Laboratory

Press Leaders

Compression and Transfer Molding Equipment

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Glossary Terms A-B
Used in the Compression, Lamination and Transfer Molding Process

ACCELERATOR:

Added to rubber to speed up vulcanization and improve the properties of the final product.

AGE:

The length of time required between molding and evaluation of molded part properties; will generally range from 24 hours on.

AMBIENT TEMPERATURE:

The temperature of the atmosphere or medium surrounding the object under consideration.

ANTIOXIDANT:

Protects rubber against chemical changes and harmful effects of heat, sunlight, and air.

BACKRIND:

A defect at the parting line where the material has shrunk inside the part.

BALANCED RUNNER SYSTEM:

Runner design to ensure common heat history and fill time for all mold cavities.

BATCH:

Normally referred to as one drop from a rubber internal mixer; batch-to-batch variations in properties may cause problems in molded part quality unless operating parameters are adjusted to compensate.

BLOOM:

A surface discoloration of a molded part after a time in which a substance has migrated to the surface; most often caused by an overabundance of an additive or if sulfur, to a state of under cure.

BULK DENSITY:

The density of loose material (powder, cubes, etc.) expressed as a ratio of weight to volume.

BULK MOLDING COMPOUND:

Raw molding material consisting of unsaturated polyesters with reinforcement systems, including glass fibers or minerals.

BUMP:

("Breathe") "bump" is more commonly used in rubber or composite molding, Clamp pressure; is relieved for a short duration, and often multiple times during a cycle to vent trapped gases in the material.