Dicyanate Ester Research Articles

New Insights into Structure–Property Relationships in Thermosetting Polymers from Studies of Cocured Polycyanurate Networks

Studies of the physical properties of the cocured networks formed from three similar dicyanate ester monomers revealed a number of unexpected variations from simple linear mixing rules. These variations shed light on important synergistic effects in cocured thermosetting networks and their possible causes. The monomers utilized were the dicyanate esters of Bisphenol A (BADCy) and Bisphenol E (LECy) and the silicon-containing analogue of Bisphenol A (SiMCy). The most important of the synergistic effects was a decrease of ∼25% in moisture uptake seen only in conetworks of LECy and SiMCy. For all other systems, a clear relationship between moisture uptake and the number density of cyanurate rings was observed. This relationship generally applies to many types of cyanate esters and gives an indication of the importance of specific sites (as opposed to free volume alone) in moisture uptake. Numerous additional examples of nonlinear mixing relations were observed in the glass transition temperature, density, and thermochemical stability of fully cured networks. Interestingly, the most widespread deviations from linear behavior were observed for conetworks of SiMCy and LECy, suggesting that factors such as the mismatch in network segment size may be more important than differences in flexibility or symmetry in driving significant physical interactions among conetwork components.

Preparation of phosphinated bisphenol from acid‐fragmentation of 1,1,1‐tris(4‐hydroxyphenyl)ethane and its application in high‐performance cyanate esters

AbstractWe reveal a route for the preparation of phosphinated bisphenol, 1,1‐bis(4‐hydroxyphenyl)‐1‐(6‐oxido‐6H‐dibenz <c,e> <1,2> oxaphosphorin‐6‐yl)ethane (2), via a one‐pot reaction of 1,1,1‐tris(4‐hydroxyphenyl)ethane and 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene 10‐oxide (DOPO) in the catalysis of p‐toluenesulfonic acid. A two‐step reaction mechanism, acid‐fragmentation of 1,1,1‐tris(4‐hydroxyphenyl)ethane followed by nucleophilic addition of DOPO, is proposed for the synthesis. Based on (2), a dicyanate ester derivative, 1,1‐bis(4‐cyanatophenyl)‐1‐(6‐oxido‐6H‐dibenz <c,e> <1,2> oxaphosphorin‐6‐yl)ethane (3) was prepared and co‐cured with a commercially available dicyanate ester, the dicyanate ester of bisphenol A (BACY). Experimental data show that incorporating (3) into BACY enhances the flame retardancy and dielectric properties with little penalty to the thermal properties. A thermoset with Tg 274 °C, coefficient of thermal expansion (CTE) 49 ppm/°C, Dk 3.04 (1 GHz), Td (5%,) N2: 435 °C, air: 424 °C, and UL‐94 V‐0 rating can be achieved via this approach. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.

Cure of Neat Resins and Properties of Composites for Interpenetrating Polymer Networks from the Novel Bismaleimide and Cyanate Containing Naphthalene

To obtain attractive properties, such as increased resistance to moisture absorption, low dielectric constant and low dielectric loss, the novel bismaleimide, viz. 2,7-bis(4-maleimidophenoxy) naphthalene (BMPN), and dicyanate ester, viz. 2,7-dihydroxynaphthalene dicyanate (DNCY), containing naphthalene ring and ether linkages, have been synthesized. The cure process of the blends including of 0.11mmol/mol Fe(AcAc)3 and 2% nonylphenol is characterized by in-situ FTIR. The result obtained from in-situ FTIR spectra of cured resin illuminates that the cure reaction is homo-polymerized respectively at this condition for the mixtures of B1C1. Interlaced network patterns are seen obviously and no visible phase separation could be detected in the region for IPNs BT resin by SEM. The structure of IPNs can be formed for the blends of BMPN and DNCY containing 0.11 mmol/mol Fe(AcAc)3 and 2% nonylphenol, which is tested by in-situ FTIR and SEM methods. The glass fiber reinforced composites for this blends are made and their properties are studied. This composites show good flexural property, low dielectric constants ( Dk ) and low moisture absorption.

Cyanate ester resin modified by hydroxyl‐terminated polybutadiene: Morphology, thermal, and mechanical properties

AbstractHydroxyl‐terminated polybutadiene (HTPB) rubber was used as a modifier for bisphenol A dicyanate ester (BADCy) to improve its toughness. The effect of catalyst on the curing behavior of the resin and the curing techniques were developed by differential scanning calorimetry. The dynamic mechanical analysis, thermogravimetry analysis, and tensile test were used to study the thermal behavior, mechanical properties, and dynamic mechanical performance of the modified BADCy resins. Results show that addition of HTPB resulted in improved toughness while maintaining relatively good thermal stability. Additional, phase separation phenomenon was confirmed by the analysis of scanning electron microscope. For the toughening of the resin, the main toughening mechanism is shear yielding and crack branching. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Modification of Bisphenol A Dicyanate Ester Resin with Poly Vinyl Pyrrolidone (K30)

Poly vinyl pyrrolidone (PVP(K30)) / Bisphenol A Dicyanate ester (BADCy) blends were fabricated to increase the toughness of BADCy by blending processing in this paper. Curing parameters were determined by gelation time curves and differential scanning calorimetry (DSC) of the systems. Fourier transform infrared spectrometry (FTIR) and DSC data were employed to show the curing behavior and kinetics of the systems. Mechanical properties of the cured resin had been improved rapidly with the increasing of PVP(K30) at low mass fraction, but would decrease when mass fractions of PVP(K30) were higher than 15%. Scanning electron micrograph (SEM) was applied to show the microstructures of the cured matrixes. Based on the thermogravimetric analysis (TGA) curves, water absorption curves, SEM images and dielectric properties of the blends, it can be concluded that the addition of PVP(K30) can improve the toughness of BADCy greatly with little loss of other properties.

Influence of cyanate content on the morphology and properties of epoxy resins with phenolphthalein poly(ether ketone)

AbstractPhenolphthalein poly(ether ketone) (PEK‐C) was blended with the diglycidyl ether of bisphenol A epoxy resin and bisphenol A dicyanate ester. The effect of cyanate content on cure behaviors, thermal and mechanical properties of PEK‐C/epoxy/cyanate mixtures was investigated. As results, the increase of cyanate content slightly hindered the cure reaction of the mixtures. Fourier transform infrared results indicated that the curing reaction of the cured mixtures was complete. When the cyanate ester content increased, the flexural properties and Tg values were enhanced, and the initial thermal decomposition temperature was reduced. A significant improvement in fracture toughness was obtained when the cyanate group in the mixtures was excessive. The fracture toughness can be well explained by SEM observations. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Hybrid effect on mechanical properties of M40‐T300 carbon fiber reinforced Bisphenol A Dicyanate ester composites

AbstractInterply and intraply hybrid composites based on Bisphenol A Dicyanate ester (BADCy), high strength carbon fibers T300, and high modulus carbon fibers M40 were prepared by monofilament dip‐winding and press molding technique. The tensile, flexural, interlaminar shear properties and SEM analysis of the hybrid composites with different fiber content and fiber arrangement were investigated. The results indicated that the mechanical properties of intraply hybrid composites were mainly determined by fiber volume contents. When the ratio of fiber volume content was close to 1:1, the intraply hybrid composites possessed lowest tensile and flexural strength. The mechanical properties of interply hybrid composite mainly depended on the fiber arrangement, instead of the fiber volume contents. The hybrid composites using T300 fiber layout as outside layer possessed high flexural strength and low flexural modulus, which was close to that of T300/BADCy composites. The hybrid composites ([(M40)x/(T300)y]S) using M40 fiber layout as outside layer and T300 fibers in the mid‐plane had high flexural modulus and interlaminar shear strength. POLYM. COMPOS., 2010. © 2010 Society of Plastics Engineers

The thermal and dielectric properties of high performance cyanate ester resins/microcapsules composites

Novel high performance bisphenol A dicyanate ester (BADCy) resins/poly(urea-formaldehyde) microcapsules filled with epoxy resins (MCEs) composites have been prepared. The effects of different contents of MCEs on the thermal and dielectric properties of cured BADCy were investigated using dynamic mechanical analyzer (DMA), thermalgravimetric analyzer (TGA) and broadband dielectric analyzer. The dielectric properties of BADCy/MCEs treated in hot water and hot air were also discussed. The morphologies of BADCy/MCEs composites were characterized by scanning electron microscopy (SEM). Results indicate that the appropriate content of MCEs can improve or maintain the thermal stability, the low dielectric constant and dielectric loss of cured BADCy mainly owing to higher conversion of cyanate ester (–OCN) groups. After aged in hot water and hot air, respectively, BADCy/MCEs composites with small content of MCEs can retain the low dielectric constant and dielectric loss.

Heat-resistant triazine compound

The cyclometrization of dicyanate ester of bisphenol A is analyzed for the purpose of producing the triazine compound on its basis. The core physicomechanical and electrophysical properties of the hardened compound are defined and the prospects of using the compound in high-voltage systems of insulation that can be applied at high temperatures are shown.

Influence of phenoxy addition on the curing kinetics for uncatalyzed and catalyzed cyanate ester resin

AbstractThe curing behavior of the dicyanate ester of bisphenol‐A (DCBA) modified with poly(hydroxy ether of bisphenol‐A) (phenoxy) is studied by differential scanning calorimetry in dynamic and isothermal tests at temperatures between 120 and 240°C. The addition of phenoxy to DCBA produces an increase in the reaction rate and a decrease in the temperature of maximum reaction rate for the uncatalyzed resin, and also for the system catalyzed with copper (II) acetyl acetonate/nonylphenol. The exothermic heat of curing for the mixtures is also dependent on the phenoxy content. These facts evidence a catalytic effect of phenoxy on the curing of the cyanate ester resin, even though an autocatalytic behavior is observed for all uncatalyzed DCBA/phenoxy mixtures. A simplified mechanistic kinetic model is used to calculate the kinetic parameters. For the uncatalyzed systems, a decrease in the kinetic constant for the initiation reactions, and an increase in the propagation constant are measured when the cyanate content increases. The thermal activation energy for the initiation reaction of the catalyzed systems is lower than that of the uncatalyzed ones, and it depends on the weight fraction of cyanate in the mixture. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Curing behavior and mechanical properties of hollow glass microsphere/bisphenol a dicyanate ester composites

AbstractHollow glass microsphere (HGS)/bisphenol A dicyanate ester (BADCy) composites have been prepared by mechanical mixing, followed by a stepped curing process. The effect of HGS on the curing behavior of BADCy was studied using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The mechanical properties of the composites were examined by mechanical tests, and the improvements of the mechanical properties were investigated by scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA). The results show that HGS is catalytic for the polycyclomerization of the BADCy, which is advantageous to reduce the maximal processing temperature. The impact strength, flexural strength, flexural modulus and storage modulus of BADCy are improved. The improvements of the mechanical properties without sacrificing thermal properties, the ability of lowing processing temperature and the low cost make HGS good filler for cyanate ester resin. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Modification of dicyanate ester resin by liquid carboxyl-terminated butadiene acrylonitrile copolymer

Bisphenol A dicyanate ester (BADCy) was modified with liquid carboxyl-terminated butadiene acrylonitrile (LCTBN). The cured BADCy resin was formed through the cyclotrimerization of cyanate functional groups into triazine rings, and there was the chemical reaction between BADCy and LCTBN. Mechanical performance indicated that the introduction of LCTBN into BADCy resin improved the impact strength with maintenance in flexural strength. Scanning electron microscopy (SEM) showed that the pure resin had a smooth glassy fracture surface, whereas cured blends containing LCTBN showed rougher fracture surfaces, and exhibited enhanced impact resistance. The TEM observation showed that the two phases in the cured resins exhibit a good interaction adhesion. Thermograms of BADCy modified with LCTBN showed the little reduction of heat deflection temperature, and a reduction in thermal stability temperature by 30 K. Dynamic mechanical analysis (DMA) showed that the pure BADCy had higher storage modulus ( E′) values than that of the BADCy modified with LCTBN, whereas the loss modulus ( E″) was lower, and that the glass transition temperature (Tg) of modified BADCy was 229 °C and lower than that (249 °C) of pure BADCy resin.

Curing, thermal stability and composite properties for blends of the novel bismaleimide and cyanate containing naphthalene

Novel bismaleimide-triazine network polymers are derived from bismaleimide and dicyanate ester containing naphthalene. Curing behaviour of blends is studied by DSC and in-situ FTIR. The result shows that the monomer of dicyanate ester is copolymerised with the monomer of BMPN, and addition polymerisation of the residual BMPN is also possible to be involved during the last period of cure reaction. PolyDNCY, polyBMPN and typical copolymerised resins show good thermal stability. Owing to existence of ether linkage and naphthalene in network structure for BT resins, glass fibre reinforced composites containing blends show good flexural properties, low dielectric constants and low moisture absorptions.

Interpenetrating polymer networks from the novel bismaleimide and cyanate containing naphthalene: Cure and thermal characteristics

The novel interpenetrating network bismaleimide–triazine polymers were derived from A bismaleimide, viz. 2,7-bis(4-maleimidophenoxy)naphthalene (BMPN), and a dicyanate ester, viz. 2,7-dihydroxynaphthalene dicyanate (DNCY), possessing similar backbone structures. The cure process of the blends including of 0.11 mmol/mol Fe(AcAc) 3 and 2% nonyl phenol is characterized by DSC and in situ FTIR. The DSC curves show two-stages curing process for the mixture systems including of 0.11 mmol/mol Fe(AcAc) 3 and 2% nonyl phenol. In the in situ FTIR spectra of cured resin, the absorption peak of the C C H bending vibrations decreases continuously until the end of cure reaction after that of the OCN group disappears mostly. These illuminate that the structure of IPNs can be formed due to the respective polymerization of two monomers for mixtures. Interlaced patterns are seen obviously in the region by SEM for IPNs BT resins. Thermal stabilities of cured resins are characterized by TGA. The pure polyDNCY, polyBMPN and typical IPNs BT resins show good thermal stability.

Mechanical properties of high temperature cyanate ester/BMI blend composites

AbstractA new Schiff base functionalized dicyanate ester was synthesized and the monomer was characterized by FTIR, 1H‐NMR, 13C‐NMR and elemental analysis techniques. This prepared dicyanate ester with catalyst was then blended with BMI resin at different ratios by solution technique. The composites were made by impregnating the fibers with the blend solution followed by curing at various time‐temperature schedules. The mechanical properties of the blend composites were tested. The fiber volume fraction of the composites were found to be in the range 41 ± 3%. The mechanical properties such as tensile modulus (32–35 GPa), flexural modulus (56–59 GPa) and Mode I fracture toughness (GIC = 104–136 J/m2) and impact response (1,121–1,218 J/m) were found to increase with increasing cyanate ester content in the Cy/BMI blends. From the DMA study it was observed that as the cyanate content increases from 3 to 9% in the blend the tan δ value increases from 0.112 to 0.126 and the storage modulus decreases from 24,750 to 22,870 MPa indicating that the crosslink density of the blends decreases. The SEM analysis shows the absence of phase separation. Moisture absorption and chemical resistance of the blend composites increase with increasing cyanate content. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers

Catalytic effect of carbon nanotubes on polymerization of cyanate ester resins

Kinetic peculiarities of polycyclotrimerization process of dicyanate ester of bisphenol A (DCBA) in the presence of multi-walled carbon nanotubes (MWCNTs) have been investigated using Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy technique. It has been found that even very small amounts of MWCNTs (0.01-0.1 wt%) catalyze the reaction of polycyclotrimerization of DCBA leading to formation of polycyanurate network (PCN)/MWCNTs nanocom- posite. However, some decrease in final degree of conversion for nanocomposites compared to the neat PCN within the temperature/time schedule used was observed. The kinetic rate constants increased with addition of MWCNTs and energies of activation were found to be significantly decreased even at low contents of MWCNTs.

Thermal, physical and flame-retardant properties of phosphorus-containing epoxy cured with cyanate ester

Two phosphorus-containing advanced epoxy resins were obtained by chain-extension of diglycidyl ether of bisphenol-A epoxy (DGEBA) resin with 2-(6-oxido-6H-dibenz(c,e)(1,2)-oxaphosphorin-6-yl)-1,4-benzenediol (DOPOBQ), at different stoichiometric ratios. The phosphorus-containing advanced epoxy was separately cured with various dicyanate esters to form flame-retardant epoxy/cyanate ester systems. The effects of phosphorus content and dicyanate ester structure were studied, and compared with those of the control (advanced bisphenol-A epoxy) system. The DOPOBQ-containing epoxy/cyanate ester systems exhibited higher glass transition temperatures, better dimensional stability and better thermal stability.

Synthesis and characterization of cyanate ester and its blends with bisphenol dicyanate ester

A new keto-ene functionalized 1, 5-bis (4-hydroxyphenyl)penta-1,4-dien-3-one (HPDO) was prepared from p-hydroxy benzaldehyde and acetone using boric acid as a catalyst. The prepared bisphenol was converted into 1,5-bis (4-cyanatophenyl) penta-1,4-diene-3-one (CPDO) by reacting with cyanogen bromide (CNBr) in the presence of triethylamine. The synthesized bisphenol and the dicyanate ester were characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (1H-NMR and 13C-NMR) and elemental analysis (EA) techniques. CPDO was then blended with a commercial bisphenol-A dicyanate ester (BADCy) at different ratios (100:0, 75:25, 50:50. 25:75, 0:100) and the cure characteristics were studied. CPDO was found to be cured at a lower temperature than BADCy. The cyanate ester blends were cured at 373 K (30 min) → 423 K (30 min) → 473 K (60 min) → 523 K (3h). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to study the thermal properties. DSC studies show that the cure (peak) temperature of CPDO with and without a catalyst was found to be 408 K and 466 K respectively. The initial degradation temperature of the cured resins was found to be in the range from 701 K to 705 K. The Limiting Oxygen Index (LOI) value, determined by Van Krevelen’s equation, shows that these blends have good flame retardant properties.

A novel cyanate ester resin/microcapsules system

AbstractPoly(urea‐formaldehyde) microcapsules filled with epoxy resins(MCEs) were applied to bisphenol A dicyanate ester (BADCy) resin to develop a novel BADCy/MCEs system. The effects of MCEs on the viscosity and the reactivity of BADCy were investigated. The mechanical properties and the hot water resistance of cured BADCy/MCEs systems were evaluated. The morphologies of the cured systems were characterized using a scanning electron microscope. The thermal property of cured systems was investigated using thermogravimetric analysis. The results indicate that MCEs may influence the reaction of BDACy. The proper addition of MCEs can significantly improve the mechanical property and the hot water resistance of cured BADCy resin. MCEs have a negative influence on the initial thermal decomposition temperature (Td) of cured BADCy resin. POLYM. COMPOS., 2010. © 2008 Society of Plastics Engineers.

Study on Glass Fabric Reinforced Polytetrafluoroethylene Composites Infused with Melted Cyanate Ester Resin

Melted bisphenol A dicyanate ester (BADCy) resin was infused into glass fabric/ PTFE(GF/PTFE) wave-transparent composites to improve the mechanical properties of GF/PTFE composites. The influence of the infusing process, the porosity of GF/PTFE composites, and the content of infused BADCy resin on the dielectric and mechanical properties of GF/PTFE composites was studied. The fracture surfaces of the broken specimens were also examined by scanning electron microscopy (SEM). It was found that when the porosity of GF/PTFE composites was 25%, the infused temperature is 85°C, and the vacuum is 0.01 MPa, the infused contents of BADCy in GF/PTFE/BADCy composites could reach 14.4%. The tensile strength, flexural strength, and interlaminar shear strength (ILSS) of GF/PTFE composites were improved from 81.6, 64.4, and 4.8 MPa to 186.6, 163.5, and 26.2 MPa, respectively. At the same time, the dielectric constant (ε) and tangent dielectric loss angle (tan δ) of GF/PTFE composites increased slightly. The wet/hot and environment-resistant investigation showed that the GF/PTFE composites infused by BADCy resin possessed low water absorption, small coefficient of thermal expansion(CTE), and good anti-environment properties.