Recycled Rubber Techniques

Recycled rubber is defined as recyclable , vulcanized rubber that has been processed to give particulates or orther forms of different shapes size and size distributions.

Techniques are used to generate recycld rubber

Reclaiming

This is done by a chemical digestion process. Aryl sulfides and other chemicals are added to rubber , and then the mixture is chemically digested. Over the years, there have been significantly decreases in use of reclaim rubber.

Ground Rubber

Vulcanized scrap rubber is first reduced to approximately 2.5 cm by 2.5 cm to 5 cm by 5 cm chips by shredding. This material is further reduced in size by use of ambient grinding mills. The finer particle size needed, the longer the rubber must be milled. Multiple grinds reduce the particle size. Any fiber is removed by air and metal is removed by magnetic seperation. The heat generated in this process can degrade rubber if the product is not cooled properly before storage or shipping.

Cryogenic Ground Rubber

This process , small rubber chips or crumb rubber , 10 to 20 mesh are cooled by chiller using liquid nitrogen and then put through a grinding mill. For finer particle, multiple cooling and grinding are usually needed. Little heat is generated in the process, thereby decreasing degradation of the rubber. All fiber and steel are separated by freeze-grinding to give a higher yield of usable product.

Wet Ground Rubber

Ground rubber is produced by passing a water suspension of rubber particle through a flour-grinding type mill.

Devulcanization Process

In sulfur-accelelator vulcanization of diene rubbers,sulfur-sulfur bonds are formed. Devulcanization is the reverse process in which either via external energy or by addition of chemicals some of the sulfur-sulfur bonds are broken. There may also be cleavage of some C-S and C-C bond in these process.The resulting devulcanized rubber can be compound as is , or mixed with virgin rubber and recured. Chemical devulcanization involves addition of certain accelerators and sulfur to the crumb rubber on the mill or in Banbury.

Relate Topic

Evaluation of recycled rubber in compounds.