Glossary Terms C-D
Used in the Compression, Lamination and Transfer Molding Process

CARBON BLACK:

Gives rubber strength, resistance to wear and its black color.

CELLULAR RUBBER:

As opposed to dense rubber, molded rubber having open cells of varying density (such as closed cell sponge rubber, for example).

CEMENT:

Solution of dissolved rubber in solvent. When cement is mixed with water, it forms a latex. See "Latex..

CHECK VALVE:

Anyone of several types of valves that only allows flow in one direction.

COLD POT:

In a transfer process, the cold pot is used to transfer the material into the mold. The material in the pot is maintained at a reduced temperature (120° - 140°F) so that it does not cure with the part, and can be used In the next shot.

COMPOUND SHELF LIFE:

The length of time that can elapse between the mixing and shaping of a rubber batch until it must be processed, or at least reprocessed.

COMPRESSION MOLDING:

A type of molding process whereby material is placed directly into the mold, and the material is heated and formed through the clamp force applied.

COMPRESSION SET:

The residual deformation after removal of the force, which compressed the sample. For example, if one uses a fingernail to depress a molded sample, the impression that remains after a time is the compression set.

CONTACT GAUGE:

A control feature that shuts the hydraulic system off at pressure set point and restarts it if the pressure bleeds off.

CORE LIFTER:

A hydraulic or mechanical device designed to separate the middle plate in a three-plate mold. May also be used to assist in part ejection.

CROSSLINKING:

The chemical reaction that occurs in rubber over time at temperature that results in a permanent change in material characteristics. Also known as curing.

CRUMB RUBBER:

Solid rubber particles coagulated from polymerized rubber solution.

CURE:

The act of vulcanization.

CURE SYSTEM:

The type of curative in the rubber compound being molded, ranging from the conventional sulfur cure to the faster, exothermic peroxide systems; the goal is the same: to effect cross- linking of the thermoset polymers.

CURING:

The process of moving from the raw, unvulcanized stage to one in which the polymer has become cross-linked to achieve the desired physical properties.

DE-ASHING:

Process of removing solid catalyst from rubber cement via water washing.

DEGREE OF POLYMERIZATION:

Number of repeating chains in a polymer.

DEFLECTION:

The tendency of the platens/bolsters to bend around the mold under-run clamp tonnage.

DUROMETER:

A measurement of the hardness of rubber and plastic, or the instrument to measure the hardness of vulcanized rubber and plastic.

DUROMETER HARDNESS:

An arbitrary numbering scale that indicates the resistance to indentation of the indentor of the, durometer. Higher values indicate harder materials.

DYNAMIC PROPERTIES:

Mechanical properties exhibited under repeated cyclic deformations.