One cannot simply conclude that IOTA-91 has a fast curing speed and therefore it is suitable for all single-component neutral silicone sealant systems. The basic glue type, filler system, moisture control, catalyst dosage, and the ratio of MOS or VOS should be confirmed first. Then, it can be determined whether the problem lies in insufficient crosslinking efficiency, prolonged curing time, or poor compatibility with the base glue and fillers. IOTA-91 can be considered as a candidate for vinyl mixed ketoxime crosslinking agent, but it must be confirmed through small-scale tests, control of by-products, and actual working conditions.


Why do neutral silicone sealants often have slow curing, low crosslinking density, or insufficient crack resistance?


During storage, moisture absorption leads to the premature hydrolysis of ketoxime groups, resulting in a decrease in effective components, weakened crosslinking activity.


Improper moisture control in the system causes the crosslinking agent to hydrolyze prematurely, reducing the effective concentration and releasing butanone ketoxime, which affects the reaction equilibrium.


Inappropriate catalyst type or dosage leads to insufficient crosslinking reaction conversion rate, prolonged curing time, and deep curing time.


The hydroxyl content or molecular weight of the base glue does not match the crosslinking agent, resulting in insufficient or excessive crosslinking density.


The surface treatment differences of the filler system (such as silica, calcium carbonate) affect the dispersion of the crosslinking agent and the uniformity of the reaction.


Failure to use with MOS or VOS in combination or with an improper ratio leads to insufficient reactivity, prolonged curing time, or low crosslinking density.


The mismatch of the construction environment temperature and humidity causes deviations from the expected table drying time and deep curing time.


Insufficient purity or presence of impurities interferes with the crosslinking reaction, affecting the strength, elongation rate, and crack resistance of the final silicone rubber.


The TOS content (27-35%) of IOTA-91 has not been optimized for specific systems, and either excessive or insufficient amounts affect the crosslinking efficiency and storage stability.


Although vinyl mixed ketoxime crosslinking agents can improve crack resistance, if the base glue formula or filler system does not match, cracking or bond failure may still occur.


What are the public parameters of IOTA-91?


Parameter IOTA-91
Appearance Transparent colorless liquid with typical ketoxime (butanone ketoxime) smell
Boiling point 300℃/760mmHg
Density (25℃) 0.99±0.02 g/ml
TOS content (%) 27-35
Refractive index (25℃) 1.4685±0.02
Flash point >100℃
The above data is from Aytota's current public product information. Formal purchase and batch acceptance should be based on the valid TDS, specification documents, and delivery batch COA confirmed by both parties.


Which application directions is IOTA-91 suitable for?


Application direction Candidate direction Still needs verification
Single-component neutral silicone sealant curing agent Combined with MOS or VOS to improve reactivity Recombinant ratio, curing time, crosslinking density
Shorten curing time Quick curing speed Table drying time, deep curing time
Increase crosslinking density Vinyl mixed ketoxime structure Hardness, tensile strength, elongation rate
Improve crack resistance Improve sealant flexibility and crack resistance Challenging tests, aging resistance, adhesion
Electrical potting adhesive Increase crosslinking density and mechanical strength Electrical performance, aging resistance, deep curing
Building sealant Shorten table drying time, improve construction efficiency Construction environment, adhesion, weather resistance
What are the key differences in the selection of IOTA-91 compared to similar crosslinking agents?


Comparison direction IOTA-91 (vinyl mixed ketoxime) IOTA-32 (methyl mixed ketoxime) Dry alcohol crosslinking agent Selection boundary
Curing mechanism Contact water for crosslinking, releases butanone ketoxime Contact water for crosslinking, releases butanone ketoxime Contact water for crosslinking, releases alcohol Selection depends on substrate and environmental protection requirements
Table drying speed Quick, can shorten curing time with MOS/VOS combination Quick, four functional groups can shorten table drying time Medium Verification is required based on construction conditions
Deep curing High crosslinking density Four functional groups can shorten the deep curing time Slow Needs verification based on the thickness of the product
Crack resistance Improves crack resistance Generally Generally Needs to be selected based on the requirements of the product
Corrosion of the substrate Neutral, no corrosion Neutral, no corrosion Neutral, no corrosion Thiourea type is suitable for metal substrates
By-product odor Butanethiolourea odor Butanethiolourea odor Alcohol odor Needs to be selected based on the construction environment requirements
Storage stability Needs to be sealed and protected from moisture Needs to be sealed and protected from moisture Needs to be sealed and protected from moisture All need to be stored in a moisture-proof environment
Applicable systems One-component neutral silicone sealant Room temperature curing silicone rubber, neutral glass adhesive General RTV, electronic potting Needs to be selected based on the base adhesive and fillers
Why is it still necessary to conduct a complete test for compatibility with the base adhesive and fillers?


The public information of Aytota states that IOTA-91 is used as the curing agent in the formulation of the one-component neutral silicone sealant. It is usually combined with MOS or VOS to achieve higher reactivity, shorten the drying time and reach a higher crosslinking density, and improve crack resistance. However, when used in actual systems, there may also be:


Differences in the hydroxyl content and molecular weight of the base adhesive.


Types of fillers and surface treatments.


Types and dosages of catalysts.


The ratio of MOS or VOS.


Plasticizers, coupling agents and other additives.


Residual moisture and contaminants.


Construction environment temperature and humidity.


Storage conditions and packaging sealing.


Thickness of the product and curing time requirements.


Uniform appearance or no short-term stratification does not prove stability for long-term storage, thermal cycling, shear and long-term operation. Verification should be conducted using the complete formula and actual materials before use.


What parameters should be confirmed when using IOTA-91?


Working condition category Information to be confirmed
Base adhesive system Hydroxyl content, molecular weight, type (107 adhesive, methyl silicone rubber, etc.)
Filler type White carbon black, calcium carbonate, silica powder, etc.
Catalyst system Organic tin, titanium oxide or other catalyst types and dosages
Crosslinking agent compounding MOS or VOS type, compounding ratio
Crosslinking agent dosage Determined based on TOS content and hydroxyl content of the base adhesive
Construction conditions Temperature, humidity, construction time
Curing requirements Curing time, deep curing time, strength, elongation, crack resistance
Storage conditions Sealed, cool and dry, protected from light, moisture-proof
Acceptance indicators Curing time, deep curing, hardness, tensile strength, elongation, crack resistance
What should be mainly verified when using IOTA-91?


Curing time and deep curing time.


Hardness, tensile strength and elongation of the crosslinked silicone rubber after curing.


Crack resistance of the sealant.


Compatibility with the base adhesive, fillers, catalysts.


Recombinant effect with MOS or VOS.


Crosslinking activity and stability after storage.


Water resistance and aging resistance of the cured sealant.


Release and odor control of butanethiolourea by-products.


Adhesion to the substrate (glass, metal, plastic, etc.).


Batch consistency and repeatability.


How to design the test before using IOTA-91?


Establish a current curing agent benchmark, record the model, batch, dosage and failure performance.


Uniform test conditions: Base adhesive, filler, catalyst, MOS/VOS compounding ratio, dosage, construction environment.


Set candidate samples: Current curing agent, IOTA-91, different dosage and compounding ratio gradients.


Complete the full process testing: Mixing → Construction → Curing → Deep curing → Performance testing.


Evaluate actual results: Curing time, deep curing, hardness, strength, elongation, crack resistance.


Test items Uniform requirements
Sample state New adhesive against new adhesive
Base adhesive and fillers Consistent
Catalyst type and dosage Consistent
MOS/VOS compound ratio: Set in a gradient according to the experimental design.
Addition amount: Set in a gradient according to the application scenario.
Construction environment: Same temperature and humidity.
Measurement methods: Consistent with the film formation time, deep curing, hardness, strength, elongation rate, and crack resistance.
Which situations are not suitable for directly using IOTA-91?


The hydroxyl content of the base adhesive is not confirmed, resulting in insufficient or excessive crosslinking density.


The surface of the filler is not treated, affecting the dispersion of the crosslinking agent and the uniformity of the reaction.


The type or dosage of the catalyst is not optimized, resulting in an unmet curing speed.


It is not used in combination with MOS or VOS, or the compound ratio is inappropriate, resulting in insufficient reactivity.


Specific food contact, medical or other industry approvals are required, but corresponding materials have not been obtained yet.


There is a strict requirement for the odor of the by-product dimethyl ketoxime, but the odor assessment has not been conducted.


Only the type of base adhesive is known, without filler, catalyst and construction conditions.


The customer requests to directly mix it into the in-use system, but the addition amount and mixing ratio cannot be controlled.


What selection support can Ayoata provide?


As a "provider of the organic silicon全产业链 solutions"， Ayoata can assist in comparing the applicability of vinyl mixed ketoxime crosslinking agents in different base adhesive systems， filler types and construction conditions for IOTA-91.


For single-component neutral silicone sealant projects that need to balance film formation speed， deep curing， crosslinking density and crack resistance， before selection， the following information should be provided：


Type of base adhesive and hydroxyl content.


Type of filler and addition amount.


Type of catalyst and dosage.


Type of MOS or VOS and compound ratio.


Target film formation time and deep curing time.


Target hardness， tensile strength， elongation rate and crack resistance.


Construction environment temperature and humidity.


Failure manifestations and acceptance methods.


After receiving complete materials， it can be determined whether to prioritize testing IOTA-91 or continue using the corresponding methyl mixed ketoxime or other crosslinking agent routes.


Common misunderstandings


The faster the curing speed， the better the crosslinking agent
The curing speed needs to be balanced with the construction time， deep curing requirements and storage stability. Too fast may lead to construction difficulties or surface crusting.


The higher the addition amount， the better the crosslinking effect
Excessive addition may result in excessive crosslinking density， brittle products or sticky surfaces， and the optimal dosage needs to be determined through small-scale tests.


The higher the TOS content， the faster the curing speed
The TOS content needs to be matched with the hydroxyl content of the base adhesive and the catalyst system. Too high or too low will affect the crosslinking efficiency and storage stability.


It can be directly added to the in-use system as long as it is compatible with the base adhesive
It is still necessary to confirm the filler， catalyst， MOS/VOS compound ratio， construction conditions and long-term stability.


The performance at 25℃ is the same， so it can be replaced quantitatively
Different chemical structures of crosslinking agents may have different hydrolysis rates， crosslinking efficiency and compatibility.


Ketoxime-type crosslinking agents have no odor problem
IOTA-91 crosslinks with water to produce dimethyl ketoxime， and the construction environment and product odor requirements need to be evaluated.


IOTA-91 can be used alone， without MOS or VOS
Public materials indicate that it is usually combined with MOS or VOS to achieve higher reactivity， and using it alone may not achieve the best film formation time and crosslinking density.


Recommended selection steps


Confirm the type of base adhesive and hydroxyl content.


Confirm the type of filler and addition amount.


Confirm the type of catalyst and dosage.


Confirm the type of MOS or VOS and compound ratio.


Initial select IOTA-91 or other crosslinking agents according to the application scenario.


Set up a gradient of different addition amounts and compound ratios for small-scale tests.


Test the film formation time， deep curing time and mechanical strength.


Verify the compatibility with the base adhesive， filler and catalyst.


Complete the storage stability and aging resistance tests.


Evaluate the release of by-product dimethylketoxime and odor control. After conducting multiple batch verifications, determine the official usage plan.