Glossary

Plastics Glossary - P

Paint mask Stencil designed to conform to the shape of the part with the areas to be decorated cut out.

Parallel circuit A circuit where baffles or bubblers are individually connected to the circuit, not to each other.

Parallel Part of the mold base which "houses" the ejector plate and retainer plate. Also referred to as a spacer between the bottom clamp plate and the support plate since it provides space for ejector movement.

Parasitic Reaction Side reaction that may interfere with a process and reduce its yield.

Parison The hollow plastic tube from which a container is blow-molded.

Partial Pressure Portion of the total pressure of a system that is the pressure contribution of a specific component of the gas mixture.

Parting agent See Mold release agent.

Parting Line The mark on a molded article caused by flow of material into the crevices between mold parts.

PBT Polybutylene terephthalate.

Pellets Tablets or granules of uniform size, consisting of resins or mixtures of resins with compounding additives which have been prepared for molding operations by extrusion and chopping into short segments.

Penetrant Surface-active agent used in the textile industry to aid dyeing and sizing operations.

Penetrometer Instrument for determining the consistency of high- viscosity materials such as asphalts, greases, waxes.

Peptization Dispersion of a substance into particles of colloidal size, caused by addition of a peptizing agent.

Peptizing Agent A protective colloid.

Percolation Extraction process, usually of a liquid acting upon a solid.

Perfect Fluid Fluid of zero viscosity.

Permanent Emulsion Emulsion in which the droplets of the dispersed phase do not coalesce or coagulate in time: a stable emulsion.

pH Value Negative logarithm of the hydrogen ion concentration and hence the acidity or alkalinity of a solution. The scale ranges from 1 (highly acidic) through 7 (neutral) to 14 (highly basic ).

Phase Interface Boundary surface between two phases or films.

Phase Rule For a heterogeneous system in equilibrium, the sum of the number of phases plus the number of degrees of freedom equals the number of components plus two.

Phase-Volume Ratio Ratio of the volume of the internal phase to that of the external phase in an emulsion.

Phenylene oxide based resin Possesses one of the lowest specific gravities of the engineering thermoplastics. It is a tough, rigid material which maintains its excellent mechanical properties, relatively unchanged, up to about 300°F. Also has excellent dimensional stability, low creep, and low moisture absorption. Amorphous.

Photodegradation Degradation of plastics due to the action of light. Pigments General term for all colorants, organic and inorganic, natural and synthetic, which are insoluble in the medium in which they are used.

Photomicrograph Photograph of the emulsion that is used for particle size determinations or other visual observations of the emulsion. Agglomeration can be seen if the particles are stabilized by the addition of a thickener, e.g. gelatin, to the continuous phase.

Physical Change Change in which the identifying chemical properties of a substance remain unchanged.

PID control A specific type of tuning used on machine controllers to maintain a setpoint accurately within a very small range.

Pigment Finely divided insoluble substance that imparts color to the material to which it is added.

Pin plate See floating plate.

Pinch point Any place on the machine where operating personnel could insert a hand or other part of the body and have it pinched in the mechanism.

Pinpoint gate Gate in an injection mold which is approximately 0.020 - 0.030 inch in diameter. This small gate minimizes the size of the mark left on the molded part.

Pipeline Mixer Device for continuous mixing and/or homogenizing within a transfer pipe.

Pit An imperfection, a small crater in the surface of the plastic.

Pitting Spot corrosion that is caused by chemical or galvanic effects.

Plastic Deformation Change in the dimensions of a material load that is not recovered when the load is removed.

Plastic memory The tendency of a thermoplastic material which has been stretched while hot to return to its unstretched shape upon being reheated.

Plastic pressure Also called melt pressure. The force applied on the polymer, usually while in molten form. This is NOT simply hydraulic pressure times a factor of ten.

Plastic Solid Substance that does not deform under a shearing stress until the stress attains the yield stress, at which point the solid deforms permanently.

Plastic A material that contains as an essential ingredient one or more organic polymeric substances of large molecular weight, is solid in its finished state, and, at some stage in its manufacture or processing into finished articles, can be shaped by flow.

Plasticate To melt or impart flexibility in a plastic through the input of heat and mechanical work as in the plasticating of the resin in an extruder or injection molding machine. To mix and melt plastic. This function is taken care of by the screw.

Plasticity The ability of a material to withstand continuous and permanent deformation by stresses exceeding the yield value of the material without rupture.

Plasticize To impart softness and flexibility in a plastic through the incorporation of a plasticizer additive.

Plasticizer Chemical material incorporated into a resin to increase its workability during processing, and to impart flexibility and other desirable properties to the finished product. An additive used to increase the flexibility and impact resistance of a plastic resin.

Plastisol Suspension of resin(s) in plasticizer(s).

Plate Puller External hardware attached to`the sides of the mold for the purpose of pulling the cavity plate away from the stationary plate during the normal opening of the mold. Also called links and claws.

Platen The steel plates on a molding machine to which the mold is attached. Generally, two platens are used; one being stationary and the other moveable, actuated hydraulically to open and close the mold. Large, steel vertical plates on the clamp end of the machine.

Plate-out A separation of a polymer component or components which results in residue on the part and/or mold surface. This is often intentional as in the case of many anti-static additives, which change the surface tension of the plastic part by migrating to the surface. Also called bloom.

Plug Flow Flow characterized by an almost square velocity profile. Under certain pressure conditions prevailing in closed tubes, mass in the middle of the pipe moves like a solid plug, with laminar flow along the wall.

Plunger injection molding The design of the plunger machine is ideally suited for molding thermoset molding compounds and bulk molding compounds. In the plunger machine, the molding compound is fed into the heating cylinder (barrel). The plunger or ram forces the compound through the cylinder where it is heated by conduction of heat from the cylinder wall. As the material is forced forward, it passes over a spreader or torpedo within the barrel that causes mixing. The plunger forces the material through the nozzle and into the mold.

Pockets The parts of the mold base that hold the cavity and core blocks.

Poise Unit of viscosity, equivalent to 1 dyne/sec/cm2.

Poiseuille Viscometer Instrument to measure viscosity based on outflow measurement of fluids. Commercial Poiseuille viscometers include Engler, Barbey, Redwood, and Saybolt units.

Poiseuille’s Equation Relation between liquid flow through a tube pressure, and length and cross-section of path, assuming uniform streamline flow.

Poisson's Ratio The constant relating the changes in dimensions which occur when a material is stretched. It is obtained by dividing the change in width per unit length by the change in length per unit length.

Polar Bond Essentially covalent chemical bond that results from the unequal sharing of valence electrons between atoms.

Polar Compound Substance that possesses a permanent electric moment.

Polar Liquids Liquids whose molecules possess a dipole moment such as alcohols, acids, aldehydes, etc.

Polyamide resin A polymer in which the structural units are linked by amide or thioamide groupings. Many amides are fiber-forming. Semi-crystalline material.See nylon semicrystalline

Polyamide-imide High-temperature thermoplastic with excellent mechanical and chemical resistant properties. Amorphous material.

Polyarylate resin Thermoplastics (polyesters of phthalic acids and bisphenols) are naturally transparent with a light gold color. Amorphous material.

Polyblend A colloquial term used for physical mixtures of two or more polymers. Such blends usually yield products with favorable properties of both components, sometimes opening markets not available to either of the separate components. The term Alloy is sometimes used for such blends.

Polybutadiene (thermoset) resin All hydrocarbon in nature and, when cured, has excellent heat, moisture, and chemical resistance. Amorphous material.

Polybutadiene (thermoset) resin All hydrocarbon in nature and, when cured, has excellent heat, moisture, and chemical resistance. Amorphous.

Polybutylene resin Polymers made with butene and ethylene as monomers. Uses are pipe, packaging, sealants, and adhesives. Semicrystalline material.

Polybutylene terephthalate (PBT) A semi-crystalline, thermoplastic polyester. Good heat and chemical resistant properties. Must be dried before processing.

Polycarbonate resin (PC) A tough, clear polymer derived from the direct reaction between aromatic and aliphatic dihydroxy compounds with phosgene or by the ester exchange reaction with appropriate phosgene-derived precursors. Must be dried before processing. Amorphous material.

Polydisperse Systems Systems that consist of various size particles droplets.

Polyester resins Family of resins produced by reaction of dibasic acids with dihydric alcohols.

Polyethersulfone resin A tough, rigid, amorphous thermoplastic.

Polyethylene resin A thermoplastic composed by polymers of ethylene. It is normally a translucent, tough, waxy solid which is unaffected by water and a large range of chemicals. Semi crystalline.

Polyethylene terephthalate (PET) is a thermoplastic that may be extruded or injected or blow molded. Unsaturated polyesters are thermoset and used in the reinforced plastics industry for applications such as boats and auto components.

Polyimide resin Aromatic polyimide is made by reacting pyromellitic dian-hydride with aromatic diamines.

Polyimide resin Aromatic polyimide is made by reacting pyromellitic dianhydride with aromatic diamines.

Polymer Structure A general term referring to the relative positions, arrangement in space, and freedom of motion of atoms in a polymer molecule.

Polymer (Synthetic) The product of a polymerization reaction. The product of polymerization of one monomer is called a homopolymer, monopolymer or simply a polymer. when two monomers are polymerized simultaneously the product is called a copolymer. The term terpolymer is sometimes used for polymerization products of three monomers.

Polymer A chemical compound formed by many small molecular units linked together to form a large, chain-like molecule. An organic compound made from a series of linked molecules called monomers.

Polymerization A chemical reaction in which the molecules of a simple substance (monomer) are linked together to form large molecules whose molecular weight is a multiple of that of the monomer.

Polyphase Emulsion Mixed, multiple, or dual emulsion that has well-defined internal and external phases; each phase contains droplets of the other phase.

Polyphenylene Oxide (PPO) A thermoplastic, linear, non-crystalline polyether obtained by the oxidative polycondensation on 2, 6-dimethylphenol in the presence of a copper-amine complex catalyst.

Polyphenylene sulfide resin A crystalline aromatic thermoplastic polymer with a symmetrical, rigid backbone chain consisting of para-substituted benzene rings connected by a single sulfur atom between rings.

Polypropylene resin A tough, lightweight, rigid plastic made by the polymerization of high purity propylene gas in the presence of an organometallic catalyst at relatively low pressure and temperatures. Semi-crystalline material.

Polystyrene resin A water-white thermoplastic produced by the polymerization of styrene (vinyl benzene). Amorphous material.

Polysulfone resin Amorphous structure, the engineering thermoplastic has inherent resistance to heat, hydrolysis, oxidation, and radiation.

Polyurethane resin, thermoplastic Polymers that have properties combining the advantages of elastomers and plastics. Formed by the reaction of bifunctional polyols with diisocyanates.

Polyurethane resin, thermoset Produced by reacting diisocyanate with organic compounds containing two or more active hydrogens to form polymers with free isocyanate groups. These groups will react with each other under heat or catalysis to form a thermoset.

Polyvinyl acetate resin A thermoplastic material composed of polymers of vinyl acetate in the form of a colorless solid. Used extensively in adhesives for paper and fabric coatings.

Polyvinyl alcohol resin A thermoplastic material composed of polymers of the hypothetical vinyl alcohol.

Polyvinyl chloride resin (PVC) Thermoplastic compounds formed by polymerization or copolymerization of vinyl or vinylidene halides and vinyl esters. They are strong with good abrasion resistance. Amorphous material.

Porous molds Molds constructed of a material through which liquids or gases can pass.

Pot life The time during which a compound remains suitable for the intended use, after compounding ingredients such as solvent or catalyst have been added. Also called working life.

Potting To embed in a container within an insulating or protective material. Potting is often accomplished within an evacuated environment, called vacuum encapsulation.

Pour Point Lowest temperature at which an oil will pour.

Powerstat Small rheostats on the end of electric heater cartridges.

Precipitate Substance separated from a solution, suspension, dispersion, or emulsion as a result of chemical or physical change.

Preplastication Premelting or heating of a resin in a separate chamber prior to transferring to the injection chamber or to the mold, as in transfer molding of thermosets and two-stage injection molding of thermoplastics.

Pressure Drop Difference in force on unit areas on the two sides of barrier.

Pressure transducer The actual pressure sensing device that can be used to measure mold cavity pressure or hydraulic pressure.

Process window A range of acceptable values of a molding parameter.

Productivity The measure of the amount of output, in either goods or services, per unit of input. The higher the productivity, the higher the output versus input. Making the maximum number of quality parts every hour.

Profile die Extrusion die for the production of continuous shapes.

Programmable controller A control system often used to operate machinery in place of the standard electromechanical relays. The controls are programmed rather than permanently wired as in standard control methods.

Projected area Area of a molded part which is projected onto a plane at right angles to the direction of the mold. The total area of the parts and runners in a mold at the parting line.

Properties The characteristics of a material that indicate how well it will perform in a variety of applications. Properties are used to compare and select thermoplastic materials.

Property loss A reduction in how well the material will perform sometimes caused by shortening the polymer chain molecules, thereby reducing the molecular weight.

Proportional Limit The greatest stress which a material is capable of sustaining without deviation from proportionality of stress and strain. (Hooke's Law).

Protective Agent Colloidal substance that stabilizes the suspension of the particles when adsorbed on suspended particles.

Protective Colloid Material that stabilizes a particular disperse system against coagulation or coalescence. It is usually a lyophilic colloid that forms a protective film (by adsorption) around each particle.

Prototype mold A simplified mold (usually a single cavity) routinely used when part quantity requirements are low; used for molding new products for the testing of the product or the mold itself.

Prototype Tool A preliminary mold built upon which the final mold will be based.

Prototype A mold suitable for use in complete evaluation of form, design, and performance.

Pseudoplasticity Property of a fluid whose consistency decreases constantly with increasing rate of shear.

Pseudostable State of a material that causes a change of its physical properties over a period of time.

Pull-in cylinder The hydraulic cylinder(s) on an injection molding machine that holds the nozzle to the sprue bushing by pulling the injection unit carriage forward. It also retracts the nozzle for purging and shutdown.

Pull-out Grooves A small groove cut into the side wall of the molding surface to assist in holding the molded piece part to that member while tho mold opens.

Pultrusion Pulling glass fibers through a resin bath to make continuous profiles, pipes and other shapes.

Purging compound Used to flush processing machines at the completion of a run of one polymer, color, flow grade, or type and prior to beginning a run of different materials.

Purging In extrusion or injection molding, the cleaning of one color or type of material from the machine by forcing it out with the new color or material to be used in subsequent production, or with another compatible purging material. The process of injecting the remaining plastic out of the barrel.

Pyrometer Practically speaking, all thermocouple-activated devices are called pyrometers. They consist of a readout device and a sensor.

Pyrometer Practically speaking, all thermocouple activated devices are called pyrometers. They consist of a readout device and a sensor. A high temperature monitoring and controlling device.