Cyanate Ester Research Articles

Nickel-plated cyanate Ester/melamine shape memory composites for stable electromagnetic shielding switch, infrared stealth, and flame retardancy

Military equipment must receive signals but is prone to malfunction due to electromagnetic interference. Moreover, operational temperature variations can be detected by infrared sensors, leading to potential exposure. Therefore, developing materials that integrate electromagnetic shielding switches with infrared stealth capabilities is crucial for enhancing target security. This study investigates a novel composite material that combines shape memory polymer (SMP) and conductive layers for integrated functionality. Utilizing melamine sponge as the substrate, a cyanate ester (CE)-nitrile rubber (NR) SMP coating is applied via dip-coating, allowing the sponge to self-fixate after deformation. The SMP demonstrates stable shape recovery. Subsequently, a conductive nickel layer is added through keratin modification and chemical plating, providing electromagnetic shielding effectiveness exceeding 30 dB and reducing infrared emissivity to 0.6. The composite material is capable of achieving controllable electromagnetic shielding switches of 35 dB and 15 dB. It maintains excellent electromagnetic shielding and infrared stealth capabilities even under acid rain conditions and extreme temperature variations. This innovative approach holds significant promise for applications requiring simultaneous electromagnetic and infrared protection.

Structural‐Functional‐Integrated Ultra‐Wideband Microwave‐Absorbing Composites Based on In Situ‐Grown Graphene Meta‐nanointerface

AbstractUltra‐wideband microwave absorbing (MA) materials covering the low‐frequency range (2–6 GHz) are highly desirable in civil and military fields. These materials can be fabricated based on the design of electromagnetic meta‐structure. Herein, a structural‐functional‐integrated ultra‐wideband SiO2 fiber reinforced cyanate ester (CE) MA composite based on an in situ‐grown graphene meta‐nanointerface layer (GrMI) (SiO2f/GrMI/CE) is reported. The relationship between the periodic structure of the graphene nano‐interface layer and the MA performance is discussed through experiments and simulations. The results show that SiO2f/GrMI/CE with a thickness of 8.78 mm exhibits an effective absorption bandwidth of 15.46 GHz (2.54–18 GHz). Remarkably, the reflection loss remains basically unchanged upon increasing the incident angle from 5° to 50°. Additionally, GrMI is an effective load‐bearing constituent, which increases the interfacial shear stress between SiO2f and the CE by ≈210% and contributes to achieving composites with an ultra‐high flexural strength (552.7 MPa). The excellent structural‐functional‐integrated performances ensure that the SiO2f/GrMI/CE composites are suitable for use as the skin materials of microwave stealth aircraft and other civil facilities. The work provides a novel pathway for the design of thinner, wider, lighter, and stronger MA components.

A comparison of X-ray attenuation, differential phase, and dark-field contrast imaging for the detection of porosity in carbon fiber reinforced cyanate ester

In this work we explore the capabilities of Talbot-Lau grating interferometry (TLGI) radiography for the inspection of porosity in structural specimens of cyanate ester carbon fiber reinforced polymer. The influence of system resolution and varying specimen thicknesses on mean values and standard deviations (STDV) in all three image modalities acquired by TLGI are addressed. Results show that mean absorption contrast (AC) values are highly affected by specimen thickness and strong negative correlation (r ≤ −0.8) is found only after correction via preliminary thickness measurements. Although dark-field contrast (DFC) is affected by changes in specimen thickness as well, the signal can be corrected by normalization with the inherently available AC. Consequently, strong positive correlation with porosity was found both in high- and low-resolution imaging (r = 0.83 and 0.71 respectively). Without the need for high image resolution or thickness measurements, the normalized DFC is a promising option for large field of view inspections. Investigations of STDV revealed strong positive correlations between porosity and AC STDV as well as differential phase contrast (DPC) STDV (r = 0.95 and 0.92 respectively) but high image resolution is required. Furthermore, results suggest increased robustness against variations in specimen thickness of AC and DPC STDV analyses.

LUNAR: Automated Input Generation and Analysis for Reactive LAMMPS Simulations.

Generating simulation-ready molecular models for the LAMMPS molecular dynamics (MD) simulation software package is a difficult task and impedes the more widespread and efficient use of MD in materials design and development. Fixed-bond force fields generally require manual assignment of atom types, bonded interactions, charges, and simulation domain sizes. A new LAMMPS pre- and postprocessing toolkit (LUNAR) is presented that efficiently builds molecular systems for LAMMPS. LUNAR automatically assigns atom types, generates bonded interactions, assigns charges, and provides initial configuration methods to generate large molecular systems. LUNAR can also incorporate chemical reactivity into simulations by facilitating the use of the REACTER protocol. Additionally, LUNAR provides postprocessing for free volume calculations, cure characterization calculations, and property predictions from LAMMPS thermodynamic outputs. LUNAR has been validated via building and simulation of pure epoxy and cyanate ester polymer systems with a comparison of the corresponding predicted structures and properties to benchmark values, including experimental results from the literature. LUNAR provides the tools for the computationally driven development of next-generation composite materials in the Integrated Computational Materials Engineering (ICME) and Materials Genome Initiative (MGI) frameworks. LUNAR is written in Python with the usage of NumPy and can be used via a graphical user interface, a command line interface, or an integrated design environment. LUNAR is freely available via GitHub.

Research and improvement of cyanoacrylate on bonding properties of silicone adhesive material

Cyanoacrylate adhesives represent the earliest discovered and most widely utilized adhesives known to date, boasting exceptional bonding properties such as the ability to cure at room temperature, rapid curing rates, and strong adhesion. However, shortcomings persist in practical applications, notably in addressing inert materials like silicone that pose challenges for ideal adhesion. To enhance the bonding performance of cyanate ester adhesives with silicone materials, this study delves into two aspects: modifying cyanate esters and pre-treating silicone surfaces to reduce surface energy. Following internal modifications, the maximum bonding strength to silicone sheets reached 2.33 MPa, while pre-treating the silicone substrate surface enabled a maximum bonding strength of 6.10 MPa. Utilizing SEM, ATR, EDS, and other analytical techniques, the mechanisms behind the improvement in silicone substrate bonding strength are characterized, revealing changes in properties pre- and post-treatment. This research paves a novel path and direction for future scientific investigations and advancements in adhesive formulation and enhancement.

Linear polyborosiloxane for improving the flame-retardancy of cyanate ester resin

The increasing demands for electronic packing materials necessitate stringent criteria for the overall properties of cyanate ester (CE) resins. In this work, a novel linear polyborosiloxane with a distinctive organic-inorganic hybrid Si–O–B backbone, featuring functional epoxy and phenyl groups (denoted as LPSi-B), was synthesized via a solvent- and catalyst-free one-pot polycondensation. Subsequently, the synthesized LPSi-B was co-crosslinked within the bisphenol A dicyanate ester (BADCy) thermoset network. The presence of abundant active epoxy groups in LPSi-B facilitated its involvement in the cyanate curing reaction, demonstrating excellent compatibility within the resin matrix. The resulting LPSi-B/BADCy composite not only exhibits outstanding mechanical properties but also demonstrates notable flame-retardant and dielectric characteristics. Specifically, the hybrid nature of LPSi-B, combining the flexibility of Si–O–B chains with the rigidity of side-chain phenyl groups, fosters intermolecular non-covalent π-π interactions directly linked to boron atoms, thus mitigating network polarization. Furthermore, the synergistic flame-retardant effect arising from boron and silicon components was harnessed to achieve halogen-free, phosphorus-free, and environmentally friendly fire safety outcomes. This innovative design ensures exceptional compatibility and interface bonding between LPSi-B and the polymer matrix, thereby endowing cyanate ester resin with superior comprehensive performance suitable for advanced applications in wave-transparent and electronic packing materials.

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.

Study on irradiation effect of insulating materials for fusion superconducting magnets: temperature dependence of mechanical strength

Insulating materials used in the superconducting magnets of fusion reactors are exposed to cryogenic temperatures, intense radiations, and strong electromagnetic forces. In the experimental fusion reactor ITER, resin mixed with epoxy resin (EP) and cyanate ester (CE) (CE content: 40 wt.%) is used as a matrix of glass reinforced plastics (GFRP) as an insulating material to maintains mechanical strength and insulating performance in such environments. This composition ratio is basically determined by strength tests at room temperature or liquid nitrogen temperature, so the study at liquid helium temperature is required. In this study, the effects of the resin composition of GFRP on interlaminar shear stress (ILSS) at room temperature, liquid nitrogen temperature, and liquid helium temperature before and after γ-ray irradiation were evaluated. The ILSS after γ-ray irradiation of EP showed a maximum value at liquid helium temperature, while the addition of CE caused the ILSS after irradiation to show a maximum value at liquid nitrogen temperature. It was also shown that the temperature dependence of the ILSS decreased with increasing CE content. The results showed that the addition of CE to EP contributes to the improvement of radiation resistance, but excessive addition of CE promotes embrittlement at LHeT.

Preparation, Cure, Characterization, and Mechanical Properties of Reactive Flame-Retardant Cyanate Ester/Epoxy Resin Blends and their Carbon Fiber Reinforced Composites

This study explores the formulation space of flame retardant thermoset polymers, specifically involving blends of epoxy and cyanate ester (EP/CE) and a reactive phosphorus-based flame retardant, poly (m-phenylene methylphosphonate) (PMP). Two CE monomers were investigated, each blended with the same epoxy monomer (DGEBA) in a 1:1 wt ratio. The impact of phosphorus concentration on the neat (neat meaning no fibers were present) resin blends was characterized using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The flammability and mechanical characteristics were assessed using micro-combustion calorimetry (MCC) and dynamic mechanical analysis (DMA). Carbon fiber composite panels were successfully fabricated using a wet layup process and autoclave curing with a fiber volume fraction (Vf) of approximately 0.5. DMA testing of the cured composite laminates pinpointed that the average Tg of the EP/CE blend was reduced with PMP addition by up to 39 °C at a phosphorous level of 3 wt%. Cone calorimetry tests confirmed the effectiveness of the flame retardant by reducing the peak Heat Release Rate (HRR) by approximately 27 %. The integration of PMP into EP/CE only marginally reduced the 3-point flexural strength (6–15 %) and modulus (7–13 %) relative to baseline samples.

Space Durable 3D Printed High‐Performance Polymers Based on Cyanate Ester/Extended‐Bismaleimide

AbstractTo accomplish the potential of the New‐Space emerging era and facilitate scientific and commercial space exploration, the development of versatile, customized, and affordable space technologies is essential. 3D printing is established as a disruptive technology, enabling the production of complex and lightweight structures with enhanced performance. However, the harsh conditions of the space environment, including atomic oxygen (AO), extreme temperatures, and ionizing radiation, pose significant challenges to the durability and longevity of additive manufacturing‐produced polymers. Until now, there are no additive‐manufacturing polymeric materials that are specifically developed and qualified to withstand space hazards. To address these challenges, novel materials for additive manufacturing, composed of cyanate ester and extended‐bismaleimide are engineered to withstand the extreme conditions in space. The developed materials demonstrate superior thermo‐mechanical properties (flexural stress of 72 MPa and Tg = 260 °C), enhanced durability to AO erosion, ionizing radiation (10 years in orbit), and thermal stability (Td5% = 360 °C). Moreover, it is found that printing orientation governs the AO erosion, thus guiding optimal printing designs for enhanced durability to AO. The materials show improved performance, endurance, and reliability, thus contributing to the development of space‐qualified components and enabling the advancement of additive manufacturing for future space missions.

Optimizing polymer composite dielectric properties via digital light processing 3D printing of ordered barium titanate skeleton

Through construction of a three-dimensional continuous ceramic network, the dielectric performance of polymer composites can be enhanced with a reduced amount of ceramic loading. However, the commonly employed methods, such as freeze casting or sacrificial template, fail to precisely control the structure of the ceramic skeleton, leading to significant randomness in content control. In this work, a Digital Light Processing (DLP) 3D printing technique is utilized to precisely fabricate ordered three-dimensional ceramic structures, which are further sintered at high temperatures to obtain a continuous barium titanate (BT) skeleton (BTS). This is then compounded with cyanate ester based polymers (CP) to prepare BTS/CP composites. Results show that when the content of BT is 61.2 vol%, the dielectric constant of the composite is 657 at 100 Hz, which is about 173 times higher than CP, while maintaining a lower dielectric loss of 0.026. Interestingly, the distribution of BTS in the composites has a significant impact on the dielectric performance of the composite. When the BT content is about 50 vol%, the dielectric constant of the “fine and dense” skeleton composite is 2.1 times higher than that of the “coarse and sparse” skeleton composite. This study proposes a novel strategy for building a structurally and compositionally controllable three-dimensional barium titanate (BT) network within polymers, demonstrating the noteworthy influence of macrostructure on the dielectric performance of polymer composites. This offers a fresh approach to the mass application of ordered three-dimensional ceramic skeleton enhanced polymer composites in the fields of electronics and electricity.

Synergistic enhancement of toughness and flame retardation for cyanate ester composites through hyperbranched polyborosiloxane

AbstractExcellent flame resistance is supposed to be taken into consideration for electronic packaging materials due to the spontaneous combustion of short circuits, except for good mechanical and dielectric properties. Herein, a hyperbranched polyborosiloxane (HPSiB) flame retardant was synthesized via a simple one‐pot transesterification as a multifunctional additive for cyanate ester (CE) resin. The HPSiB with many active terminals features good compatibility with the resin matrix, while catalyzing the curing reaction that conducts at a lower temperature. With as little as 2 wt% HPSiB incorporated, the HPSiB/bisphenol A cyanate ester (BADCy) resin achieves a UL‐94 V0 rating and 32.4% LOI value, and its peak heat release and total smoke production are simultaneously reduced. Its flexural strength and impact strength were significantly enhanced by 30.0% and 85.4%. Besides, the minimum values of dielectric constant and loss can reach 2.77 and 0.0024 at 10 GHz, which are, respectively, reduced by 7.9% and 88.5%. The integration of unique hyperbranched SiOB backbone of HPSiB with CE crosslinked network was responsible for the enhanced overall performance. This work paves a facile strategy to develop multifunctional flame retardant as a promising candidate for the high‐performance electronic packaging materials.Highlights A novel hyperbranched polyborosiloxane flame retardant was synthesized. HPSiB shows good compatibility and catalyzes the curing reaction of CE resin. HPSiB/CE resin with significantly enhanced flame retardancy was obtained. Simultaneously high toughness and low dielectric loss were achieved. Hyperbranched structure containing SiOB chains led to the great enhancement.

3D printing of cyanate ester resins with interpenetration networks for enhanced thermal and mechanical properties

AbstractCyanate ester (PT‐30) resin possesses exceptional thermal and mechanical properties, including high heat distortion temperature, high glass transition temperature (Tg), and outstanding mechanical characteristics. Conversely, the Tg of the homopolymer of tris(2‐hydroxyethyl)isocyanurate triacrylate (T‐acrylate) surpasses that of other acrylates. The combination of PT‐30 and T‐acrylate results in the formation of an interpenetrating polymer network (IPN) through a dual curing mechanism. Furthermore, the combination of these two polymers enables the tuning of rheology for shear thinning behavior for Ink Extrusion 3D printing technology by adjusting the amount of photoinitiator and rheological modifier. Here, 3D printable ink was formulated using PT‐30, T‐acrylate with a higher Tg, a photoinitiator, and a powdered rheological additive. The printed structures underwent a dual‐curing process involving exposure to UV light and thermal curing. Thermomechanical properties of the printed samples were characterized using dynamic mechanical analysis, thermogravimetric analysis, and tensile testing. The successful formation of an IPN structure through the polymerization of T‐acrylate and PT‐30 was observed, resulting in improved mechanical properties and an elevated Tg. The Fourier transform infrared spectroscopy analysis verified the formation of cross‐linked samples. Overall, this study demonstrates the feasibility of Ink Extrusion 3D printing, using a cyanate ester resin and tris(2‐hydroxyethyl)isocyanurate triacrylate with a dual‐curing mechanism. The enhanced mechanical properties at elevated temperatures (~80% retention of room temperature tensile strength at 200°C for sample with 70/30 wt%) and high Tg of 349 ± 3°C for printed structures shown in this study make them suitable for high‐performance structural applications in industries such as aerospace, defense, and microelectronics.

The Recent Advances of Polymer-POSS Nanocomposites With Low Dielectric Constant.

This study provides a comprehensive overview of the preparation methods for polyhedral oligomeric silsesquioxane (POSS) monomers and polymer/POSS nanocomposites. It focuses on the latest advancements in using POSS to design polymer nanocomposites with reduced dielectric constants. The study emphasizes exploring the potential of POSS, either alone or in combination with other materials, to decrease the dielectric constant and dielectric loss of various polymers, including polyimides, bismaleimide resins, poly(aryl ether)s, polybenzoxazines, benzocyclobutene resins, polyolefins, cyanate ester resins, and epoxy resins. In addition, the research investigates the impact of incorporating POSS on improving the thermal properties, mechanical properties, surface properties, and other aspects of these polymers. The entire study is divided into two parts, discussing systematically the role of POSS in reducing dielectric constants during the preparation of POSS composites using both physical blending and chemical synthesis methods. The goal of this research is to provide valuable strategies for designing a new generation of low dielectric constant materials suitable for large-scale integrated circuits in the semiconductor materials domain.

Synchronously improved toughness and dielectric properties of cyanate ester resins via modification with biobased poly(N‐phenylmaleimide‐co‐limonene)

AbstractHigh‐performance cyanate ester (CE) resins have attracted intensive interests due to low‐k and heat resistant properties. However, the extreme high curing temperature and inherent brittleness severely limit their practical application. Herein, novel biobased poly(N‐phenylmaleimide‐co‐limonene) (PML) microspheres were specially designed and synthesized by self‐stabilized precipitation polymerization, which could simultaneously serve as effective curing agents and toughening modifiers for 2,2‐bis(4‐cyanatophenyl) propane (BADCy). The high density of unreacted endocyclic vinyl groups in PML could effectively react with BADCy, leading to lower curing temperature and good interfacial compatibility. Benefitting from both the weakly polarizable flexible chains and the highly crosslinked semi‐interpenetrating network formed during the curing process, BADCy/PML resins exhibited highly enhanced toughness and reduced dielectric constant (ε). Specifically, the BADCy/PML resins showed minimum values of ε and dielectric loss of 2.61 and 0.0032 at 106 Hz, much lower than BADCy resins (2.88, 0.0052). More importantly, a maximum impact strength of 15.6 kJ/m2 was achieved at 10 wt% loading of PML, which was 86% higher than BADCy resin. In summary, this work developed a novel strategy to simultaneously improve toughness and dielectric properties of CE resins using bio‐based PML copolymer, which have great potential in the fields of electronics and information technology.

Tailoring the cage and functionality of POSS for scalable low-dielectric and tough cyanate ester hybrid resin

2EGEP-POSS and 4EGEP-POSS with larger cage size and lower functionality were synthesised to copolymeize with cyanate ester (CE) resin. The CE/2(or 4)EGEP-POSS hybrid resins exhibit remarkable toughness and low-dielectric characteristics.

Si, B-containing dynamic covalent bonds enable excellent flame retardancy and reduced fire hazards for cyanate ester resin.

Cyanate ester (CE) resins are distinguished by excellent dielectric properties in electronic packaging materials but face significant fire risks, with existing strategies often compromising their processability or original properties. Herein, we propose an innovative strategy involving the exchange of dynamic covalent bonds under heat stimuli aimed at forming a continuous and compact char layer to enhance the fire safety of CE resin. Using a straightforward one-pot method, dynamic Si-O and B-O bonds were integrated into a novel hyperbranched polymer (HPSiB), ensuring good compatibility with CE resin while lowering its peak curing temperature by 185 °C for facile processability. The resulting material with 6 wt% HPSiB exhibits a LOI value of 32.8% and UL-94 V0 rating, especially a low total smoke production of 6.7 m2, demonstrating excellent flame retardancy and reduced fire hazards compared to reported Si or B-containing flame-retardant materials. Moreover, its glass transition temperature increased by 35 °C, along with enhanced mechanical properties and an ultra-low dielectric loss of 0.0031 at 10 GHz. These advancements highlight the significant potential of this work in developing high-performance fire-resistant materials.

Synergistic improvements in the processability and mechanical properties of cyanate esters via aminobenzonitrile-induced chemical tailoring

Aminobenzonitrile homologues (ABNx), acting as both cross-linkers and catalysts, synergistically enhance the processability and mechanical properties of cyanate ester resins.

Experimental study on hole quality characteristics in abrasive waterjet machining of quartz cyanate ester polymeric composite

Experimental study on hole quality characteristics in abrasive waterjet machining of quartz cyanate ester polymeric composite

Experimental study on hole quality characteristics in abrasive waterjet machining of quartz cyanate ester polymeric composite

Experimental study on hole quality characteristics in abrasive waterjet machining of quartz cyanate ester polymeric composite