What is acrylic light-curing adhesive? Which silane coupling agent is recommended for acrylic light-curing adhesive to improve adhesion?
Overview of acrylic light-curing adhesive:
Acrylic light-curing adhesive (UV-curing acrylic adhesive) is an adhesive that cures quickly under ultraviolet (UV) or visible light. The main ingredients include:
Acrylate monomers/oligomers (such as HDDA, TPGDA, epoxy acrylate, etc.)
Photoinitiators (such as TPO, 1173, 184, etc.)
Additives (leveling agents, stabilizers, pigments, etc.)
Features of acrylic light-curing adhesive:
Fast curing (curing in seconds, improving production efficiency);
Environmentally friendly (solvent-free, low VOCs);
High transparency (suitable for bonding optical devices);
Adjustable performance (hardness and flexibility can be adjusted through formula).
Application areas of acrylic light-curing adhesive:
Electronic devices (touch screens, LED packaging);
Glass/metal bonding (decorative parts, automotive parts);
Plastic bonding (acrylic, PC, etc.);
3D printing, printed coatings, etc.
The key to improving the adhesion of acrylic photocuring adhesive: silane coupling agent
The adhesion of acrylic photocuring adhesive on non-polar substrates (such as glass, metal, and some plastics) may be insufficient and needs to be improved by silane coupling agent. Its mechanism of action:
1. Organic-inorganic bridging: Silane's -Si (OR)₃ is hydrolyzed and combined with the hydroxyl group (-OH) on the surface of the substrate to form a Si-O-Si bond;
2. Organic end reaction: amino, epoxy and other functional groups copolymerize with acrylic resin or form hydrogen bonds to enhance interfacial bonding.
Recommended silane coupling agents and selection criteria
Based on the chemical properties of acrylic light-curing adhesives and the type of substrate, the following silane coupling agents are recommended:
1. General type: γ-methacryloxypropyltrimethoxysilane (SF-S570)
Chemical formula: CH₂=C(CH₃)COO(CH₂)₃Si(OCH₃)₃
Advantages:
Contains methacryloyloxy groups and has excellent copolymerizability with acrylic resins;
Applicable to glass, metal, and polar plastics (such as PC and PMMA).
Addition method: Add directly to the adhesive solution (0.5~2% mass ratio), or pre-treat the substrate (coating with 1~5% ethanol solution).
2. Highly active type: γ-aminopropyltriethoxysilane (SF-S550)
Chemical formula: H₂N(CH₂)₃Si(OC₂H₅)₃
Advantages:
Amino group (-NH₂) can react with carboxyl group of acrylate or free radical after light curing;
Particularly suitable for metal (aluminum, copper) and ceramic substrates.
Note: It may accelerate the storage period of the glue, and compatibility needs to be tested.
3. Epoxy silane: γ-glycidyloxypropyltrimethoxysilane (SF-S560)
Chemical formula: CH₂OCHCH₂O(CH₂)₃Si(OCH₃)₃
Advantages:
Secondary reaction of epoxy group with acrylate (such as hydroxyl, carboxyl) enhances adhesion;
Excellent moisture and heat resistance, suitable for outdoor or high humidity environment.
4. Long-chain flexible silane: Octyltrimethoxysilane (SF-S831)
Applicable scenarios:
Coatings or bonding that require flexibility (such as flexible electronics);
Hydrophobic substrates (such as certain modified plastics).
Selection and use recommendations
1. Substrate matching:
Glass/ceramics: SF-S570 and SF-S560 are preferred;
Metal: SF-S550 or SF-S560;
Plastic: Non-polar plastics (PP/PE) need to be plasma treated before using silane.
2.Addition method:
Direct addition: Before adding silane to the glue, the compatibility with the photoinitiator needs to be tested (may affect the curing speed);
Substrate pretreatment: 1~5% silane ethanol solution is applied and then dried (to avoid moisture residue).
3.Verification test:
Evaluate the adhesion improvement effect by cross-hatch method (ASTM D3359) or tensile test.
Summary
For acrylic light-curing adhesives, SF-S570 (methacryloxysilane) is the most common choice, taking into account both reactivity and compatibility; if higher moisture and heat resistance is required, SF-S560 can be selected; SF-S550 is recommended for metal substrates. In actual applications, the addition amount and process conditions need to be optimized through experiments.