| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
PARALLELS. Spaces or supports used under the top and/or bottom halves of the mold to prevent deflection, or to provide space for an ejector mechanism.
PARISON. The hollow plastics tube from which a container, toy, etc., is blow molded.
PART. In its proper literal meaning, a component of an assembly. However, the word is widely misused to designate any individual manufactured article, even when (like a cup, a comb, a doll) it is complete in itself, not part of anything.
PERMANENCE. Resistance of a plastic to appreciable changes in characteristics with time and environment.
PHENOLIC PLASTICS. Plastics based on resins made by the condensation of phenols such as phenol and cresol, with aldehydes.
PHENOLIC RESIN. A synthetic resin produced by the condensation of an aromatic alcohol with an aldehyde. Phenolic resins are used for thermosetting molding materials and laminated sheets.
PHTHALATE ESTERS. A main group of plasticizers, produced by the direct action of alcohol on phthalic anhydride.
PLASTIC. The adjective plastic indicates that the noun modified is made of, consists of, or pertains to plastic. The above definition may be used as a separate meaning to the definitions contained in the dictionary for the adjective plastic.
PLASTIC. (noun) A material that contains as an essential ingredient an organic substance of large molecular weight, is solid in its finished state, and at some stage in its manufacture or its processing into finished articles, can be shaped by flow.
PLASTICATE. To soften a material and make it moldable by the use of a plasticizer.
PLASTICITY. A property of plastics or adhesives which allows the material to be deformed continuously and permanently without rupture upon the application of a force that exceeds the yield value of the material.
PLASTICIZE. To soften by addition of plasticizer.
PLASTICIZER. Chemical agent (elastomer or plastics) added to plastics compositions to make them softer, more flexible, and more workable.
PLASTIC, RIGID. A plastic which has a stiffness or apparent static modulus of elasticity greater than 100,000 psi (689.48 MPa) at 23°C, when determined in accordance with the Standard Method of Test for Stiffness in Flexure of Plastics (ASTM Designation: D 747).
PLASTICS. (noun) A generic term for the industry and its products. This term is properly used only as a plural word. The plastics products include polymeric substances, natural or synthetic, and exclude rubber materials.
PLASTIC, SEMIRIGID. A plastic which has a stiffness or apparent modulus of elasticity of between 10,000 and 100,000 psi (68.948 and 689.48 MPa) at 23°C, when determined in accordance with the Standard Method of Test for Stiffness in Flexure of Plastics (ASTM Designation: D 747).
PLASTIC WELDING. The joining of two or more pieces of plastic by fusion of the material in the pieces at adjoining or nearby areas, either with or without the addition of plastic from another source.
PLASTICIZER. A material incorporated in a plastic or an adhesive to increase its workability and its flexibility or distensibility. The addition of the plasticizer may lower the melt viscosity, the temperature of the glassy transition, or the elastic modulus of the plastic.
PLASTIFY. (See PLASTICATE.)
PLASTIGEL. A plastisol exhibiting gel-like flow properties; one having an effective yield value.
PLASTISOL. A suspension of finely-divided resin in a plasticizer. The resin does not dissolve appreciably in the plasticizer at room temperature, but does at elevated temperature. On cooling, a homogeneous plastic mass (plasticized resin) results.
PLATFORM BLOWING. A special technique for blowing large parts by use of a moveable table to support the material.
PLUG-AND-RING. Method of sheet forming in which a plug, functioning as a male mold, is forced into a heated plastic sheet that is held in place by a clamping ring.
PLUG FORMING. A thermoforming process in which a plug or male mold is used to partially preform the part before forming is completed by the use of vacuum or pressure. Also called plug assist.
PLUNGER. (See FORCE, POT PLUNGER.)
PLYWOOD. A cross-bonded assembly made of layers of veneer or veneer in combination with a lumber core or plies joined with an adhesive. Two types of plywood are recognized, namely (1) veneer plywood and (2) lumber-core plywood.
POISE. A unit of viscosity in which the shearing stress is expressed in dynes per square centimeter to produce a velocity gradient of one centimeter per second per centimeter. Under SI, viscosity is measured in pascal-seconds, where 1 poise = 0. 100 Pa.s. (See VISCOSITY, CENTIPOISE.)
POLYAMIDE PLASTICS. (See NYLON PLASTICS.)
POLYCONDENSATION. (See CONDENSATION.)
POLYESTER. A resin formed by the reaction between a dibasic acid and a dihydroxy alcohol, both organic. Polyesters modified with fatty acids are called alkyds.
POLYETHYLENE. A thermoplastic material comprised of polymers of ethylene. Normally it is a crystalline, translucent, tough, waxy solid that is unaffected by water and a large variety of chemicals.
POLYMER. A high-molecular-weight organic compound, natural or synthetic, whose structure can be represented by repeated small units (mers). Examples include polyethylene, cellulose, and rubber. Synthetic polymers are formed by addition or condensation polymerization of monomers. If two or more monomers are involved, a copolymer is obtained. Some polymers are elastomer, others are plastics.
POLYMERIZATION. A chemical reaction in which the molecules of a monomer are linked together to form large molecules whose molecular weight is a multiple of that of the original monomer.
POLYPROPYLENE. Tough, lightweight, rigid, crystalline plastics made by the polymerization of high-purity propylene gas in the presence of an organo-metallic catalyst at relatively low pressures and temperatures.
POLYSTYRENE. A water-white thermoplastic produced by the polymerization of styrene (vinyl benzene). The electrical insulating properties of polystyrene are very good and the material is relatively unaffected by moisture, but it generally is brittle.
POLYURETHANE RESINS. A family of resins produced by reacting diisocyanate with organic compounds containing two or more active hydroxyl units to form polymers having free isocyanate groups. These groups, under the influence of heat or catalysts react with each other, or with water, glycols, etc., to form thermosetting or thermoplastic materials.
POLYVINYL ACETATE. A resin prepared by the polymerization of vinyl acetate alone.
POLYVINYL ALCOHOL. A polymer prepared by the hydrolysis of polyvinyl esters.
POLYVINYL CHLORIDE. A resin prepared by the polymerization of vinyl acetate alone.
POLYVINYL CHLORIDE-ACETATE. Copolymer of vinyl chloride and vinyl acetate.
PORT. Inlet or outlet of oil, water, or steam channel.
POSTFORMING. A method of shaping substantially cured thermoset plastic sheets or other forms by heating and stressing into other configurations.
POT. Chamber to hold and heat molding material for a transfer mold.
POT PLUNGER. A plunger used to force softened molding material into the closed cavity of a transfer mold.
POT-RETAINER. Plate channeled for heat and used to hold pot of transfer mold.
PREFORM. A coherent block of granular or fibrous plastic molding compound, or of fibrous material with or without resin. A preform is made by compressing the material sufficiently to produce a coherent block for convenience in handling.
PREPOLYMER. A chemical structure intermediate between that of the monomer or monomers and the final polymer or resin.
PRESSURE PAD. Hardened steel reinforcements distributed around a mold to help the land to absorb the final closing pressure.
PRIMER. A coating applied to a surface, prior to the application of an adhesive or lacquer, enamel, or the like, to improve the performance of the bond.
PROGRESSIVE GLUING. A method of curing a resin adhesive in successive steps or stages by application of heat and pressure, between the platens of a hot press. Used only for a wood of larger area than the press platens.
PSEUDOPLASTIC. A pseudoplastic fluid is one whose apparent viscosity or consistency decreases instantaneously with increase in rate of shear; i.e., an initial relatively high resistance to stirring decreasing abruptly as the rate of stirring is increased.
< Previous | Next >