Product Overview

Carboxyl-Functional Silicone Oil

What Are Carboxyl-Functional Silicone Oil ?

Carboxyl-Functional Silicone Oils are modified polysiloxane fluids in which carboxyl groups (–COOH) are chemically introduced onto the siloxane backbone or at the chain ends. Unlike standard dimethyl silicone oil (PDMS), which is chemically inert, carboxyl-functional silicone oils contain reactive acidic functional sites that enable chemical bonding, crosslinking, or interaction with other polymers and substrates.

SiliconChemicals Carboxyl-Functional Silicone Oil is a reactive polysiloxane fluid engineered with pendant or terminal carboxyl (–COOH) functional groups along the siloxane backbone. By introducing controlled acidic functionality into a thermally stable Si–O–Si structure, this product bridges the gap between inert silicone fluids and chemically interactive polymer systems. Unlike standard dimethyl silicone oil (PDMS), which primarily delivers lubrication and thermal stability, SiliconChemicals™ Carboxyl-Functional grades provide enhanced adhesion, crosslinking capability, and compatibility with polar substrates and resin matrices.

Model CodeProduct TypeFunctional Density (COOH wt%)Viscosity (25°C, cSt)Molecular StructureAcid Value (mg KOH/g)Application Positioning
CFS-50-LLow Functional Grade0.2–0.5%50Pendant COOH1–3Textile finishing
CFS-100-LLow Functional Grade0.2–0.5%100Pendant COOH1–3Resin modifier
CFS-200-MMedium Functional0.5–1.0%200Pendant COOH3–6Adhesion promoter
CFS-350-MMedium Functional0.5–1.0%350Pendant COOH3–6PU compatibility
CFS-500-MMedium Functional0.5–1.0%500Pendant COOH4–8Coating additive
CFS-1000-HHigh Functional1.0–2.0%1000Pendant COOH8–15Reactive crosslinking
CFS-2000-HHigh Functional1.0–2.0%2000Pendant COOH8–15Polymer integration
CFS-5000-HHigh Functional1.0–2.0%5000Pendant COOH10–18Elastomer systems
CFS-T100Terminal Functional0.5–1.5%100End-functional4–10Controlled chain extension
CFS-T500Terminal Functional0.5–1.5%500End-functional6–12Crosslinkable intermediate
CFS-DUAL-300Dual Functional0.5–1.0%300Pendant + Terminal5–12Hybrid resin systems
CFS-ULV-200Ultra-Low Volatile0.5–1.0%200Pendant COOH3–6Electronics
CFS-HT-350High Temp Stable0.5–1.0%350Phenyl-modified4–8High-temp coatings
CFS-AERO-500Aerospace Grade0.5–1.5%500Stabilized backbone6–10Advanced composites
CFS-WET-100Wetting Grade0.2–0.8%100Surface-modified2–5Surface treatment
CFS-PU-400Polyurethane Reactive0.5–1.5%400Reactive COOH5–12PU systems
CFS-EP-350Epoxy Compatible0.5–1.0%350Resin-compatible4–8Epoxy modification
CFS-TEX-200Textile Reactive0.3–0.8%200Flexible backbone2–6Textile finishing
CFS-ELAST-1000Elastomer Grade1.0–2.0%1000High MW8–15Rubber blending
CFS-CUSTOMCustom FunctionalAdjustable50–10000+TailoredCustomOEM formulation

 

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Product Range & Functional Classification

Carboxyl-Functional Silicone Oil (COOH-Functional Polysiloxane) is a reactive silicone platform designed for adhesion enhancement, polymer modification, and controlled crosslinking systems. Its product range is defined primarily by functional density (COOH content), molecular architecture, viscosity range, and application-oriented performance tuning.

1️⃣ By Functional Density (COOH Content)
CategoryCOOH ContentAcid Value (mg KOH/g)Performance Focus
Low Functional0.2–0.5%1–3Surface modification & compatibility
Medium Functional0.5–1.0%3–8Adhesion promotion
High Functional1.0–2.0%8–18Crosslinking & reactive systems
Custom FunctionalAdjustableCustomOEM polymer integration

Higher functional density increases reactivity but may also affect viscosity and polarity.

2️⃣ By Molecular Architecture
Structure TypeDescriptionApplication Direction
Pendant FunctionalCOOH groups grafted along side chainsAdhesion & resin compatibility
Terminal FunctionalCOOH groups at chain endsControlled chain extension
Dual FunctionalBoth terminal and pendantHybrid polymer networks
Phenyl-Stabilized ReactiveCOOH + Phenyl modifiedHigh-temp reactive systems
High Molecular WeightIncreased backbone lengthElastomer reinforcement
3️⃣ By Viscosity Range (25°C)
Viscosity ClassRange (cSt)Typical Use
Low Viscosity50–200Coating additives
Medium Viscosity200–1000Resin modifiers
High Viscosity1000–5000Crosslinkable intermediates
Ultra-High5000–10000+Elastomer blending
Custom MWOn requestSpecialized formulations
🔹 Adhesion Promoter Grade

Improves bonding to metal, glass, textile fibers, and polar polymers through hydrogen bonding and ionic interaction.

🔹 Polymer Reactive Modifier

Designed for polyurethane, epoxy, acrylic, and hybrid resin systems to enhance compatibility and network integration.

🔹 Crosslinking Intermediate

Used in controlled condensation or esterification reactions for elastomer and specialty coating systems.

🔹 Textile Finishing Grade

Provides improved fiber interaction while maintaining silicone softness and flexibility.

🔹 Surface Treatment Additive

Balances silicone hydrophobicity with controlled polarity for better wetting and film formation.

🔹 Elastomer Reinforcement Fluid

Improves polymer dispersion and mechanical performance in rubber systems.

ParameterCoverage
Functional Density0.2–2.0% COOH
Acid Value1–18 mg KOH/g
Viscosity50–10000+ cSt
ArchitecturePendant / Terminal / Dual
CustomizationMolecular weight & reactivity adjustable

Carboxyl-Functional Silicone Oil is positioned as a reactive silicone modifier platform, not merely a lubricating fluid. Its classification revolves around reactivity level, molecular structure, and integration capability within polymer matrices. By controlling functional density and backbone design, performance can be precisely tuned for adhesion, crosslinking efficiency, resin compatibility, or elastomer reinforcement.

Siliconchemicals Carboxyl-Functional Silicone Oil

SiliconChemicals™ Carboxyl-Functional Silicone Oil is a high-performance reactive polysiloxane engineered with controlled carboxyl (–COOH) functional groups integrated into the siloxane backbone. By combining the thermal stability and flexibility of silicone with chemically active acidic functionality, this product line is designed for advanced adhesion promotion, polymer modification, and crosslinkable systems.

Unlike conventional dimethyl silicone fluids that primarily serve as lubricants or release agents, SiliconChemicals™ Carboxyl-Functional grades act as reactive modifiers, enabling chemical interaction with polyurethane, epoxy, acrylic, and hybrid polymer matrices.

SiliconChemicals™ Carboxyl-Functional Silicone Oil is positioned as a reactive silicone modifier platform, designed for formulators who require chemical integration rather than passive surface lubrication.

For OEM projects, custom acid value control, molecular weight tuning, or formulation consultation, SiliconChemicals™ provides precision-engineered silicone solutions with consistent global supply reliability.

Chemical Structure & Functional Mechanism

SiliconChemicals™ Carboxyl-Functional Silicone Oil is a modified polysiloxane in which reactive carboxyl groups (–COOH) are chemically introduced onto a siloxane backbone. This modification transforms a typically inert silicone fluid into a chemically interactive polymer modifier.

1️⃣ Base Backbone: Siloxane Chain

The fundamental framework is the polysiloxane chain:

−Si−O−Si−repeatingbackbone-Si-O-Si- repeating backbone

This backbone provides:

  • High thermal stability
  • Excellent flexibility
  • Low glass transition temperature
  • Chemical inertness (before modification)
2️⃣ Functional Group Introduction

Carboxyl-functional silicone oils incorporate organic spacer groups bearing a terminal –COOH group.

Representative structural unit:

−Si−O−Si−R−COOH-Si-O-Si-R-COOH

Where:

  • Si–O–Si = siloxane backbone
  • R = organic linker (e.g., alkyl or propyl spacer)
  • –COOH = carboxyl functional group

The carboxyl group may be:

  • Pendant (side-chain grafted)
  • Terminal (chain-end functional)
  • Dual-functional (side + terminal)
3️⃣ Molecular Design Parameters

The final structure is determined by:

  • Functional density (COOH content %)
  • Acid value (mg KOH/g)
  • Molecular weight
  • Distribution of functional sites
  • Presence of secondary modifications (phenyl, alkyl, etc.)

These parameters directly influence reactivity and compatibility behavior.

The introduction of the –COOH group fundamentally changes the interaction profile of silicone oil.

1️⃣ Hydrogen Bonding Mechanism

The carboxyl group can form hydrogen bonds with:

  • Metal oxides
  • Glass surfaces
  • Textile fibers
  • Polar polymer chains

This enhances interfacial adhesion and surface anchoring.

2️⃣ Ionic Interaction & Salt Formation

In alkaline environments, –COOH groups can form carboxylate salts:

R−COOH−>R−COO−+H+R-COOH -> R-COO^- + H^+

This increases polarity and improves compatibility in aqueous or polar systems.

3️⃣ Esterification / Condensation Reaction

Carboxyl groups can react with hydroxyl groups to form ester linkages:

R−COOH+R′−OH−>R−COOR′+H2OR-COOH + R’-OH -> R-COOR’ + H2O

This enables:

  • Controlled crosslinking
  • Network formation
  • Polymer chain extension
  • Enhanced mechanical stability
4️⃣ Amide Formation (With Amines)

In systems containing amines:

R−COOH+R′−NH2−>R−CONHR′+H2OR-COOH + R’-NH2 -> R-CONHR’ + H2O

This reaction pathway is particularly relevant in polyurethane and epoxy formulations.

5️⃣ Surface Polarity Adjustment

Pure PDMS is highly hydrophobic.
Carboxyl functionalization:

  • Increases polarity
  • Improves wetting of polar substrates
  • Enhances dispersion in resin systems
  • Maintains silicone flexibility
Structural FeatureResulting Functional Effect
Siloxane backboneThermal stability & flexibility
COOH functional groupChemical reactivity
Increased polarityImproved adhesion
Controlled acid valueTunable crosslinking
Molecular weight tuningViscosity control

SiliconChemicals™ Carboxyl-Functional Silicone Oil is not a passive lubricant-grade fluid. It is a reactive silicone integration platform.

Its mechanism can be summarized as:

  1. Flexible siloxane backbone provides durability
  2. Carboxyl groups provide chemical bonding capability
  3. Controlled functional density enables system tuning
  4. Polymer compatibility improves formulation performance

The result is a silicone fluid capable of chemically anchoring into polyurethane, epoxy, acrylic, elastomer, and hybrid polymer networks while maintaining silicone-derived flexibility and thermal resistance.

Typical Applications

SiliconChemicals™ Carboxyl-Functional Silicone Oil is primarily positioned as a reactive silicone modifier, used in systems where chemical interaction, adhesion improvement, or controlled crosslinking is required. Unlike inert PDMS fluids, its –COOH functional groups enable integration into polymer networks and enhanced substrate bonding.

Carboxyl groups interact with isocyanate or hydroxyl-containing systems, improving:

  • Interfacial bonding
  • Polymer dispersion
  • Mechanical stability
  • Compatibility between silicone and PU phases

Used in:

  • PU coatings
  • PU elastomers
  • PU sealants
  • Flexible foam modification

Carboxyl-functional silicone oil enhances adhesion to:

  • Metal surfaces
  • Glass substrates
  • Mineral fillers
  • Textile fibers
  • Engineering plastics

Applications include:

  • Industrial protective coatings
  • Functional primers
  • Metal treatment systems
  • Anti-corrosion coatings

Due to the –COOH functionality, these materials participate in:

  • Esterification reactions
  • Amide formation
  • Salt formation in alkaline systems

This makes them suitable for:

  • Controlled network formation
  • Hybrid polymer systems
  • Silicone-organic resin blends

In textile processing, carboxyl-functional silicone oils provide:

  • Improved fiber anchoring
  • Enhanced durability after washing
  • Balanced softness and surface interaction
  • Better bonding to natural and synthetic fibers

Used in:

  • Fabric softeners
  • Functional textile coatings
  • High-performance fiber treatments

In elastomer systems, they serve as:

  • Compatibility enhancers
  • Dispersion improvers
  • Reactive plasticizers
  • Interfacial bonding promoters

Applicable to:

  • Silicone rubber blends
  • Hybrid elastomer systems
  • Specialty composite rubbers

The increased polarity from –COOH groups improves:

  • Wetting behavior
  • Surface energy adjustment
  • Interfacial bonding performance

Used in:

  • Surface modification additives
  • Specialty resin formulations
  • Adhesive systems

For high-performance applications requiring both flexibility and chemical bonding capability:

  • Hybrid silicone-organic materials
  • Composite matrix systems
  • High-durability coatings
  • Engineering polymer blends

SiliconChemicals™ Carboxyl-Functional Silicone Oil is best suited for:

  • Systems requiring chemical bonding
  • Adhesion enhancement
  • Resin compatibility improvement
  • Controlled crosslinking
  • Interfacial performance tuning

It functions not as a simple lubricant, but as a reactive silicone integration platform, enabling formulators to combine the durability of silicone with the bonding strength of organic polymer systems.

Why Use Carboxyl-Functional Silicone Oil ?

Carboxyl-Functional Silicone Oil is selected when a formulation requires chemical interaction, not just lubrication or surface slip. By introducing reactive carboxyl groups (–COOH) into the siloxane backbone, the material becomes capable of bonding, crosslinking, and integrating into polymer systems while maintaining silicone flexibility and thermal stability.

Below are the primary engineering reasons to use this technology.

Standard PDMS is chemically inert.
Carboxyl-functional silicone oil contains reactive sites:

R−COOHR-COOH

These groups allow:

  • Hydrogen bonding
  • Ionic interaction
  • Esterification
  • Amide formation

This transforms silicone from a passive additive into an active network participant.

The –COOH group increases polarity and enhances bonding to:

  • Metals
  • Glass
  • Mineral fillers
  • Textiles
  • Engineering plastics

This is critical in coating and composite systems where interfacial failure is a risk.

Carboxyl groups react with hydroxyl or amine-containing systems:

R−COOH+R′−OH−>R−COOR′+H2OR-COOH + R’-OH -> R-COOR’ + H2O

Result:

  • Improved dispersion
  • Reduced phase separation
  • Stronger polymer network integration
  • Enhanced mechanical durability

In reactive formulations, –COOH groups allow:

  • Controlled condensation reactions
  • Tunable crosslink density
  • Improved film integrity
  • Enhanced abrasion resistance

This is especially important in high-performance coatings and elastomer systems.

Despite its reactivity, it retains:

  • Thermal stability
  • Low glass transition temperature
  • Chemical resistance
  • Flexibility
  • Weather resistance

You gain bonding capability without sacrificing silicone durability.

Hybrid silicone-organic systems often suffer from poor interfacial compatibility.
Carboxyl-functional silicone oil:

  • Acts as a compatibilizer
  • Improves stress distribution
  • Reduces microphase separation
  • Enhances mechanical longevity

Functional density and molecular weight can be tailored to:

  • Adjust reactivity level
  • Control acid value
  • Modify viscosity
  • Balance polarity and hydrophobicity

This allows precision tuning for OEM applications.

Use Carboxyl-Functional Silicone Oil when your system requires:

  • Adhesion enhancement
  • Polymer compatibility improvement
  • Reactive integration into PU/epoxy systems
  • Controlled crosslinking
  • Surface energy adjustment
  • Interfacial bonding reinforcement

It is not merely a silicone fluid — it is a reactive silicone integration platform designed for advanced formulation engineering.

How to Choose the Right Carboxyl-Functional Silicone Oil ?

Selecting the correct Carboxyl-Functional Silicone Oil requires aligning functional density, molecular structure, viscosity, and system chemistry with your formulation objectives. Unlike inert silicone fluids, reactive COOH-functional grades must be matched precisely to polymer chemistry and performance requirements.

Below is a structured engineering selection framework.

First determine whether your formulation requires:

  • Hydrogen bonding only
  • Esterification with hydroxyl groups
  • Amide formation with amines
  • Salt formation in alkaline systems

Representative reaction pathway:

R−COOH+R′−OH−>R−COOR′+H2OR-COOH + R’-OH -> R-COOR’ + H2O

If chemical bonding is required, select medium to high functional density grades.
If only surface compatibility is needed, low functional grades are sufficient.

Application TypeRecommended COOH Level
Surface modification0.2–0.5%
Adhesion promotion0.5–1.0%
Reactive crosslinking1.0–2.0%
OEM polymer integrationCustom

Higher functional density increases reactivity but may raise polarity and viscosity.

ArchitectureWhen to Use
Pendant FunctionalResin compatibility & adhesion
Terminal FunctionalChain extension control
Dual FunctionalHybrid network formation
High Molecular WeightElastomer reinforcement

Terminal-functional grades are preferred in controlled crosslink systems, while pendant-functional types improve dispersion and substrate bonding.

Viscosity impacts processability and dispersion:

ApplicationTypical Viscosity
Coating additives50–200 cSt
Resin modifiers200–1000 cSt
Crosslink intermediates1000–5000 cSt
Elastomer blending5000–10000+ cSt

Always evaluate viscosity–temperature behavior across processing conditions.

Check compatibility with:

  • Polyurethane systems
  • Epoxy resins
  • Acrylic formulations
  • Hybrid silicone-organic matrices

If phase separation risk exists, consider:

  • Lower functional density
  • Modified backbone structure
  • Optimized molecular weight distribution

Acid value influences:

  • Reactivity rate
  • Cure kinetics
  • Stability during storage

For moisture-sensitive systems, ensure compatibility with curing mechanism and catalyst system.

For systems exposed to:

  • High temperature
  • Humidity
  • Mechanical stress

Select grades with:

  • Stabilized backbone design
  • Controlled impurity levels
  • Optimized functional distribution
Quick Decision Matrix
Primary ObjectiveRecommended Grade Type
Improve adhesionMedium functional, pendant type
Enhance PU compatibilityMedium functional
Enable crosslinkingHigh functional, terminal type
Elastomer reinforcementHigh MW functional
Surface polarity adjustmentLow functional
Custom reactive systemTailored COOH density
Engineering Principle

Choose Carboxyl-Functional Silicone Oil based on:

Reaction Chemistry + Functional Density + Molecular Architecture + Viscosity + Resin Compatibility

This ensures the silicone component integrates chemically rather than acting as a passive additive.

If you provide:

  • Base resin type
  • Target viscosity
  • Desired bonding strength
  • Processing temperature
  • Cure mechanism

I can generate a precise grade recommendation tailored to your formulation.

Packaging & Storage

Packaging:  500 g / 1 kg / 5 kg / 25 kg / 200 kg drums / 1000L IBC container (Customized packaging is available).

Ready to Enhance Adhesion & Reactive Performance?

Selecting the right Carboxyl-Functional Silicone Oil is not just about viscosity — it is about achieving precise chemical integration within your polymer system. Whether you are formulating polyurethane coatings, hybrid resins, elastomers, or advanced surface treatments, the correct COOH functional density and molecular architecture directly determine bonding strength, compatibility, and long-term durability.

At SiliconChemicals™, we provide engineered carboxyl-functional silicone solutions designed for controlled reactivity, optimized acid value, and consistent global quality standards.

We support you with:

  • Detailed Technical Data Sheets (TDS)
  • Acid Value & Functional Density Control
  • Viscosity–Temperature Profiles
  • Compatibility Testing Guidance
  • OEM Molecular Weight Customization
  • Bulk & Tailored Supply Programs

If you share:

  • Base resin system (PU, epoxy, acrylic, etc.)
  • Target viscosity range
  • Required adhesion level
  • Cure mechanism & processing conditions

Our technical team will recommend a precisely matched grade for your formulation.

SiliconChemicals
Reactive Silicone Technology · Precision Functional Control · Global Supply Reliability

Contact us today to discuss your application requirements and receive a customized technical recommendation.

Disclaimer

“The information provided herein is based on general industry experience and is intended for reference purposes only. Actual performance and optimal usage conditions may vary depending on formulation, processing methods, substrate characteristics, and end-use requirements. Users are responsible for conducting their own tests and evaluations to determine suitability for their specific applications. No warranty, express or implied, is made regarding the completeness, accuracy, or applicability of this information.”

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Comprehensive Sourcing Guide for Silicone oils 2026

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