In two-component polyurethane adhesives, isocyanate propyl triethoxysilane (SF-S025), chemical name: γ-isocyanate propyl triethoxysilane, referred to as IPTS) is a multifunctional modifier, which covers interface enhancement, reaction activity regulation and system stability optimization. The following are its core functions and technical analysis:
1. Interface bonding enhancement
Mechanism of action
Chemical bonding:
Silanol group (-Si-OH): The silanol group generated after silane hydrolysis forms a covalent bond (Si-O-M, M is the substrate atom) with the hydroxyl group (-OH) on the surface of metal, glass, ceramic and other substrates, significantly improving the interface bonding force.
Isocyanate group (-NCO): The -NCO group in IPTS reacts with the polyol or amine (component B) in the polyurethane matrix to anchor the silane in the polymer network to form a "bridging structure".
Performance improvement
Bond strength: The tensile shear strength of metal/plastic substrates is increased by 20%-40% (such as steel-aluminum bonding from 10MPa to 14MPa).
Resistant to heat and humidity aging: The hydrophobic effect of silane (-Si-O-bond) inhibits the penetration of water molecules, and the strength retention rate after aging for 500 hours at 85℃/85%RH is ≥80% (only 60% when not added).
2. Optimization of filler-matrix compatibility
Application scenarios
When the formula contains inorganic fillers (such as nano calcium carbonate, fumed silica), IPTS improves dispersibility in the following ways:
Surface modification: After hydrolysis, the ethoxy group of silane bonds with the hydroxyl group on the filler surface, and the organic chain segment (propyl isocyanate) is compatible with the polyurethane matrix, reducing filler agglomeration.
Rheological control: Reduce the viscosity of the system (adding 1% IPTS can reduce the viscosity from 5000mPa·s to 3500mPa·s) and improve construction properties.
3. Reactivity synergy
Matching with polyurethane curing system
Dual role of NCO group
- Participation in the main reaction: -NCO of IPTS reacts with -OH/-NH₂ of component B to become part of the cross-linked network and enhance cohesive strength.
- Avoid side reactions: The amount of silane added needs to be controlled (usually 0.5%-2%) to avoid excessive consumption of -NCO of component A, resulting in incomplete curing.
- Catalytic requirements: IPTS hydrolysis requires acidic conditions (pH 4-5), and 0.1%-0.3% acetic acid or lactic acid can be added to promote hydrolysis without affecting the main reaction (organic tin catalysts are commonly used for polyurethane curing).
4. System stability control
Storage and process points
Moisture sensitivity: IPTS is easily hydrolyzed, and a dehydrating agent (such as molecular sieves or p-toluenesulfonyl isocyanate) needs to be added to component A to ensure a storage period of ≥6 months (viscosity change ≤15% at 25°C). Addition order: It should be added after vacuum dehydration and before filling to avoid high temperature causing silane self-condensation (recommended process temperature ≤ 60°C).

Matching solution
Epoxy silane (SF-S560): suitable for scenes with higher requirements for weather resistance.

Through the reasonable application of IPTS, the comprehensive performance of two-component polyurethane adhesives can be significantly improved, especially for fields such as automobiles and electronic packaging that have strict requirements for fast curing and high reliability.