Analysis of the Differences in the Use of Common Silane Coupling Agents (KH550, KH560, KH570) ​

In the industrial fields of composite materials, coatings, and adhesives, silane coupling agents play an important role in improving the interfacial properties of materials. KH550、KH560、KH570 These are three commonly used products. Although their names are similar, there are significant differences in their practical applications. This article will analyze the core differences between the three from aspects such as chemical name, molecular formula, chemical structure, applicable materials, and usage points, providing a reference for practical applications.

I. Chemical Name, Molecular Formula, and Structure: The Root of Performance Differences

The general formula for the structure of silane coupling agents is Y-Si (OR)₃ where 中 Y represents the organic functional group ， OR represents the hydrolyzable alkoxy group The main difference between the three lies in the Y group, and their chemical names and molecular formulas are as follows:

KH550 KH550: The chemical name is 3-aminopropyltriethoxysilane, and the molecular formula is H₂N (CH₂)₃Si (OC₂H₅)₃ The Y group is an amino group (-NH₂ ) ） belonging to aminosilane. The amino group has strong polarity and reactivity and can form chemical bonds with active groups in resins such as epoxy and phenolic resins.

KH560 KH560: The chemical name is 3-glycidoxypropyltrimethoxysilane, and the molecular formula is CH₂OCHCH₂O (CH₂)₃Si (OCH₃)₃ The Y group is an epoxy group (-NH₂ -C₂H₃O ） belonging to epoxy silane. The epoxy group can undergo ring opening under acidic or alkaline conditions and react with hydroxyl groups, amino groups, etc.

KH570 KH570: The chemical name is 3-methacryloxypropyltrimethoxysilane, and the molecular formula is CH ₂ = C (CH₃) COO (CH ₂ )₃Si (OCH₃)₃ The Y group is methacryloxy (-NH₂ -OCOC (CH ₃ ) = CH ₂） belonging to acryloyl silane. The double bond structure allows it to undergo polymerization reactions with unsaturated resins such as acrylates and styrene.

The alkoxy group (usually methoxy or ethoxy) determines the hydrolysis rate. All three can be hydrolyzed to generate silanol (-NH₂ -SiOH） and react with hydroxyl groups on the surface of inorganic materials (such as glass, metal, and fillers) to form a strong bond.

II. Applicable Materials: Matching with Resins and Substrates

1. KH550

Suitable Resins Epoxy, phenolic, urea-formaldehyde, nylon, and other polar resins. The amino group has good compatibility with these resins and can significantly improve the mechanical properties of composite materials.

Suitable Substrates Glass fiber, metal, ceramic, calcium carbonate, and other inorganic fillers. In glass fiber reinforced plastics, using KH550 can increase tensile strength by more than 30%.

Typical Scenarios Casting resin sand, metal surface treatment agents, adhesive tackifiers.

2. KH560

Suitable Resins Epoxy resin, unsaturated polyester, polyurethane, etc. The epoxy group has a strong reactivity with epoxy resin and is a commonly used coupling agent in epoxy composites.

Suitable Substrates Glass, silicate minerals, aluminum hydroxide, etc. In electronic packaging materials, KH560 can improve the interfacial bonding between resin and ceramic powder and reduce water absorption.

Typical Scenarios Coating scratch-resistant additives, electronic potting compounds, glass fiber wetting agents.

3. KH570

Suitable Resins Acrylates, polyethylene, polypropylene, rubber, and other non-polar or weakly polar polymers. The double bond can form a chemical bond with the resin through free radical polymerization.

Suitable Substrates Silicon dioxide, talc, fumed silica, and other fillers. In plastic modification, KH570 can solve the problem of filler agglomeration and improve impact strength.

Typical Scenarios Plastic masterbatches, coating adhesion promoters, silicone rubber reinforcing agents.

III. Usage Points: Key Factors Affecting Effectiveness

1. Hydrolysis Conditions

KH550: The amino group is easily soluble in water and the hydrolysis rate is fast. The pH value needs to be controlled at 9-10 (alkaline conditions) to avoid excessive condensation.

KH560: Hydrolysis requires an acidic catalyst (such as acetic acid), and the pH value is controlled at 3-5. The stability of the hydrolysis solution is poor, so it is recommended to prepare and use it immediately.

KH570: Hydrolysis requires acidic conditions. Because the double bond is easily polymerized at high temperatures, the hydrolysis temperature should not exceed 50℃.

2. Amount Added

Usually 0.5%-3% of the filler or base material. Excessive use may result in an excessively thick interface layer, thus reducing performance. For example, in calcium carbonate-filled PP, the optimal amount of KH570 is 1.2%, at which point the flexural strength reaches its peak.

3. Processing Methods

Dry method: Directly mix with the filler, using mechanical force to coat the surface of the base material with the coupling agent.

Wet method: First prepare a hydrolyzed solution, then immerse or spray the base material. Suitable for scenarios with higher requirements (such as electronic materials).

IV. Impact of Incorrect Selection and Alternative Solutions

If an unsuitable coupling agent is selected, problems such as delamination of the composite material, coating peeling, and reduced strength may occur. For example, if KH550 is mistakenly used in polypropylene modification, the poor compatibility between the amino group and non-polar PP will cause a 15% decrease in impact strength.

When the required model is out of stock, the principle of similar polarity can be used as a reference for substitution. For example, if KH550 is out of stock, KH792 (bis-amino silane) can be used as a substitute; KH570 can be substituted with A174 (methacryloxy silane).

Understanding the differences between KH550, KH560, and KH570 silane coupling agents will help to fully utilize the interfacial performance of the materials in practical applications and ensure that the selected coupling agent meets the requirements.