Cyanate Ester Composites Research Articles

Cyanate Ester/TiO2 Composites for High‐Temperature and Miniaturized Microwave Substrate Applications

High‐temperature‐withstanding TiO2‐reinforced cyanate ester composites are developed by mechanical stirring, followed by curing at elevated temperatures. The uniform dispersion of the filler is confirmed using scanning electron microscopy and electron dispersive spectroscopy. All composites, up to a filler fraction of 30 vol%, exhibit a density of more than 90% while it reduces significantly after that. A high relative permittivity of 7.6 and a low loss tangent of 0.0112 are observed for the optimally filled 30 vol%. The addition of the filler further improves the temperature‐withstanding capability of the cyanate ester matrix. Moreover, a high thermal conductivity of 0.543 W mK−1, improved hardness of 24.88 HV, ultimate tensile strength of 11.68 MPa, and a low coefficient of thermal expansion of 36.44 ppm °C−1 are also shown by the optimally filled sample. A moisture absorption of 0.072 vol% observed for the optimal filled sample comes within the limit for microwave substrate applications. Thus, the developed composites are suitable candidates for high‐temperature microwave electronic applications.

Enhanced interfacial, mechanical, and anti-hygrothermal properties of carbon fiber/cyanate ester composites with the catalytic sizing agents of titanium epoxy

The mechanical properties of composites are closely related to the interfacial behavior, especially under the hygrothermal circumstance. A catalytic sizing agent of titanium epoxy is designed to enhance interfacial, mechanical, and anti-hygrothermal properties of high modulus carbon fiber (HMCF)/cyanate ester composites simultaneously. The mechanisms of interface enhancement and low hygroscopicity of composites are investigated. The titanium epoxy is synthesized and its catalytic effect on the curing of cyanate ester is proved. The interfacial properties of HMCF composites with catalytic sizing agents are improved to 95.5 MPa, which is attributed to the interphase with high crosslinking density and sufficient triazine rings and oxazolidinone structure due to preferential curing induced by interfacial catalysis, stimulating the smooth transition of interphase modulus. Further, the formed interphase exhibits few interface defects and low content of hydroxyl groups, which changes the moisture diffusion path and reduces saturated water absorption of composites to only 0.36 %, resulting in the release of interfacial wet stress concentration and high retention of mechanical properties in hygrothermal environment. The resultant composites with high stiffness, excellent temperature resistance, superior dimensional stability and low moisture absorption are expected to be applied to high-orbit space, aerospace, precision instruments.

Space-deployable device based on shape memory cyanate ester composites

Shape memory cyanate ester is a class of shape memory polymers with high thermal stability and excellent space environmental adaptability. In this study, a space-deployable device based on cyanate ester-based shape memory polymer composite (CE-SMPC) was proposed, and its thermomechanical properties and shape memory behavior were experimentally evaluated. The space-deployable device maintained a high shape fixity rate even after prolonged exposure to high or low temperatures, which ensured its locking reliability in space applications. The results of self-deployment experiments indicated that the space-deployable device exhibited good shape recovery performance in both atmospheric and vacuum environments. The SMPC-based space-deployable device presented in this study was applied to China's first Mars exploration mission to achieve autonomous locking and release of the deployable engineering measurement subsystem on the probe.

Study on the effect of porosity on properties of cyanate ester composites

Cyanate ester composites have the advantages of high-temperature resistance, low moisture absorption, excellent dielectric properties, and excellent mechanical properties. It is the most promising composite of the new generation radome. The key step in forming cyanate ester composites is thermal curing. There is no relevant experimental data on the influence of porosity on the mechanical properties of cyanate ester composites. This paper studied the influence law of different porosity on the properties of cyanate ester composites. Meanwhile, the performance data of cyanate ester composites were accumulated to provide a reference for the engineering treatment of faulty parts.

Synergistic enhancement of interfacial and anti-hydrothermal properties of HMCF reinforced Cyanate Ester composites by matrix stiffening and interphase optimization

Cyanate ester (CE) matrix and high-modulus carbon fiber (HMCF) surface were modified by epoxy-functionalized polyhedral oligomeric silsesquioxane (POSS), and the correlations of stiffened matrix and optimized interphase with interfacial and anti-hydrothermal properties of various HMCF/CE composites were investigated. The improved tensile modulus and reduced free volume contributed to decreasing coefficient of thermal expansion (CTE) of POSS-CE (PCE) matrix, and a layer of POSS nanoparticles on fiber surface caused the enhancement of surface chemical activity and roughness of POSS-HMCF (P-HMCF), which resulted in 30.9%, 48.9% and 79.8% increment of interfacial shear strength (IFSS) in P-HMCF/PCE composites from the broader modulus intermediate layer, compared to HMCF/CE, HMCF/PCE and P-HMCF/CE composites. After aging 30 days, P-HMCF/PCE composites exhibited the minimum moisture uptake (0.80%) and the highest interlaminar shear strength (ILSS) retention (84.9%), and thickness broadening and cracks propagation at interphase were hardly generated based on the quantitative analysis of interphase modulus distribution, which was attributed to suppressive moisture uptake of PCE matrix and superior interfacial adhesion between resin and P-HMCF.

Characterization of Environmentally Conditioned Quartz–Cyanate Ester Composites for Radome Applications

Because quartz–cyanate ester (QCE) composites are employed to fabricate missile and aircraft radomes, retaining their structural and electromagnetic (EM) integrity after prolonged exposure to environmental stresses is essential for long-term deployment as radar protectors. Therefore, in this study, QCE composite samples were subjected to environmental conditioning tests, namely, transient temperature (transition from −67 to 145 °C), high-temperature storage (cycling between 35 and 85 °C), thermal shock (cycling between −55 and 100 °C), fluid contamination (immersion in mineral and turbine oils), and humidity cycles (conditioning at 30 °C and 85% RH), to observe the effect of conditioning on the physical, morphological, thermal, mechanical, and dielectric properties of composites. Interfacial damage was observed in all the conditioned samples. Samples after fluid immersion test were found to have the highest deviation in properties compared to unconditioned ones. Fluid diffusion led to higher surface crack width, lower impact damaged area, and higher EM energy dissipation (higher dielectric loss tangent). High-temperature storage tested samples had the highest surface crack intensity, while humidity cycles caused matrix plasticization, resulting in lower density and thermal conductivity values. A high degree of postcuring in thermally shocked samples resulted in brittleness of cyanate ester, leading to an increase in density and impact damaged area. Although a slight degree of damage is reported, the change in QCE composite properties postconditioning is not significant enough to prevent its application as uncoated radome materials, except for rain erosion at 150 m/s.

Effect of repeated thermal cycle on compressive properties of cyanate ester/quartz-based composites

The continuous fibre reinforced polymer composites are used in electronic circuits and radar radomes of defence aircraft due to lower transmission loss in the broadband microwave frequency region. Quartz fibre-reinforced cyanate ester composites are one of the best-suited materials for the radome structure of an aircraft offering exceptional electromagnetic transparency in varying operational temperatures. Moreover, this material possesses high-temperature capability with excellent mechanical and dielectric properties. The radome structure usually undergoes multiple thermal cycles during fabrication. In this work, to determine the compressive strength, a quartz/cyanate ester laminate was prepared with repeated thermal infusion followed by final curing (CE/Q_M) using resin film infusion (RFI) technique. The volume fraction of fibre, resin and void fraction were evaluated using the resin-burn off method. Finally, Ultrasonic C-scanning, a non-destructive quality evaluation and raster scanning using a multi-axis squirter system was carried out to detect and characterize the defects induced in the laminate. These data were compared to a sample produced with regular infusion followed by a curing cycle (CE/Q_S). The compressive strength of CE/Q_M (372.48 MPa) is measured to be 12% more than that of CE/Q_S (332.084 MPa). This is attributed to increased crosslink density in CE resin and strong interfacial adhesion between the resin and the fibre in the latter due to multiple thermal infusion cycles.

Dual-functional carbonized loofah@GNSs-CNTs reinforced by cyanate ester composite with highly efficient electromagnetic interference shielding and thermal management

Using natural non-polluting raw materials to develop absorption-based electromagnetic interference shielding composites is significantly desirable. Herein, a novel kind of carbonized loofah@graphene nanosheets (GNSs)-carbon nanotubes (CNTs)/epoxy resin modified cyanate ester (CL@GC/CE) composites were successfully prepared through high-temperature carbonization and variable temperature curing process, which show the absorption-based electromagnetic interference (EMI) shielding performance. The as-prepared composites present a favorable electrical conductivity of 32.66 S/cm, exceptional EMI shielding efficiency of 35.57 dB in conjunction with a high absorption coefficient of 0.58. The main reasons for the excellent absorption capacity and EMI shielding performance of the CL@GC/CE composites are the good impedance matching performance of carbonized loofah sponge with a 3D conductive framework, and the multiple reflection scattering and interface polarization effect between the conductive framework and GNSs-CNTs. In view of the remarkable comprehensive properties, the low-cost biomass-derived carbon composites are highly promising materials for practical EMI shielding applications in the fields of telecommunication and aerospace.

Weibull Probabilistic Model of Moisture Concentration Build Up in a Fiber Graphite/Epoxy Polymer Composite under Varying Hydrothermal Conditions

Advanced mechanical and structural applications require accurate assessment and better knowledge of the damage state during elaboration and service. The development of life prediction methodologies for Glass Fiber Reinforced Polymers (GFRPs) has increased with the use of composites in different industries. It is important to develop through thickness degradation analyses due to ageing in order to predict its effect on the lifetime of composite structures. This study aims to model the moisture absorption, the concentration of the absorbed fluid and the reduction of mechanical properties in the through the thickness direction of a GFRPs structure. The water absorption behavior of woven glass fiber reinforced cyanate ester composites used in the plenum of the air conditioning pack of aircraft environmental control system has been modeled. The combined models describe the diffusion procedure primarily at material level and continuously at structure level. The amount of the absorbed moisture can be crucial for the mechanical behavior of the structure. Therefore, there is a need for a better understanding of the evolution of mechanical properties during ageing. The procedure utilizes the results of the diffusion model to calculate the moduli degradation during the water uptake process. Predictive models have been proposed by considering different sections throughout the thickness and provide a solid background for modeling the long term behavior of a structure exposed at different temperature and different time period. This work performed the numerical studies on the effect of moisture, temperature and presents some useful instructions for the evaluation of such composite structures.

Ameliorated Mechanical and Dielectric Properties of Heat-Resistant Radome Cyanate Composites.

In order to improve the mechanical and dielectric properties of radome cyanate, a synergistic reinforcement method is employed to develop a resin-based ternary-composite with high heat-resistance and preferable radar-band transmission, which is expected to be applied to fabricate radomes capable of resisting high temperature and strong electric field. According to copolymerization characteristics and self-curing mechanism, epoxy resin (EP) and bismaleimide (BMI) are employed as reinforcements mixed into a cyanate ester (CE) matrix to prepare CE/BMI/EP composites of a heat-resistant radome material by high-temperature viscous-flow blending methods under the catalysis of aluminum acetylpyruvate. The crystallization temperature, transition heat, and reaction rate of cured polymers were tested to analyze heat-resistance characteristics and evaluate material synthesis processes. Scanning electron microscopy was used to characterize the micro-morphology of tensile fracture, which was combined with the tensile strength test and dynamic thermomechanical analysis to investigate the composite modifications on tenacity and rigidity. Weibull statistics were performed to analyze the experimental results of the dielectric breakdown field, and the dielectric-polarization and wave-transmission performances were investigated according to alternative current dielectric spectra. Compared with the pure CE and the CE composites individually reinforced by EP or BMI, the CE/BMI/EP composite acquires the most significant amelioration in both the mechanical and electrical insulation performances as indicated by the breaking elongation and dielectric breakdown strength being simultaneously improved by 40%, which are consistently manifested by the obviously increased transverse lines uniformly distributed on the fracture cross-section. Furthermore, the glass-transition temperature of CE/BMI/EP composite reaches the highest values of nearly 300 °C, with the relative dielectric constant and dielectric loss being mostly reduced to less than 3.2 and 0.01, respectively. The experimental results demonstrate that the CE/BMI/EP composite is a highly-qualified wave-transmission material with preferences in mechanical, thermostability, and electrical insulation performances, suggesting its prospective applications in low-frequency transmittance radomes.

Study on the Effect of Fabric Parameters on the properties of Wave-Transparent Composites

Novel fabric structures of wave-transparent composites having excellent dielectric property were successfully prepared using autoclave moulding. The influence of fabric parameters (such as weaving patterns, hollow ratio, mix structure) on the properties of quartz fiber-reinforced modified cyanate ester composite were systematically investigated. The results show that satin weave fabric-reinforced composites have better mechanical performance than plain weave fabric--reinforced composites. With hollow ratio of fabric increasing the dielectric properties of composites becomes better, except for the mechanical performance. The prepared hollow/solid quartz fabric-reinforced composites in this study display lower dielectric constant and better mechanical properties than quartz/Aramid III and quartz/Poly-p-phenylene benzobisoxazole(PBO).

Synergetic effect of thermal conductivity and flame retardancy of cyanate ester composites containing DOPO and BN with great dielectric properties

DOPO and boron nitride (BN) fillers with different particle sizes and several loadings were employed to improve the properties of cyanate ester (CE) resin. The effects of BN content and particle size on the thermal conductivity of the BN‐DOPO/CE ternary composites were discussed. The influence of enhancing the thermal conductivity of the ternary composites on their flame retardancy was studied. The consequences showed that increasing the thermal conductivity of BN‐DOPO/CE composites had an active impact on their flame retardancy. Approving flame retardancy of the ternary composites was certified by the high limiting oxygen index (LOI), UL‐94 rating of V‐0, and low heat release rate (HRR) and total heat release (THR). For instance, in contrast with pure CE matrix, peak of HRR (pk‐HRR), average of HRR (av‐HRR), THR, and average of effective heat of combustion (av‐EHC) of CEP/BN0.5 μm/10 composite were decreased by 51.7%, 33.8%, 18.7%, and 18.9%, respectively. Thermal gravimetry analysis (TGA) showed that the addition of BN fillers improves the thermal stability of the composites. Moreover, the ternary composites possess good dielectric properties. Their dielectric constants (ε) are less than 3, and dielectric loss tangent (tgδ) values are lower than neat CE resin.

Preparation and Mechanism of High Energy Density Cyanate Ester Composites with Ultralow Loss Tangent and Higher Permittivity through Building a Multilayered Structure with Conductive, Dielectric, and Insulating Layers

High energy density polymer composites with ultralow loss tangent and higher permittivity for embedded capacitors are urgently required by new generation printed circuit boards. Herein, starting from a conductive layer (C-layer) with negative dielectric permittivity, a dielectric layer (D-layer) with positive dielectric permittivity, and insulating layer (I-layer), six multilayer composites, coded as DCI, CDI, IDCI, DCICD, DCIDC, and CDIDC according to their spatial stacking order, were prepared; among them, the C-layer is a graphite/polyvinylidene fluoride composite, the D-layer is a reduced graphene oxide–(K0.5Na0.5)NbO3/cyanate ester composite, and the I-layer is a boron nitride/cyanate ester composite. The effects of relative position and spatial stacking order of three-, four- and five-layer structures on performances were intensively discussed for the first time. Results show that CDIDC has the highest dielectric permittivity (886, 100 Hz) and biggest dielectric ratio of dielectric permittivity to l...

Cyanate ester composites containing surface functionalized BN particles with grafted hyperpolyarylamide exhibiting desirable thermal conductivities and a low dielectric constant.

Surface functionalized BN particles with grafted hyperbranched polyarylamide (BN-HBP) were prepared and used to improve the thermal conductivity and low dielectric constant of BN-filled cyanate ester resin (BN-HBP/CE) composites. The thermal stability, dielectric properties, thermal conductivity and dynamic mechanical properties of the BN-HBP/CE composites were investigated. The results illustrate that BN-HBP/CE composites with a load of 32 wt% exhibit a high glass transition temperature of 283 °C, low dielectric constant of 3.29 at 1 MHz, and a desirable thermal conductivity of 0.97 W/(m·K). Additionally, these novel materials exhibit a high decomposition temperature of 5% weight loss at 407 °C and low curing shrinkage of −0.64%. When the loading is 38 wt%, the thermal conductivity of BN-HBP/CE composites is 1.27 W/(m·K). These findings have significant implications for the preparation of high-performance substrates that meet the requirements for application as printed circuit board substrates.

High-performance cyanate ester composites with plasma-synthesized MgSiO3-SiO2-hBN powders for thermally conductive and dielectric properties

Thermally conductive composites aimed for dielectric application were achieved by embedding spherical MgSiO3-SiO2-hBN powders into cyanate ester resin as functional fillers. The MgSiO3-SiO2-hBN particles were prepared by plasma sythesized process employing talc and hexagonal boron nitride (hBN) as sources. The morphology, phase structure of the MgSiO3-SiO2-hBN powders were characterized by changing the content of BN. Meanwhile, the thermal and dielectric properties of the composites with different filler loading were investigated.Results show that phase transformation from talc to protoenstatite and critobalite occurred. The thermal conductivity shows a drastic enhancement with the increase of the filler loading. Further contrast analyzed by Bruggeman model shows that the tested values agree well with estimated ones when fillers fraction are less than 15 vol%. However, an obvious deviation for the values of thermal conductivities is thought to arise from the randomly oriented hBN and the formation of the thermal conductive networks in composites. Relatively low dielectric constants and dielectric losses (tanδ) are obtained for all the composites.

Thermal Ageing of Carbon Fiber‐Reinforced Cyanate Ester Composites Under Inert and Oxidative Environment

This work investigates the effect of thermal ageing under two different exposure environments on the mechanical and thermo‐mechanical properties of carbon fiber‐reinforced cyanate ester composites. A large test campaign was realized to this direction. Samples were manufactured by RTM technique and were subjected in isothermal exposure at 2300 C under two different gas environments: inert (nitrogen) and air at 1 atmosphere, for up to 30 days. Weight measurements followed by dynamic mechanical analysis as well as a series of mechanical tests were conducted at regular intervals during the ageing process. In addition, scanning electron microscopy was utilized to identify the exact degradation mechanisms that are active and dominant in the different ageing periods. POLYM. COMPOS., 40:E1388–E1396, 2019. © 2018 Society of Plastics Engineers

Investigation on thermal stability and tribological properties of ZrB2 particles filling cyanate ester resin composites by experiments and numerical simulation

The thermal stability and tribological properties of cyanate ester (CE) composites filled with Zirconium boride (ZrB2) particles were investigated by experimental and numerical simulation. The results of thermogravimetric analysis and differential scanning calorimetry showed that the thermal stability of composites was improved by introduction of ZrB2 particles. The tribological properties of composites including friction coefficient and wear rate measured by pin‐on‐disk friction and wear tester were enhanced. Friction coefficient and wear rate of composites were decreased significantly with an increase of ZrB2 particles content under dry and oil sliding conditions. The 5 wt% ZrB2 particles reinforced CE resin composite presented optimal thermal stability and tribological performance due to good dispersion of ZrB2 particles. The worn surfaces of composites were observed by scanning electron microscopy to explore wear mechanism, indicating that the dominant wear mechanism of composites was transformed from adhesive wear to abrasive wear after incorporation of ZrB2 particles. Finite element model was established to study the distribution of friction stress. The results revealed that filling ZrB2 particles in the friction process of composites could bear more friction stress than CE resin matrix, which further illustrated that abrasive wear is main wear mechanism of ZrB2/CE resin composites. POLYM. ENG. SCI., 59:602–607, 2019. © 2018 Society of Plastics Engineers

Fabrication, proposed model and simulation predictions on thermally conductive hybrid cyanate ester composites with boron nitride fillers

DCPDCE/BADCy hybrid resin and BN fillers were performed to fabricate the thermally conductive BN/DCPDCE/BADCy composites. When the molar ratio of DCPDCE/BADCy was 0.4/0.6, the dielectric constant (ε) and dielectric loss tangent (tgδ) value of the DCPDCE/BADCy hybrid resin was decreased to 2.92 and 5.08 × 10−3, respectively. Impact and flexural strength was increased to 10.7 kJ/m2 and 100.7 MPa, respectively. And the heat-resistance index (THRI) was 201.6 °C. Furthermore, the thermally conductive coefficient (λ) of the BN/DCPDCE/BADCy composite with 30 wt% BN fillers was improved to 0.64 W/mK, about 3 times in comparison to that of pristine DCPDCE/BADCy hybrid resin. Compared to that of Maxwell and Russell models, our proposed thermally conductive model could predict the experimental λ values more precisely. THRI value was enhanced from 201.6 °C (Pristine DCPDCE/BADCy hybrid resin) to 206.6 °C. Moreover, the BN/DCPDCE/BADCy composite with 10 wt% BN presented the optimal impact strength (11.7 kJ/m2) and flexural strength (108.4 MPa).

Carbon-fibre-reinforced modified cyanate ester winding composites and their thermomechanical properties

Although the extensive research has expanded on the modification of cyanate ester (CE) resins and the mechanical properties of CE composites, very few studies have been conducted on carbon fibre (CF)/modified CE winding composites and the thermomechanical properties of the composites. In this research, epoxy (EP)-modified novolac cyanate ester (NCE) and bismaleimide (BMI)-modified NCE resins were prepared. The CF/modified CE winding composites were manufactured, and their thermomechanical properties were tested. The optimal winding process was determined, and a preheating technique was implemented. Then, the EP/CE resin (10:90) and the BMI–DBA/CE resin (10:90) were selected as the resin matrix of the winding composite based on the viscosity properties, mechanical properties and thermal analysis (using thermogravimetric analysis and differential scanning calorimetry) of the modified CE resin. The selected resin exhibited good manufacturability at 70°C, good thermal stability and high Tg (above 370°C). The thermomechanical property tests indicate that the modified CE resin composite exhibits an outstanding mechanical strength at room temperature and at high temperatures (130°C, 150°C and 180°C) compared with that of the pure CE resin composite. The reasons for this enhancement can be attributed to a toughening mechanism and the effect of sizing agents on the CFs.

Synergistic effect of graphene nanosheets and carbonyl iron–nickel alloy hybrid filler on electromagnetic interference shielding and thermal conductivity of cyanate ester composites

Graphene nanosheets and carbonyl iron-nickel alloy powder were used in a synergistic manner to fabricate cyanate ester nanocomposite with an excellent EMI shielding effectiveness and high thermal conductivity.