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Why do rubber need vulcanization or curing

Rubber raw cann't be directly used ,it need to be processed with heat and sulfur during production , so that to improve its physical properties. This process ,we call it as curing, it is also known as vulcanization. By ways of vulcanization, it makes the rubber material stronger and more elastic.

Before we talk about curing or vulcanzation ,we need to know what is vulcanization?

vulcanization ,it is one curing process in which the rubber's elastomers harden in response to heat and sulfur under a temperature of about 300 to 400 degrees .

Through curing or vulcanization , it caused in  polymer chains crosslinked . With sulphur, accelerator and activator at 140–160°C, it would form a stable polymer ,it become more strong and stable. It would prevent the chains from moving independently, thus allow the raw rubber material to stretch under stress.

By vulcanization, the physical properties of natural or synthetic rubber are improved. These finished rubber products have higher tensile strength and resistance to swelling and abrasion. Through vulcanization,the rubber material become being elasticity, resilience, tensile strength, viscosity, hardness and weather resistance.

From tires and footwear to keypads and gaskets, countless products are made of vulcanized rubber.

Since valcanization is so important to rubber ,how does it work?

Firstly, the rubber is put around sulfur and additives. sulfur would be very imprant to facilitate vulcanization, other additives are mixed accordingly.

then the rubber is molded into the desired shape and size. Vulcanized rubber can’t be easily molded. It becuase the vulcanized rubber is more strong and elastic ,thus it is difficult to mold.

After being molded, the rubber is heated in an oven-like chamber. While sulfur alone can vulcanize rubber, the addition of heat helps to speed up the process.  The rubber is heated to 

At the end,these vulcanized rubber would be taken out from the heating chamber and allowed to cool.