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Introduction
3-Ureidopropyltrimethoxysilane (UPTMS) is an organosilane compound widely employed as a coupling agent to improve the compatibility between inorganic and organic materials.
The molecule contains two distinct functional moieties: a trialkoxysilane group capable of forming covalent bonds with inorganic substrates such as glass, metals, and mineral fillers; and a ureido group which provides reactive sites for hydrogen bonding and interaction with organic polymers.
CAS Number: 23843-64-3
Synonyms:
N-[3-(Trimethoxysilyl)propyl]urea, γ-Ureidopropyltrimethoxysilane,3-TMSU,UPTMS,Silane, trimethoxy(3-ureidopropyl)-,3-(Trimethoxysilyl)propylurea
The use of silane coupling agents like UPTMS revolutionized material science, enabling enhanced mechanical properties, improved adhesion, and chemical resistance in composites, coatings, and adhesives.
The ureido functional group distinguishes UPTMS from other silanes by enabling additional interactions, making it a valuable additive in high-performance materials and surface modification.
This article explores the full scientific profile of 3-ureidopropyltrimethoxysilane, from chemical identity, synthesis, and reaction mechanisms to applications in various industries, safety considerations, and future prospects.
Chemical Identity and Structure
Chemical Name and Identifiers
IUPAC Name: 3-(Trimethoxysilyl)propylurea
Common Name: 3-Ureidopropyltrimethoxysilane
CAS Number: 23843-64-3
Molecular Formula: C7H18N2O4Si
Molecular Weight: 222.32 g/mol
Molecular Structure
The molecule consists of:
A silicon atom bonded to three methoxy groups (–OCH3), which are labile and readily hydrolyze to silanols (–Si–OH) in the presence of moisture.
A propyl linker (three carbon chain) connecting the silicon to the ureido group.
A ureido functional group (–NH–CO–NH2) which is capable of hydrogen bonding and can engage in secondary chemical reactions.
The silicon center allows for covalent bonding with inorganic substrates, while the urea group increases interaction possibilities with organic materials, providing multifunctionality.
Physicochemical Properties
Physical Properties
Appearance: Colorless to pale yellow liquid
Odor: Mild, characteristic of silanes
Density: Approximately 1.07 g/cm³ at 25 °C
Boiling Point: Approximately 270 °C at atmospheric pressure
Flash Point: >100 °C, indicating moderate flammability
Refractive Index: ~1.426
Viscosity: Low to moderate, facilitating easy mixing in formulations
Chemical Properties
Hydrolysis: Highly moisture sensitive; the methoxy groups hydrolyze to silanols rapidly in presence of water, releasing methanol.
Reactivity: Reacts with hydroxyl groups on surfaces to form siloxane bonds (Si–O–Si), establishing strong covalent attachments.
Solubility: Insoluble in water but hydrolyzes when exposed to moisture. Soluble in organic solvents like alcohols, toluene, and acetone.
pH: Neutral to slightly acidic in aqueous solution after hydrolysis.
Stability
Shelf Life: Generally stable for 6-12 months if stored under dry, inert atmosphere conditions.
Sensitivity: Sensitive to moisture and acidic/basic conditions which can accelerate polymerization and degradation.
Synthesis and Manufacturing
Raw Materials
3-Aminopropyltrimethoxysilane (APTMS): serves as the precursor silane with an amino group.
Urea or isocyanates: provide the ureido functionality by reacting with the amine.
Synthetic Route
The primary synthetic route involves nucleophilic addition of urea to the amino functional group of APTMS under controlled conditions.
The reaction is usually performed in anhydrous organic solvents such as toluene or methanol to prevent premature hydrolysis of the methoxy groups.
Catalyst: Sometimes acid or base catalysts facilitate the urea formation step.
Purification: Removal of unreacted materials by distillation or recrystallization.
Alternative Methods
Isocyanate intermediates may also be used for urea group introduction, providing higher selectivity and yield in some processes.
Industrial Considerations
Moisture exclusion is critical during production to prevent premature silane condensation.
Careful control of temperature and stoichiometry optimizes product purity and yield.
Methanol is a by-product and is removed under reduced pressure.
Analytical Methods
Nuclear Magnetic Resonance (NMR)
1H NMR and 13C NMR confirm the presence of methoxy groups, propyl chain, and urea functionality.
Characteristic chemical shifts appear for methyl protons (~3.6 ppm), methylene protons (~1.4–3.5 ppm), and urea NH protons (6–8 ppm).
Fourier-Transform Infrared Spectroscopy (FTIR)
Strong absorption bands:
Si–O–CH3 stretching near 1100 cm⁻¹
N–H stretching of ureido group around 3300 cm⁻¹
C=O stretching of urea at ~1650 cm⁻¹
Si–O–Si bands after hydrolysis and condensation (~1000–1100 cm⁻¹)
Gas Chromatography-Mass Spectrometry (GC-MS)
Used for purity analysis and to detect volatile impurities like methanol.
Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC)
Determine thermal stability and decomposition profile.
Surface Analytical Techniques
X-ray Photoelectron Spectroscopy (XPS) assesses elemental composition on treated surfaces.
Atomic Force Microscopy (AFM) evaluates surface morphology changes after silane treatment.
Hydrolysis and Condensation Behavior
Hydrolysis Kinetics
The hydrolysis rate depends on:
pH: Acidic and basic conditions accelerate hydrolysis; neutral pH slows it.
Temperature: Higher temperatures increase reaction rates.
Water concentration: Higher moisture increases hydrolysis rate.
Condensation and Polymerization
After hydrolysis, silanol groups condense forming polysiloxane networks.
The degree of polymerization impacts film formation, crosslink density, and final material properties.
Applications
Adhesion Promoters
UPTMS enhances the bonding between organic resins and inorganic substrates by chemically linking both phases.
Its ureido functionality allows secondary bonding mechanisms that improve interfacial strength.
Used in epoxy and polyurethane adhesives for glass and metal bonding.
Improves durability and resistance to moisture and thermal cycling.
Coatings and Sealants
In coatings, UPTMS contributes to:
Improved surface adhesion
Increased weather and abrasion resistance
Enhanced chemical resistance
Water repellency through siloxane networks
Mineral Surface Treatment
UPTMS treats fillers such as:
Silica
Talc
Calcium carbonate
This treatment improves dispersion within polymer matrices and strengthens composite interfaces.
Composites
Enhances mechanical properties (tensile strength, impact resistance) of fiber-reinforced composites.
Used in automotive, aerospace, and construction industries.
Hybrid Organic–Inorganic Materials
In sol-gel chemistry, UPTMS acts as a molecular bridge forming hybrid materials with tailored properties, such as transparent, flexible, or hydrophobic coatings.
Industrial Use Case Studies
Automotive Industry
Used to bond glass to polyurethane adhesives in windshields, providing weatherproof and durable seals.
Electronics
Surface functionalization of glass and silica substrates to improve adhesion of polymeric dielectrics.
Construction
Enhances sealants and adhesives used for concrete and masonry, improving longevity and moisture resistance.
Compatibility with Resins and Polymers
Epoxy resins: Forms strong covalent and hydrogen bonds, excellent compatibility.
Polyurethanes: Reacts well with isocyanate groups, improving toughness.
Acrylics: Moderate compatibility via hydrogen bonding.
Polyesters: Good adhesion enhancement.
Phenolics: Suitable for specialty adhesives.
Compatibility testing is essential for each formulation to optimize performance.
Reactivity with Substrates
UPTMS forms strong chemical bonds with substrates containing hydroxyl groups:
Glass and silica: Covalent Si–O–Si bonds form robust interfaces.
Metals with oxide layers (Al, Ti, Fe): Covalent Si–O–M bonds create adhesion sites.
Mineral fillers: Enhances filler–matrix interaction.
Surface Modification Capabilities
Imparts hydrophilicity/hydrophobicity depending on treatment conditions.
Reduces filler agglomeration and improves dispersion.
Increases interfacial adhesion leading to better mechanical properties.
Functionalization in Nanotechnology
Surface modification of silica and titania nanoparticles enhances dispersion and interfacial bonding in nanocomposites.
Functionalized surfaces improve compatibility with polymers in electronic and biomedical applications.
SAFETY INFORMATION ABOUT 3-UREIDOPROPYLTRIMETHOXYSILANE
First aid measures:
Description of first aid measures:
General advice:
Consult a physician.
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
If inhaled:
If breathed in, move person into fresh air.
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off contaminated clothing and shoes immediately.
Wash off with soap and plenty of water.
Consult a physician.
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
If swallowed:
Do NOT induce vomiting.
Never give anything by mouth to an unconscious person.
Rinse mouth with water.
Consult a physician.
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment.
Avoid breathing vapours, mist or gas.
Evacuate personnel to safe areas.
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste.
Keep in suitable, closed containers for disposal.
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place.
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles.
Faceshield (8-inch minimum).
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
Skin protection:
Handle with gloves.
Gloves must be inspected prior to use.
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product.
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices.
Wash and dry hands.
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls.
If the respirator is the sole means of protection, use a full-face supplied air respirator.
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions.
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company.
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product
