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.