A high-performance bismaleimide resin with good processing characteristics

A new bismaleimide (BMI) resin system, designated 4504, with excellent heat resistance and good mechanical properties for advanced composites was developed. The 4504 resin was made up of 4,4′-bismaleimidodiphenyl methane, diallyl bisphenol A, and desirable catalysts. The reactivity of 4504 was investigated by gel characteristics and differential scanning calorimetry (DSC). Data showed that 4504 had a long work life under 100°C, but would gel within 7 min or 40 s at 140 or 160°C, respectively. The glass transition temperature (T_g) and heat-deflection temperature (HDT) of the cured 4504 resin were 315 and 290°C, respectively, which were much higher than the postcure temperature (200°C). In addition, the cured resin is also tough. Thermogravimetric analysis (TGA) in a nitrogen atmosphere revealed that the neat resin was stable up to 450°C; its char yield at 700°C under anaerobic conditions was 29.4%. Carbon fiber T300 laminates based on 4504 were prepared and characterized. In the case of short-beam (SBS) strength, when tested at 230°C, 51% of the original room temperature strength was retained. © 1996 John Wiley & Sons, Inc.     

Fluorinated bismaleimide resin with good processability,high toughness,and outstanding dielectric properties

In this study, novel fluorinated bismaleimide (BMI) resins were prepared by the copolymerization of 2,2′‐bis[4‐(4‐maleimidephenoxy)phenyl]hexafluoropropane (6FBMP) and diallyl hexafluorobisphenol A (6FDABPA) to enhance their dielectric properties. The dielectric properties of the resins were investigated in the frequency range 7–18 GHz through a cavity method. Through the incorporation of a hexafluoroisopropyl group with the polymer chain, the dielectric constant (ε) was effectively decreased because of the small dipole and the low polarizability of the carbon‐fluorine (C? F) bonds. The 6FBMP/6FDABPA resin possessed excellent dielectric properties, with ε being 2.88 and the dielectric loss being 0.009 at 10 GHz and 25°C. In comparison with the 4,4′‐bismaleimidodiphenylmethane (BDM)/2,2′‐diallyl bisphenol A (DABPA) resin, the glass‐transition temperature (T_g) of 6FBMP/6FDABPA decreased. The flexible ether group in the long chain of 6FBMP was considered to disrupt chain packing and cause a decreased crosslinking density and a lower T_g. 6FBMP/6FDABPA showed a similar thermal decomposition temperature and good thermal properties like the BDM/DABPA resin, whereas the impact strength of the 6FBMP/6FDABPA resin was almost 1.6 times higher than that of the BDM/DABPA resin. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42791.     

Bismaleimide resin modified with diallyl bisphenol A and diallyl p‐phenyl diamine for resin transfer molding

O,O′‐diallyl bisphenol A (DBA) and N,N′‐diallyl p‐phenyl diamine (DPD) were used for the reactive diluents of 4,4′‐bismaleimidodiphenol methane (BDM). The objective was to obtain a modified BDM resin system suitable for resin transfer molding (RTM) process to prepare the advanced composites. The processing behavior was determined by time–temperature–viscosity curves, gel characteristics, and differential scanning calorimetry (DSC). The injection temperature of the resin system in RTM could be 80°C, at which its apparent viscosity was only 0.31 Pa/s, and the apparent viscosity was still less than 1.00 Pa/s after the resin was held at 80°C for 16 h. The gel time test result indicated that at low temperatures, the reactivity of the resin system is low, whereas at high temperatures, the resin could cure very fast, which was beneficial to RTM. The postcure of the cured resin at a given temperature was necessary because the resin had a wide and flat cure exothermic peak, observed by DSC curve. The cured resin displayed both high heat and hot/wet resistance and high mechanical properties, especially tensile strength, tensile modulus, and flexural strength at room temperature, which reached 96.2 MPa, 4.8 GPa, and 121.4 MPa, respectively. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2245–2250, 2001     

二烯丙基双酚A催化改性酚醛型氰酸酯树脂的催化固化

研究了二烯丙基双酚A（DBA）催化改性酚醛型氰酸酯树脂（cy-5）,通过差示扫描量热法（DSC）、热重分析（TG）、冲击性能和动态热机械分析（DMA）测试,分析了改性树脂的热性能和力学性能。研究表明：DBA对cy-5有催化和增韧的双重作用,当DBA的添加量为5%（质量分数）时,催化效果最为明显,含10% DBA的改性树脂固化物的冲击强度达到7.41 kJ/m2,改性树脂固化物的玻璃化转变温度（Tg）和储能模量（E'）均有所降低,但幅度不大。     

Novel adamantane‐containing epoxy resin

A novel adamantane‐containing epoxy resin diglycidyl ether of bisphenol‐adamantane (DGEBAda) was successfully synthesized from 1,3‐bis(4‐hydroxyphenyl)adamantane by a one‐step method. The proposed structure of the epoxy resin was confirmed with Fourier transform infrared, ¹H‐NMR, gel permeation chromatography, and epoxy equivalent weight titration. The synthesized adamantane‐containing epoxy resin was cured with 4,4′‐diaminodiphenyl sulfone (DDS) and dicyandiamide (DICY). The thermal properties of the DDS‐cured epoxy were investigated with differential scanning calorimetry and thermogravimetric analysis (TGA). The dielectric properties of the DICY‐cured epoxy were determined from its dielectric spectrum. The obtained results were compared with those of commercially available diglycidyl ether of bisphenol A (DGEBA), a tetramethyl biphenol (TMBP)/epoxy system, and some other associated epoxy resins. According to the measured values, the glass‐transition temperature of the DGEBAda/DDS system (223°C) was higher than that of the DGEBA/DDS system and close to that of the TMBP/DDS system. TGA results showed that the DGEBAda/DDS system had a higher char yield (25.02%) and integral procedure decomposition temperature (850.7°C); however, the 5 wt % degradation temperature was lower than that of DDS‐cured DGEBA and TMBP. Moreover, DGEBAda/DDS had reduced moisture absorption and lower dielectric properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis of epoxy‐functionalized hyperbranched poly(phenylene oxide) and its modification of cyanate ester resin

High curing temperature is the key drawback of present heat resistant thermosetting resins. A novel epoxy‐functionalized hyperbranched poly(phenylene oxide), coded as eHBPPO, was synthesized, and used to modify 2,2′‐bis (4‐cyanatophenyl) isopropylidene (CE). Compared with CE, CE/eHBPPO system has significantly decreased curing temperature owing to the different curing mechanism. Based on this results, cured CE/eHBPPO resins without postcuring process, and cured CE resin postcured at 230°C were prepared, their dynamic mechanical and dielectric properties were systematically investigated. Results show that cured CE/eHBPPO resins not only have excellent stability in dielectric properties over a wide frequency range (1–10⁹Hz), but also show attractively lower dielectric constant and loss than CE resin. In addition, cured CE/eHBPPO resins also have high glass transition temperature and storage moduli in glassy state. These attractive integrated performance of CE/eHBPPO suggest a new method to develop high performance resins. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of Phenol/Formaldehyde Stoichiometry on the Modification of Epoxy Resin Using Epoxidized Novolacs

ABSTRACT

Unmodified epoxy resins based on bisphenol A exhibit brittleness and low elongation after cure. This article reports the results of a study for improving the properties of epoxy resin by blending with suitable thermosets. Hybrid polymer networks of diglycidyl ether of bisphenol A (DGEBA) resin with epoxidized phenolic novolac resins (EPN) containing phenol and formaldehyde in different stoichiometric ratios were prepared by physical blending. The modified epoxy resins were found to exhibit improved mechanical and thermal properties compared to the neat resin. DGEBA resins containing 2.5 to 20 wt% of epoxidized novolac resins (EPN) prepared in various stoichiometric ratios (1:0.6, 1:0.7, 1:08, and 1:0.9) between phenol and formaldehyde were cured using a room temperature amine hardener. The cured samples were tested for mechanical properties such as tensile strength, modulus, elongation, and energy absorption at break. All the EPNs are seen to improve tensile strength, elongation, and energy absorption at break of the resin. The blend of DGEBA with 10 wt% of EPN-3 (1:0.8) exhibits maximum improvement in strength, elongation, and energy absorption. EPN loading above 10 wt% is found to lower these properties in a manner similar to the behavior of any filler material. The property profiles of epoxy–EPN blends imply a toughening action by epoxidized novolac resins and the extent of modification is found to depend on the molar ratio between phenol and formaldehyde in the novolac.     

Liquid crystalline epoxy resin modified cyanate ester for high performance electronic packaging

A high performance modified cyanate ester (CE) resin system with significantly improved toughness, water resistance and dimensional stability was developed by copolymerizing CE resin with liquid crystalline epoxy resin (LCE) for electronic packaging. Four LCE/CE resins with different contents of LCE were prepared to systemically evaluate the effect of the content of LCE on the key properties of the modified system such as mechanical, dielectric and thermal properties as well as water resistance. Results reveal that the addition of LCE to CE can not only decrease the curing temperature of CE, but also significantly improve the integrated properties including mechanical and dielectric properties, thermal resistance as well as water resistance of cured resin. For example, compared with the whole exothermic peak of CE, that of LCE10/CE significantly shifts toward low temperature with a gap of about 15°C. On the other hand, the impact strength of cured LCE10/CE resin (22 kJ/m²) is about 2.1 times of that of CE resin; while the water absorption of the former is only 81.2% of that of the latter. In addition, cured LCE/CE resins also exhibit lower and more stable dielectric loss than CE resin over the whole frequency range from 10 to 10⁶ Hz. All these improvements in macro-performance by the addition of LCE to CE resin are not only ascribed to the cross-linked chemical structure, but also attributed to the rigid structure of liquid crystalline resin. The outstanding integrated properties of LCE/CE resins suggest great potential to be applied in the field of high performance electronic packaging.     

Synthesis and properties of trifluoromethyl groups containing epoxy resins cured with amine for low Dk materials

The study synthesized a trifluoromethyl (CF₃) groups with a modified epoxy resin, diglycidyl ether of bisphenol F (DGEBF), using environmental friendly methods. The epoxy resin was cured with 4,4′‐diaminodiphenyl‐methane (DDM). For comparison, this study also investigated curing of commercially available diglycidyl ether of bisphenol A (DGEBA) with the same curing agent by varying the ratios of DGEBF. The structure and physical properties of the epoxy resins were characterized to investigate the effect of injecting fluorinated groups into epoxy resin structures. Regarding the thermal behaviors of the specimens, the glass transition temperatures (T_g) of 50–160°C and the thermal decomposition temperatures of 200–350 °C at 5% weight loss (T_d5%) in nitrogen decreased as amount of DGEBF increased. The different ratios of cured epoxy resins showed reduced dielectric constants (D_k) (2.03–3.80 at 1 MHz) that were lower than those of pure DGEBA epoxy resins. Reduced dielectric constant is related to high electrronegativity and large free volume of fluorine atoms. In the presence of hydrophobic CF₃ groups, the epoxy resins exhibited low moisture absorption and higher contact angles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mechanical and thermal properties of bisphenol A-based cyanate ester and diallyl phthalate blends

Cyanate ester resins are a high performance class of compounds. They have excellent mechanical properties, dielectric properties and thermal properties; however, their major drawback is their brittleness. An attempt was made to improve the impact strength of the cyanate ester resin. In the present study a commonly used cyanate resin, bisphenol A dicyanate (BADCy), was modified by the addition of diallyl phthalate (DAP) and was cured with benzoyl peroxide. The properties of the blends such as thermal and mechanical properties were investigated in detail by scanning electron microscope, dynamic mechanical analysis, thermogravimetric analysis, and mechanical measurement. The results indicate that the addition of the appropriate amount of DAP can effectively improve the impact toughness and the flexural strength while sacrificing the thermal properties of the blends. The maximum impact strength and flexural strength were observed on addition of 15 phr DAP content. However, the thermal stability of the blends was found to be lower than that of the unmodified BADCy resin.     

新型低温固化双马来酰亚胺树脂基体研究

双马来酸亚胶树脂基体耐热性好，具有优异的使用性能；但固化温度往往高于２００℃。引发剂可有效地降低固化温度，但所得树脂基体脆性很大。本文在二元胺扩链、烯丙基双酚Ａ共聚后的双马来酰亚胺树脂锄中加入引发剂，制得一种软化点低、韧性适中、耐热性好、贮存稳定的低温固化双马来酰亚胺树脂ＢＤＤＤ体系。为今后该树脂在复合材料构件上的应用奠定了良好的基础。     

Thermal and dielectric properties of bismaleimide‐triazine resins containing octa(maleimidophenyl)silsesquioxane

Octa(maleimidophenyl)silsesquioxane (OMPS) was synthesized, characterized, and employed to modify the BT resin which composed of 4,4′‐bismaleimidodiphenylmethane (BMI) and 2,2′‐bis(4‐cyanatophenyl)propane (BCE). The curing reaction between OMPS and BT resin was first investigated. It was found that OMPS accelerate the curing reaction of BCE, and the onset temperature of the cyclotrimerization was reduced up to 95.5°C (by DSC). As demonstrated by DSC and FTIR, there was no evidence that indicated the coreaction between maleimide and cyanate ester. 2,2′‐diallyl bisphenol A (DBA) and diglycidyl ether of bisphenol A (E‐51) (Wuxi Resin Factory, Jiangsu Province, China) were also used to enhance the toughness of BT resin, and the formulated BTA (containing DBA) and BTE (containing E‐51) resins were obtained. The thermal properties of BT, BTA, and BTE resins incorporated with OMPS were then investigated. The results of DMA and TG showed that the BT, BTA, and BTE resins containing 1 wt % of OMPS exhibit enhanced thermal properties in comparison with their pristine resins respectively, while more contents of OMPS may impair the thermal properties of the polymer matrix, though the effect of OMPS was slight. Finally, the dielectric constant of these hybrid materials were detected, and their dielectric constant were distinctly reduced by the incorporation of OMPS, while overmuch contents of OMPS were disadvantageous for dielectric constant because of the aggregation of OMPS. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Synthesis and properties of methyl hexahydrophthalic anhydride‐cured fluorinated epoxy resin 2,2‐bisphenol hexafluoropropane diglycidyl ether

The fluorinated epoxy resin, 2,2‐bisphenol hexafluoropropane diglycidyl ether (DGEBHF) was synthesized through a two‐step procedure, and the chemical structure was confirmed by ¹H n uclear magnetic resonance (NMR), ¹³C NMR, and Fourier transform infrared (FTIR) spectra. Moreover, DGEBHF was thermally cured with methyl hexahydrophthalic anhydride (MHHPA). The results clearly indicated that the cured DGEBHF/MHHPA exhibited higher glass transition temperature (T_g 147°C) and thermal decomposition temperature at 5% weight loss (T₅ 372°C) than those (T_g 131.2°C; T₅ 362°C) of diglycidyl ether of bisphenol A (DGEBA)/MHHPA. In addition, the incorporation of bis‐trifluoromethyl groups led to enhanced dielectric properties with lower dielectric constant (D_k 2.93) of DGEBHF/MHHPA compared with cured DGEBA resins (D_k 3.25). The cured fluorinated epoxy resin also gave lower water absorption measured in two methods relative to its nonfluorinated counterparts. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2801–2808, 2013     

Influence of cure schedule and solvent exposure on the dynamic mechanical behavior of a vinyl ester resin containing glass fibers

This study deals with the dynamic mechanical properties of a glass-reinforced vinyl ester resin. The viscoelastic parameters of the loss factor and the storage modulus as a function of the cure temperature were used as a criterion to determine the optimum cure conditions to be employed. It is shown that the cure temperature usually used to cure these resins is not enough to reach the maximum glass transition temperature, and, therefore, an additional postcure should be used. The influence of several solvents on the dynamic mechanical behavior of these resins cured following the cure pathway proposed by the supplier was also analyzed. This behavior was compared with the solvent uptake at various exposure times, and the changes observed were related to the crosslink density as well as to the chemical structure of both the resin and the solvent. Finally, the effects of varying the exposure temperature were also investigated for the resin exposed to a liquid which simulates petroleum fluid. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2595–2602, 1998     

双酚A二氰酸酯的合成与固化反应特性研究

采用二步法合成双酚A二氰酸酯(BCE)：由氰化钠和液溴反应合成溴化氰，溴化氰与双酚A在三乙胺的催化下合成BCE，合成产率在85％以上。运用红外光谱和差热分析等手段对合成的BCE树脂进行了表征，并研究了BCE树脂的固化反应特性。结果表明，合成BCE的纯度对氰酸酯树脂的固化反应特性和固化物性能有很大影响。     

Flame retardancy and dielectric properties of dicyclopentadiene‐based benzoxazine cured with a phosphorus‐containing phenolic resin

A dicyclopentadiene‐based benzoxazine (DCPDBZ) was prepared and separately copolymerized with melamine–phenol formaldehyde novolac or phosphorus‐containing phenolic resin (phosphorus‐containing diphenol) at various molar ratios. Their curing behaviors were characterized by differential scanning calorimetry. The electrical properties of the cured resins were studied with a dielectric analyzer. The glass‐transition temperatures were measured by dynamic mechanical analysis. The thermal stability and flame retardancy were determined by thermogravimetric analysis and a UL‐94 vertical test. These data were compared with those of bisphenol A benzoxazine and 4,4′‐biphenol benzoxazine systems. The effects of the diphenol structure and cured composition on the dielectric properties, moisture resistance, glass‐transition temperature, thermal stability, and flame retardancy are discussed. The DCPDBZ copolymerized with phosphorus‐containing novolac exhibited better dielectric properties, moisture resistance, and flame retardancy than those of the melamine‐modified system. The flame retardancy of the cured benzoxazine/phosphorus‐containing phenolic resins increased with increasing phosphorus content. The results indicate that the bisphenol A and 4,4′‐biphenol systems with a phosphorus content of about 0.6% and the dicyclopentadiene system with a phosphorus content of about 0.8% could achieve a flame‐retardancy rating of UL‐94 V‐0. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and properties of novel dicyanate with low dielectric and water absorption performance

The 1,4‐bis (3,5‐dimethyl‐4‐cyanatobenzyl) benzene (BBZCy) was synthesized successfully by the reaction of 1,4‐bis (3,5‐dimethyl‐4‐hydroxybenzyl)benzene(BBZ) with cyanogen chloride in the presence of triethylamine at −5–0°C. Its structure was confirmed by means of FTIR, elemental analysis, MS, and ¹H NMR spectra. The monomer of BBZCy was cured by itself or cured with catalysts to form sym‐triazine structure. Thermal properties of cured BBZCy were studied using DSC, DMA, TMA, and TGA. Compared with the commercial bisphenol A dicyanate resin (BADCy), the cured BBZCy resin exhibited a lower dielectric constant (2.66 at 1 GHz), a lower dissipation factor (0.0054 at 1 GHz), lower water absorption (0.8% at 100 h), less thermal stability, and lower glass transition temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and Application of a New Curing Agent for Epoxy Resin

A new curing agent based on palmitoleic acid methyl ester modified amine (PAMEA) for epoxy resin was synthesized and characterized. Diglycidyl ether of bisphenol A (DGEBA) epoxy resins cured with different content of PAMEA along with diethylenetriamine (DETA) were prepared. The mechanical properties, dynamic mechanical properties, thermal properties, and morphology were investigated. The results indicated that the PAMEA curing agent can improve the impact strength of the cured epoxy resins considerably in comparison with the DETA curing agent, while the modulus and strength of the cured resin can also be improved slightly. When the PAMEA/epoxy resin weight ratio is 30/100, the comprehensive mechanical properties of the cured epoxy resin are optimal; at the same time, the crosslinking density and glass transition temperature of the cured epoxy resin are maximal.     

Microstructural effects and the toughening of thermoplastic modified epoxy resins

We have studied an epoxy resin formulation consisting of the diglycidyl ether of bisphenol-A (DGEBA), modified with phenolic hydroxyl-terminated polysulfone (PSF) and cured with an aromatic amine curing agent, diaminodiphenyl sulfone (DDS). A range of microstructures and fracture properties have been obtained by controlling the formulation cure conditions (cure temperature and cure cycle in an isothermal mode). The chemical conversion of the cured resins has been monitored by near-infrared spectroscopy (NIR). Although only a single material formulation was used, three distinct types of microstructure were identified by scanning electron microscope (SEM) observations on samples prepared at different cure temperatures. Surprisingly, the thermal and fracture properties of the cured samples did not vary noticeably, in spite of the significant microstructure variations. The consistency of these fracture toughness results with cure temperature changes was an unexpected result in the light of our earlier observations of a strong dependence of fracture toughness on cure temperature in neat resin systems. The difference in behavior between neat and modified resins reveals that the fracture toughness of the latter is dependent on a combination of the microstructure and the matrix resin properties. This hypothesis was also supported by an observation of high fracture thoughness in a sample cured in a two-step process, which we believe is due to the optimum microstructure and matrix resin properties, being achieved separately during precure and postcure, respectively. The increase in fracture toughness values caused by the modification (ΔG_IC) was calculated from the fracture toughness values of neat and modified resins, prepared under the same cure conditions, using a proposed theoretical equation. © 1993 John Wiley & Sons, Inc.     

Toughening epoxy resins with polyepichlorohydrin

Polyepichlorohydrin (PECH) rubbers were found to toughen epoxy resins based on the diglycidyl ether of bisphenol A (DGEBA) and cured with piperidine. The degree of toughening depends on the molecular weight of the PECH and on the curing temperature. Best toughening was achieved with PECH of the highest nominal molecular weight of 3400 (Hydrin 10 × 2). Hydrin 10 × 1 (nominal molecular weight 1700) did not toughen the epoxy resin unless bisphenol A was also added, whereas Hydrin 10 × 2 toughened it in the absence of bisphenol A. Curing resins containing bisphenol A and Hydrin 10 × 1 at 160°C resulted in a slightly more brittle resin than when cured at 120°C. The effect of PECH rubbers on the T_g, modulus, and hot/wet properties is similar to that of carboxy-terminated butadiene-acrylonitrile rubbers (CTBN). Dynamic mechanical thermal analysis (DMTA) and scanning electron micrographs (SEM) of fractured surfaces show that the PECH separates as a discrete phase during curing. © 1993 John Wiley & Sons, Inc.