Rubber Chemical

Rubber is a polymer that has the primary property to stretch and shrink. It is an elastomer that can come back to its original shape after being deformed. It is made by polymerisation of isoprene (2 methyl-1,3-butadiene). Natural rubber is extracted from the bark of a rubber tree. In order, to meet its huge demand, rubber was synthesized artificially, and this led to a revolution in the field of polymers.

Once rubber (natural or synthetic) is manufactured, they are sent to processor plants for processing to the final product, which can be further used for manufacturing various commodities. The four steps of processing rubber are compounding, mixing, shaping, and vulcanizing.

  1. Compounding: Certain additives and chemicals are added to rubber to increase its tensile strength and enhance its properties. For example, carbon black fillers are added to rubber to increase its tensile strength and protect the degradation of rubber from ultra-violet rays.
  2. Mixing: Rubber is needed to be thoroughly mixed with the additives. For this purpose, the temperature is increased and additives are mixed properly.

3. Shaping: Shaping rubber products occurs by using four general techniques: extrusion, calendering, moulding or coating, and casting. Rubbers are extruded by forcing a highly plastic rubber through a series of screw extruders. After this step, calendering passes the rubber through a series of increasingly smaller gaps between rollers.

This roller-die process combines both extrusion and calendering, producing a better product. The coating is a process to apply a coat of rubber or force rubber into fabric or other material. Tires, waterproof cloth tents, raincoats, conveyor belts, etc. are made by coating materials with rubber. Rubber products like shoe soles and heels, seals, suction cups, and bottle stops are cast using moulds. 

4. Vulcanization: Vulcanization completes the rubber-processing process. Vulcanization creates sulfur cross-connections between the polymers of rubber. Less cross-connection between the rubber polymers creates a softer rubber. Increasing the number of cross-connections decreases the elasticity of the rubber, which creates harder rubber. Without vulcanization, rubber would be sticky when hot and brittle when cold.