Silane Coupling Agents

|Our Product list|  Basic Structure  |  Functions   |  How to use  |  Applications   |  Handling Precautions|

      Silane coupling agents are organosilicon compounds that are widely used to bond organic materials to inorganic materials. In many cases, these are materials that might otherwise be considered too dissimilar to form strong interactions. As a result, silane coupling agents are extensively used to greatly improve the interfacial adhesion in composites and other materials systems, significantly improving desirable qualities such as mechanical strength, moisture or chemical resistance, electrical properties, etc. In general, silane coupling agents are used to tailor the composition, functionality, compatibility, and reactivity of a given system, enhancing its desirable properties while minimizing the disadvantages that may be inherent. This typically includes the direct modification of resins, other organic components, and/or inorganic surfaces and it is accomplished by adding one or more specific functional groups via one or more organosilane coupling agents.

• Our product list

1. 3-aminopropyltriethoxysilane [919-30-2]

2. 3-aminopropyltrimethoxysilane [13822-56-5]

3. (3-glycidoxypropyl)trimethoxysilane [2530-83-8]

4. methacryloxypropyltrimethoxysilane [2530-85-0]

5. N-(2-aminoethyl)-3-aminopropyltrimethoxysilane [1760-24-3]

6. N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane [3069-29-2]

7. 3-aminopropylmethyldiethoxysilane [3179-76-8]

8. vinyltriethoxysilane [78-08-0]

9. vinyltrimethoxysilane [2768-02-7]

10. 3-chloropropyltrichlorosilane [2550-06-3]

11. 3-chloropropyltrimethoxysilane [2530-87-2]

12. 3-chloropropyltriethoxysilane [5089-70-3]

13. 3-chloropropylmethyldichlorosilane [7787-93-1]

14. 3-chloropropylmethyldimethoxysilane [18171-19-2]

15. chloromethyltrichlorosilane [1558-25-4]

16. chloromethyltriethoxysilane [15267-95-5]

17. chloromethyltrimethoxysilane [5926-26-1]

18. vinyldimethylethoxysilane [5356-83-2]

19. methyltriacetoxysilane [4253-34-3]

20. methyltris(methylethylketoxime)silane [22984-54-9]

21. vinyltris(methylethylketoximino)silane [2224-33-1]

22. vinyltrichlorosilane [75-94-5]

23. phenyltris(methylethylketoximino)silane [34036-80-1]

24. vinylmethylbis(methylethylketoximino)silane [73160-32-4]

25. 3-mercaptopropyltrimethoxysilane [4420-74-0]

26. 3-mercaptopropyltriethoxysilane [14814-09-6]

27. vinyltris(2-methoxyethoxy)silane [1067-53-4]

28. bis[3-(triethoxysilyl)propyl]-tetrasulfide [40372-72-3]

29. tetrakis(methylethylketoximino)siane [34206-40-1]

30. (N,N-diethyl-3-aminopropyl)triethoxysilane [41051-80-3]

31. N-methylaminopropyltrimethoxysilane [3069-25-8]

32. ureidopropyltrimethoxysilane [23843-64-3]

33. (3-glycidoxypropyl)methyldiethoxysilane [2897-60-1]

34. (3-trimethoxysilylpropyl)diethylenetriamine [35141-30-1]

• Basic Structure

  Silane coupling agents have two different types of reactive functional groups.

  	X represents the functional group that reacts with organic materials like synthetic resins and may be selected from the following types of functional groups: ¡ñ /span>vinyl    ¡ñ epoxy   ¡ñ amino    ¡ñ methacryl   ¡ñ acryl   ¡ñ isocyanato   ¡ñ mercapto
  	OR represents the functional group that reacts with inorganic materials like glass, metals, and silica and may be selected from the following types of functional groups: ¡ñ methoxy group    ¡ñ ethoxy group    ¡ñ acetoxy group

• Functions

  1. Inorganic Reactive Silanes
       In the presence of water, coupling agents produce highly reactive silanols. Subsequently, these silanols begin to condense, forming oligomeric structures while also forming weak hydrogen bonds to the surface of inorganic materials. Finally, drying the inorganic materials leads to further condensation and dehydration between the coupling agent and the surface. This process yields multiple strong, stable, covalent bonds to the surface.

  

  2. Organic Reactive Silanes
       The improved adhesion between the surfaces of inorganic materials treated with silane coupling agents and  organic resins is caused by:
  (1) Improved wetting of the treated inorganic surface by the resin.
  (2) Improved compatibility between the treated inorganic surface and the resin.
  (3) Hydrogen bonding between the treated inorganic surface and the resin.
  (4) Multiple covalent bonds between the treated inorganic surface and the resin.

      Many different factors affect the above four items, such as the type of thermoplastic or thermosetting resins, whether or not functional groups remain, the abundance and reactivity of the remaining functional groups, and the overall polarity or non-polarity of the resins.

  • Thermoplastic resins
      For thermoplastics, the chemical bonds introduced by reactive silanes are often relatively weak. A limited number of highly polar thermoplastics will develop weak interactions with some silane coupling agents. In these specific situations, both the thermoplastic resin and the silane are capable of forming hydrogen bonds. Therefore, the effectiveness of resin modification is highly dependent on the compatibility of each organic resin and its ability to form hydrogen bonds.

  • Thermosetting resins
      Unlike thermoplastics where considerations such as the critical surface tension, the dissolution parameters, and other similar factors may be used to evaluate resin compatibility, these factors are not meaningful for predicting the strength of composite materials prepared from thermosetting resins. To maximize the strength and other physical properties of a thermosetting composite, it is generally recommended to first react the organic functional group of the silane with the thermosetting resin before curing the composite. It is important to use a reactive silane coupling agent bearing an appropriate functional group that matches the functional reactivity of the thermosetting resins.

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• How to use

There are two basic approaches for using silane coupling agents. The silane can either be used to treat the surface of the inorganic materials before mixing with the organic resin or it can be added directly to the organic resin.

1. The Surface Treatment of Inorganic Materials

There are two general methods for treating the surfaces of inorganic filler materials before they are added to the organic resins.

(1) Wet Method
By mixing a slurry of the inorganic materials in a dilute solution of the silane coupling agent, a highly uniform and precise surface treatment of the inorganic material can be obtained.

(2) Dry Method
A high shear, high speed, mixer is used to disperse the silane coupling agent into the inorganic materials. The silane is generally applied either neat or as a concentrated solution. When compared to the Wet Method, the Dry Method is most often preferred for large-scale production, treating a large amount of filler in a relatively short time and generating relatively little mixed waste; however, it is more difficult to obtain uniform treatment with this method.


2. Addition To Organic Materials

Compared to the methods for the surface treatment of inorganic materials, adding the silane to the organic resin is more widely used in industries because of its excellent process efficiency, although curing may be more difficult. There are two general methods.

(1) Integral Blending
This method involves simple blending of the silane coupling agent into the composite formula as the inorganic and organic materials are mixed together.

(2) Master Batch
In this method, the silane coupling agent is first added to a small amount of the organic resin material to form what is referred to as a "master batch". Usually in the form of pellets or large granules, the master batch can be easily added along with the pellets of the organic resin when producing the composite materials.

• Applications

1. Thermosetting Resins

(1) Glass fiber reinforced epoxy resins
In order to meet the electrical properties and heat resistance requirements of epoxy resin laminated plates used with molten solder alloys, silane coupling agents are recommended as a resin modifier for the thermosetting composites. In this case, silane coupling agents are generally used to treat glass fibers that have been pre-treated with a water solution and then dipped in a resin vanish.

(2) Encapsulating semiconductors
The most common use for coupling agents in epoxy molding compounds is as a semiconductor sealing agent that improves the moisture resistance and electrical characteristics of the resultant composite materials. The coupling agents form an interfacial bond between the resins and the filler that is stronger and more hydrolytically stable, yielding a better moisture resistant interface. In this case, volume resistivity and bending strength are also greatly improved.

(3) Coated sand
The casting parts are comprised of fire resistant aggregates (sand) and adhesives. The quality of the resultant casting is reflects the strength of the adhesives coated on the surface of the sand particles. The coupling agents play an important role by improving the strength of the cast as well as preventing moisture. In most cases, the coupling agents are pre-added directly to the resins.

2. Thermoplastics

The results obtained from using coupling agents in thermoplastic resins are generally lower than when compared with that of thermosetting resins. However, in a limited number of systems such as nylon and plastic magnets, good results are achieved due to the high polarity of the thermoplastic resins that are used.

3. Resin modification

The uses of silane coupling agents are not limited to the interfaces of composite materials. Resin modification can create high performance resins with unique and superior characteristics. Typically, resins modified with silanes display improved adhesion to inorganic materials and moisture curable properties at low temperature, as well as superior resistance to weathering, acid, heat, and solvents. Product development continues, including the applications of polyolefins for electrical wires and acrylic resins for modified sealants.

For resin modifications with the silicon-based compounds, the following reactions are possible:

(1) Grafting

Grafting is widely used to produce polyolefin based materials for sealing electrical wires. Polyolefins that incorporate an unsaturated silane couplant (e.g., vinyltrimethoxysilane, É¡-methacryloxypropyltrimethoxysilane, etc.) have a silyltrimethoxy group grafted to the polyolefin backbone that enables moisture crosslinkable resins. Moisture crosslinkable polyolefins are highly preferred for electrical wire applications because of their reasonable cost and excellent electrical insulation, as well as their dielectric and mechanical stability. In these applications, common silanol condensation catalysts such as dibutyltindilaurate, dibutyltindioleate, dibutyltindiacetate, tetrabutyltitanate, and stannous octanoic acid are used in conjunction with the a peroxide for the grafting reaction.

(2) Chemical Reactions

Given the variety of silane coupling agents that are available bearing different organic functional groups as well as the many different types of organic resins produced, a large number of chemical reactions can be developed between using these compounds as reactants. Examples of applications for this type of silane modified resins include modified sealants, where polyoxyalkylene resins bearing a terminal aryl group react with a hydrosilane in the presence of platinum catalyst, and moisture curable urethane resins, where thermoplastic urethane resins have been modified by an amino functional alkoxysilane. These types of methods for resin modification are expected to continue to produce new resins in the future.

(3) Copolymerization

Copolymerization of an unsaturated silane monomer along with one or more organic monomers is widely used to modify acrylic resins for paints. This method often uses a silane couplant with a methacrylic functional group with compatible co-monomers.

• Handling Precautions

  1. Quality, Storage and Handling
  (1) The products should be kept in a cool, dark, and dry place.
  (2) The coupling agents may deteriorate when in contact with water or moisture, producing byproducts such as hydrogen chloride from chlorosilanes and methanol or ethanol from methoxy silanes or ethoxysilanes, respectively. These products should be handled with special care when kept in the open air. After opening, they should be tightly sealed to limit exposure to water or moisture. It is recommended that dry nitrogen be used to replace the air in opened containers.
  (3) Please contact our Sales Department for the MSDS and read it carefully before using any of these products.

  2. Safety
  (1) These products should be handled with adequate ventilation to avoid contact with water or moisture. For example, when KA-1003 reacts with water or moisture in the air, it may generate corrosive hydrogen choloride gas, which is harmful to skin and membranes.
  (2) To avoid contact with skin or membranes, it is recommended to wear gloves and goggles for protection. If contact occurs, flush immediately with large amounts of water.
  (3) When eye contact occurs, flush the eyes immediately with large amounts of water and consult a doctor, if necessary. In the case of KA-1003 or aminosilanes, special and prompt care is required.
  (4) If contact with clothes occurs, flush the exposed clothing with water and then wash the clothes immediately.
  (5) After using silanes, wash hands very thoroughly before eating or drinking.
  (6) If silane fluids are spilled, either flush the exposed area with large amounts of water or clean with rags or sand, which should be promptly disposed of by burning.

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  The above content was quoted from www.silicone.jp/e/