What is Rubber Curing?

Author: Ankit Patwal

Curing is widely known as vulcanization. Curing treatment of rubber is the process of giving it certain qualities like strength, elasticity. In other terms, it involves the formation of cross-linking between polymer chains of the rubber molecules. Cross-linking prevents the chain from moving independently, letting the material stretch under stress and then return to its original shape when stress is released.

Guide of Rubber Curing

Curing is also known as vulcanization. Curing treatment of rubber process includes giving rubber special qualities like strength, elasticity, and moveability. In scientific terms, it refers to the formation of cross-linking connecting polymer chains of the rubber molecules. By this Cross-linking we can stop the chain from moving independently and unwantedly, this lets the material stretch under stress and then return to its original shape when stress is released.

Different methods of Rubber Curing

There are a lot of methods of curing rubber in this industry. Let's discuss deeply:

Sulfur based rubber curing: In this method, Sulphur or Insoluble sulfur is used along with accelerators during the final stage of mixing compounds. Loading sulfur above the level 1.5 PHR can lead to sulfur blooming when the compound is stored over a longer period of time, hence Insoluble sulfur is most of the time recommended.

Sulfur less rubber curing: In this method, other chemicals are used to cross-link polymers like Monochloride, Tellurium, Selenium, Thiuram Accelerator, Polysulphide polymers, p-Quinone Dioxime S, Metallic Oxides, Organic Peroxides, Di-isocyanates etc.

Sulfur is the most successful and economical cross-linking agent even today.

How to ensure uniform rubber curing

When curing rubber with sulfur, there is a chance of some uncured and over cured zones. To prevent this, We can use a Masterbatch of sulfur, which is also known as Pre dispersed sulfur. Pre-dispersed sulfur, as the name suggests, it is a Mixture of Rubber and Sulfur in the form of pallets. Pre dispersed sulfur ensures uniform curing of the compound.

Further, there are several benefits of using Pre dispersed sulfur-like

  • Dust Free & Eco-Friendly

  • No-fly loss, no loss due to spillages

  • Easy handling & housekeeping

  • No health hazards

  • Excellent dispersion in Rubber Matrices

  • Low scrap rate

  • No Static charge generation

  • Reduced mixing cycle time

  • Less power consumption

  • Increase in productivity

  • Automated feeding is highly effective

  • Single-stage mixing is possible

We all know manufacturing Pre dispersed sulfur is not possible, As per the leader in the market a lot of them recommend OCCL, they manufacture Pre dispersed sulfur under the brand name of Diamix, which can easily achieve these goals.

Insoluble Sulphur is the polymeric state of Sulphur that is used in the form of a vulcanizing agent in the rubber industry. It protects the rubber compound from blooming, which is the migration of Sulphur onto the surface of the product.

This poses a huge challenge for compounders since adhesion among several components of rubber product goes for a toss.

Insoluble sulfur, by way of not migrating on the surface, aids in better tackiness among rubber components.

In radial tire, where rubber to metal bonding is required, Insoluble sulfur plays a critical role. Almost all tyre majors across the globe use insoluble sulfur in Radial tyres.