Damping: The effect on a mass that causes decreasing amplitude.

Deflection Temperature: The measurement of temperature at which a specimen deflects to a set point under a defined load.

Degassing: The momentary opening and closing of a mold during the early stages of the cycle to permit the escape of air or gas from the heated compound.

Degradation: A deleterious change in the chemical structure, physical properties or appearance of a plastic caused by exposure to heat, light, oxygen, weathering or other external influence.

Delamination: When the surface of a finished part separates. Strata or fish-scale-type appearance may be visible where the layers may be separated.

Density: Mass per unit volume of a substance.

Design Review: A review of a blueprint, of an application, to be molded in a plastic material, with recommendations given for design, material, processing, tooling.

Diaphragm Gate: Used in symmetrical cavity filling to reduce weld-line formations and improve fill rates.

Dielectric Strength: The voltage that an insulating material can withstand before dielectric breakdown occurs.

Differential Cooling: occurs when one area of the part cools at a different rate or when the mold surfaces are at different temperatures. Warping can result from differential cooling.

Dimensional Stability: Retention of the precise shape of the part.

Direct Gate: A sprue that feeds directly into the mold cavity.

Discoloration: Any change from the designated color of the material or component.

Dispersion Aids: Flow alteration components placed at the entry point of an additive to aid in mixing or dispersing actions of a compounding process.

Dominant Flow Path: At the juncture of two confronting flows the dominant flow will reverse the direction of the other.

Draft: A Slight taper in a mold wall designed to facilitate removal of the molded object from the mold.

Drag Marks: A form of deep scratch or scratches on the surface of the component usually caused by the ejection of the part.

Drooling: The extrudate or leakage of molten resin from nozzle or nozzle sprue bushing area while filling or shooting the mold.

Drying: The removal of moisture from the resin pellets by exposure to certain time and temperature. All Hydroscopic Material must be dried prior to molding.

Durometer: An instrument used for measuring the hardness of a material.

Dwell :  A pause in the applied pressure to a mold during the injection cycle just before the mold is completely closed. This dwell allows any gases formed or present to escape from the molding material.

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