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Casting: The process of forming solid or hollow articles from fluid plastic mixtures or resins by pouring or injecting the fluid into a mold or against a substrate with little or no pressure, followed by solidification and removal of the formed object.

Cavity: A depression, or a set of matching depressions, in a plastics-forming mold which forms the outer surfaces of the molded articles.

Charge: The amount of material used to load a mold at one time or during one cycle.

Charge: The measurement or weight of material necessary to fill a mold during one cycle.

Charpy Impact Test: A destructive test of impact resistance, consisting of placing a test coupon in a horizontal position between two supports, then applying a blow of known magnitude. If the specimen does not break, a new specimen is put in position and the magnitude is increased until the specimen breaks.

Chopped Strand: A type of fiber reinforcement consisting of strands of individual glass fibers which have been chopped into short pieces.

Clamp: The part of an injection molding machine incorporating the platens that provides the force necessary to hold the mold closed during injection of the molten resin and open the mold to eject the molded part.

Clamping Area: The largest rated molding area an injection press can hold closed under full molding pressure.

Clamping Force: The force applied to the mold to keep it closed, in opposition to the fluid pressure of the compressed molding material within the mold cavity and the runner system.

Clamping Plate: A plate fitted to a mold and used to fasten the mold to a platen.

Clamping Pressure: The pressure applied to the mold to keep it closed during the molding cycle.

Clarifiers: Additive used in resins to improve transparency or translucency.

Closed-loop Control: System for monitoring and automatically adjusting injection molding process conditions such as temperature, pressure and time. The automatic changes keep part production within preset tolerances.

Coefficient of Thermal Expansion (CTE): The change in length of a material for a unit change in temperature, per unit of length.

Co-Injection: Simultaneous or near simultaneous injection of multiple materials. Cold Flow Lines: Imperfections within the part wall due to thickening or solidification of resin prior to full cavity fill.

Cold Molding: The process of compression molding involving shaping an unheated compound in a mold under pressure then heating the article to cure it.

Color Concentrate (also know as Colorant, Pigment): A plastic compound which contains a high percentage of pigment, to be blended in appropriate amounts with the base resin so that the correct final color is achieved.

Composite: A structural non-homogenous material consisting of a combination of materials. Typically, one of the materials is a strengthening agent, the other being a thermoset or thermoplastic resin.

Compound: A mixture of resin(s) and additives usually formed in a separate machine downstream for the primary reactor.

Compounding: The process required to mix polymer(s) with all of the additives that are necessary to provide the end user with a finished grade with suitable properties.

Compression Molding: A method of molding in which the molding material, generally
horizontal position between two supports, then applying a blow of known magnitude. If the specimen does not break, a new specimen is put in position and the magnitude is increased until the specimen breaks.

Compression Molding: A method of molding in which the molding material, generally preheated, is placed in an open heated mold cavity, the mold is closed with a top force, the pressure is applied to force the material into contact with all mold areas.
Compressive Strength: The ability of a material to sustain a force in a direction opposite of tension.

Conditioning: Subjecting a material to standard environmental and/or a non-standard stress state prior to testing or use.

Constant pressure gradient: pressure drop per unit length. The constant pressure gradient principle says that the most efficient filling pattern is when the pressure gradient is constant along the flow path.

Cooling Channels: Channels located within the body of a mold through which a cooling medium is circulated to control the mold surface temperature.

Cooling time: the elapsed time required for the melt to reach it’s Vicat softening temperature.

Copolymer: The chemical reaction of two different monomers with each other, resulting in a unique new polymer.

Core: A protrusion, or set of matching protrusions, in a plastics forming mold which forms the inner surfaces of the molded articles.

Corona Treatment: Impingement of AC power on a component to bombard with free radicals thus improving the ability to bond to a surface.

Corrosion Resistance: A broad term applying to the ability of plastics to resist degradation in many environments, usually due to oxidation.

Crack/Splits/Chips: A physical separation or tearing of the part.

Crazing: Defect in plastics articles characterized by distinct surface cracks or minute frost-like internal cracks, resulting from stresses within the article which exceed the tensile strength of the plastic.

Creep: Due to its viscoelastic nature, a plastic subjected to a load for a period of time tends to deform more than it would from the same load released immediately after application, and the degree of this deformation is dependent of the load duration.

Cross-linking: The formation of chemical links between the molecular chains in polymers. This process can be achieved by chemical reaction, vulcanization, and electron bombardment.

Cryogenic Processes: Reduction of parts to very low temperatures usually associated with liquid nitrogen. Commonly used to create assemblies or to deflash or degate a part.

Crystal: A homogeneous solid having an orderly and repetitive three-dimensional arrangement of its atoms.

Crystallinity: A state of molecular structure in some resins attributed to the existence of solid crystals with a definite geometric form, Such structures are characterized by uniformity and compactness.

CSA: Abbreviation for the Canadian Standards Association.

C-stage: This term describes the final stage of the reaction where a thermoset material is relatively insoluble and infusible.

Cure Cycle: The time periods at defined conditions to which a reacting thermosetting material is processed to reach the desired property level.

Cure: The process of changing the properties of a polymer into a more stable and usable condition. This is accomplished by the use of heat, radiation, or reaction with chemical additives.

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