Static and dynamic mechanical properties of modified bismaleimide and cyanate ester interpenetrating polymer networks

Interpenetrating polymer networks (IPNs) based on different ratios of modified bismaleimide (BMI) resin [BMI/2,2′‐diallylbisphenol A (DBA)] and cyanate ester (CE) (b10) have been synthesized via prepolymerization followed by thermal curing. A systematic study of both static and dynamic mechanical properties of the cured BMI/DBA–CE IPN resin systems was conducted through flexural, impact testing, and dynamic mechanical analysis (DMA). The static mechanical investigation shows that the flexural strength, flexural strain at break, and impact strength of the cured BMI/DBA–CE IPN resin systems are relatively lower than that calculated by rule of mixture of two individuals: BMI/DBA and b10. However, the flexural moduli of the IPN resin systems have more consistent features compared to that calculated by rule of mixture. Single damping peaks are detected for the cured BMI/DBA–CE IPN resin systems, which suggests a substantial degree of interpenetration between two networks. The damping peaks of the cured BMI/DBA–CE IPN resin systems do tend to become broader with increasing concentration of BMI/DBA, whereas the intensity of damping peaks of the IPN resin systems decreases. The obtained results not only provide insight information about the characteristic structures of these BMI/DBA‐–CE IPN resin systems, but also give guidelines for their applications. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2000–2006, 2003     

Study on cure reaction of the blends of bismaleimide and dicyanate ester

In this work, the cure reaction of the blends of bisphenol A dicyanate ester (BADCy) and 4,4′-bismaleimidodiphenylmethane (BMI) was investigated by using DSC, in situ FTIR, DMA and generalized 2D correlation analysis. The results clarified that there existed different kinds of cure mechanism in the blends of bismaleimide and dicyanate ester. In non-catalyzed blends, the dicyanate ester and bismaleimide cured independently and formed two kinds of network: polycyanurate and polybismaleimide. A cyanate curing catalyst accelerated the cure of dicyanate ester but did not change the independent cure mechanism of two components. Moreover a commercial ring closure catalyst, which was usually used in the synthesis of bismaleimide, resulted in the co-reaction between two components and formed a homogeneous network. Thus, the cure mechanism of the blends of dicyanate ester and bismaleimide was related to the catalyst presented in the blends systems.     

Determination of thermal cure kinetics of thin films of photocatalysed dicyanate ester by FTIR emission spectroscopy

Emission Fourier transform infrared (FTIR) spectroscopy has been found to be a suitable technique for monitoring the thermal cure of thin films of photocatalysed dicyanate ester resins. The kinetics of the polymerization of a commercial cyanate ester resin (AroCy RTX‐366) catalysed by an organometallic compound, tricarbonyl cyclopentadienyl manganese (CpMn(CO)₃), have been determined using this technique and the results compared with those obtained from transmission FTIR. The trimerization reaction rate of the resin is found to have a first order dependence upon both the cyanate fraction and the active catalyst concentration until diffusion control occurs. To elucidate the mechanism, a system with premade catalyst, which was the photoreaction product of the resin and the organometallic compound, has also been studied. The activation energy for this system is 91 ± 10 kJ mol⁻¹ compared to 72 ± 8 kJ mol⁻¹ for the directly irradiated system. This may arise from different distributions of three photoproducts identified as complexes between manganese and the cyanate ester. © 2000 Society of Chemical Industry     

Thermal degradation study of interpenetrating polymer network based on modified bismaleimide resin and cyanate ester

Interpenetrating polymer networks (IPNs) based on different ratios of a modified bismaleimide resin (BMI/DBA) and cyanate ester (b10) have been synthesized via prepolymerization followed by thermal curing. A systematic thermal degradation study of these new BMI/DBA‐CE IPN resin systems was conducted by thermogravimetric analysis at different heating rates both in N₂ (thermal stability) and in air (thermal‐oxidative stability). The cured BMI/DBA‐CE IPN resin systems show excellent thermal stability, which could be demonstrated by 5% weight loss temperature (T_5%) ranging between 409 and 423 °C, maximum decomposition rate temperature (T_max) ranging between 423 and 451 °C, and the char yields at 800 °C ranging from 37% to 41% in nitrogen at a heating rate of 10 °C min^?1. The apparent activation energy associated with the main degradation stage of the cured BMI/DBA‐CE IPN resin systems was determined using the Kissinger method. The obtained results provide useful information in drawing correlation between thermal properties and structure. © 2003 Society of Chemical Industry     

Rheological study of crosslinking and gelation in bismaleimide/cyanate ester interpenetrating polymer network

In searching for high performance polymer resins that have a combination of low dielectric constant and loss, high temperature resistance, ease of being processed, and other desirable properties, an interpenetrating polymer network (IPN) based on cyanate ester (CE) and 2,2′‐diallylbisphenol A (DBA) modified bismaleimide resin (BMI) was prepared via prepolymerization followed by thermal curing. This work discusses the use of multiple waveform rheological technique to investigate the crosslinking and gelation behavior of this resin system at various temperatures. The gel point can be accurately determined from a single experiment using this technique. At the point of gelation, both the storage modulus (G′) and loss modulus (G″) of the IPN follow a similar power law equation with oscillation frequency used in the rheological measurement. Both the relaxation exponent n, a viscoelastic parameter related to the cluster size of the gel, and gel strength S, related to the mobility of the crosslinked chain segments, were determined via a curve fitting method. Both n and S were found to be temperature dependent in this BMI/DBA–CE IPN system. The apparent activation energy of gelation or curing reaction was found to be approximately 47.6 kJ/mol. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2437–2445, 2001     

Biobased thermosetting resins composed of L‐lysine methyl ester and bismaleimide

Lysine methyl ester (LME), which was generated in situ by the reaction of lysine methyl ester dihydrochloride and triethylamine in dimethyl sulfoxide (DMSO), was prepolymerized with 4,4′‐bismaleimidodiphenylmethane (BMI) at 80°C for 2 h in DMSO. Then, the formed prepolymer was precipitated in water. The obtained LME/BMI prepolymers with molar ratios of 2:2, 2:3, and 2:4 were compression‐molded at a final temperature of 230°C for 2 h to produce cured lysine methyl ester/4,4′‐bismaleimidodiphenylmethane resins (cLBs; cLB22, cLB23, and cLB24, respectively). Fourier transform infrared (FTIR) analyses revealed that the Michael addition reaction of amino groups to the C?C bonds of the maleimide group occurred in addition to the homopolymerization of the maleimide group. The glass‐transition temperature (T_g) and 5% weight loss temperature (T₅) of the cured resin increased with increasing BMI feed content, and cLB24 showed the highest T_g (343°C) and T₅ (389°C). The flexural strengths (131–150 MPa) and moduli (3.0–3.6 GPa) of the cLBs were comparable to those of the conventionally cured resins of BMI and 4,4′‐diaminodiphenylmethane. Field emission scanning electron microscopy analysis revealed that there was no phase separation for all of the cured resins. Although cLB23 and cLB24 were not biodegradable, cLB22 had a biodegradability of 8.5% after 30 days in an aerobic aqueous medium containing activated sludge. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40379.     

In situ FT‐IR and DSC investigation on the cure reaction of the dicyanate/diepoxide/diamine system

Cure reactions of a liquid aromatic dicyanate ester (1,1′‐bis(4‐cyanatophenyl)ethane, BEDCy) with a liquid bisphenol A epoxide (2,2‐bis(4‐glycidyloxyphenyl)propane, BADGE) and 4,4′‐diaminodiphenyl sulfone (DDS) were studied through correlation of the in situ FT‐IR spectroscopy and DSC in dynamic scanning mode. Before this system was examined, cure reactions of precursory systems of BADGE/DDS, BEDCy/BADGE and BEDCy/DDS were investigated separately. Cure reaction paths for each system are proposed. Some reactions in the precursory systems, such as polycyclotrimerization of dicyanate to form sym‐triazine and formation of alkyl isocyanurate, were not observed in the combined curing system BEDCy/BADGE/DDS. Four principal reaction paths are proposed for this curing system: (1) formation of oxazoline from the reaction between the epoxide and cyanate group; (2) reaction of epoxide with primary amine to form a hydroxyl group; (3) reaction of epoxide with the hydroxyl group to form an ether linkage; and (4) rearrangement of oxazoline to form oxazolidinone. Two distinct, but somewhat overlapping, exothermic peaks were observed on the DSC thermogram. The lower temperature peak on the DSC thermogram was primarily contributed by the first reaction path, whereas the higher temperature peak can mainly be attributed to the reaction paths 2, 3 and 4. © 2001 Society of Chemical Industry     

新型双马来酰亚胺改性氰酸酯树脂及其复合材料

采用双马来酰亚胺封端的硫醚酰亚胺低聚物对氰酸酯树脂进行了改性(SBMI),通过红外光谱对改性树脂(SBT)的结构作了表征,通过流变分析,热失重分析研究了其粘度特性及耐热性,并对其玻纤复合材料的力学性能进行了测试。结果表明,当SBMI质量分数为氰酸酯树脂的的37.5%时,SBT树脂的5%热失重温度为415℃,其复合材料在常温下的拉伸强度为438.8 MPa,弯曲强度为657.3 MPa,断裂伸长率为9.2%;200℃时拉伸强度为310.5 MPa,弯曲强度为307.4 MPa,断裂伸长率为12.5%。该树脂具有良好的加工性,耐热性和力学性能。     

Effect of blending polyethersulfone on the cure kinetics and physical properties of dicyanate resin

The curing behavior and thermomechanical properties of dicyanate/polyethersulfone (PES) blends were investigated. Differential scanning calorimetry (DSC) was used to study the curing behavior of the dicyanate/PES blends. A second‐order autocatalytic reaction mechanism was used to describe the cure kinetics of the blends. The reaction kinetic parameters were determined by fitting DSC conversion data to the kinetic equation. The main glass‐transition temperatures of the blends decreased with increasing PES content. Two glass‐transition temperatures indicating phase‐separated morphology of the blends were observed. The thermal decomposition behavior of the blends was measured using thermogravimetric analysis. Mechanical and electrical properties of the blends were investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1952–1962, 2001     

Synthesis, cure kinetics and thermal properties of the 2,7-dihydroxynaphthalene dicyanate

The novel dicyanate ester resin containing the naphthalene ring (DNCY) was synthesized from 2,7-dihydroxynaphthalene and cyanogen bromide by two-step method. The monomer of DNCY was characterized by FT-IR, ¹H NMR, ¹³C NMR and elemental analyses (EA). The cure behavior of DNCY was studied by means of nonisothermal DSC, and the kinetics parameters were determined by the Kissinger method. The thermal properties of DNCY resin were studied by thermal degradation analysis at a heating rate of 10 °C min⁻¹ both in N₂ (thermal stability) and in air (thermal-oxidative stability). The DNCY resin showed excellent thermal stability, compared with that of bisphenol A dicyanate (BACY) resin, which could be demonstrated by the extensional onset temperature (435.8 °C), the temperature of maximum weight loss rate (450.3 °C) and the percentage char yields at 700 °C (60.5%) in N₂, and thermal-oxidative stability, which could be demonstrated by the extensional onset temperature (435.4 °C), the first temperature of maximum weight loss rate (450.7 °C), the second temperature of maximum weight loss rate (580.0 °C) and the temperature of complete degradation (704.4 °C) in air. The DNCY resin exhibited higher T_g and thermal degradation temperature than BACY resin.     

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.     

Modification of bismaleimide resin by soluble poly(ester imide) containing trimellitimide moieties

Poly(ester imide)s containing trimellitimide moieties have been used to reduce the brittleness of the bismaleimide resin composed of 4,4′‐bismaleimidediphenyl methane and o,o′‐diallyl bisphenol A. The poly(ester imide)s include poly[ethylene phthalate‐co‐ethylene N‐(1,4‐phenylene)trimellitimide dicarboxylate]s containing 20–40 mol% trimellitimide (TI) unit, and poly[trimethylene phthalate‐co‐trimethylene N‐(1,4‐phenylene)trimellitimide dicarboxylate]s (PESIP) containing 20 mol% TI unit. The poly(ester imide)s are effective modifiers for reducing the brittleness of the bismaleimide resin. For example, when using 30 wt% of PESIP (20 mol% TI unit, M_w 13 500 g mol^?1), the fracture toughness (K_IC) for the modified resin is increased by 80% with retention in flexural properties and a slight loss of the glass transition temperature, compared with the values of the unmodified cured bismaleimide resin. Microstructures of the modified resins have been examined by scanning electron microscopy and dynamic viscoelastic analysis. The toughening mechanism is discussed in terms of the morphological and dynamic viscoelastic behaviour of the modified bismaleimide resin system. © 2004 Society of Chemical Industry     

Study on the cure behavior of 2,7‐dihydroxynaphthalene dicyanate

The cure behavior of 2,7‐dihydroxynaphthalene dicyanate (DNCY) was studied by means of nonisothermal DSC, isothermal DSC, and FTIR. In nonisothermal DSC, the cure kinetics parameters of DNCY were calculated by the Coats–Redfern method and compared with those of biphenol A dicyanate (BACY). It was revealed that the activation energy of DNCY was enhanced compared with that of BACY because of the presence of naphthalene, and the gelation of DNCY occurred within the conversion range 50–55%, which is lower than that of BACY. In isothermal DSC, a good time–temperature superposition of the conversion profiles of DNCY was obtained during conversions below about 50%. These results were consistent with those obtained by nonisothermal DSC. For the catalyzed system, the autocatalytic behavior prevailed at conversions below 30%, whereas the catalytic behavior occurred only at conversions above 30%. In situ FTIR spectra revealed that a triazine network was formed by cyclotrimerization of the OCN functional group during the cure process for systems with and without catalysts. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3927–3939, 2004     

Reactive Alder‐ene blend of diallyl bisphenol A novolac and bisphenol A bismaleimide: synthesis,cure and adhesion studies

A novel, addition‐curable novolac resin (ABPF) was synthesized by the reaction of diallyl bisphenol A with formaldehyde using p‐toluene sulfonic acid as the catalyst. The synthesis conditions were optimized to obtain soluble polymer of desirable molecular weight distribution which was characterized by FT‐IR, NMR and SEC. ABPF was reactively blended with bisphenol A bismaleimide (BMIP) and cured through an Alder‐ene reaction at high temperatures. The cure characteristics of BMIP–ABPF blend with a maleimide:allyl phenol stoichiometry of 1:1 were studied using FT‐IR, DSC and DMA, which evidenced the multi‐step cure reactions taking place in the system. Cure optimization was evaluated by DSC, DMA and adhesive property tests. The moderately crosslinked blend was conducive for achieving the optimum adhesive properties on aluminium substrates. Retention of the adhesive properties was greater than 100% at 150 °C. © 2001 Society of Chemical Industry     

环氧树脂改性双马来酰亚胺/氰酸酯树脂固化工艺研究

采用差示扫描量热(DSC)法和红外光谱(FT-IR)法对缩水甘油胺型环氧树脂(AG-80)与脂环族缩水甘油酯型环氧树脂(TDE-85)共同改性双马来酰亚胺(BMI)/氰酸酯树脂(CE)的固化反应历程进行了研究,并按照Kissinger和Crane法计算出该改性树脂体系固化反应的动力学参数。结果表明:改性树脂体系的固化反应表观活化能为68.11 kJ/mol,固化反应级数为0.860(接近于1级反应);环氧树脂(EP)可促进CE固化,当固化工艺条件为"150℃/3 h→180℃/2 h"时,改性树脂体系可以固化完全。     

Curing kinetics and mechanism of novel high performance hyperbranched polysiloxane/bismaleimide/cyanate ester resins for resin transfer molding

Curing kinetics and mechanism determine the structure and property of thermosetting resins and related composites. The curing kinetics and mechanism of a novel high performance resin system based on hyperbranched polysiloxane (HBPSi), 2,2′‐diallylbisphenol A modified bismaleimide (BD), and cyanate ester (CE) resins for Resin Transfer Molding (RTM) technique were systemically studied by Differential Scanning Calorimetry (DSC), Fourier Transform Infrared (FTIR) spectra, and torque rheometer. Results show that the addition of HBPSi to BD/CE resin not only decreases the initial curing temperature and apparent activation energy, but also changes the curing mechanism, and thus the structure and properties of resultant crosslinked networks. An “Interpenetrating network (IPN)‐coupling structure” is proposed to be formed in the HBPSi/BD/CE system, which is different from traditional “IPN” structure in BD/CE resin. The simulation of curing reaction suggests that the variety of the curing activity leads to the difference between the curing behaviors of BD/CE and HBPSi/BD/CE resins, which is in good agreement with FTIR and DSC analyses. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Water sorption and diffusion behaviors in composite films of poly(ether imide) and bismaleimide

The effect of a crosslinkable imide moiety, bismaleimide (BMI), on the water sorption properties of poly(ether imide) (PEl) was gravimetrically measured and interpreted together with the chemical and morphological structures in composite films. The morphological structure of composite films was investigated by using a prism coupler and X‐ray diffraction pattern. It indicated that the in‐plane orientation and intermolecular packing order increased as the content of BMI in composite films increased. The water sorption behaviors showed dependence on the morphological change originating from the addition of BMI to PEI. The composite film with relatively high content of BMI exhibited a relatively high degree of in‐plane orientation and a small mean intermolecular distance, which resulted in a decrease in the diffusion rate and water sorption and an increase in the activation energy in composite films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1692–1697, 2006     

Blends of bisphenol A‐based cyanate ester and bismaleimide: Cure and thermal characteristics

A dicyanate ester, namely, 2,2‐bis‐(4‐cyanatophenyl)propane, and a bismaleimide, namely, 2,2‐bis[4‐(4‐maleimido phenoxy)phenyl]propane, possessing closely resembling backbone structures, were cured together to derive bismaleimide–triazine network polymers of varying compositions. The blend manifested a eutectic melting behavior at a 1 : 1 composition with a eutectic melting point of 15°C. The cure characterization of the blends was done by DSC and dynamic mechanical analyses (DMA). The near simultaneous cure of the blend could be transformed to a clear sequential one by catalyzing the dicyanate cure to lower temperature using dibutyl tin dilaurate. The two‐stage, independent cure of the components of the blend evidenced in DSC was confirmed by DMA. The cure profile of the bismaleimide component predicted from the kinetic data derived from nonisothermal DSC was found to be in league with the isothermal DMA behavior. Both techniques led to optimization of the cure schedule of the blends. The cured polymers were characterized by FTIR and TGA. The cured blends underwent decomposition in two stages, each corresponding to the polycyanurate and polybismaleimide. Enhancing the bismaleimide component did not alter the initial decomposition temperature, but led to reduced rate of thermal degradation at higher temperature. Interlinking of the two networks and enhancing crosslink density through coreaction of the blend with 4‐cyantophenylmaleimide unaffected the initial decomposition properties but was conducive for increasing the char residue significantly. Computation of activation parameters for the thermal decomposition of the polymers confirmed that the first step in the degradation of the blends is caused by the polycyanurate component. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3365–3375, 1999     

Biobased thermosetting resins composed of terpene and bismaleimide

Prepolymers prepared by reactions of 1,1′‐(methylenedi‐4,1‐phenylene)bismaleimide (BMI) with myrcene (Myr) and limonene (Lim) in 1,3‐dimethyl‐2‐imidazolidinone (DMI) at 150°C were compressed at 250°C to produce crosslinked Myr/BMI [molar ratio = 2:2–2:5 (MB22–MB25)] and Lim/BMI [molar ratio = 1:1 (LB11)] resins. The ¹H‐NMR analysis of the model reaction products of Lim and Myr with N‐phenyl maleimide (PMI) in DMI at 150°C revealed that a Diels–Alder reaction for Myr/PMI and a vinyl copolymerization for Lim/PMI preferentially proceeded in addition to the occurrence of the ene reaction to some extent. The Fourier transform infrared data of the cured resins were consistent with the results of the model reactions. All of the cured resins, except for MB22, showed tan δ peak values and 10% weight loss temperatures that were higher than 330 and 440°C, respectively. The flexural strength and modulus values of the MBs were higher than those of LB11. Field emission scanning electron microscopy analysis revealed that MB22–MB24 were homogeneous, whereas some combined particles appeared in LB11. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

聚醚酰亚胺对共聚双马来酰亚胺树脂的增韧作用

采用二烯丙基双酚A、烯丙基酚醛改性4,4'-二氨基二苯甲烷双马来酰亚胺共聚制备了一类新型的双马来酰亚胺树脂(简称ABD)。以ABD为基体,选用热塑性树脂聚醚酰亚胺(PEI)为增韧剂,采用共混法制备了共聚双马来酰亚胺/聚醚酰亚胺(PEI)树脂体系。采用DSC和流变仪对ABD树脂的固化行为进行了研究,结果表明,该树脂粘度较低,室温下为液态,树脂的冲击强度为8.99 kJ/m2。通过DMA、TGA和扫描电镜对PEI加入量对树脂热性能和微观形貌的影响表明,添加质量分数为15%聚醚酰亚胺时,树脂冲击强度达到16.9 kJ/m2,比基体树脂提高了88%。