One cannot simply rely on the data of the product H11500 regarding its tensile strength at 1300-1500℃ or at a certain temperature to directly determine that it is suitable for all bonding and sealing systems involving graphite, metal, ceramic or composite materials. One should first confirm the type of substrate, surface treatment, layer thickness, curing temperature curve, operating temperature and atmosphere, thermal cycling conditions, sealing structure, and ammonia emission conditions, and then determine whether the problem is caused by poor interface wetting, incomplete curing, thermal expansion mismatch, high-temperature oxidation, or adhesive layer defects, or due to poor compatibility with the substrate and working conditions. Product H11500 can be considered as a candidate for borosilicon nitrogen-based high-temperature adhesives, but it must be verified through small-scale tests, bonding strength tests, and actual high-temperature working conditions.


1. Why does the strength of borosilicon nitrogen-based adhesives often decrease in high-temperature bonding or sealing?


The surface of the substrate is not cleaned or is contaminated with oil, release agents, oxide layers, or dust, which affects the wetting and interface bonding of the adhesive to graphite, metal, or ceramic.


The graphite material has a high porosity, and when the viscosity and coating amount of the adhesive do not match, the adhesive layer may over-penetrate or be locally deficient, forming a weak interface.


The curing temperature curve does not match the product requirements. If the curing temperature is not increased to 170℃, the adhesive is not cured for 2 hours, and then cooled in the furnace, it may result in incomplete curing or internal stress.


The thickness of the adhesive layer is not controlled properly. If it is too thick, the shrinkage and thermal mismatch at high temperatures increase, and if it is too thin, it may not be adequately filled. Both cases will reduce the tensile strength.


Using temperatures beyond the long-term tolerance range of the materials or undergoing high-temperature cycling repeatedly causes the adhesive layer to develop microcracks and gradually expand.


The improper control of the high-temperature atmosphere, such as in an oxidative atmosphere where graphite or the adhesive layer oxidizes, leads to a decrease in interface strength.


The product is a single-component borosilicon nitrogen-based adhesive. If left for a long time or opened, ammonia gas may escape, and poor ventilation will affect the operating environment and may mask changes in the adhesive material state.


Switching from phosphate-based adhesives, organic silicone adhesives, phenolic resins, or other high-temperature adhesives without adjusting the surface treatment, adhesive layer thickness, and curing curve leads to deviations in strength from the target.


The thermal expansion coefficients of metals, ceramics, or composites differ significantly from that of graphite. There is no buffer for thermal stress through adhesive layer thickness, transition layers, or structural design.


In the sealing structure, the adhesive layer is subjected to pressure, shear, and thermal cycling, and only the tensile strength data is selected without verifying the actual sealing conditions.


Storage conditions do not meet the requirements of a cool and dry environment or exceed the shelf life of 1 year, resulting in a decrease in adhesive material activity and fluctuations in curing quality and high-temperature strength.


The understanding of typical data of tensile strength at 1500℃ greater than 2MPa is insufficient. The strength already decreases at high temperatures, and it is not designed based on actual load and safety factors.


2. Determine which stage of high-temperature bonding or sealing the problem occurs


Failure stage Possible causes Preferred inspection direction
The adhesive layer does not wet or is locally deficient after coating Unclean substrate, porosity of graphite, high viscosity of adhesive Surface treatment, adhesive viscosity, coating amount
Insufficient room-temperature strength after curing Deviation of curing curve, thick adhesive layer, interface contamination Heating curve, adhesive layer thickness, substrate treatment
The tensile strength at 400-1000℃ is lower than expected Incomplete curing, thermal mismatch, adhesive layer defect Adhesive curing quality, thermal expansion matching, adhesive layer uniformity
The tensile strength at 1500℃ rapidly decreases High-temperature ceramicization shrinkage, oxidation, microcrack expansion Using atmosphere, thermal cycling, structural design
The adhesive layer cracks or detaches after thermal cycling Thermal expansion coefficient difference, thick adhesive layer, rapid heating Thermal expansion matching, adhesive layer thickness, heating and cooling rate
Leakage of the sealing structure Non-continuous adhesive layer, pores, interface detachment Coating process, curing curve, sealing structure
A strong ammonia smell or thickening of the adhesive after opening the lid Improper storage conditions, long-term storage, poor sealing Storage temperature, container sealing, shelf life
Variations in strength or curing behavior between batches Discrepancies in rubber batch, inaccurate measurement or coating Inspection upon entry, coating records, curing curve records
If only focusing on "whether product H11500 was used", without recording substrate treatment, rubber layer thickness, curing curve, usage atmosphere and thermal cycling conditions, it is usually difficult to accurately determine whether it is a material issue or a process issue.


III. Why is it not necessarily effective to only increase the curing temperature or increase the rubber layer thickness?


Product H11500 plays a role as a high-temperature ceramicizing adhesive in the bonding system. It is influenced by the substrate, rubber layer thickness, curing curve, usage temperature and atmosphere. Simply increasing the temperature or adding thickness may bring side effects.


Increasing the curing temperature may accelerate curing, but exceeding the recommended curve may lead to increased rubber layer shrinkage, internal stress concentration or substrate damage.


Extending the curing time may improve the curing degree, but it may affect production efficiency and is ineffective for contaminated or expired rubber materials.


Increasing the rubber layer thickness may enhance the filling capacity, but too thick will increase high-temperature shrinkage and thermal mismatch, reducing shear strength.


Reducing the rubber layer thickness may reduce thermal stress, but it may result in missing glue, pores or discontinuous sealing.


When the substrate surface is not cleaned, only adjusting the curing temperature or rubber layer thickness cannot solve the interface wetting and bonding problems.


When the graphite porosity is high, increasing the rubber quantity may cause excessive penetration of the rubber material and insufficient surface rubber layer.


When high-temperature oxidation or thermal cycling leads to microcracks, only increasing the curing temperature cannot restore the strength.


When the rubber material has deteriorated after storage or ammonia gas overflows, adjusting the process cannot restore the original performance.


Therefore, when optimizing, one should observe the substrate treatment, rubber viscosity, rubber layer thickness, curing curve, usage atmosphere and thermal cycling conditions simultaneously, rather than only adjusting a single parameter.


IV. What are the differences in product H11500's selection priorities compared to similar high-temperature adhesive solutions?


Comparison direction Product H11500 (boron-silicon-nitrogen type) Organic silicone adhesive Phosphate adhesive Phenolic resin adhesive Epoxy adhesive Selection boundary
Temperature range Marked as 1300-1500℃ Usually 200-400℃ Up to 1000℃ Usually 200-300℃ Usually 150-200℃ Prioritize boron-silicon-nitrogen or phosphate systems for ultra-high temperature applications
Curing temperature Medium-temperature curing, 170℃×2h Heating or room temperature High-temperature curing Heating curing Room temperature or heating Selected based on substrate's high-temperature resistance and production line
Curing time Short, furnace heating to 170℃×2h Varies by system Varies by system Longer Shorter Selected based on production rhythm
Graphite bonding >5MPa at room temperature, >8MPa at 400-1000℃, >2MPa at 1500℃ Limited high-temperature strength High-temperature strength better Highly prone to decomposition at high temperatures Insufficient high-temperature resistance Prioritize verification of this product for graphite high-temperature bonding
Metal/ceramic/composite materials Used for bonding and sealing Used Used Limited Used at medium-low temperatures Selected based on substrate and temperature
Solvent-free Yes Varies by product Usually water-based or solvent-based Contains solvent Varies by product Solvent-free requirements prioritize this product
Ammonia emission Ammonia may overflow when opening or left for a long time Generally no Generally no May release May release Ventilation operation required
Storage conditions Shaded and dry, with a shelf life of 1 year Varies by product Varies by product Varies by product Varies by product Manage according to storage conditions
V. What parameters should be confirmed when using product H11500?


Parameter category Information to be confirmed
Application direction Graphite bonding, metal bonding, ceramic bonding, composite material bonding, sealing, high-temperature coating
Substrate type Graphite, metal, ceramic, composite materials and surface condition
Surface treatment: Cleaning method, degreasing, removal of oxide layer, drying degree, pore treatment
Material state: Appearance gray, viscosity 3000-4000 cp, whether placed for a long time, ammonia gas situation after opening
Coating process: Coating amount, coating layer thickness, uniformity, whether multiple coatings are required
Curing curve: Furnace heating to 170℃, holding for 2 hours, furnace cooling
Operating temperature: Long-term temperature, peak temperature, 1500℃ short-term exposure condition
Operating atmosphere: Air, inert gas, vacuum, oxidation or reduction atmosphere
Thermal cycling: Heating and cooling rate, number of cycles, high and low temperature holding time
Sealing structure: Gap, pressure, loading method, leakage requirements
Storage conditions: Cool and dry place, sealed, shelf life 1 year
Acceptance indicators: Room temperature bonding strength, 400/800/1000/1500℃ shear strength, sealing performance, strength retention rate after thermal cycling
Six. What should be mainly verified when using product H11500?


Wetting property of the substrate surface after surface treatment and continuity of the coating layer.


Whether the curing curve is executed as 170℃×2 hours, and whether the furnace cooling is sufficient.


Whether the room temperature bonding strength is greater than 5 MPa.


Whether the 400℃, 800℃, 1000℃ shear strength is greater than 8 MPa.


Whether the 1500℃ shear strength is greater than 2 MPa and the safety factor is evaluated.


The influence of coating layer thickness on shear strength and thermal mismatch.


The strength retention rate and interface integrity after thermal cycling.


The impact of operating atmosphere on the oxidation of the coating layer, graphite oxidation and sealing performance.


The bonding consistency of different substrates such as graphite, metal, ceramic, and composite materials.


The leakage rate and pressure holding capacity of the sealing structure.


The influence of opening ammonia gas emission and ventilation conditions on the operation.


The consistency of coating viscosity, curing behavior and high-temperature strength among batches.


Seven. How to design tests before using product H11500?


Establish a current high-temperature adhesive benchmark, record model, surface treatment, coating layer thickness, curing curve and failure performance.


Uniform test conditions: substrate, surface treatment, coating layer thickness, curing curve, operating temperature, atmosphere and thermal cycling conditions.


Set candidate samples: current adhesive, product H11500, different coating layer thickness or curing curve gradients.


Complete the full process tests: surface treatment → coating → curing → room temperature strength → high-temperature shear strength → thermal cycling → sealing performance test.


Evaluate actual results: room temperature strength, shear strength at various temperatures, strength retention rate after thermal cycling, sealing performance.


Test items Uniform requirements
Substrate and surface treatment Keep consistent or set gradients according to the test design
Coating layer thickness Set gradients according to the test design
Curing curve Set gradients based on 170℃×2h benchmark
Operating temperature Set according to 400/800/1000/1500℃
Operating atmosphere Set according to actual working conditions
Thermal cycling conditions Set according to actual heating and cooling rate and cycle number
Measurement method Uniform room temperature strength, shear strength, sealing performance, strength retention rate after thermal cycling
Eight. Under which circumstances should product H11500 not be directly used?


The substrate surface is not cleaned or has oil stains, oxide layer, or release agent, which affects interface bonding.


The porosity of graphite has not been evaluated, and the coating viscosity and coating amount cannot be matched.


The curing curve cannot be executed as 170℃×2 hours or the furnace cooling conditions are not available.


The operating temperature exceeds 1300-1500℃ for a long time, and the high-temperature creep and oxidation have not been evaluated.


The operating atmosphere is highly oxidizing, and the antioxidant capacity of the coating layer and substrate has not been verified.


The sealing structure can withstand high pressure or strong vibration, and the actual sealing working condition verification has not been conducted.


Specific food contact, medical or airworthiness approval is required, but corresponding materials have not been obtained.


Only the temperature is mastered, without the substrate, the thickness of the adhesive layer, the curing curve and the atmosphere data.


The customer requests to directly mix it into the existing system, but cannot control the surface treatment, coating and curing conditions.


When switching from phosphate, organic silicon or other high-temperature resistant adhesives, the process has not been re-adjusted.


The storage conditions do not meet the requirements of cool and dry, sealed, or exceed the shelf life of 1 year.


The operating environment has poor ventilation, and ammonia gas escapes when the lid is opened, affecting the health of the operators.


The safety factor and load design for the 1500℃ shear strength greater than 2MPa have not been evaluated.


IX. What selection support can our company provide?


As a provider of the entire organic silicon value chain solutions, our company can assist in comparing the applicability of borosilicon nitrogen-based adhesives in different substrates, adhesive layer thickness, curing curves and high-temperature conditions for product H11500.


For projects that need to balance the bonding and sealing of graphite, metal, ceramic or composite materials, as well as the preparation of high-temperature coatings, before selection, the following information should be provided:


Application direction and substrate type.


Target room temperature bonding strength and shear strength at 400-1500℃.


Surface treatment method and graphite porosity.


Adhesive layer thickness and coating process.


Curing curve and furnace cooling conditions.


Operating temperature, atmosphere and thermal cycling requirements.


Sealing structure, pressure and leakage requirements.


Current adhesive model, process and failure performance.


Acceptance method and applicable standards.


After receiving complete materials, we can determine whether to prioritize testing a coating and curing scheme of product H11500 or choose the phosphate, organic silicon or other high-temperature resistant adhesive route.


X. Common Misconceptions


It is possible to use at 1500℃ continuously for a long time when the temperature is 1300-1500℃.
The data gives a shear strength greater than 2MPa at 1500℃, but the strength decreases under high temperature, and it should be evaluated based on actual load, safety factor and time, not just based on the upper limit of the temperature.


The higher the curing temperature, the higher the strength.
The curing should be carried out according to 170℃×2 hours and furnace cooling. Exceeding the recommended curve may cause shrinkage, internal stress and substrate damage.


The thicker the adhesive layer, the stronger the bonding.
An excessively thick adhesive layer will increase high-temperature shrinkage and thermal mismatch, reducing the shear strength, and the thickness should be optimized according to the substrate and structure.


A rough graphite surface will definitely stick well.
The porosity and surface contamination of graphite will affect the penetration of the adhesive and interface bonding, and it is necessary to clean and evaluate the coating amount.


Compatibility with the substrate means direct coating.
It is still necessary to confirm surface treatment, adhesive layer thickness, curing curve, operating atmosphere and thermal cycling conditions.


The same strength at 25℃ can be replaced quantitatively.
The high-temperature strength, thermal mismatch and curing behavior of different high-temperature adhesives are different, and replacement should be re-verified.


Product H11500 can be used for all high-temperature bonding and sealing.
This product is suitable for bonding and sealing of graphite, metal, ceramic, composite materials and high-temperature coatings, and for systems with special industry approval requirements, it needs to be specifically verified.


The ammonia smell can be ignored.
Opening the product or leaving it for a long time may have ammonia gas overflow, and it should be used in a ventilated environment and protected.


XI. Recommended Selection Steps


Confirm the application direction: graphite bonding, metal/ceramic/composite material bonding, sealing or high-temperature coating.


Confirm the substrate type, surface treatment and graphite porosity.


Confirm the adhesive state, viscosity and storage period.


Confirm the adhesive layer thickness and coating process.


Confirm the curing curve as furnace heating to 170℃, curing for 2 hours, and furnace cooling.


Confirm the operating temperature, atmosphere and thermal cycling conditions.


Select product H11500 or other high-temperature resistant adhesives based on the application scenario.


Carry out small tests with different adhesive layer thickness and curing curve gradients.


Test the room temperature bonding strength and the peel strength at 400/800/1000/1500℃.


Carry out thermal cycling, atmosphere and sealingity verification.


Evaluate the consistency of the rubber material state and high-temperature strength among batches.


Confirm that the ventilation, moisture-proof and storage conditions are in place.


After completing multiple batch and actual working condition verifications, determine the official usage plan.