Study on Properties of Low Dieletric loss Resin Matrix

Summary One new high performance modified BMI resin matrix with enhanced processing characteristics, made from 4,4-bismaleimidodiphenyl methane (BDM) and allyl phenyl compounds, allyl epoxy resins and epoxy acrylate resins, were developed. Solubility, differential scanning calorimetry (DSC), gel time, and Fourier transform infrared (FTIR) spectroscopy were used to detect the structure and processing characteristics of the modified BMI resin and neat BDM. Results show that the new modified BMI resin systems have enhanced processability compared with neat BDM, especially improved solubility and faster thermal polymerization rate. In addition, the new cured systems have more than two times improved impact strength without a great decrease in excellent dielectric properties or thermal and hot–wet resistance of neat BDM resin.     

Study on properties of low dielectric loss resin matrix

Allyl phenyl compounds, allyl epoxy resins, and epoxy acrylate resins are adapted to copolymerize with bismaleimide (BMI) resins and to modify mechanical properties and processing properties. Reaction activity, physical properties, mechanical properties, dielectric properties, and thermal stability were investigated. Impact strength and flexural strength of modified BMI resin are increased about twice and 42% than that of pure BMI resin, respectively. Fracture elongation is from 1.6 to 2.3%. The fracture surfaces of the broken specimens are examined by scanning electron microscopy (SEM). As a result, modified BMI resins put up typical toughness rupture. The modified BMI resins possess excellent dielectric properties, and dielectric constant and dielectric loss almost hold the line with increasing epoxy concentration. When the test frequency scope is from 1 to 20 GHz, the dielectric constant and dielectric loss of modified BMI resins is 3.05–3.12 and 0.0089–0.012, respectively. The modified BMI resins still possess fine properties after hydrothermal aging. After 100 h in boiling water, the reservation ratios of both the impact strength and flexural strength of modified system exceeded 90%, and the water absorption and heat distortion temperature (HDT) is 2.6% and 235°C, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 315–319, 2006     

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 Systems for High-Performance Radomes

Three modified bismaleimide resin systems (designated as systems I, II, and III) for high-performance radomes are introduced. Their glass transition temperatures are 274°, 268°, and 265°C, respectively; and their dielectric loss tangents at 10 GHz are 0.0117, 0.0108, and 0.0118, respectively. System I and system II are suitable for hot-pressing process; and system III, which has attractive processing characteristics, is suitable for resin transfer molding (RTM). The injection temperature of system III is room temperature, at which its viscosity is only 0.38 Pa·sec. In addition, its working life is more than 40 h. Properties of neat resins and composites are investigated; all data show that they have good thermal and mechanical properties as well as excellent dielectric properties. These indicate that the three modified bismaleimide resins can be used as matrix resins for advanced radomes.     

Carbon fiber cardanol-epoxy composites

Carbon fiber composites based on tetrafunctional epoxy resin N,N,N′,N′-tetraglycidyl-2,2-bis[4-(4-aminophenoxy)phenyl]propane modified with cardanol were investigated. The differential scanning calorimetric technique was used to study the curing reaction of the neat resins. The dielectric properties of the composites were compared. The use of cardanol in epoxy resins at cardanol/epoxy molar ratios less than 0.3/1 improved the chemical resistance as well as the mechanical properties of the composites, such as the flexural strength and modulus, tensile strength and modulus, and interlaminar shear strength. Higher cardanol contents decreased such properties. The highest properties of the composites were observed with the epoxy-cardanol resin having a cardanol/epoxy molar ratio of 0.3/1. © 1996 John Wiley & Sons, Inc.     

Aging and Thermal Studies on Epoxy Resin Modified by Epoxidized Novolacs

Epoxy resins are thermosetting polymers widely used for polymer composites, adhesives, high performance coatings, potting and encapsulation, and numerous other applications. These resins have excellent mechanical and electrical properties, low cure shrinkage, and good adhesion to most substrates. This study is an attempt to improve the thermal and aging characteristics of epoxy resin by blending with other multifunctional epoxies such as EPN and ECN. Bis-phenol A epoxy resins containing 2.5 to 20 wt% of epoxy novolac were cured in the presence of a polyamide hardener and tested for thermal and mechanical properties, hardness, water absorption, etc. Blends containing 10 to 15 wt% of epoxy novolac show substantial improvement in properties such as tensile strength, elongation, and energy absorbed to break. The novolac derived from p-cresol was better than that based on phenol in enhancing the properties. TGA, DSC, and DMA were employed for studying the thermal properties of the modified resin. The study reveals that modification using epoxy phenol and p-cresol novolac resins (EPN and ECN, respectively) improves the aging characteristics of the epoxy resin in addition to overall improvement of the mechanical properties.     

Effects on Dielectric Properties of Modified Bismaleimide Resins

Abstract

Six modified bismaleimide (BMI) resin systems are developed. The modifier is diallyl bisphenol A, diallyl bisphenol A ether. TDE-85 epoxy/MNA anhydride, and styrene. respectively. In view of structure of those cured resins, relationships between structure and dielectric properties have been studied emphatically, while effects of postcure temperature and catalysts on dielectric properties were also shown. Results indicate that dielectric properties lie on structure of cured resin and postcure temperature; catalysts can strikingly improve the heat-resistance of materials, but has little effect on the dielectric properties. In addition, mechanical and thermal properties of neat resins were also shown.     

Epoxy hybrid composites cured with octaaminophenyl polyhedral oligomeric silsesquioxane

Polyhedral oligomeric silsesquioxane-containing hybrids of epoxy resins are prepared via the cocuring reaction between octaaminophenyl polyhedral oligomeric silsesquioxane (OAPS) and brominated epoxy resin (EP). The gel time, dispersion, thermal properties, mechanical properties, water absorption, and dielectric properties of the OAPS/EP composites are studied. The gel time of the 1 wt % OAPS composites is significantly higher compared with that of the epoxy resin control. Wide angle X-ray diffraction and scanning electron microscopy show that, at the molecular level, the appropriate amount of POSS cages was dispersed in the epoxy matrix because the POSS monomer participated in the crosslinking reaction. The thermal and mechanical properties of the composites are enhanced as 1 wt % OAPS was added to the epoxy system. The water absorption of the 1 wt % OAPS composite significantly declines. The dielectric constant of the 1 wt % OAPS composite is 0.5 less than that of the epoxy resin control in the range of 100 Hz–40 MHz. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

High performance self‐healing bismaleimide/diallylbisphenol a/poly(phenylene oxide) microcapsules composites with low temperature processability

Novel high performance self‐healing 4,4′‐bismaleimidodiphenylmethane (BDM)/diallylbisphenol A(BA)/poly(phenylene oxide) microcapsules filled with epoxy resin (PPOMCs) systems with low temperature processability were developed. The effects of PPOMCs on the reactivity of BDM/BA resin system were investigated; the properties of cured BDM/BA/PPOMCs systems such as fracture toughness, dynamic mechanical property, dielectric property, and self‐healing ability were discussed. The morphologies of the cured resin systems were characterized using scanning electronic microscope and light microscopy. Results reveal that the addition of PPOMCs can catalyze the polymerization reaction of BDM/BA resins. BDM/BA systems with appropriate PPOMCs content cured at low temperature possess excellent fracture toughness, high glass transition temperature (T_g), and low dielectric property. The self‐healing ability of BDM/BA can be realized by the introduction of PPOMCs owing to the polymerization of the released core materials from PPOMCs. The self‐healing efficiency of healed BDM/BA/PPOMCs systems can be influenced by the size and content of PPOMCs and the contact areas between the crack surfaces. © 2013 Society of Plastics Engineers     

环氧树脂/石英纤维透波复合材料制备

为改善环氧树脂的介电性能及提升石英纤维的界面性能,使用缩水甘油醚基笼型倍半硅氧烷(G–POSS)和γ–氨丙基三乙氧基硅烷(KH–550)分别对环氧树脂和石英纤维进行改性。利用差示扫描量热法研究改性后环氧树脂的固化过程,并通过外推法确定了其固化工艺,根据固化工艺制备环氧树脂/石英纤维复合材料,分别对该复合材料的热稳定性、介电性能和弯曲性能进行表征,结果表明,使用G–POSS和KH–550改性后的环氧树脂/石英纤维复合材料热稳定性、介电性能和弯曲性能达到最佳,初始分解温度达到369.59℃,常温下在12~18 GHz的介电常数稳定在3.2~3.5之间,介电损耗角正切值在0.005~0.02之间,弯曲强度达到376.4 MPa,弯曲弹性模量为21.7 GPa。     

High‐performance hyperbranched poly(phenylene oxide) modified bismaleimide resin with high thermal stability,low dielectric constant and loss

High‐performance hyperbranched poly(phenylene oxide)‐modified bismaleimide resin with high thermal stability, low dielectric constant, and loss was developed, which is made up of hyperbranched poly(phenylene oxide) (HBPPO), 4,4′‐bismaleimidodiphenylmethane (BDM), and o, o′‐diallylbisphenol A (DBA). The curing reactivity, morphology, and performance of BDM/DBA/HBPPO resin were systemically investigated, and similar investigations for BDM/DBA resin were also carried out for comparison. Results show that BDM/DBA/HBPPO and BDM/DBA resins have similar curing mechanism, but the former can be cured at lower temperature than the later; in addition, cured BDM/DBA/HBPPO resin with suitable HBPPO content has better thermal stability and dielectric properties (lower dielectric constant and loss) than BDM/DBA resin. The difference in macroproperties between BDM/DBA/HBPPO and BDM/DBA resins results from the different chemical structures and morphologies of their crosslinking networks. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Selected biotrends in development of epoxy resins and their composites

Epoxy resins and their fibre or particulate composites are widely used in various industries, including building, naval, aircraft, automotive and aerospace. Modern polymer science and technology focus on the development of green polymers and composites. There are two major areas of interest in the case of epoxy resins: the development of bio-based resins and the production of composites with natural fibres. One of the most interesting challenges is developing fully bio-based composites: that is, epoxy resins based on renewable resources and natural fibres. This paper presents a review of literature on epoxy resins and hardeners based on renewable resources (especially vegetable oils) and epoxy composites with natural fibres. We also describe some of the effective methods of improving the mechanical properties of epoxy–natural fibres composites, including chemical modification of the fibre surface and the application of hybrid reinforcements.     

5528氰酸酯树脂基玻璃纤维增强复合材料性能研究

本文对新型的5528改性氰酸酯树脂基玻璃纤维增强复合材料的耐热性能、力学性能、耐湿热性能、介电性能进行研究，结果表明：5528氰酸酯树脂基玻璃纤维增强复合材料具有良好的力学性能和介电性能。其中石英玻璃纤维增强复合材料的介电常数为3．40，介电损耗正切值为0．00393，并且对频率显示出优秀的稳定性；而高强玻璃纤维增强复合材料的介电损耗正切值为0．00925，远远优于环氧和双马树脂基复合材料。5528氰酸酯基玻璃纤维复合材料适合高性能透波材料或高频印刷电路板应用。     

Modification of epoxy resin by addition of bismaleimide and diallyl phthalate

Epoxy resins are a very versatile class of compounds. They have excellent mechanical properties and are easily processable; however, their major drawback is their brittleness. An attempt was made to improve the impact strength of the epoxy without decreasing its other properties. In the present study a commonly used epoxy resin, diglycidyl ether of Bisphenol‐A, was modified by the addition of bismaleimide (BMI) and diallyl phthalate (DAP) and was cured with diaminodiphenylmethane and benzoyl peroxide. The composition incorporating 5 phr BMI showed maximum heat deflection temperature (HDT) and flexural strength with impact properties remaining almost unaffected. Further addition of BMI reduced the HDT and flexural properties but increased the impact strength. For epoxy‐DAP systems the maximum HDT and flexural strength were observed on addition of 5 phr DAP. Further addition of DAP lead to a decrease in all properties except impact strength, which was observed to increase. Incorporation of both BMI and DAP, simultaneously, into the epoxy resin resulted in improvement in mechanical properties for most of the compositions. However, the HDT was found to be less than that for unmodified epoxy. POLYM. ENG. SCI., 47:1881–1888, 2007. © 2007 Society of Plastics Engineers     

Glass fibre reinforced composites of triglycidyl-p-aminophenol

Glass fibre reinforced epoxy composites were fabricated from the matrix resins diglycidyl ether of bisphenol A (DGEBA) and triglycidyl-p-aminophenol (TGAP) using diethylene triamine as curing agent. The epoxy laminates were evaluated for their mechanical properties, dielectrical properties and chemical resistance. Significant improvement in fiexural strength but a slight deterioration in dielectrical properties were observed on incorporation of an epoxy fortifier into the resin system before fabricating the composites.     

Fracture Behaviour of Thermoplastic Modified Epoxy Resins

This work has shown that the addition of polyetherimide (PEI) can significantly increase the toughness of highly cross-linked epoxy resins, whilst retaining a high T_g and modulus. These combined properties indicate the potential of PEI modified epoxy resins for use as matrices for advanced composite materials. In terms of G_IC, addition of 20wt% PEI raised the toughness by a factor of eight. Evidence from SEM fracture surfaces suggests that the toughening mechanism operating in bulk PEI modified epoxy resin is ductile drawing of the PEI. Carbon fibre composites based on 30wt% PEI modified epoxy resin matrices show considerable improvement in toughness at low and high strain rates when compared with CFRP possessing unmodified or 20wt% modified PEI content epoxy resins.     

热固性树脂/炭黑复合材料的微波介电性能

将导电性能良好的乙炔炭黑加入环氧树脂和双马来酰亚胺两种树脂体系中，研究了炭黑对它们的微波介电性能和力学性能的影响。研究表明，填充少量乙炔炭黑（≤３质量份）可明显提高环氧村脂和双马来酰亚胺树脂的复介电系数和介电损耗，而弯曲强度略有下降。     

Mechanical and thermal properties of biphenyldiol formaldehyde resin/gallic acid epoxy composites enhanced by graphene oxide

In this study, the gallic acid‐based epoxy resin (GA‐ER) and alkali‐catalysed biphenyl‐4,4′‐diol formaldehyde resin (BPFR) are synthesized. Glass fibre‐reinforced GA‐ER/BPFR composites are prepared. Graphene oxide (GO) is used to improve the mechanical and thermal properties of GA‐ER/BPFR composites. Dynamic mechanical properties and thermal, mechanical, and electrical properties of the composites with different GO content are characterized. The results demonstrate that GO can enhance the mechanical and thermal properties of the composites. The glass transition temperature, T_g, of the BPFR/GA‐ER/GO composites is 20.7°C higher than the pure resin system, and the 5% weight loss temperature, T_d5, is enhanced approximately 56.6°C. When the BPFR: GA‐ER mass ratio is at 4 : 6 and GO content is 1.0–1.2 wt %, the tensile and impact strengths of composites are 60.97 MPa and 32.08 kJ/m² higher than the pure resin composites, respectively. BPFR/GA‐ER composites have better mechanical properties, and can replace common BPA epoxy resins in the fabrication of composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42637.     

双马来酰亚树脂基体的湿热特性研究

本文以四官能环氧树脂基体作参比物、选择两种典型的双马来酰亚胺树脂基体（环氧改性双马基体、烯丙基双酚Ａ／双马共聚基体）作为对象，研究其吸湿特性以及吸湿对树脂基体性能的影响，结果表明，树脂基体的化学结构和交联密度对吸湿特性有较大的影响，吸湿量对树脂基体性能的影响也与基体材料的类型，交联密度有关，不能简单地用给定时间下的吸湿率来评定树脂基体的湿热性能优劣。     

二烯丙基双酚A改性双马来酰亚胺三嗪树脂的固化工艺及性能

以烯丙基化合物改性的方法制得了改性双马来酰亚胺三嗪(BT)树脂,研究了改性BT树脂体系的固化动力学,求得表观活化能为45.9 kJ/mol,反应级数为0.842,确定了固化工艺,并采用力学性能分析和动态热机械分析等手段对树脂浇铸体的性能进行了研究.结果表明,对于烯丙基化合物改性BT树脂体系,二烯丙基双酚A具有改善双马来...