Fillers
Fillers are typically used to cut costs and alter the physical qualities of a rubber compound. For a rubber compounder, knowing the true specifications of the rubber product is crucial. The necessary performance qualities are compromised when non-reinforcing filler is added to a compound to save costs.
It is crucial to optimize the trade-off between properties and costs. In the rubber business, filler is the second most significant material, after rubber. Physical characteristics like modulus and other failure parameters are typically improved by the use of reinforcing filler. The next paragraphs will address a few fillers that are available. Nonetheless, carbon black is the filler most frequently utilized in the rubber sector.
Function of Fillers
Filler serves one or more of the following purposes:
• To enhance the vulcanizates’ (reinforcing fillers’) wear and failure properties;
 • To increase a compound’s cost/economics
• To handle a compound’s processing characteristics;
 • To add unique qualities, such as electrical or flame resistance;
 • To provide a compound the appropriate color when needed
In general, the fillers’ varying impacts can be attributed to their particle size, shape, and surface activity. Fillers come in various varieties and are utilized in rubber composites. Two common fillers found in the rubber business are silica and carbon black. The majority of carbon black is made up of extremely small particles of elemental carbon with an amorphous molecular structure.
Whereas thermal grades are created in a cyclical process, all furnace grades are created continuously. To improve the bulk density, the carbon particles created by this process are pelletized after being conventionally separated from the process gas stream.
Rubber-Grade Carbon Black Designation by ASTM
A letter and three numbers are used to identify carbon black. The first digit represents the average particle size, the letter defines the cure rate, and the final two digits are randomly assigned to identify blacks within a certain particle group.
Cure rate is denoted by the letters N and S. S represents a slower cure rate, while N represents a normal cure rate. Particle size is acknowledged as a basic property of carbon black in the first number. Below Table displays the ten groups that were arbitrarily created from the particle size pattern normal to rubber grade carbon blacks.
• The unit of measurement for particle size is nanometers. Though not all black people belong to the same group, the groupings are selected so that black people who are now classified as SRF, ISAF, and HAF do not.
