reduction of the water uptake at equilibrium in the presence of substantial amounts of BMI in the system (43.5% body weight). Finally, the dynamic-mechanical analysis of wet samples demonstrated a reduction of the plasticizing efficiency of the absorbed water in the presence of BMI. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1029–1042, 1998     

A diallyl bisphenol A ether and diallyl phenyl ether modified bismaleimide resin system for resin transfer molding

A modified bismaleimide (BMI) resin system for resin transfer molding was prepared by using o,o′‐diallyl bisphenol A ether and 1,4‐diallyl phenyl ether as reactive diluents for BMI. The processing behavior was studied through time–temperature–viscosity curves, gel characteristics, and differential scanning calorimetry. The results indicate that the injection temperature can be 80°C, at which its apparent viscosity is only 0.30 Pa · s. Moreover, after it had been maintained at 80°C for 15 h, the apparent viscosity was still less than 1.00 Pa · s. The cured resin had remarkable heat resistance, hot/wet resistance, and mechanical properties. The heat stability and mechanical properties of the composite based on this resin system and woven glass cloth are also discussed. For short beam shear strength, in tests at 150 and 180°C, 90 and 65% of the original room temperature strength was retained. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1649–1653, 1999     

Mold filling analysis in vacuum-assisted resin transfer molding. Part I: SCRIMP based on a high-permeable medium

Mold filling in SCRIMP based on a high-permeable medium is complicated because of the considerable difference in the permeabilities of the fiber reinforcement, the peel ply and the high permeable medium. The objectives of this paper are to understand the flow mechanism through flow visualization experiments and to present models that can be used to predict the filling time and flow pattern. Permeabilities of a stitched fiber mat, a high-permeable medium and a peel ply were measured. Flow visualization of SCRIMP mold filling was carried out under various molding conditions. It was found that although the resin flowed faster in the high-permeable medium than in the fiber reinforcement, the flow front lead-lag was not very large and it remained nearly constant through the entire mold filling process. A three-dimensional Control Volume/Finite Element Method (CV/FEM) was adopted to solve the flow governing equations, i.e. the Darcy's law, and the influences of the flow properties of the high-permeable medium, the fiber reinforcement and the peel ply on filling time were investigated. Based on experimental observations and CV/FEM simulation, a simplified leakage flow model is also presented. The comparison of experimental and simulation results show good agreement.     

Modelling acid attack on concrete: Part I. The essential mechanisms

At present, a computer model is being developed to predict the corrosion of concrete construction components subjected to acidic solutions with pH values ranging between 4.0 and 6.5, i.e. exposure classes XA3 down to XA1 according to DIN EN 206-1. The concrete may contain Portland cement based binders with dissolvable or acid resistant aggregate. Calcium aluminate cement is also considered. The concrete degradation is characterised by a corroded layer of high porosity whose thickness is determined by the combination of dissolution, precipitation and transport processes which depend on cement chemical composition, binder reactivity, aggregate reactivity, grading curve as well as concrete composition. It is also intended to include the effect of abrasion. The model components will be described in detail in forthcoming publications.     

Influence of Cure Conditions on the Adhesion of Rubber Compound to Brass-plated Steel Cord. Part I. Cure Temperature

The effect of the cure temperature of rubber compound on the adhesion with brass-plated steel cord was investigated in conjunction with the formation, growth and degradation of the adhesion interphase formed between the rubber compound and brass-plated steel cord. With increasing cure temperature from 130°C to 190°C, the pull-out force after cure decreased linearly. This decrease in adhesion force at higher temperature may be explained by the limitation of the mass transfer of vulcanizing agents into the adhesion interphase and/or rubber compound near the adhesion interphase, resulting in a deficiency of sulfur due to the fast cure of the rubber compound which significantly retards the diffusion of vulcanizing chemicals. Also, at a high temperature, an adhesion interphase with a ZnS-rich layer, which may act as a barrier to copper diffusion for the formation of the adhesion interphase of copper sulfide, was formed. After thermal aging of the adhesion samples, the pull-out force decreased in comparison with that of the unaged. The decrease of pull-out force after thermal aging stemmed mainly from the decline of the tensile properties after thermal aging. The adhesion property after humidity aging was completely different from that after thermal aging. With increase in the cure temperature to 160°C, the pull-out force increased. But further increase in the cure temperature caused a decline in pull-out force. This phenomenon can be explained by the degradation of the adhesion interphase. At lower cure temperatures, a severe growth of copper sulfide and a large extent of dezincification were observed in the adhesion interphase. At higher cure temperatures, a significant growth of copper sulfide in the adhesion interphase appeared. The proper formation of the adhesion interphase and good physical properties of the rubber compound at a moderate cure temperature can result in high retention of adhesion properties.     

Influence of Cure Conditions on the Adhesion of Rubber Compound to Brass-plated Steel Cord. Part I. Cure Temperature

The effect of the cure temperature of rubber compound on the adhesion with brass-plated steel cord was investigated in conjunction with the formation, growth and degradation of the adhesion interphase formed between the rubber compound and brass-plated steel cord. With increasing cure temperature from 130°C to 190°C, the pull-out force after cure decreased linearly. This decrease in adhesion force at higher temperature may be explained by the limitation of the mass transfer of vulcanizing agents into the adhesion interphase and/or rubber compound near the adhesion interphase, resulting in a deficiency of sulfur due to the fast cure of the rubber compound which significantly retards the diffusion of vulcanizing chemicals. Also, at a high temperature, an adhesion interphase with a ZnS-rich layer, which may act as a barrier to copper diffusion for the formation of the adhesion interphase of copper sulfide, was formed. After thermal aging of the adhesion samples, the pull-out force decreased in comparison with that of the unaged. The decrease of pull-out force after thermal aging stemmed mainly from the decline of the tensile properties after thermal aging. The adhesion property after humidity aging was completely different from that after thermal aging. With increase in the cure temperature to 160°C, the pull-out force increased. But further increase in the cure temperature caused a decline in pull-out force. This phenomenon can be explained by the degradation of the adhesion interphase. At lower cure temperatures, a severe growth of copper sulfide and a large extent of dezincification were observed in the adhesion interphase. At higher cure temperatures, a significant growth of copper sulfide in the adhesion interphase appeared. The proper formation of the adhesion interphase and good physical properties of the rubber compound at a moderate cure temperature can result in high retention of adhesion properties.     

Rheology of flexible PVC compounds. Part I: The influence of resin crystallinity

The changes occurring in torque during PVC processing in a torque rheometer have been interpreted in terms of the destruction of the supramolecular structure followed by a fusion of the grain fragments. In contrast to changes in torque, changes in elasticity occur in the absence of grain breakdown. It is proposed that the change in elasticity during processing is the result of changing crystallinity of the resin. In the early stages of processing, crystallites melt and elasticity decreases. As grains fuse together, new crystallites are formed in the previously unoccupied grain boundaries and the elasticity increases.     

双马来酰亚胺树脂的改性研究进展

介绍了目前双马来酰亚胺（BMI）树脂的几种主要改性途径及其反应机理,并指出了双马来酰亚胺树脂的发展趋势。     

Cure kinetics of biphenyl epoxy resin system using latent catalysts

The investigation of the cure kinetics of a biphenyl epoxy–phenol resin system with different kinds of latent catalysts was performed by differential scanning calorimetry using an isothermal approach. All kinetic parameters of the curing reaction including the reaction order, activation energy, and rate constant were calculated and reported. The results indicated that the curing reaction of the biphenyl epoxy resin system in this experiment proceeded through an autocatalytic kinetic mechanism, irrespective of the kind of catalyst. The epoxy resin system with acid/diazabicycloundecene (DBU) salt as the latent catalyst showed a second overall reaction order; however, a third reaction order was represented for microencapsulated triphenylphosphine (TPP). The storage stability tests for these systems were performed, and a good shelf life was observed in the epoxy resin system with pyromellitic acid/DBU salt, trimellitic acid/DBU salt, and microencapsulated TPP as the latent catalyst. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2711–2720, 2001     

双马来酰亚胺树脂增韧改性研究进展

详细介绍了烯类化合物、二元胺、热塑性树脂、橡胶等增韧双马来酰亚胺(BMI)和新型BMI单体合成等的原理、研究进展。分析了这些增韧方法的优缺点及使用范围。