One cannot simply rely on the IOTA-130 (Si28) content being ≥ 98% or the presence of the ethyl silicate structure to directly determine its suitability for all glass or plastic lens hard coating systems. One must first confirm the substrate type, surface pretreatment method, hydrolysis catalyst system, hydrolysis degree, coating thickness, and curing conditions before determining whether the problem lies in an incompatible hydrolysis process, excessive internal stress in the coating, or poor interface bonding with the substrate. IOTA-130 (Si28) can be considered as a candidate for the ethyl silicate precursor, but it must be confirmed through small-scale tests, adhesion tests, and actual working conditions verification.


Why do positive silicon acid ethylate coatings still crack or have insufficient adhesion?


Positive silicon acid ethylate forms a SiO₂ network through hydrolysis and condensation, and is a commonly used precursor for preparing transparent hard coatings and stone reinforcement treatments. However, a content of ≥ 98% does not necessarily mean that the coating performance is up to standard. The following factors are equally crucial:


The hydrolysis catalyst system (acid/alkali/fluoride ions) directly determines the hydrolysis and condensation rate, affecting the network structure and internal stress of the coating.


Insufficient or excessive hydrolysis results in a deviation from the target crosslinking density or excessive Si-OH residues causing subsequent contraction and cracking.


When the coating thickness exceeds the critical cracking thickness, internal stress accumulates leading to crack formation.


The surface oxide species of plastic substrates are limited, and Si-OH is difficult to form sufficient interface bonds with the substrate, resulting in inherent poor adhesion.


The mismatch of curing temperature and time, and the failure of the solvent and by-product ethanol to fully escape, result in the formation of bubbles or pores.


The substrate surface is not activated or not cleaned, with the presence of release agents, oils, or low surface energy contamination layers.


The interface thermal expansion coefficient difference between the coating and the substrate causes interface stress.


The prolonged storage time of the hydrolysis solution after preparation leads to excessive condensation or gelation, resulting in a decline in coating performance.


Studies have shown that TEOS-based sol-gel coatings have贯穿 structures of cracks under various processing conditions， with crack diameters reaching 6-11 μm， mainly due to the coating exceeding the critical cracking thickness and having excessively high internal stress. Under acidic conditions (pH 0-2)， regardless of the coating thickness or aging time， partial delamination phenomena were observed.


What are the public parameters of IOTA-130 (Si28)?


Parameter IOTA-130 (Si28)
Appearance Colourless transparent liquid
Boiling point 168℃/760mmHg
Density (25℃) 0.94 g/ml
Content (%) ≥98.0
Refractive index (20℃) 1.382
Hydrolysis by-products Ethanol
The above data is from Aytota's current public product information. Formal procurement 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-130 (Si28) suitable for?


Application direction Candidate direction Still needs verification
Glass lens hard coating Provide ultra-hard scratch-resistant coating Adhesion， light transmittance， weather resistance
Plastic lens hard coating Provide ultra-hard scratch-resistant coating Substrate activation， interface bonding， thermal matching
Stone reinforcement treatment Form SiO₂ through hydrolysis to enhance substrate strength Penetration depth， enhancement effect， color difference
Building material reinforcement Form silicon sol-like inorganic substances Adhesion strength， water resistance， weather resistance
Organic-inorganic hybrid coating As an inorganic precursor， combined with silane coupling agent Hybrid ratio， dispersion， curing conditions


What are the key differences in the selection of IOTA-130 (Si28) compared to similar siloxane precursor candidates?


Comparison direction IOTA-130 (Si28) (ethyl silicate) IOTA-130 (Si40) (polyethyl silicate) Other siloxane precursor candidates Selection boundary
Main Components: Tetraethoxysilane monomer, polysilazane prepolymer, silica sol, alkoxysilane. The selection depends on the hydrolysis rate and SiO₂ content.
SiO₂ Content (%) : Approximately 28 (theoretical value), 40-42, varies depending on the product. The selection depends on the target coating thickness and curing shrinkage.
Boiling Point: 168℃/760mmHg. N.A. (varies depending on the product). The selection depends on the volatility and curing conditions.
Hydrolysis Rate:较快， requires control of catalyst and water volume. Slower， the pre-polymer hydrolysis is more controllable. Varies depending on the product. The selection depends on the coating application process and shelf life.
Internal Stress of Coating： High， prone to cracking. Low， but high SiO₂ content may still cause cracking. Varies depending on the product. The critical cracking thickness needs to be evaluated.
Suitable Systems： Glass， plastic lenses， stone reinforcement. General hard coatings， enhancement treatment. The selection depends on the substrate and performance requirements.
Why do complete hydrolysis and coating tests still need to be conducted despite compatibility with the substrate?


Aydota's public information states that IOTA-130 (Si28) is used for stone or other building material reinforcement， as well as providing an ultra-hard scratch-resistant coating in glass and plastic lenses. However， in the actual coating system， there are still：


Differences in hydrolysis catalyst type and concentration.


Watering volume and solvent ratio for hydrolysis.


Aging time and storage conditions of the hydrolysis solution.


Pre-treatment method of the substrate surface.


Coating process (immersion coating， spin coating， spraying) and pulling speed.


Curing temperature curve and atmosphere conditions.


Coating thickness control.


Inter-layer matching of multi-layer coating.


Appearance (transparent or no short-term delamination)， which cannot prove that the coating remains intact after long-term use， thermal cycling， or water immersion. Existing research has shown that TEOS-cured coatings show increased roughness， cracks， and erosion pits after immersion in water.


What parameters should be confirmed before coating?


Parameter Categories： Information to be confirmed
Substrate Type： Glass， PC， PMMA or other plastics， stone types
Surface Pre-treatment： Cleaning method， activation method (plasma/etching/undercoating)
Hydrolysis Catalyst： Acid type (HCl/HF/HOAc)， concentration， pH range
Watering Volume： Water/TEOS molar ratio
Hydrolysis Solution Concentration： SiO₂ content dilution ratio
Coating Process： Immersion coating/spin coating/spraying， pulling speed， coating times
Coating Thickness： Target dry film thickness， critical cracking thickness assessment
Curing Conditions： Temperature， time， atmosphere
Acceptance Indicators： Adhesion， hardness， light transmittance， water resistance， weather resistance
What should be focused on verifying?


Clearness and homogeneity of the hydrolysis solution.


Applicability period and gelation time of the hydrolysis solution.


Coating appearance (transparency， no cracks， no orange peel).


Coating thickness and thickness uniformity.


Adhesion (grid test or pull test).


Pencil hardness or nanoindentation hardness.


Light transmittance and haze.


Water resistance and adhesion retention rate after water immersion.


Thermal cycling coating integrity.


Batch-to-batch consistency and repeatability of the hydrolysis solution.


How to design a hydrolysis and coating verification plan?


Establish a current coating benchmark， record model， batch， hydrolysis conditions and coating parameters.


Uniform test conditions： substrate type， surface pre-treatment， hydrolysis catalyst， hydrolysis time， coating method， curing conditions.


Set candidate samples： current coating solution， IOTA-130 (Si28) with different hydrolysis degrees and concentration gradients.


Complete the entire process testing： hydrolysis → aging → coating → curing → performance testing.


Evaluate actual results： adhesion， hardness， light transmittance， water resistance.


Test Items： Uniform requirements
Substrate type and pre-treatment： remain consistent
Hydrolysis catalyst and pH： set gradients according to the test design
Hydrolysis time： control according to the test design
Coating method and thickness Keep consistent or set a gradient
Curing conditions Same temperature and time
Measurement methods Consistent adhesion, hardness, light transmittance, water resistance
Which situations are not suitable for directly using IOTA-130 (Si28)?


The substrate surface is not activated or cleaned, especially for plastic substrates.


The hydrolysis catalyst system has not been screened, and it is prone to layering under high acidic conditions.


The coating thickness has not evaluated the critical cracking thickness, and a thick coating is directly applied.


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


There are strict requirements for light transmittance, but optical performance verification has not been conducted.


Only the substrate type is known, without hydrolysis conditions, coating process and curing parameters.


The customer requests to directly mix it into the in-use coating system, but cannot control the hydrolysis degree and mixing ratio.


When switching from IOTA-130 (Si40) or other poly silazane to IOTA-130 (Si28), the water usage for hydrolysis and catalyst system have not been re-adjusted.


What selection support can Aytota provide?


As a "provider of the organic silicon全产业链 solutions"， Aytota can assist in comparing the applicability of polysilazane in different substrates， hydrolysis processes and coating conditions for IOTA-130 (Si28).


For lens hard coatings or stone reinforcement projects that need to balance coating hardness， adhesion and transparency， the following information should be provided before selection：


Substrate type and surface pre-treatment method.


Type of hydrolysis catalyst and pH range.


Water usage and concentration of hydrolysis liquid.


Coating process and coating thickness requirements.


Curing temperature and time.


Target adhesion， hardness and light transmittance.


Current coating model and hydrolysis conditions.


Failure manifestations and acceptance methods.


After receiving complete materials， it can be determined whether to prioritize testing IOTA-130 (Si28)， or choose IOTA-130 (Si40) or other siloxane precursor routes.


Common misunderstandings


The higher the content， the higher the coating hardness
The content affects the final inorganic network density， but hardness also depends on the degree of crosslinking， coating thickness and curing conditions.


The hydrolysis liquid can be prepared randomly
The type of hydrolysis catalyst， pH， water usage and aging time directly affect the hydrolysis degree and coating quality， and need to be controlled according to the recommended process.


The thicker the coating， the better the protection and wear resistance
After exceeding the critical cracking thickness， internal stress accumulates in the coating causing cracking， and thin coatings often perform better with multiple thin coatings than a single thick coating.


Compatibility with glass allows for direct use in plastic lenses
The oxide species of the plastic substrate are limited， additional activation treatment is required， and the thermal expansion coefficient matching with glass is significantly different.


Highly acidic catalysts facilitate rapid curing
Under highly acidic conditions (pH 0-2)， the hydrolysis and condensation rate is too fast， and the coating is prone to layering defects， and coatings without layering can be obtained under pH 3-5 conditions.


The hydrolysis liquid can be stored for a long time
The hydrolysis liquid continues to condense during storage， has a limited shelf life， and the coating performance deteriorates after expiration， and it needs to be used within the specified time.


IOTA-130 (Si28) and IOTA-130 (Si40) can be interchanged freely
Si28 is the monomer of positive silazane， and Si40 is the pre-polymer of poly silazane， and their hydrolysis speed， SiO₂ content and internal stress in the coating are different， replacement requires re-adjusting the water usage for hydrolysis and catalyst system.


Recommended selection steps


Confirm the substrate type and surface pre-treatment method.


Confirm the type of hydrolysis catalyst， pH and water usage.


Evaluate the shelf life and gelation time of the hydrolysis liquid.


Select IOTA-130 (Si28) or IOTA-130 (Si40) based on the application scenario.


Set different hydrolysis degrees and coating thickness gradients for small tests.


Test adhesion， hardness， light transmittance and water resistance.
Verify the interface bonding with the substrate and the thermal cycling stability.


After completing multiple batch verifications, a final usage plan will be determined.