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Carboxy-Terminated Nitrile Butadiene Rubber(CTBN) CAS No. 25265-19-4 CTBN

Carboxyl-terminated butadiene-acrylonitrile

CTBN

CAS No. 25265-19-4

Chemical name: Carboxyl-terminated butadiene-acrylonitrile

Other name: Carboxy-Terminated Nitrile Butadiene Rubber

Code: CTBN

CAS No.: 25265-19-4

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Product Description
Product Properties
Applications
Packing & Storage
Technical Index

Product Description

CTBN (Carboxyl-Terminated Butadiene-Acrylonitrile) is a high-molecular polymer polymerized from butadiene and acrylonitrile monomers, with carboxyl groups at the ends of its molecular chains. It appears as a brown viscous liquid at room temperature.

Structural Features:

Reactive terminal carboxyl groups for chain extension & crosslinking
Acrylonitrile segments in the main chain offer high polarity, oil resistance, wide temperature tolerance, superior adhesion and stability.
It can blend with thermosetting structural resins for modification and enhance crack resistance.
acrylonitrile content: 8%–28% (Customizable)

NOTE：The viscosity of CTBN increases significantly with the rise of nitrile group content in the molecular chain. The dosage of additives including colorants, stabilizers, curing agents and fillers shall be determined according to viscosity. Viscosity is a vital indicator of its service performance.

As the most critical parameter of CTBN, acrylonitrile content directly governs the overall properties and exerts a profound influence on its processability and applications.

The incorporation of acrylonitrile into molecular chains improves the compatibility of CTBN with epoxy resins and phenolic resins, and enhances adhesion, oil resistance and crack resistance.

Acrylonitrile Content	Characteristics	Suitable Applications
Low nitrile (~10%)	Low viscosity, good low-temperature performance	Applications requiring low-temperature toughness
Medium nitrile (~18%)	Balanced comprehensive performance	General toughening, structural adhesives
High nitrile (~28%)	High polarity, good compatibility with epoxy, excellent oil resistance	High-performance composites, oil-resistant seals

Product properties & Features

High-efficiency toughening & flexibility
Strong adhesion to difficult substrates
Superior impact & crack resistance
Excellent fatigue durability
High reactivity
Wide temperature tolerance (heat & low-temperature resistance)
Good chemical resistance
Excellent resin compatibility

Key Property Comparison (CTBN vs. Conventional HTPB)

Polarity: CTBN (strong, with acrylonitrile) > HTPB
Adhesion: CTBN superior to metals/polar substrates
Oil Resistance: CTBN significantly better than HTPB
Reactive Sites: CTBN (dicarboxyl end groups); HTPB (dihydroxyl end groups)
Typical Uses: CTBN prioritizes epoxy toughening, oil-resistant adhesives/sealants; HTPB prioritizes polyurethanes, propellants, low-temperature flexible materials.

Applications

1. Epoxy Resin Toughening

Reduce brittleness of epoxy systems, enhance impact, crack and fatigue resistance, applied in wind power and aerospace composite matrices

2. High-performance Adhesives & Sealants

Improve bonding strength of metals and composites, optimize temperature, oil, humidity resistance and low-temperature toughness for automotive and wind power sealing parts
Suitable for bonding plexiglass and polyester tapes with remarkably enhanced properties; it can also be used for impregnating glass fiber, polyester, carbon fiber and other fabrics.
As abrasive binder for grinding wheels and cut-off wheels, it requires less binder and offers outstanding wear resistance, excellent polishing effect, as well as good resistance to hot water and cutting fluids.

3. Aerospace Composites

Fabricate structural adhesives and heat-resistant laminates to strengthen mechanical properties of aviation components

4. Electronic Encapsulation Materials

Modify packaging resins to boost corrosion and impact resistance for electronic potting and chip encapsulation

5. Rubber & Special Resin Modification

Toughen phenolic, BMI and cyanate ester resins; improve oil resistance and low-temperature ductility of rubber substrates

Packing & Storage

50kg/plastic drum or 170kg/metal drum packaging.

The shelf life is 12 months, after the expiration of the re-inspection can still be used.

Storage should be cool, dry and ventilated.

Avoid rain and sun during transportation. Do not mix with strong oxidants.

Technical Index

Item	CTBN-1	CTBN-2	CTBN-3	CTBN-4	CTBN-5
Carboxyl value(mmol/g)	0.45-0.55	0.45-0.65	0.45-0.65	0.65-0.75	0.45-0.70
Appearance	Amber Viscous liquid, no visible impurities
Viscosity (27℃,Pa.S)	≤180	≤200	≤300	≤200	≤600
Acrylonitrile content,%	8.0-12.0	8.0-14.0	18.0-22.0	18.0-22.0	24.0-28.0
Moisture,wt% ≤	0.05	0.05	0.05	0.05	0.05
Volatile Content,% ≤	1.0	1.0	1.0	1.0	1.0
Molecular weight	3600-4200	3000-4500	3000-4500	2500-3000	3000-4500

*NOTE: We are able to customize CTBN based on customers' intended applications and required specifications.

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