Z94.12.6 Plastics

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C-STAGE. The final stage in the reactions of a thermosetting resin in which the material is relatively insoluble and infusible. Thermosetting resins in fully cured plastics are in this stage.

CARBURIZE. To increase carbon content of surface of any steel

CAST. (1) The act of forming a plastics object by pouring a fluid monomer-polymer into an open mold, where it finishes polymerizing. (2) The act of forming plastics film and sheet by pouring liquid resin onto a moving belt or by precipitation in a chemical bath.

CAST FILM. A film made by depositing a layer of liquid plastic onto a surface and stabilizing this form by evaporation of solvent, by fusing after deposition, or by allowing a melt to cool. Cast films are usually made from solutions or dispersions.

CATALYST. A substance which when added in minor proportion accelerates a chemical reaction.

CAUL. In plywood manufacture, a sheet the size of the platens used in hot pressing. Aluminum sheet approximately 1/16 in. thick is generally used. Plywood assemblies are inserted between a pair of cauls, to facilitate loading the press, and to protect plywood faces from contact with the steel plates of the hot press. At one time plywood cauls, 1/16" to 1/4" thick were used; they were replaced by aluminum for quicker heating and better durability.

CAUL, CANVAS-COVERED PLYWOOD. A special type of plywood caul used in progressive gluing, to control heat and moisture. Also used for two-plying fragile veneer faces in hot presses.

CAUL, PLYWOOD. Used in cold-pressing with conventional adhesives, to assure undamaged faces and to prevent transmission of defects to adjacent assemblies. Usually 1/4" to 3/8" thick, with waxed surfaces to prevent adhesion.

CAVITY. That portion of the mold which forms the outer surface of the molded article.

CELL. A single cavity formed by gaseous displacement in a plastic material. (See CELLULAR PLASTIC.)

CELLULAR PLASTIC. A plastic whose density is decreased substantially by the presence of numerous cells disposed throughout its mass. (See CELL, FOAMED PLASTICS.)

CELLULAR STRIATION. A layer of cells within a cellular plastic which differs greatly from the characteristic cell structure of the material.

CELLULOSIC PLASTICS. Plastics based on cellulose compounds, such as esters (cellulose acetate) and ethers (ethyl cellulose).

CEMENT. (See ADHESIVE, BOND.)

CENTIPOISE. A unit of viscosity, conveniently and approximately defined as the viscosity of water at room temperature. The following table of approximate viscosities at room temperature may be useful for rough comparisons: liquid viscosity in centipoises water 1 kerosene 10 motor oil SAE 10 100 castor oil; glycerine 1000 corn syrup 10000 molasses 100000.  Note: Under SL, centipoise has been replaced by pascal-second (Pa-s) where 1 centipoise = 0.001 Pa-s.

CENTRIFUGAL CASTING. A method of forming thermoplastic resins in which the granular resin is placed in a rotatable container, heated to a molten temperature, and rotated to force the liquid resin to conform to the shape of the container.

CHALKING-DRY. Chalk-like appearance or deposit on the surface of a plastic. (See HAZE, BLOOM.)

CHANNEL. (See PORT.)

CHASE. The main body of the mold which contains the molding cavity or cavities, or cores, the mold pins, the guide pins (or the bushings), etc.

CHASE RING. A ring used in hobbing to restrain the blank against spreading during the sinking of the hob.

CHEMICALLY FORMED PLASTIC. A cellular plastic whose structure is produced by gases generated from the chemical interaction of its constituents.

CLAMPING PLATE. A mold plate fitted to the mold and used to fasten the mold to the machine.

CLAMP IRONS. In plywood manufacture, the pressure-maintenance equipment, which includes the "I'' beams or double channel irons, together with clamp screws or turnbuckle rods, to hold bales under pressure after cold gluing.

CLOSED-CELL FOAM. A cellular plastic in which there is a predominance of non-interconnecting cells.

COEXTRUSION. A process for extruding two or more materials in a single film or sheet. Two identical polymers can be laminated by coextrusion. Two or more extruders are used, and the extrudate is usually moved through a common die.

COHESION. The forces holding a single substance together.

COLD FLOW. (See CREEP.)

COLD MOLDING. The shaping of an unheated compound in a mold under pressure, followed by heating the article to cure it.

COLD PRESSING. A bonding operation in which an assembly is subjected to pressure without the application of heat.

COLD SLUG. The first material to enter an injection mold, so called because in passing through the sprue orifice it  is cooled below effective molding temperature.

COLD-SLUG WELL. Space provided directly opposite the sprue opening of the injection mold to trap the cold slug.

COMMODITY PLASTICS. The term commodity identifies a group of plastics that are characterized by high-volume usage and general availability from sources other than the prime resin suppliers. Polyethylene, polystyrene, and polyvinylchloride are examples of commodity plastics.

COMPREGNATED WOOD. A consolidation of the term compressed-impregnated wood, referring usually to an assembly of layers of veneer impregnated with a liquid resin and bonded under very high pressures. More commonly, but not always, the veneer layers have parallel grain, i.e., laminated wood construction.

COMPRESSION MOLDING. A technique for thermoset molding in which the molding compound is placed in the open mold cavity, the mold is closed, and heat and pressure are applied until the material is cured.

COMPRESSION RATIO. In an extruder screw, compression ratio is the ratio of volume available in the first flight at the hopper to the last flight at the end of the screw.

CONDENSATION. A chemical reaction in which two or more molecules combine, with the separation of water or some other simple substance. If a polymer is formed, the process is called polycondensation. (See POLYMERIZATION.)

CONSISTENCY. The resistance of a material to flow or permanent deformation when shearing stresses are applied to it. The term is generally used with materials whose deformations are not proportional to applied stresses. Viscosity is generally considered to be a similar internal friction that results in flow in proportion to the stress applied. (See VISCOSITY, VISCOSITY COEFFICIENT.)

CONTINUOUS TUBE PROCESS. A blow-molding process that uses a continuous extrusion of tubing to feed into the blow molds.

COOLING FIXTURE. Equipment used to hold molded article while cooling after removal from the mold; it may be channeled to be cooled with water.

COPOLYMER. (See HOMOPOLYMER.)

COPOLYMERIZATION. (See POLYMERIZATION.)

CORE. That portion of the mold that forms the required inner surfaces of the molded article.

CORES, CENTERS. A term usually applied to the central layer of plywood, which in lumber-core construction is the principle strength factor. It is also applied when the central layer is a veneer. The terms are sometimes used in the Pacific Northwest to designate the layer that is spread with adhesive, which agrees with the above in 3-ply construction but is inconsistent when applied to 5-ply. Under this latter usage, center is used to indicate the middle ply. Core may refer also to the remaining part of the log that is too small to be cut into rotary veneer on a lathe.

CRAZING. Development of fine cracks on the surface of a plastic, sometimes extending into the body of the material.

CREEP. The dimensional change with time of a plastic under load, following the instantaneous elastic or rapid deformation. It is the permanent deformation resulting from prolonged application of a stress below the elastic limit. Creep at room temperature is sometimes referred to as cold flow.

CROSSBANDING. The transverse veneer layers that distinguish plywood from laminated wood.  Their presence counteracts the tendency of wood to split, as well as to shrink and swell.  In standard 5-ply construction, it is the layer between the face and the core and between the back and the core, sometimes called face crossing and back crossing, respectively.

CROSS-LINKING. Applied to polymer molecules, the setting-up of chemical links between the chains. The thermoset plastics are cross-linked at the molecular level.

CRYSTALLINITY. A state of molecular structure in some resins which denotes uniformity and compactness of the molecular chains that form the polymer.

CULL. Material remaining in the transfer pot after the mold has been filled.

CURE. The act of changing the physical properties of a material by chemical reaction, which may be condensation or addition-type polymerization, or vulcanization; accompanied by heat and catalysts, with or without pressure. For room temperature curing systems, heat is generated by an exothermic reaction.

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