Technical Data Sheet: TAM 3 Accelerator
S         S
ll         ll
C3H7-O-C-S-S-C-O-C3H7

Dipropyl xanthogen disulfide

FORM:
Free-flowing yellow to amber liquid

SPECIFIC GRAVITY:
1.20

SOLUBILITY:
Insoluble in water. Soluble in acetone, benzene. Gasoline and ethylene dichloride.

STORAGE STABILITY:     
In excess of six(6) months when stored in a cool,  dry place away from any direct sources of heat and light.

HANDLING PRECAUTIONS:
Exposure to vapors can cause headaches, nausea, dizziness, shortness of breath, fatigue and unconsciousness. Chronic exposure can cause damage to the nervous system, liver and kydneys. Observe good personel hygiene.

FEATURES:
Ultra-accelerator for natural, SBR, nitrile rubbers and Neoprene rubbers. When activated with dibenzylamine (DBA), cures take place at room temperature between 5 and 7 days. At higher temperature ( 80 deg C) curing takes place within 1 to 3 hours.

FDA STATUS:
177.2600- Rubber Articles Intended for repeated use- Limitation- 1.5 % Max


Download Material Safety Data Sheet

Rubber lining of chemical plants and equipment.

Rubber lining is used to protect a plant, equipment, pipes and fittings from damage. The use of quality rubber sheeting, bonded to the vessel can reduce the damage to the plant and improve the plant efficiency.

It is important to select the correct rubber compound for the application. It needs input of a skilled rubber technologist to choose the correct compound for the specific application as well as the correct vulcanizing agent.

As important as the selection of the rubber to be used, is the selection of the bonding system. Will the equipment to be lined, be cured in an autoclave, by low pressure steam or by chemical cure method. The bonding system will be determined by the circumstances.

In chemical curing you need a primer together with a vulcanization agent ( tie coat). Chemical curing can be carried out at ambient pressures and temperatures and is suitable for large vessels.

Vulcanization is achieved by the combination of sulphur with the rubber molecules to form a 3 dimensional network. The reaction needs the application of heat to reach a satisfactory state of cure in a reasonable time. In conventional rubbers, accelerators are incorporated into the rubber.

In order to obtain a satisfactory state of cure ( cold cure) at room temperature more active chemicals have to be used. The common material used for this process is N- Propyl Dixanthogen (CCA).

The presence of zinc oxide and stearic acid in the rubber compound is needed. An addition of a further accelerator is needed. There are four amine type accelerators to choose from:

Di Benzyl Amine ( DBZA)
Di Butyl Amine (DBA)
Mono Benzyl Amine (MBZA)
Cyclohexyl Ethyl Amine (CEA)

Of these the DBZA is the most popular. The amine must be incorporated during the mixing stage of the rubber compound ( about 2 pphr for standard flexible natural rubber sheeting).

The process of chemically curing rubber linings involves the application of the dixanthogen on to the rubber sheeting. The chemical must be applied by swabbing with a lint free cloth, brush or paint roller.The chemical should be applied in two coats to ensure total and complete coverage. It should be applied at a rate of 0.8 to 1 litre ( total amount for the two coats) per square meter of rubber surface. The length of time required for adequate vulcanization is dependant upon the surrounding temperatures. To speed up the vulcanization , allow the sheet to stand for 24 hours and than apply additional heat.
To obtain the maximum bond strengths, the curing agent must penetrate through the rubber to the substrate. It is critical that the lining be allowed sufficient time to cure before being tested and/ or placed in service.

Special compounds

• For electroplating tanks- compounds must not contain any free sulphur since this will tarnish the plating. The lining must be cured to zero free sulphur content.
• For very aggressive acid conditions at elevated temperatures use either chloro sulphonate polyethylene ( hypalon) or butyl rubber lining.
• For oil or fuel resistant lining use nitrile rubber.
• Cold cure compounds require specific compounding. Standard rubber compounds cannot be used for this purpose without modification.

Reference

Dave Ransom FPRI & Dave Wardle FPRI – A guide to rubber lining of chemical plant & equipment for designers, contractors and applicators.