Silane Coupling
Agents
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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.
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3-aminopropyltriethoxysilane [919-30-2]
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3-aminopropyltrimethoxysilane [13822-56-5]
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(3-glycidoxypropyl)trimethoxysilane [2530-83-8]
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methacryloxypropyltrimethoxysilane [2530-85-0]
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N-(2-aminoethyl)-3-aminopropyltrimethoxysilane [1760-24-3]
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N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane [3069-29-2]
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3-aminopropylmethyldiethoxysilane [3179-76-8]
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vinyltriethoxysilane [78-08-0]
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vinyltrimethoxysilane [2768-02-7]
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3-chloropropyltrichlorosilane [2550-06-3]
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3-chloropropyltrimethoxysilane [2530-87-2]
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3-chloropropyltriethoxysilane [5089-70-3]
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3-chloropropylmethyldichlorosilane [7787-93-1]
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3-chloropropylmethyldimethoxysilane [18171-19-2]
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chloromethyltrichlorosilane [1558-25-4]
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chloromethyltriethoxysilane [15267-95-5]
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chloromethyltrimethoxysilane [5926-26-1]
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vinyldimethylethoxysilane [5356-83-2]
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methyltriacetoxysilane [4253-34-3]
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methyltris(methylethylketoxime)silane [22984-54-9]
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vinyltris(methylethylketoximino)silane [2224-33-1]
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vinyltrichlorosilane [75-94-5]
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phenyltris(methylethylketoximino)silane [34036-80-1]
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vinylmethylbis(methylethylketoximino)silane [73160-32-4]
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3-mercaptopropyltrimethoxysilane [4420-74-0]
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3-mercaptopropyltriethoxysilane [14814-09-6]
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vinyltris(2-methoxyethoxy)silane [1067-53-4]
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bis[3-(triethoxysilyl)propyl]-tetrasulfide [40372-72-3]
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tetrakis(methylethylketoximino)siane [34206-40-1]
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(N,N-diethyl-3-aminopropyl)triethoxysilane [41051-80-3]
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N-methylaminopropyltrimethoxysilane [3069-25-8]
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ureidopropyltrimethoxysilane [23843-64-3]
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(3-glycidoxypropyl)methyldiethoxysilane [2897-60-1]
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(3-trimethoxysilylpropyl)diethylenetriamine [35141-30-1]
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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.
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.
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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.
The above content was quoted from
www.silicone.jp/e/
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