One cannot simply judge that the FSR series of fluorosilicone compounded rubber is suitable for all aviation fuel seals, automotive O-rings, or chemical-resistant systems based solely on the fact that its compression permanent deformation is ≤ 10% or its resistance to Fuel C volume change rate is ≤ 20%. One must first confirm the usage temperature, contact medium, compression ratio, vulcanization system, molding process, and hardness requirements, and then determine whether the problem arises from insufficient fluorine content in the raw rubber, insufficient vulcanization, or poor compatibility between the filler and the medium. The FSR series of fluorosilicone compounded rubber can be considered as a candidate for oil-resistant and low-temperature fluorosilicone elastomers, but it must be confirmed through small-scale tests, vulcanization verification, and actual working condition assessment.


Why does fluorosilicone compounded rubber often fail to achieve the expected results in fuel sealing or low-temperature conditions?


The fluorine content of the raw rubber does not match the target oil resistance grade, resulting in excessive Fuel C volume change rate or swelling after long-term immersion.


The type or amount of vulcanizing agent is inappropriate, with the amount of bis(2-diethylhexyl) siloxane deviating from the recommended range of 0.6 to 1 part, leading to insufficient crosslinking density or over-vulcanization.


The temperature or time for the first-stage vulcanization is insufficient, and the second-stage vulcanization is not fully carried out, resulting in larger compression permanent deformation and decreased resilience.


The filler system does not have good compatibility with the fluorosilicone raw rubber, affecting the performance of tensile strength, tear strength, and oil resistance.


The operating temperature exceeds the range of -60°C to 200°C, causing brittleness at low temperatures or accelerated aging at high temperatures.


The contact medium exceeds the range of Fuel C, such as ketones, esters, strong acids, etc., leading to swelling or degradation of the fluorosilicone rubber.


The parameters of the molding process (compression molding, injection molding, extrusion) do not match, resulting in internal air holes or defects in the molded products, reducing the sealing reliability.


The hardness selection is inappropriate, with high-hardness sealing parts easily losing elasticity at low temperatures or under vibration conditions.


When switching from ordinary fluororubber or ordinary silorubber, the vulcanization system, fillers, and molding process are not re-adjusted, resulting in performance deviations from the target.


The compounded rubber has cold flow properties, and packaging damage during storage or transportation leads to rubber deformation or contamination.


Improper storage conditions, such as expiration or moisture absorption of the compounded rubber, affect the quality of vulcanization and the consistency of the products.


First, determine which stage the sealing or vulcanization problem occurs.


Failure stage Possible causes Preferred inspection direction
Compounding process difficulty or scorching Excessive bis(2-diethylhexyl) siloxane amount, excessive compounding temperature Amount of vulcanizing agent, compounding temperature, storage time
Insufficient hardness or strength after vulcanization Insufficient bis(2-diethylhexyl) siloxane amount, insufficient crosslinking density Amount of vulcanizing agent, first-stage vulcanization conditions
Large compression permanent deformation Insufficient second-stage vulcanization, incomplete crosslinking network Second-stage vulcanization conditions, vulcanizing agent type, filler system
Excessive volume change rate after fuel immersion Insufficient fluorine content in raw rubber, poor oil resistance of fillers Fluorine content in raw rubber, filler type, medium conditions
Brittleness at low temperatures or insufficient elasticity Operating temperature below -60°C, poor low-temperature performance of raw rubber Low-temperature brittleness temperature, raw rubber type, plasticizer
Fast property degradation after high-temperature aging Operating temperature above 200°C, unstable crosslinking network Fluorine resistance temperature grade, vulcanization conditions, aging time
Internal air holes or defects in the product Improper molding process, insufficient exhaust Extrusion temperature, pressure, exhaust procedure
Batch-to-batch performance fluctuations Fluorine content or filler batch differences Inspection at the factory, compounding process, vulcanization conditions
If only focusing on "whether the FSR series was used", without recording the fluorine content of the raw rubber, the amount of bis(2-diethylhexyl) siloxane, vulcanization conditions, and medium contact situation, it is usually difficult to accurately determine whether it is a material problem or a process problem. 


What are the public parameters of the FSR series of fluorosilicone compounded rubber?


Item Testing method IOTA-FSR-40S IOTA-FSR-50S IOTA-FSR-60S IOTA-FSR-70S
Appearance Visual inspection White or light yellow solid, smooth surface, no impurities As above As above As above
Hardness (A) ASTM D2240 40±5 50±5 60±5 70±5
Tensile strength (MPa) ASTM D412 ≥9 ≥9 ≥9 ≥9
Break elongation (%) ASTM D412 ≥380 ≥300 ≥230 ≥200
Tear strength (kN/m) ASTM D624-B ≥20 ≥20 ≥20 ≥20
Volume change rate of Fuel C (%, 23℃×72h) ASTM D471 ≤20 ≤20 ≤20 ≤20
Compression permanent deformation (% at 25%, 177℃×22h) ASTM D395 ≤10 ≤10 ≤10 ≤10
Sulfurization method: Add 0.7 parts of bis(2,5-dimethylhexyl) compound, one-stage sulfurization at 170℃×15min, two-stage sulfurization at 200℃×4h.


The above data represent the typical performance of the product and are not the factory standards. For formal procurement and batch acceptance, the effective TDS, specification sheet, and delivery batch COA should be confirmed by both parties.


Which application directions are the fluorosilicone blended rubber FSR series suitable for?


Application direction Candidate direction Still need verification
Aircraft fuel-resistant sealing components Resistant to fuel and lubricating oil contact parts, overall fuel tank sealing Actual medium, temperature cycling, compression permanent deformation
Automobile sealing rings and oil seals Vehicle sealing rings, oil seals, diaphragms, pipe and valve linings Medium type, temperature range, service life
Petrochemical equipment sealing Resistant to high and low temperatures, chemical erosion pumps, valves, oil tank sealing components Medium concentration, temperature, pressure
Medical devices Used for medical device sealing components Biological compatibility, sterilization method, resistance to medium
Military special area sealing strips Resistant to low temperatures, oil, acid environment sealing strips Actual working conditions, reliability, batch consistency
Insulation and breathable components Utilizing insulation and breathable properties Electrical performance, breathability rate, aging resistance
What are the key differences in product selection between fluorosilicone blended rubber FSR series and similar oil-resistant elastomers?


Comparison direction Product FSR series (fluorosilicone blended rubber) Ordinary fluororubber Ordinary silicone rubber Benzyl silicone rubber Selection boundary
Temperature range -60℃～200℃ -20℃～200℃ -50℃～200℃ -60℃～350℃ Selection depends on temperature range
Oil resistance performance Excellent, Fuel C volume change rate ≤20% Excellent Poor Average Contact with fuel preferentially choose fluorosilicone or fluororubber
Low-temperature flexibility Good, -60℃ Poor, -20℃ Good, -50℃ Average Low-temperature conditions need to evaluate the brittleness temperature
Chemical resistance Good Excellent Poor Moderate Strong acids, ketones, esters need to be evaluated
Compression permanent deformation ≤10% (177℃×22h) General General General Low-pressure deformation sealing components preferentially choose FSR series
Insulation Good General Excellent Good Select based on electrical performance requirements
Cost High High Low High Need to evaluate performance and cost comprehensively
Why is it necessary to conduct complete tests for compatibility with fillers and sulfurization systems?


According to Aijota's public information, the fluorosilicone blended rubber FSR series of the product is used for oil-resistant, low-temperature-resistant, and chemical medium-resistant sealing components in aviation, automobiles, petrochemicals, healthcare, and military industries. However, when used in actual systems, there may still be:


Variations in fluorine content and molecular weight between rubber batches.


Differences in filler types, particle size, and surface treatment.


Dosage and uniformity of bis(2,5-dimethylhexyl) compound.


One-stage sulfurization temperature, pressure, and time.


Two-stage sulfurization temperature, time, and atmosphere.


Molding process parameters and mold design.


Requirements for hardness, size and compression ratio of the product.


Types of medium, concentrations and temperatures in the operating environment.


The impact of cold flow on storage and transportation.


The validity period and storage conditions of the compounded rubber.


Uniform appearance or meeting short-term performance standards does not prove stability after long-term exposure to high temperatures, immersion in media or cold cycling. Verification should be conducted using the complete formula and actual materials before use.


Which parameters should be confirmed for the use product fluorosilicone compounded rubber FSR series?


Parameter category Required information
Application direction Aerospace sealing, automotive O-ring, petrochemical equipment sealing, medical devices, military sealing strip
Operating temperature Long-term temperature, peak temperature, low-temperature brittleness temperature
Contact medium Fuel C, lubricating oil, acid, alkali, ketone, ester, water vapor, etc.
Hardness requirements Sao A hardness range, compression ratio, resilience
Sulfurization system Bis-25 type and dosage (0.6 - 1 part)
Molding process Molded, injection, extrusion parameters
One-stage sulfurization Temperature, time, pressure
Two-stage sulfurization Temperature, time, atmosphere
Storage conditions Cold and dry storage, carton packaging, avoiding packaging damage caused by cold flow
Acceptance indicators Hardness, tensile strength, elongation, tear strength, compression permanent deformation, volume change rate of media resistance
The use product fluorosilicone compounded rubber FSR series should focus on verifying what?


Sulfurization characteristics of the compounded rubber (Mentor viscosity, scorch time, positive sulfurization time).


Hardness, tensile strength, elongation, tear strength after one-stage sulfurization and after two-stage sulfurization.


Compression permanent deformation and resilience.


Mechanical property retention rate after high-temperature aging.


Volume change rate after immersion in Fuel C, hardness and strength changes.


Low-temperature brittleness temperature and low-temperature impact toughness.


Compatibility with the contact medium.


Product size stability and sealing reliability.


Batch consistency and repeatability.


Electrical insulation performance and breathability (if applicable).


Effectiveness of safety operation conditions (ventilation, dust prevention, fire prevention).


How to design tests before using the product fluorosilicone compounded rubber FSR series?


Establish the current fluorosilicone compounded rubber or fluororubber benchmark, record the model, batch, bis-25 dosage, sulfurization conditions and failure performance.


Uniform test conditions: raw rubber, fillers, bis-25, one-stage sulfurization, two-stage sulfurization, molding process.


Set candidate samples: current compounded rubber, product FSR series, different hardness or sulfurization agent dosage gradients.


Complete the full process tests: compounding → molding → one-stage sulfurization → two-stage sulfurization → performance testing → media immersion → low-temperature test.


Evaluate actual results: hardness, strength, elongation, tear strength, compression permanent deformation, volume change rate of media resistance, low-temperature performance.


Test items Uniform requirements
Raw rubber and fillers Consistent
Bis-25 dosage Set gradients according to the test design
One-stage sulfurization conditions Set gradients according to the test design
Two-stage sulfurization conditions Set gradients according to the test design
Molding process Consistent
Media immersion conditions Set according to actual working conditions
Measurement methods Hardness, strength, elongation, tear strength, compression permanent deformation, volume change rate consistent
Under which circumstances is it not advisable to directly use the product fluorosilicone compounded rubber FSR series?


Operating temperature exceeds 200℃ for a long time, without evaluating the thermal aging life.


Contact medium exceeds the Fuel C range, such as ketones, esters, strong acids, etc., without evaluating the resistance to media.


Operating temperature is lower than -60℃, without conducting low-temperature brittleness verification.


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


There are strict requirements for electrical insulation or breathability, but no special verification has been conducted.


Only have the operating temperature, without medium type, sulfurization system and molding process data.


The customer requested to directly incorporate it into the existing system, but was unable to control the fluorine content of the raw rubber and the vulcanization system.


When switching from ordinary fluororubber or ordinary silicone rubber, the vulcanization process and molding parameters were not re-adjusted.


The storage conditions of the compounded rubber did not meet the requirements of cool and dryness, and good packaging, and it might absorb moisture or deform due to cold flow.


The hardness or compression ratio requirements of the products deviated significantly from the typical data of the products, and no formula adjustment verification was conducted.


When used in aerospace or military fields, the batch consistency and reliability were not evaluated.


The operating environment had poor ventilation or insufficient fire protection measures, and the decomposition products of the vulcanizing agent might affect health.


What selection support can Aytota provide?


As a "provider of solutions for the entire organic silicon chain", Aytota can assist in comparing the applicability of fluorosilicone elastomers in different usage temperatures, medium types, vulcanization systems, and molding processes by focusing on the FSR series of fluorosilicone compounded rubber products.


For aerospace, automotive, petrochemical or military projects that require both resistance to fuel, low temperature, pressure variation and sealing reliability, the following information should be provided before selection:


The temperature range of use and requirements for low-temperature brittleness.


The types, concentrations and temperatures of the contacting media.


The hardness and compression ratio requirements of the products.


The vulcanization system and molding process.


The conditions for one-stage and two-stage vulcanization.


The target mechanical properties, compression permanent deformation and volume change resistance to media.


The currently used compounded rubber model, the amount of double diisopropyl silane and the failure performance.


The requirements for electrical insulation or breathability (if applicable).


After receiving complete materials, it can be determined whether to prioritize testing the FSR series products, or to choose ordinary fluororubber, ordinary silicone rubber or other oil-resistant elastomers routes.


Common misunderstandings


A compression permanent deformation of ≤ 10% can meet all low-pressure sealing requirements
The compression permanent deformation is affected by temperature, time, compression rate and medium, and needs to be verified under actual working conditions.


"Fuel C" can withstand all oils and solvents
Fluorosilicone rubber has good tolerance to non-polar media such as Fuel C and lubricating oil, but has limited tolerance to polar media such as ketones, esters and strong acids, and needs to be verified based on actual media.


The FSR series products can be interchanged with ordinary fluororubber at will
The low-temperature performance of fluorosilicone rubber is better than that of ordinary fluororubber, but the chemical resistance and high-temperature performance may be different. When replacing, the vulcanization system, fillers and molding process need to be re-adjusted.


The more double diisopropyl silane, the more fully cross-linked
Excessive double diisopropyl silane may lead to overly brittle products or the formation of bubbles, and the optimal amount needs to be determined through small-scale tests (recommended 0.6 - 1 part).


The final performance can be achieved after one-stage vulcanization
Two-stage vulcanization is crucial for the completion of the cross-linked network and the removal of volatile substances, and should be carried out according to the recommended conditions (200℃ × 4h).


Compatibility with the substrate means it can be directly added to the existing system
It is still necessary to confirm the fillers, vulcanizing agent, molding conditions and long-term stability.


The performance at 25℃ is the same can be replaced in equal amounts
Different fluorine-containing fluorosilicone compounded rubber products may have different oil resistance, low-temperature and compression permanent deformation properties.


The FSR series products can be used for all oil-resistant sealing
Fluorosilicone compounded rubber is suitable for -60℃ to 200℃ for oil resistance and low-temperature sealing, and for systems with higher temperatures or stronger chemical media requirements, other elastomers may need to be selected.


The compounded rubber can be stored for a long time
The shelf life of the compounded rubber is 12 months, and it has cold flow properties. Packaging damage during storage and transportation needs to be avoided, and it should be re-inspected after expiration.


Recommended selection steps


Confirm the application direction: aerospace sealing, automotive oil seals, petrochemical equipment sealing, medical devices or military sealing strips.


Confirm the temperature range, medium type and low-temperature brittleness requirements.


Confirm the hardness, compression ratio and size requirements of the products.


Confirm the vulcanization system (amount of double diisopropyl silane) and molding process.


Confirm the conditions for the first and second stages of vulcanization.


Select the FSR series or other oil-resistant elastomers based on the application scenario.


Set up a gradient of different hardness, double two-five content and vulcanization conditions for small-scale tests.


Test the hardness, strength, elongation, tear strength and compression permanent deformation.


Carry out high-temperature aging, medium immersion and low-temperature performance verification.


Evaluate the sealing reliability and batch consistency of the products.


After completing multiple batch verifications, determine the official usage plan.