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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

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 low-molecular-weight butadiene-acrylonitrile copolymer with carboxyl groups (-COOH) at both ends of the molecular chain, classified as a reactive telechelic liquid rubber.

Appearance: Amber-colored viscous liquid (viscosity: ~8,000–12,000 cP at 25°C).
Structural Features:

Reactive carboxyl end groups
main chain with flexible butadiene segments and polar acrylonitrile units
acrylonitrile content: 18%–26%
number-average molecular weight: 3,000–4,000
Tg: approx. -40°C to -20°C

Key Advantages: Combines oil/solvent/aging resistance with low-temperature flexibility, high polarity, and strong adhesion; carboxyl groups chemically bond with epoxy, phenolic, polyurethane, and other resins, forming a stable “island-sea structure” that delivers toughening without significant loss of heat and medium resistance.

Product properties & Features

Enhances the toughness and flexibility of thermoset resins
lmproves adhesion to substrates that are difficult to bond to
Increases impact and crack resistance
Improves durability (fatique resistance)
Increases low-temperature mechanical properties

Application

1. Epoxy Resin Toughening
- Addition of 10%–15% boosts epoxy impact strength by 300%+, significantly reducing brittleness and improving crack and fatigue resistance.
- Used in aerospace structural adhesives, electronic potting compounds, advanced composite matrices, wind turbine blade adhesives.
2. Adhesives and Sealants
- Metal/composite bonding: Enhances peel strength, humidity/heat resistance, oil resistance, and low-temperature toughness.
- Sealants: Oil-resistant seals, weld seals, wind power seals for automotive/construction machinery.
3. Solid Propellants
- Serves as an energetic binder, improving propellant mechanical properties (elongation, low-temperature toughness) and processability.
4. Paints and Coatings
- Epoxy/phenolic coating modification: Improves impact resistance, abrasion resistance, salt spray resistance, and adhesion for heavy-duty anticorrosion, marine, pipeline, and automotive undercarriage applications.
5. Other Resin Modifications
- Toughening of phenolic, BMI, and cyanate ester resins for high-temperature structural components, electronic packaging, and high-performance laminates.

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.

Packing & Storage

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

Storage should be cool, dry and ventilated.The shelf life is 12 months, after the expiration of the re-inspection can still be used.

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 can research and develop any new versions of CTBN according to the special demand of our customers.

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