Fluoroelastomers

Viton™ Curing Agents

Technical Information
Introduction
There are three members of the family of Viton™ curingagents—Viton™ Curatives No. 1A (VC-1A), No. 3 (VC-3),
and No. 7 (VC-7).
VC-1A and VC-3 are diamines and find application in thecuring of the A, B, and E types of Viton™ fluoroelastomer.
VC-7, a reactive polyfunctional triazine, is a coagent
necessary for use with the “G-family” of peroxide-curable
Viton™ fluoroelastomers.
Viton™ curing agents differ in their curing activity
depending upon the conditions and the polymer in which
they are used. This bulletin gives product descriptions forthe three Viton™ curing agents as well as their principal
properties and applications. Also included are appropriate
references to technical literature reporting test resultsof Viton™ curing agents in different polymers and underdifferent conditions.
The data in this report compares the performance of thevarious Viton™ curing agents with each other. Many of theproperty and processing characteristics for compoundsof Viton™ (particularly compression set, scorch safety,and cure rate) can be improved still further through theuse of Viton™ Curative Masterbatches (Curative No. 20and No. 30). For information on curing with the Curative
Masterbatches, see the Chemours technical bulletin,“Compounding with Viton™ Curative Masterbatches.”
General Comments
VC-1A and VC-3 are widely used to cure the A, B, andE types of Viton™ fluoroelastomer. The main difference
between the Viton™ curing agents is in processing safety.
VC-1A gives the least processing safety, while VC-3 gives
the best and, at the same time, exhibits some plasticizing
effect. In general, the compression set and physicalproperties obtained with VC-3 are not quite as good aswith VC-1A.

Where FDA-approved vulcanizates of Viton™ are requiredin the formulation of rubber articles intended for repeateduse in contact with food, VC-1A should be used. For
more information, see the Chemours technical bulletin,“Viton™ in Applications Regulated by the Food and Drug
Administration.”
Handling Precautions
VC-1A and VC-3 may form flammable dust-air mixtures.
Also, they may cause irritation of eyes and skin. Keepaway from heat, sparks, and open flame. Use only in areas
provided with grounded equipment. Breathing of dust andcontact with eyes, skin, and clothing should be avoided.
Wash thoroughly after handling. Good ventilation should
be provided during all processing and curing operations;avoid dust hazards. Avoid breathing vapors during
processing.
In rat inhalation studies on VC-3, the approximate lethal
concentration (ALC) was found to be 6.2 mg/L of air foran exposure period of 4 hr. Observations indicated that
there was an irritating effect on the respiratory system.
If VC-3 is inhaled, remove to fresh air. If not breathing,give artificial respiration, preferably mouth-to-mouth. If
breathing is difficult, give oxygen. Call a physician.
VC-7 should be stored and used above its melting point(25 ± 2 °C [77 ± 4 °F]). Preferable temperature range
for storage and use is 30–40 °C (85–105 °F). Like theother Viton™ curing agents, it may cause irritation. Contact
with eyes, skin, and clothing should be avoided. Wash
thoroughly after handling.
For all three Viton™ curing agents, in case of contact,
immediately flush eyes with plenty of water for at least
15 min. Call a physician. Flush skin with water.

Viton™

Fluoroelastomers

Viton™ Curative No. 1A—Properties and Applications

Viton™ Curative No. 1A—Product Description

VC-1A provides excellent vulcanizate properties in theA, B, and E types of Viton™. Stocks containing VC-1A are
fast curing and have good physical properties, particularlyresistance to compression set and aging. However, suchcompounds have lower processing safety than those
cured with VC-3. Satisfactory cures are produced withroughly 1–1.5 phr of VC-1A.

Chemical Composition

Hexamethylenediamine carbamate_CO2+H3N—(CH2)6 —NHIn the A types of Viton™, in general, VC-1A producescompounds with higher tensile strength in both theoriginal and heat-aged conditions than those producedwith VC-3. In Viton™ B and B-50, VC-1A producescompounds having lower original tensile strength, buthigher tensile strength after heat-aging, than those
produced with VC-3.
For more complete information and data including test
results on the use of VC-1A in the A types of Viton™
and Viton™ B and B-50, see the Chemours technicalbulletins, “The Viton™ A-Type Fluoroelastomers,” “Viton™
B-50,” and “Compounding and Curing Viton™ for Maximum
Compression Set Resistance.”

Physical Form

Very fine powder

ColorWhiteOdor

Slight amine

Specific Gravity at
25/4 °C (77/39 °F)

1.28 ± 0.02

Decomposition Point

154.0 °C (309.2 °F) min.

Ash

0.1% max.

Moisture

0.5% max.

Purity98.0% min.

Solubility

Soluble in water; insoluble in non-polar solvents

Storage Stability

Excellent

CAS Registry No.

143-06-6

Viton™ Curative No. 3—Properties and Applications
VC-3 is a blocked diamine curing agent for Viton™. It gives
better processing safety than VC-1A and has someplasticizing effect, but, in general, vulcanizate properties
are not as good as those obtained with VC-1.

Viton™ Curative No. 3—Product Description
Chemical Composition

N,N’-dicinnamylidene-1,6 hexanediamine

H H H

Satisfactory cures in the A, B, and E types of Viton™ areproduced with roughly 3 phr of VC-3.

H H H—C=C—C=N—(CH2)6—N=C—C=C—

For more complete information and data including test
results on the use of VC-3 in the A types of Viton™ andViton™ B and B-50, see the Chemours technical bulletins,“The Viton™ A-Type Fluoroelastomers,” “Viton™ B-50,”
and “Compounding and Curing Viton™ for Maximum
Compression Set Resistance.”

Physical Form

Coarse powder

ColorTanOdor

CinnamonSpecific Gravity at
25/4 °C (77/39 °F)

1.09 ± 0.02

Viton™ Curative Nos. 1A and 3—Compounding andProcessing

Melting Point

80 °C (176 °F) min.

Ash

0.5% max.

For use with VC-1A and VC-3, the general-purpose acidacceptor system is low activity magnesium oxide. Calciumoxide may be used in place of magnesia to reduce theshrinkage of compounds of Viton™ during cure, eliminatevoids in thick sections, and improve compression set
resistance.

Moisture

0.5% max.

Particle Size

0.0% max. retained on No. 8 screen

Solubility

Slightly soluble in water; soluble in polar solvents

Storage Stability

Excellent

CAS Registry No.

140-73-8

Compounds of Viton™ cured with VC-1A or VC-3 should
be mixed on a mill that is kept as cool as possible. The
Viton™ curing agent should be blended thoroughly with thefiller before either it or the filler is added to the polymer.

2Viton™

Fluoroelastomers

This procedure minimizes dusting and, at the same time,improves dispersion considerably. Short scorch times withVC-1A may dictate its addition during a second pass on acool mill, especially in harder stocks.

The G-type Viton™ fluoroelastomers may be mixed using
conventional techniques. VC-7 should be blended withthe filler and all other ingredients and then added to thepolymer. This procedure improves dispersion considerably.

Stocks containing VC-1A or VC-3 are molded and cured
at temperatures and in a manner that is similar for all.
In general, press temperatures of 149–163 °C (300–325 °F) are satisfactory. Oven post-cure temperaturesof 204–260 °C (400–500 °F) are recommended
for applications involving high temperature service—
particularly those requiring high temperature compression
set resistance.

For more complete information and data including test
results on the use of VC-7 in the G-types of Viton™,
see the Chemours technical bulletins, “Viton™ GF” and“Viton™ GLT.”

Viton™ Curative No. 7—Product Description

Viton Curative No. 7—Properties and Applications™

Chemical Composition

VC-7 is a reactive polyfunctional triazine. It is a coagent
necessary for use with the “G-types” of peroxidecurable Viton™ fluoroelastomers. The “G-family” offluoroelastomers requires a peroxide and a coagent forcuring; peroxides, by themselves, are ineffective. VC-7, in
combination with peroxide, produces an excellent balanceof tensile properties and high temperature compression
set resistance, without sacrifice in heat resistance. VC-7
serves an entirely different purpose and should not be
confused with the other Viton™ curing agents—VC-1A andVC-3. The latter are all diamines and find application in
the curing of the A, B, and E types of Viton™.

Triallyl isocyanurate containing a small amountof a hydroquinone inhibitor for storage stability

CH2CH=CH2
O=C
CH2=CHCH2—NNC

C=O
N—CH2CH=CH2O

Because its melting point is near that of ambient room
temperature, VC-7 can be either in solid or liquid state,
depending on storage conditions. For both convenienceand consistent cure characteristics, it is recommended
that when a container of VC-7 is received, it bemelted thoroughly and stirred to ensure homogeneity.
Temperature while being melted should not exceed 50 °C(122 °F). It should then be stored above its melting
point, preferably between 30–40 °C (85–105 °F). Useof partially crystallized VC-7 can impart erratic curecharacteristics.
Generally, 2.5 to 4 parts of VC-7 provide a fast cure ratewith good processing safety and excellent vulcanizateproperties. The amount will vary with the particularpolymer and properties required. As would be expected,
increasing the amount of VC-7 will produce a vulcanizate
with a higher modulus and lower elongation. In Viton™ GLT,
4 parts of VC-7 provide the best balance of properties. In
Viton™ GF, 2.5 to 3 parts are preferred.

3Physical Form

Liquid above 27 °C (81 °F)

Color

Straw yellow

Odor

Pungent

Specific Gravity at
30/4 °C (86/39 °F)

1.16 ± 0.02

Melting Point

25 ± 2 °C (77 ± 4 °F)

Brookfield Viscosity at
30 °C (86 °F), cP

100 ± 15

Purity98.5% min.

Moisture

0.03% max.

Solubility

Slightly soluble in water; soluble in benzene,ethyl alcohol, acetone, and heptane

Storage Stability

Temperature in storage or while being melted
should not exceed 50 °C (122 °F)

CAS Registry No.

1025-15-6

Viton™

Fluoroelastomers

Test Procedures
Property Measured

Test Procedure

Compression Set

ASTM D395-85, Method B (25% deflection)

Compression Set—Low Temperature

ASTM D1299-87, Method B (25% deflection)

Compression Set, O-Rings

ASTM D1414-78 (87)

Hardness

ASTM D2240-87, durometer A

Mooney Scorch

ASTM D1646-87, using the small rotor. Minimum viscosity and time to a1-, 5-, or 10-unit rise are reported.

Mooney Viscosity

ASTM D1646-87, ten pass 100 °C (212 °F), 121 °C (250 °F)

ODR (vulcanization characteristics measured with an oscillating disk cure meter)

ASTM D2084

Property Change After Oven Heat-Aging

ASTM D573-88

Stress/Strain Properties
100% Modulus
Tensile Strength
Elongation at BreakASTM D412-87, pulled at 8.5 mm/sec (20 in/min)

Stiffness, Torsional, Clash-Berg

ASTM D1043-87

Temperature Retraction

ASTM D1329-88

Volume Change in Fluids

ASTM D471-79

Note: Test temperature is 24 °C (75 °F), except where specified otherwise.

NO PART OF THIS MATERIAL MAY BE REPRODUCED, STORED IN A RETRIEVAL SYSTEM OR TRANSMITTED IN ANY FORM OR BY ANY MEANS ELECTRONIC, MECHANICAL, PHOTOCOPYING, RECORDING OR OTHERWISEWITHOUT THE PRIOR WRITTEN PERMISSION OF CHEMOURS.

© 2023 The Chemours Company FC, LLC. Viton™ and any associated logos are trademarks or copyrights of The Chemours Company FC, LLC. Chemours™ and the Chemours Logo aretrademarks of The Chemours Company.

C-10981 1121

The information set forth herein is furnished free of charge and based on technical data that Chemours believes to be reliable. It is intended for use by persons having technical skill, at their own
discretion and risk. The handling precaution information contained herein is given with the understanding that those using it will satisfy themselves that their particular conditions of use present
no health or safety hazards. Because conditions of product use are outside our control, Chemours makes no warranties, express or implied, and assumes no liability in connection with any useof this information. As with any material, evaluation of any compound under end-use conditions prior to specification is essential. Nothing herein is to be taken as a license to operate under or arecommendation to infringe any patents.

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