Rubber Compounding

This post continue from previous post Rubber Compounding.

 Fillers

Functions of fillers are reinforcing the rubber, improving hardness of rubber, increasing the volume of rubber for low cost production, facilitating processing of rubber, and enhance age resistance.

Features for selection of fillers

•      Particle size (determines surface area per gram)

•      Surface activity (physio-chemical nature)

•      Persistent structure

•      porosity

Classification of fillers,

Processing aids/ softeners/ plasticizers

Processing aids have many uses like Prevent rubber mass from adhering to hot machinery surfaces during processing, disperse filler uniformly, and modify physical properties such as elasticity, flexibility

•      Softeners for non-polar rubbers

                Petroleum products: bitumen, waxes, petroleum oils

        Vegetable by-products: pine tar, fatty acids and salts, factice             

Synthetic products: reclaimed rubber, partially cross-linked polymers, plastic materials, liquid rubber

•      Softeners for polar rubbers

Ester plasticizers

Protective agents

Antioxidants

Anti-oxidants are used to inhibit rubber ageing due to oxidation reaction, which is accelerated by heat, light and salts of transitional metals. Examples are Amines and their derivatives, phenols and their derivatives.

There are two types of antioxidant,

• React with free radicals in the stage of their formation and inhibit development of the chain reaction
• Decompose hydro-peroxide into products that are inactive for the development of an oxidizing chain

Auxiliary ingredients 

Blowing agents for production of cellular products

Flame retardants (eg: for fire retardants mats)

Antistatic agents (eg: for Conveyor belts, textile rollers, trolley wheels used in hospitals)

Abrasives (eg: for erasers)
Pigments and dyes