One cannot simply judge that the fluorosilicone sealant FLSR4000 is suitable for all oil-based environmental sealing, flange sealing or the overall oil tank system of aircraft based solely on its oil resistance or surface drying time. One should first determine the type of substrate, the contact medium, the operating temperature, the curing type, the extrusion property, the bonding requirements and the construction conditions, and then compare the products FLSR4140 and FLSR4340. Product FLSR4000 can be considered as a candidate for oil-resistant fluorosilicone sealants, but it must be verified through small-scale tests, medium immersion and actual working conditions.


Why do fluorosilicone sealants often fail to achieve the expected results in oil-based environments or flange sealing?


The surface of the substrate is not cleaned or is contaminated with oil, release agents, or oxide layers, which affects the adhesion of the sealant to aluminum, steel, composite materials, etc.


The contact medium exceeds the verified range, such as ketones, esters, strong acids or high aromatic fuel, resulting in excessive volume change rate or adhesive failure.


The operating temperature exceeds the temperature resistance range, becoming brittle at low temperatures or accelerating aging at high temperatures, and reducing compression rebound.


The selection of deacetic acid type and deketoxime type is inappropriate, not matching the corrosiveness of the substrate, the surface drying speed and the deep curing requirements.


The extrusion property or viscosity does not match the construction process, resulting in incomplete filling of the joint and incomplete filling of the flange gap.


The surface drying time does not match the assembly window, drying too early affecting the adhesion and too slow affecting the production rhythm.


The bonding surface is not coated with primer or the primer does not match the sealant, resulting in insufficient peel strength.


The acetate or ketoxime by-products released during curing have adverse effects on sensitive substrates or electronic components.


The sealant is stored past its expiration date, the packaging is damaged or absorbs moisture, resulting in abnormal curing.


When switching from ordinary silicone sealant or fluororubber sealant, the surface treatment, primer and curing conditions are not adjusted, resulting in deviation from the target in bonding or oil resistance.


What are the public parameters of product FLSR4000?


Item Testing method Product FLSR4140 Product FLSR4340
Type — Deacetic acid type Deketoxime type
Color Visual inspection White Lacquered white
Viscosity (Pa·s, shear rate 10 s⁻¹) Q/371002WXH028-2016 188 226
Extrusion property (g/min) GB/T13477.3 126 90
Surface drying time (min) GB/T13477.5 5 8
Density (g/cm³, 23℃×50%×7d) ASTM D792 1.44 1.44
Hardness (Shore A) ASTM D2240 40 37
Tensile strength (MPa) ASTM D412 4.0 3.6
Tensile elongation (%) ASTM D412 292 425
Tear strength (kN/m) ASTM D624-B 10.6 11.2
Peel strength (aluminum, kN/m) GB/T15254 0.83 1.25
IRM903 (%, 150℃×168h) ASTM D471 1.5 1.8
Fuel F Diesel (%, 40℃×168h) ASTM D471 2.0 3.3
Fuel C (%, 60℃×168h) ASTM D471 18.6 20.5
FAM B (%, 60℃×168h) ASTM D471 26.5 27.0
Jet Fuel No.3 (%, 23℃×168h) ASTM D471 3.9 4.2
Packaging is in a net content of 300ml plastic barrel, and the unopened original packaging can be stored for six months. The above data are typical performance of the product and not as the factory standard. Formal procurement and batch acceptance should be based on the valid TDS, specification documents, and delivery batch COA confirmed by both parties.


How should the deacetic acid type and deketamine type be selected?


Operating conditions FLSR4140 candidate direction of the product FLSR4340 candidate direction of the product Still need verification
Surface drying speed priority Surface drying in 5 minutes, suitable for rapid assembly Surface drying in 8 minutes, suitable for slightly longer operation time Actual environmental temperature and humidity, extrusion time
Aluminum substrate bonding 剥离强度 0.83kN/m 剥离强度 1.25kN/m， aluminum bonding is better Undercoat， surface treatment， long-term immersion after剥离
High elongation requirement Elongation 292% Elongation 425% Compression rebound， tearing， low-temperature performance
Resistance to diesel and IRM903 Lower volume change rate Higher volume change rate Actual medium， temperature， time
Resistance to Fuel C and FAM B 18.6%/26.5% volume change rate 20.5%/27.0% volume change rate High aromatic fuel， long-term immersion
Electronic or sensitive substrate Deacetic acid type may corrode sensitive metals Deketamine type has relatively lower corrosiveness Substrate compatibility， impact of by-products
Overall aircraft fuel tank Need to verify resistance to Jet Fuel No.3 and bonding Need to verify resistance to Jet Fuel No.3 and bonding Adherence to airworthiness requirements， long-term oil resistance， low-temperature flexibility
Not only should the drying time be considered， as the extrusion properties， peel strength and elongation of the two models differ. The final selection depends on the substrate， medium， assembly window and bonding target.


What are the differences in product selection between FLSR4000 and ordinary silicone sealant or fluororubber sealant?


Comparison direction FLSR4000 (fluorosilicone sealant) Ordinary silicone sealant Fluororubber sealant Selection boundary
Oil resistance Excellent， low volume change rate for IRM903， diesel， Jet Fuel Poor Excellent Choose fluorosilicone or fluororubber in oil environments
Temperature range Fluororubber wide temperature range General Better Choose based on high and low temperature requirements
Low-temperature flexibility Good General Poor Choose fluorosilicone for low-temperature conditions
Adhesion Excellent for aluminum， steel and other substrates， requires undercoat cooperation General General Verify substrate and undercoat
Curing type Deacetic acid or deketamine， single-component room temperature curing Deacetic acid， dealcohol， deketamine Generally two-component Choose based on construction and substrate
By-products Acetic acid or butyronitrile Acetic acid， alcohol or nitrile Depending on the system Need to assess impact on sensitive substrates
Application Engine， transmission， oil tank， flange Construction， general sealing Sealing for strong chemical media Choose based on medium and temperature
Why is it still necessary to conduct complete tests for compatibility with substrates and media?


According to Aytota's public information， product FLSR4000 is used as an oil-resistant sealant and filler in oil environments for applications such as engines， transmissions， drive systems， braking systems， pipeline flanges and overall aircraft fuel tanks. However， when used in actual systems， there may be：


Differences in substrate type and surface treatment.


Types of undercoats and coating processes.


Types of contact media， concentrations and temperatures.


Assembly gap， compression rate and flange stiffness.


Construction environmental temperature and humidity.


Match between drying time and assembly window.


Depth of curing and by-product release.


Long-term immersion-induced volume change and bond retention rate.


Low-temperature cycling and high-temperature aging.


Storage conditions and packaging sealing.


Appearance uniformity or short-term no leakage， cannot prove stability after long-term oil immersion， thermal cycling or vibration. Before use， verification should be conducted using the complete formula and actual materials.


What parameters should be confirmed when using product FLSR4000?


Parameter category Information to be confirmed
Application direction: Engine, transmission, powertrain, braking system, pipe flange, aircraft integral fuel tank
Base material type: Aluminum, steel, stainless steel, composite material, coated surface
Surface treatment: Cleaning method, degreasing, sanding, primer application
Contact medium: IRM903, diesel, Fuel C, FAM B, Jet Fuel No.3, lubricating oil
Operating temperature: Long-term temperature, peak temperature, low-temperature embrittlement
Curing type: Acetic acid removal type or ketoxime removal type
Construction conditions: Temperature, humidity, extrudability, surface dry time, assembly window
Gap and compression: Flange gap, compression rate, sealing thickness
Storage conditions: Cool and dry, unopened, six months
Acceptance indicators: Peel strength, volume change rate, tensile strength, elongation, hardness, low-temperature flexibility
What should be verified for the product FLSR4000?


Surface drying time and extrudability.


Peel strength with aluminum and steel and other base materials.


Volume change rate in IRM903, diesel, Fuel C, FAM B, Jet Fuel No.3.


Hardness and strength retention after high-temperature aging.


Flexibility and sealing reliability at low temperatures.


Flange gap filling and compression rebound.


Impact on base materials and electronic components by by-products.


Adhesion retention rate after long-term immersion in oil.


Batch-to-batch consistency and repeatability.


Effectiveness of safety operation conditions (ventilation, eye protection).


How to design tests before using the product FLSR4000?


Establish a current sealant benchmark, record model, batch, surface treatment, primer application and failure performance.


Uniform test conditions: Base material, surface treatment, primer, gap, temperature, humidity, assembly time.


Set candidate samples: Current sealant, product FLSR4140, product FLSR4340.


Complete the full process tests: Surface treatment → coating → assembly → curing → medium immersion → performance testing.


Evaluate actual results: Peel strength, volume change rate, hardness, strength, elongation, low-temperature performance.


Test items Uniform requirements
Base material and surface treatment Consistent
Primer type According to test design
Coating amount and gap Consistent
Curing conditions Equal temperature, humidity, time
Immersion conditions According to actual working conditions
Measurement method Equal peel strength, volume change rate, hardness, strength, elongation, low-temperature performance
Under which circumstances should the product FLSR4000 not be directly used?


Base material surface not cleaned or not coated with primer, affecting adhesion.


Contact medium beyond the verification range, such as ketones, esters, strong acids.


Operating temperature beyond the applicable range of fluorosilicone sealants.


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


Base materials or electronic components sensitive to by-products such as acetic acid or butanone oxime, without compatibility verification.


Only knowing the medium type, without base material, gap and assembly conditions.


Customer requests to directly mix into the in-use system, but cannot control surface treatment and curing conditions.


When switching from ordinary silicone sealant, do not re-adjust primer and assembly process.


Storage conditions do not meet the requirements of cool and dry, unopened, sealant may expire or cure abnormally.


Poor ventilation in the operating environment, release of acetic acid or butanone oxime affects the health of operators.


Strictly demanding low-temperature flexibility, but no low-temperature sealing test after medium immersion.


Aydota can provide which selection support?


Aydota, as a "provider of the organic silicon全产业链 solutions"， can assist in comparing the applicability of acetic acid removal type and ketoxime removal type fluorosilicone sealants in different base materials， media and construction conditions.


For engine, transmission, fuel tank or flange sealing projects that require both oil resistance, high/low temperature resistance, bonding and reliable sealing, the following information should be provided before selection:


Material type and surface treatment method.


Type of contact medium, concentration and temperature.


Operating temperature range and low-temperature requirements.


Flange gap, compression rate and assembly window.


Preference for curing type and compatibility of by-products.


Target peel strength, volume change rate and elongation.


Current sealant model, primer and failure performance.


Acceptance method and applicable standards.


After receiving complete information, it can be determined whether to prioritize testing product FLSR4140, product FLSR4340, or choose another oil-resistant sealing agent route.


Common misunderstandings


The better the oil resistance, the more suitable for all oil-containing environments.
Different fuels and lubricants have different swelling effects on fluorosilicone sealants. Media such as Fuel C, FAM B, and Jet Fuel No.3 need to be verified separately.


Deacetic acid type and deketimoxyl type can be interchanged at will.
The drying time, extrudability, peel strength and by-products of the two are different. Replacement requires revalidation of bonding, curing and the impact on the substrate.


The faster the drying time, the better.
If the drying time is too fast, it may shorten the assembly window, affect flange sealing and bonding, and it needs to be matched with the construction rhythm.


Compatibility with the substrate allows for direct application.
It is still necessary to confirm surface cleanliness, primer, gap, compression rate and long-term oil immersion stability.


The performance at 25°C is the same, so it can be replaced in equal amounts.
Sealants of different curing types and fluorosilicone formulations may have different resistance to media, low-temperature flexibility and bonding properties.


By-products can be ignored.
Deacetic acid type releases acetic acid, and deketimoxyl type releases butanone oxime. It is necessary to assess the impact on the substrate, electronic components and construction environment.


Product FLSR4000 can be used for all oil-resistant sealing.
Fluorosilicone sealants are suitable for oil-containing environments, but may not be applicable to strong polar solvents, ketones, esters and strong acid environments. Selection depends on the medium.


It can still be used normally after storage for six months.
The unopened original packaging has a storage period of six months. After the expiration, it is necessary to retest the extrudability, drying time and curing performance.


Recommended selection steps


Confirm the application direction: engine, transmission, powertrain system, braking system, pipeline flange or overall fuel tank of the aircraft.


Confirm the material type and surface treatment method.


Confirm the contact medium, operating temperature and low-temperature requirements.


Confirm the flange gap, compression rate and assembly window.


Confirm the curing type (deacetic acid type or deketimoxyl type) and compatibility of by-products.


Choose product FLSR4140 or product FLSR4340 based on the application scenario.


Set up different primers, application amounts and curing conditions gradients for small tests.


Test the drying time, extrudability, peel strength and volume change rate.


Conduct high-temperature aging, low-temperature performance and long-term oil immersion verification.


Evaluate the sealing reliability and batch consistency of the product.


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