| HS Code | 532149 |
| Chemical Name | Cyanate Ester Resin |
| Cas Number | 1156-51-0 (typical bisphenol A dicyanate monomer) |
| Chemical Formula | C17H14N2O2 (typical) |
| Density | 1.2 g/cm³ |
| Glass Transition Temperature | 250-300°C (cured) |
| Curing Temperature | 180-250°C |
| Dielectric Constant | 2.8-3.2 at 1 MHz |
| Dissipation Factor | 0.002-0.005 at 1 MHz |
| Tensile Strength | 70-100 MPa |
| Flexural Modulus | 3.0-4.0 GPa |
| Water Absorption | 0.5-2.0% after 24h immersion |
| Thermal Conductivity | 0.2-0.3 W/(m·K) |
| Coefficient Of Thermal Expansion | 60-80 ppm/°C (below Tg) |
As an accredited Cyanate Ester (CE) factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Cyanate Ester (CE) is packaged in 1 kg sealed aluminum pouches under inert nitrogen, with desiccant to ensure dryness. |
| Container Loading (20′ FCL) | Load Cyanate Ester drums in 20′ FCL, secure tightly, protect from moisture, and label as hazardous chemical. |
| Shipping | Cyanate Ester (CE) should be shipped in sealed, moisture-resistant containers, preferably under inert gas, to prevent hydrolysis. Use dedicated, clearly labeled packaging compatible with resins. Avoid high temperatures, ignition sources, and contact with moisture. Transport per applicable hazardous materials regulations, ensuring secondary containment and proper documentation. |
| Storage | Store cyanate ester (CE) in tightly sealed, original containers in a cool, dry, well-ventilated area, away from direct sunlight and heat sources. Protect from moisture and humidity, as CE is hydroscopic. Keep away from strong oxidizers, acids, and bases. Maintain temperatures between 10–30°C and follow manufacturer’s shelf-life guidelines. |
| Shelf Life | Cyanate ester (CE) has a typical shelf life of 6–12 months when stored sealed, cool, dry, and away from moisture. |
Continuous carbon fiber prepregs formulated around bisphenol A dicyanate are specified for autoclave-cured monolithic laminates where post-cure glass transition temperature above 250 °C and moisture uptake below 1.0 wt% after 30 days at 85 °C/85% RH are mandatory design boundaries. Mechanical qualification data for this application class are generated under ASTM D3039/D3039M-17 for tensile modulus and strength, ASTM D6641/D6641M-16e1 for compression, and ASTM D3518/D3518M-18 for in-plane shear; flammability screening for cabin-facing laminate panels is conducted under FAR 25.853 Appendix F Part I. The matrix is commonly a BADCy homopolymer catalyzed with copper(II) acetylacetonate at 0.05–0.3 phr and a nonylphenol co-catalyst at 2–4 phr, blended at 80–100 °C before film-resin transfer onto unidirectional or woven carbon fiber. Prepreg resin content is held at 35–42 wt% with cured laminate fiber volume fraction of 58–62 vol%; this window balances fiber-dominated mechanical translation against the need for sufficient resin film thickness to prevent microvoid formation in ply-drop regions. Autoclave processing uses a first ramp of 0.5–1.5 °C/min to 177 °C, a 2 h hold to achieve gelation without uncontrolled exotherm, and a free-standing post-cure at 250 °C for 2–4 h. Sections thicker than 10 mm require thermocouple mapping because the cyclotrimerization exotherm can produce mid-laminate temperature overshoots exceeding 20 °C when ramp rates are not reduced for thick-ply stacking. Humidity exposure before cure is an operational boundary: prepreg stored beyond 7 days at 23 °C/50% RH may exhibit surface tack drift and should be screened for residual carbamate formation by Fourier-transform infrared spectroscopy before layup. Terminal product types include engine cowl blocker-door skins, wing flap-track fairings, and launch vehicle interstage panels.
Lamination of cyanate ester–epoxy prepregs for high-speed printed circuit boards is dominated by B-stage control and moisture ingress in the resin varnish rather than by glass transition deficiencies. Base materials are qualified against IPC-4101E; dielectric constant and loss tangent at 10 GHz are determined per IPC-TM-650 2.5.5.13; copper peel strength follows IPC-TM-650 2.4.8; flammability is evaluated under UL 94 V-0. Blends of BADCy and bisphenol A epoxy are run at 60:40 by weight for multilayer backplane constructions; fused silica is added at 10–20 phr to reduce in-plane expansion, and organometallic catalyst loading is limited to 0.05–0.2 phr. Prepreg resin content on low-Dk woven glass is maintained at 48–55 wt% to control resin-flow window during press consolidation. Varnish mixing is carried out in methyl ethyl ketone at 55–65 wt% solids with moisture specification below 500 ppm; the treater operates at 150–180 °C in a two-zone oven to achieve controlled resin advancement. Layup of 8–16 plies between electrodeposited copper foil is pressed under vacuum at 190–220 °C and 1.5–2.5 MPa. The principal production failure is not insufficient Tg but B-stage drift caused by cyanate ester hydrolysis during varnish storage; viscosity rise and gel-particle formation are observed on the meter-mix line when solvent moisture limits are exceeded. This is a critical threshold because gel particles create dielectric inhomogeneity in the final laminate and reduce copper peel consistency.
| Resin matrix | Dk at 10 GHz | Df at 10 GHz | Water absorption |
|---|---|---|---|
| Bisphenol A dicyanate homopolymer | 2.9–3.0 | 0.005–0.007 | 0.6–0.8 wt% |
| Cyanate ester–epoxy 60:40 | 3.2–3.4 | 0.008–0.011 | 1.0–1.3 wt% |
| Bismaleimide triazine | 3.4–3.6 | 0.009–0.013 | 0.8–1.0 wt% |
| FR-4 epoxy control | 4.2–4.5 | 0.020–0.026 | 1.2–1.5 wt% |
Terminal product types include 77 GHz automotive radar boards, high-speed server backplanes, and microwave test fixtures. The operational boundary for this segment is moisture control before B-staging; once the varnish exceeds the 500 ppm water limit or prepreg resides too long in unconditioned lamination rooms, dielectric loss and copper adhesion become batch-variable even when cure temperature and pressure remain unchanged.
Radome wall construction from quartz fabric and cyanate ester matrix is specified where low dielectric loss, moisture resistance, and thermal shock survival are simultaneous procurement requirements. Electrical qualification uses ASTM D2520-13 for complex permittivity; environmental screening follows MIL-STD-810G Method 503.5 for temperature shock and Method 507.5 for humidity. Rain erosion resistance may be evaluated by whirling-arm apparatus under ASTM G73, though published pass/fail thresholds for cyanate ester radomes are procurement-specific. The matrix is typically more than 90 wt% BADCy with bisphenol E dicyanate at 5–10 wt% to suppress monomer crystallization in cold storage; quartz fabric prepreg resin content is held at 32–38 wt%. Prepreg is compression molded in matched steel tooling at 160–180 °C and 0.5–1.0 MPa, followed by free-standing post-cure at 250 °C for 2–4 h. Wall thickness tolerance is maintained at ±0.05 mm in the critical antenna window region; ultrasonic C-scan void content is specified below 1.0% because a localized void larger than 0.5 mm creates a measurable dielectric discontinuity. The dominant failure mode is microcracking after repeated thermal shock; incomplete post-cure leaves residual cyanate functionality that later reacts with absorbed water, raising dissipation factor after 500 thermal cycles. Terminal product types include tactical missile radomes, airborne weather radar covers, and electronic warfare pod windows.
Spacecraft primary and secondary structures processed from cyanate ester unidirectional tape are used where low outgassing and dimensional stability under thermal cycling are mandatory. Vacuum outgassing is characterized under ASTM E595-15 and typically must remain below 1.00% total mass loss and 0.10% collected volatile condensable material; European programs commonly require ECSS-Q-ST-70-02C documentation. Published data for the exact toughener concentration in cyanate ester optical benches are limited; the stated range reflects commercial aerospace prepreg datasheet guidance rather than part-specific batch data. Formulation uses a higher-functionality novolac cyanate ester blended with 10–20 phr thermoplastic toughener to raise Tg above 300 °C after post-cure; tape fiber volume is 58–62 vol%. Automated fiber placement and hot debulk at 70–80 °C are used before autoclave cure at 177 °C with a subsequent free-standing post-cure at 250 °C for 4–6 h. The operational boundary is microcracking in cryogenic thermal cycling from -196 °C to 150 °C; laminate stacking sequences with high transverse thermal stresses require microcrack density evaluation under ASTM E228 CTE measurement and optical microscopy after 200 cycles. Terminal products include optical benches, star-tracker brackets, antenna reflectors, and satellite bus shear panels.
Bonding of honeycomb core to face sheets with a co-cured cyanate ester film adhesive is performed where the core-adhesive-prepreg system must survive 177 °C continuous service and retain flatwise tension strength after moisture conditioning. Compliance is established by ASTM D1002-10 single-lap shear for metal-to-metal screening, ASTM D1781-98 climbing drum peel for honeycomb adhesion, and ASTM C297/C297M-16 flatwise tension for sandwich panels. Published data for this exact toughener loading range are limited; the stated range is derived from aerospace film-adhesive patents and supplier development bulletins rather than production-validated laminate allowables. Formulation is typically a 50:50 BADCy–bisphenol A epoxy blend with 10–20 phr carboxyl-terminated butadiene acrylonitrile elastomer and 3–5 phr fumed silica thixotrope; film areal weight is controlled at 0.15–0.45 kg/m² depending on core cell size. The process consists of solvent casting on release paper, B-staging in a forced-air oven at 70–90 °C, then co-curing under autoclave pressure of 50–100 psi at 177 °C for 2 h. The main manufacturing defect is excessive resin flow into the honeycomb cells when the adhesive viscosity at gel point drops below the critical threshold; edge bleed and reticulation are controlled by pre-gel viscosity measured on a parallel-plate rheometer at 120 °C. Terminal products include aircraft nacelle acoustic panels, cabin floor sandwich panels, and secondary control surface layups.
Autoclave master molds and production fixtures fabricated from cyanate ester-based tooling prepreg are selected when polyester and epoxy tooling exhibit unacceptable dimensional drift during repeated excursions to 200–230 °C. The tooling prepreg is typically formulated with a novolac cyanate ester matrix and graphite or carbon fiber reinforcement; resin content is 35–45 wt%, and graphite powder filler is added at 10–20 phr to reduce surface porosity and improve vacuum integrity. Compliance testing uses ASTM D638-14 for cast unreinforced resin tensile properties and ASTM D648-18 for heat deflection temperature; tooling repairs are evaluated by ASTM D790-17 flexural strength retention after thermal aging at 230 °C for 500 h. The production process involves layup over a master plug, vacuum bagging, autoclave cure at 177–190 °C, and free-standing post-cure at 250 °C for 4–8 h. Dimensional stability is maintained only when post-cure is complete; residual heat of reaction measured by differential scanning calorimetry must fall below 5 J/g to avoid mold spring-back during the first high-temperature production cycle. Terminal product types include autoclave master molds for complex-shape composite parts, vacuum forming tools, and high-temperature drill fixtures.
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Cyanate ester (CE) resin systems are polyfunctional aromatic monomers in which at least two cyanate (–OCN) groups are attached to a phenylene or novolac backbone. Industrial grades include bisphenol A dicyanate, bisphenol E dicyanate, phenol novolac cyanate ester, and bisphenol M-based cyanate ester. Commercial model designations such as Primaset BA-230, Primaset LECy, Primaset PT-30, and AroCy B-10 represent these chemical families. The monomers are supplied as semi-solid flakes, low-viscosity liquids, or solids, and are cured by cyclotrimerization to triazine rings at 150–250 °C. Unlike epoxy-amine crosslinking, cyanate ester homopolymerization releases no condensable volatile by-products; the reaction enthalpy is approximately 100–120 kJ mol−1 per cyanate group. Cured networks exhibit glass transition temperatures from 250 °C to 400 °C when measured by dynamic mechanical analysis per ASTM E1640-18, with bisphenol A dicyanate at 289–310 °C and novolac grades exceeding 350 °C.
Typical cured-state specifications include density 1.16–1.35 g/cm³ per ISO 1183-1:2019, tensile modulus 2.8–3.5 GPa per ASTM D638-14, dielectric constant 2.6–3.1 at 1 MHz per ASTM D150-18, dissipation factor 0.002–0.008 at 1 MHz, and 24 h moisture absorption 0.6–1.3% per ASTM D570-22. The low dielectric constant and dissipation factor differentiate CE from epoxy and bismaleimide matrices in microwave and millimeter-wave hardware. Primary uses include quartz-fiber radomes, low-loss printed circuit board laminates, satellite antenna feed components, electronic packaging, and structural composites demanding hot-wet mechanical retention.
The industrial grade selection is governed by viscosity and final service temperature. Primaset BA-230 and AroCy B-10 are bisphenol A dicyanate semi-solids used in prepreg where tack and B-stage latitude are required. Primaset LECy is a bisphenol E dicyanate liquid with room-temperature viscosity near 0.25 Pa·s; it is specified for resin transfer molding and filament winding because of its low injection viscosity. Primaset PT-30 is a phenol novolac cyanate ester solid with higher aromatic content; it is selected when glass transition temperatures above 350 °C are required. The higher melt viscosity of Primaset PT-30 restricts its use in low-pressure infusion and requires hot-melt coating or solvent processing.
Epoxy networks evaluated by ASTM D150-18 at 1 MHz typically present dielectric constants of 3.5–4.5 and dissipation factors of 0.018–0.030. Bismaleimide systems, although resistant to thermal oxidation, show dielectric constants of 3.2–4.0 and dissipation factors of 0.008–0.020. CE resins reduce the dielectric constant to 2.6–3.1 and dissipation factor to 0.002–0.008 because the triazine ring network has a low concentration of polar hydroxyl groups. Moisture uptake values differ in the same direction: CE absorbs 0.6–1.3% after 24 h water immersion per ASTM D570-22, while many epoxies absorb 1.5–4.0% and bismaleimides 2.0–4.5%. The comparative dataset is summarized below.
| Property | Test standard | Cyanate ester | Epoxy | Bismaleimide |
|---|---|---|---|---|
| Glass transition temperature by DMA tan δ | ASTM E1640-18 | 250–400 °C | 120–220 °C | 220–320 °C |
| Dielectric constant at 1 MHz | ASTM D150-18 | 2.6–3.1 | 3.5–4.5 | 3.2–4.0 |
| Dissipation factor at 1 MHz | ASTM D150-18 | 0.002–0.008 | 0.018–0.030 | 0.008–0.020 |
| Moisture absorption after 24 h water immersion | ASTM D570-22 | 0.6–1.3% | 1.5–4.0% | 2.0–4.5% |
| Tensile modulus | ASTM D638-14 | 2.8–3.5 GPa | 2.4–3.2 GPa | 3.0–4.0 GPa |
| Thermal decomposition onset in nitrogen | ASTM E1131-20 | 400–450 °C | 320–380 °C | 400–450 °C |
Processing differences are equally significant. CE gelation occurs under organometallic catalysis without amine hardeners; primary or secondary amines should not be substituted for epoxy-type curatives because they can form imidocarbonates and trigger premature exotherm. Bismaleimide typically requires cure at 180–230 °C and postcure above 250 °C, whereas catalyzed bisphenol A dicyanate laminates can be staged and cured with a 177 °C gel plateau followed by 200–250 °C postcure. CE exhibits lower fracture toughness than toughened epoxy and is often modified with thermoplastic or rubber for structural applications with high impact requirements. Compared with benzoxazine, CE generally provides higher attainable glass transition temperature but narrower processing latitude and higher monomer cost.
For prepreg manufacturing, the processing window is narrow. Bisphenol A dicyanate is usually impregnated at 80–100 °C as a low-viscosity melt or from solution, with B-staging conducted in a forced-air treater at 150–175 °C for 45–90 s and chilled compaction rolls held at 10–15 °C. The target volatile content after B-staging is ≤1.0%. If B-stage temperature exceeds 180 °C or dwell time exceeds 120 s, the resin can advance beyond the tack window and produce dry prepreg or non-conforming laminate consolidation. Conversely, under-staged prepreg may flow excessively under autoclave pressure and carry fiber wash. The B-stage oven is therefore controlled to ±5 °C on the web surface, with continuous infrared thermography or multiple contact thermocouples. B-stage advancement can be monitored by residual cyanate absorbance at 2270 cm−1 in infrared spectra; prepreg is typically staged to 10–25% conversion.
Resin transfer molding grades based on bisphenol E dicyanate are degassed at 80–100 °C under residual pressure ≤10 mbar before injection. Tooling is preheated to 90–120 °C, and injection pressures are maintained between 0.2 MPa and 0.7 MPa depending on fabric architecture. The catalyzed resin at 120 °C typically provides a useful injection window of 60–120 min before complex viscosity exceeds 1.0 Pa·s. In thick sections above 12 mm, the cyclotrimerization exotherm can elevate the centreline temperature 15–35 °C above the autoclave set point. Autoclave cure schedules therefore include an intermediate dwell at 150–160 °C for 60–90 min to allow heat dissipation before the 177 °C gel plateau is engaged.
Chemorheology measurements on a parallel-plate rheometer at 177 °C show minimum complex viscosity of catalyzed bisphenol A dicyanate near 0.1–0.5 Pa·s, followed by gelation at the storage/loss modulus crossover after 15–45 min. The gel-point conversion measured by differential scanning calorimetry is 45–60%, after which flow ceases. For novolac cyanate ester, gelation at 177 °C occurs earlier, typically 10–30 min, because of higher functionality. Autoclave pressure must be applied before gelation; after gelation, additional pressure cannot close voids. Postcure is not optional for space and electrical applications. Omission of the final 200–250 °C postcure can leave residual cyanate functional groups and depress the glass transition temperature by 30–60 °C. Postcure cycles are ramped at 0.5–1.0 °C/min through the polymerization exotherm to prevent under-cured core gradients. Laminates above 6 mm thickness are held at 250 °C for 4–8 h; thin laminates may be postcured for 2–4 h.
Moisture management is a critical threshold because liquid water has a dielectric constant near 80. A fully cured CE laminate exposed to 50 °C/95% RH typically reaches equilibrium moisture content of 0.8–1.6%, depending on resin content and fiber type. The corresponding increase in measured dielectric constant at 1 MHz per ASTM D150-18 is generally 0.08–0.15. Pre-drying is therefore required for radomes and antenna windows before electrical test or deployment. Drying cycles at 60–80 °C for 4–8 h under air with dew point ≤−30 °C are used when prepreg or cured laminates have been exposed to relative humidity above 60%. Plasticization by absorbed moisture can also depress the wet glass transition temperature by 20–40 °C compared with dry values.
Space-facing hardware requires outgassing compliance. Fully postcured CE laminates are commonly tested per ASTM E595-15; published data for specific quartz/CE constructions is limited, but qualified systems typically record total mass loss below 1.0% and collected volatile condensable material below 0.1%. Values are dependent on postcure completeness, surface contamination, and handling. CE systems with organometallic catalysts and alkylphenol co-catalysts can pass these thresholds when the final postcure exceeds 230 °C; lower postcure temperatures may leave catalyst fragments and unreacted monomer that elevate outgassing. Catalyst packages are typically transition metal acetylacetonates or naphthenates at 0.05–0.20 phr combined with an alkylphenol co-catalyst at 2–8 phr.
Thermal oxidative stability of CE is sufficient for continuous service up to 200–230 °C in air for bisphenol A dicyanate and up to 250 °C for novolac grades; bismaleimide can be selected for continuous service above 230 °C but carries higher dielectric loss. Thermogravimetric analysis per ASTM E1131-20 records decomposition onset at 400–450 °C in nitrogen, providing margin for lead-free soldering at 260–288 °C.
Printed circuit board and electronic packaging applications use CE laminates for halogen-free high-frequency layers where lead-free solder processing requires short-term exposure to 260–288 °C. Formulations can be modified with phosphorus-based flame retardants to meet UL 94 V-0 at 1.5–1.6 mm. Dielectric constant and dissipation factor are measured by ASTM D150-18; board shops require dimensional stability after thermal stress per IPC-TM-650 2.4.24.1. Lower moisture absorption relative to epoxy reduces pad cratering and improves through-hole reliability in thermal cycling from −55 °C to 125 °C.
Storage conditions define the operational boundary. Neat catalyzed cyanate ester resins are stored below −18 °C in sealed containers and allowed to equilibrate to 20–25 °C before opening to prevent condensation. Sealed catalyzed resin stored below −18 °C typically retains specification viscosity and gel time for 12 months. B-staged prepreg is stored below 5 °C and has an outlife at 20–25 °C/50% RH of 5–10 days. Once exposed beyond the outlife, tack and flow characteristics degrade, and the material should not be re-cooled to extend handling. In production environments above 60% RH, pre-drying and controlled layup rooms are mandatory because absorbed moisture accelerates carbamate hydrolysis and can reduce final laminate density. Amine-based additive packages from epoxy processing lines must be kept segregated; even trace contamination can change gelation kinetics and dielectric properties.
