One cannot simply rely on the fact that product H21000 has a temperature resistance of 1000-1100°C or a bonding strength greater than 8 MPa at room temperature to directly conclude that it is suitable for all metal, ceramic or composite material bonding and sealing systems. One must first confirm the type of substrate, surface treatment, the ratio of the two components and the homogeneity of the mixture, the thickness of the adhesive layer, the curing temperature curve, the operating temperature and atmosphere, the thermal cycling conditions, and the sealing structure before making a judgment. Then, determine whether the problem is caused by poor interface wetting, uneven mixing, incomplete curing, high-temperature shrinkage, oxidation, or adhesive layer defects, or due to an unsuitable match between the substrate and the working conditions. Product H21000 can be considered as a candidate for silicon-nitrogen-based high-temperature adhesive, but it must be verified through small-scale tests, bonding strength tests, and actual high-temperature working conditions.


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


The substrate surface 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 metals, ceramics, or composite materials.


The ratio of the two components is inaccurate or the mixture is not uniform, resulting in incomplete curing in some areas, insufficient crosslinking density, or inconsistent ceramic behavior at high temperatures.


The viscosity of the adhesive is in the range of 1000-3000 cp, and the coating amount or thickness is improperly controlled. When it is too thick, there is excessive high-temperature shrinkage and thermal mismatch, and when it is too thin, there is insufficient filling.


The curing was not carried out according to the furnace heating to 170°C, curing for 2 hours, and furnace cooling, resulting in incomplete curing or the generation of internal stress.


The operating temperature exceeds 1000-1100°C, or it undergoes repeated expansion and contraction in high-temperature cycles, causing micro cracks in the adhesive layer and their gradual expansion.


The high-temperature atmosphere is not controlled properly, such as oxidation of the adhesive layer or the substrate in an oxidative atmosphere, resulting in a decrease in interface strength.


When switching from phosphate-based adhesives, organic silicon adhesives, borosilicon-nitrogen or polycarbon-silane adhesives, the surface treatment, ratio, thickness of the adhesive layer, and curing curve were not re-adjusted, resulting in a deviation from the target strength.


The sealing structure is subjected to pressure, shear, and thermal cycling simultaneously, and only a single tensile-shear strength data was selected without verifying the actual sealing conditions.


The opening of the product or prolonged storage may result in ammonia gas leakage, poor ventilation affecting the operating environment, and may also mask changes in the adhesive material state.


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


The expiration period of the two-component mixture is not controlled properly, causing the adhesive to thicken or react prematurely, affecting the uniformity of coating and interface bonding.


The understanding of data with a tensile-shear strength of 1000°C greater than 1 MPa is insufficient. The strength is already low at high temperatures, and it was not designed according to the actual load and safety factor.


First, determine which stage the high-temperature bonding or sealing problem occurs.


Failure stage Possible causes Preferred inspection direction
The adhesive layer does not wet or has local lack of adhesive after coating Unclean substrate, high viscosity of the adhesive, improper coating amount Surface treatment, adhesive viscosity, coating amount
The adhesive layer thickens after mixing or the expiration period is insufficient Improper ratio of the two components, prolonged storage after mixing Accuracy of ratio, mixing uniformity, expiration period
The room temperature bonding strength is insufficient after curing Deviation of the curing curve, thick adhesive layer, interface contamination Temperature curve, adhesive layer thickness, substrate treatment
The 600°C tensile-shear strength is lower than 2 MPa Incomplete curing, thermal mismatch, adhesive layer defect Curing quality, thermal expansion matching, adhesive layer uniformity
The 1000°C tensile-shear strength is lower than 1 MPa High-temperature shrinkage, oxidation, micro-crack expansion Operating 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 Discontinuous adhesive layer, pores, interface detachment Coating process, curing curve, sealing structure
After opening the cover, the ammonia smell is obvious or the rubber material becomes thicker. Improper storage conditions, long-term storage, and poor sealing. Storage temperature, container sealing, and usage period.
Variations in strength between batches or during curing. Discrepancies in two-component batches, unstable ratios or coating. Inspection upon entry, ratio records, and curing curve records.
If only focusing on "whether product H21000 was used" without recording substrate treatment, ratios of the two components, 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.


Why is merely increasing the curing temperature or adding the rubber layer thickness not necessarily effective?


Product H21000 plays a role as a high-temperature resistant adhesive in the bonding system. It is influenced by the substrate, ratio, 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, expired or unevenly mixed rubber materials.


Increasing the rubber layer thickness may improve the filling capacity, but too thick will increase high-temperature shrinkage and thermal mismatch, reducing tensile 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 ratio of the two components deviates or the mixture is uneven, only adjusting the curing curve cannot restore the crosslink density and high-temperature strength.


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


When the product has expired or the rubber material's activity has decreased, only adjusting the process cannot restore the original performance.


If the coating is applied beyond the applicable period after mixing, only adjusting the curing conditions cannot restore fluidity and interface wetting.


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


What are the differences in product selection between H21000 and H11500, H21500 and similar high-temperature adhesive schemes?


Comparison direction Product H21000 (silazane type) Product H11500 (borosilazane type) Product H21500 (polycarbon silane type) Phosphate-based adhesive Organic silicon adhesive Selection boundary
Temperature range Marked as 1000-1100℃ Marked as 1300-1500℃ Marked as greater than 1500℃ Reach above 1000℃ Usually 200-400℃ For ultra-high temperature applications, select according to actual temperature
Number of components Two-component Single-component Two-component Usually single-component or dual-component Single-component or dual-component Dual-component requires control of ratio and applicable period
Appearance Grey-black Grey Grey Varies by product Varies by product Choose based on coating process
Viscosity 1000-3000 cp 3000-4000 cp 3000-4000 cp Varies by product Varies by product Choose based on coating requirements
Curing temperature Heating to 170℃×2h in furnace Heating to 170℃×2h in furnace 220℃×2h Medium-high temperature curing At room temperature or heating Select according to substrate's high-temperature resistance and production line
Room temperature bonding strength Greater than 8MPa Greater than 5MPa Greater than 10MPa Varies by product Generally Select according to load requirements
600℃ tensile shear strength Greater than 2MPa 400℃ shear greater than 8MPa 500℃ shear greater than 15MPa High-temperature strength is better High-temperature strength is limited Compare according to temperature nodes
1000℃ tensile shear strength > 1 MPa 1000℃ compressive shear > 8 MPa 900℃ compressive shear > 15 MPa Varies by product Not applicable Select according to actual high-temperature load
Solvent-free Yes Yes Yes Usually water-based or solvent-based Varies by product Solvent-free requirement takes precedence for this product
Ammonia emission Ammonia may leak when the lid is opened or left for a long time Ammonia may leak Not specially marked Generally no Generally no Ventilation operation is required
Storage conditions Shaded and dry, with a shelf life of 1 year Shaded and dry, with a shelf life of 1 year Shaded and dry, with a shelf life of 1 year Varies by product Varies by product Manage according to storage conditions
Parameters that need to be confirmed when using product H21000?


Parameter category Information to be confirmed
Application direction Metal bonding, ceramic bonding, composite material bonding, sealing, high-temperature resistant coating
Base material type Metal, ceramic, composite material and surface condition
Surface treatment Cleaning method, degreasing, oxide removal, drying degree
Two-component mixing ratio Confirm the ratio according to the effective TDS, measurement accuracy and mixture uniformity
Gelatin applicability period Usable time after mixing, viscosity change and coating window
Coating process Gelatin application volume, gelatin layer thickness, uniformity, whether multiple coatings are required
Curing curve Heating to 170℃ in the furnace, curing for 2 hours, cooling in the furnace
Operating temperature Long-term temperature, peak temperature, exposure conditions of 1000-1100℃
Operating atmosphere Air, inert gas, vacuum, oxidizing or reducing atmosphere
Thermal cycling Heating and cooling rate, number of cycles, high and low temperature holding time
Sealing structure Gap, pressure, load-bearing method, leakage requirements
Storage conditions Shaded and dry, with a shelf life of 1 year
Acceptance indicators Room temperature bonding strength, 600℃ and 1000℃ tensile shear strength, sealing performance, strength retention rate after thermal cycling
What should be primarily verified when using product H21000?


Two-component mixing ratio accuracy and mixture uniformity.


Applicability period of the mixed gelatin and coating window.


Wetting property of the base material surface treatment and continuity of the gelatin layer.


Whether the curing curve is executed as heating to 170℃ in the furnace, curing for 2 hours, and cooling in the furnace.


Room temperature bonding strength greater than 8 MPa.


Tensile shear strength at 600℃ greater than 2 MPa.


Tensile shear strength at 1000℃ greater than 1 MPa and assessment of safety factor.


Impact of gelatin layer thickness on tensile shear strength and thermal mismatch.


Strength retention rate and interface integrity after thermal cycling.


Effect of operating atmosphere on gelatin layer oxidation and sealing performance.


Consistency of bonding between metal, ceramic and composite materials.


Leakage rate and pressure holding capacity of the sealing structure.


How to design tests before using product H21000?


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


Uniform test conditions: base material, surface treatment, two-component mixing ratio, mixing method, gelatin layer thickness, curing curve, operating temperature, atmosphere and thermal cycling conditions.


Set candidate samples: current adhesive, product H21000, different gelatin layer thickness or curing curve gradients.


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


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


Test items Uniform requirements
Base material and surface treatment Keep consistent or set gradients according to test design
Two-component mixing ratio Confirm and maintain consistency according to effective TDS
Mixing method Set gradients according to test design
Layer thickness: Set gradient according to the test design.
Curing curve: Set gradient based on the reference of 170℃×2h.
Operating temperature: Set according to 600/1000℃.
Operating atmosphere: Set according to actual working conditions.
Thermal cycling conditions: Set according to the actual heating and cooling rate and the number of cycles.
Measurement method: The strength at room temperature, tensile shear strength, sealing performance, and the retention rate of strength after thermal cycling are consistent.
Which situations are not suitable for directly using product H21000?


If the substrate surface is not cleaned or there is oil stains, oxide layer, or release agent, it will affect the interface bonding.


The mixing ratio of the two groups cannot be accurately controlled according to the effective TDS or the mixture is not uniform.


After mixing, it cannot be coated and assembled within the applicable period.


The curing curve cannot be executed according to the furnace heating to 170℃, curing for 2 hours, and furnace cooling.


If the operating temperature exceeds 1000-1100℃ for a long time, the high-temperature creep and oxidation have not been evaluated.


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


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


Specific food contact, medical or airworthiness approval is required, but the corresponding data has not been obtained.


Only the operating temperature is known, but the substrate, mixing ratio, layer thickness, curing curve and atmosphere data are not available.


The customer requests to directly mix it into the in-use system, but the surface treatment, mixing ratio, coating and curing conditions cannot be controlled.


When switching from phosphate, organic silicon, borosilicon nitride or polycarbon silane adhesives, the process should not be re-adjusted.


Storage conditions do not meet the requirements of cool and dry, or the shelf life exceeds 1 year.


Poor ventilation in the operating environment, ammonia gas overflowing from the lid affects the health of the operators.


For the safety factor and load-bearing design of 1000℃ tensile shear strength greater than 1MPa, the assessment of the thermal stability at 1100℃ and the oxidation resistance of the adhesive layer and the substrate has not been made.


Our company can provide which selection support?


As a provider of the entire organic silicon chain, our company can assist in comparing the applicability of silicon azane adhesives in different substrates, mixing ratios, layer thicknesses, curing curves and high-temperature working conditions for product H21000.


For projects that need to balance the bonding and sealing of metals, ceramics 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 tensile shear strength at 600-1000℃.


Surface treatment method.


Mixing ratio, mixing method and applicable period requirements.


Layer thickness and coating process.


Curing curve and heating and 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 data, it can be determined whether to prioritize testing a certain mixing ratio, coating and curing scheme of product H21000, or to choose product H11500, product H21500 or other high-temperature adhesives route.


Common misunderstandings


It is possible to use adhesives with a temperature resistance of 1000-1100℃ for long-term operation at 1100℃ full load.
The 1000℃ tensile shear strength given in the data may continue to decrease at higher temperatures, and it should be evaluated according to actual load, safety factor and time, not just based on the upper limit of temperature resistance.


Two-component adhesives can be mixed randomly by proportion.
The mixing ratio of the two groups needs to be confirmed according to the effective TDS. Deviation in the mixing ratio or uneven mixing will lead to incomplete curing, decreased high-temperature strength, and require precise measurement and sufficient stirring.


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


The thicker the adhesive layer, the stronger the bonding.
Excessive thickening of the adhesive layer will increase high-temperature shrinkage and thermal mismatch, reducing tensile shear strength, and it is necessary to optimize the thickness according to the substrate and structure.


Compatibility with the substrate allows for direct gluing.
It is still necessary to confirm surface treatment, the ratio of the two components, the thickness of the adhesive layer, the curing curve, the usage atmosphere and the thermal cycling conditions.


Equal strength at 25°C allows for substitution in equal amounts.
The high-temperature strength, thermal mismatch, component number and curing behavior of different high-temperature adhesive materials vary. Revalidation is required when substituting.


Product H21000 can be used for all high-temperature bonding and sealing.
This product is suitable for bonding and sealing of metals, ceramics, composite materials, and high-temperature coatings. Special verification is required for systems subject to strong oxidation, high-pressure sealing or special industry approval requirements.


The ammonia smell can be ignored.
Ammonia may overflow when the product is opened or left for a long time. It should be used in a ventilated environment and protective measures should be taken.


It does not affect usage after being mixed and left for a period of time.