Rubber Compounding

Rubber compounding is important to improve mechanical properties, enhance weatherability and manipulate processing etc. of a rubber product. Compounding ingredients play a major role in rubber compounding. Some of them are explained below.

Peptizer (Chemical Plasticizer)

Peptizer is used mainly for natural rubber to increases the efficiency of mastication due to chemical reaction with O₂ which is affected to the efficiency of mastication, reduces time of mastication of long molecules and softens rubber for shaping etc.

Examples for peptizer are Pepton 2 (Di-o-benzamide-diphenyl disulfide), Renacit 4 (zinc penta chlorophenol), organic mercaptants etc.

 Vulcanizing system

The functions of the vulcanizing system are controls vulcanization, influence processing, modified tensile and other physical properties and affects heat resistance and other ageing characteristics. There are different types of vulcanizing systems as follows,

• Sulfur vulcanizing system
• Sulfur donor vulcanizing system
• Non-sulfur vulcanizing system

The components of a vulcanizing system are,

• Vulcanizing agent which reacts with active sites in the polymer to form cross links
• Accelerator which accelerates the vulcanizing rate

Type	Rate	Examples
Guanidines	slow	Diphenyl-guanidene (DPG)
Thizoles	medium fast	Mercaptobenzothiasole (MBT)
Sulfonamides	Long delayed action	N-cyclohexyl-2 benzothiasole sulfonamide (CBS)
Thiurams	fast	Tetramethyl thiuram disulfide (TMTD)
Carbamates	ultra-fast	zinc diethyl-dithio-carbamate (ZDC)

• Activator which improves acceleration and cross linking potential and it can be organic and inorganic  

Eg: Organic activator -stearic acid, lauric acid

       Inorganic activator - ZnO, MgO

• Retarder which reduces the tendency of premature vulcanization

Eg: Phthalic anhydride, salicylic acid 

Other compounding ingredients like Fillers, Processingaids, Protectiveagents, Auxiliaryingredients   will be discussed.