"P"

Packaging - A unit that provides protection and containment of items plus ease of handling by manual or mechanical means.

Packing - An adjustable sealing device on a ram, valve stem or pump shaft --- old technology and leakage is required for lubrication. If packing leaks, it is simply tightened slightly to 'control' the leakage. For pumps and valves, packings can be rope-like, braided into continuous lengths and then cut to size to fit a shaft. For hydraulic applications, v-shaped fabric reinforced rubber rings are used. Early hydraulic packings were made from leather. For a rubber o-ring, that particular item can be found called a seal, a gasket and a packing ring - even in U.S. government technical specifications dating back 50 years.

Pads - A rubber part used as an anti-vibration device.

Parachute Packings - Also called V-Packing, Vee packing, Chevron Packing, Parachute packing or v-set packing. A complete vee packing set contains multiple "V" shaped sealing rings stacked and nested together with a male adapter on one end and a female adapter on the other end.

Parbacks - A back-up ring with a concave shape on one side, used as an anti-extrusion ring for an o-ring.

Permanent set - The amount by which an elastic material fails to return to its original form after deformation.

Permanent Set - The amount by which an elastic material fails to return to its original form after a deformation. in the case of elongation, the difference between the length after retraction and the original length, expressed as a percentage of the original length, is called the permanent set. Permanent set is dependent on quality and type of rubber, degree and type of filler loading, state of vulcanization, and amount of deformation.

Permeability - To permit passage of gas through the molecular structure of a given material.

Piston Bearing Rings - Also called guide rings, wear rings, piston guide rings.

Piston Guide Rings - Also called guide rings, wear rings, piston rings usually made from nylon or POM.

Piston Rings - Any ring used on the piston of a hydraulic or pneumatic cylinder.

Piston Seals & Packings - Any seal or packing ring used on the piston of a hydraulic or pneumatic cylinder.

Piston T-Seals - A "T" shaped rubber seal, with back-up rings of a harder material on each side, used as a piston seal.

Plasticity - (1) A measure of the resistance to shear of an unvulcanized elastomer; (2) A tendency of a material to remain deformed after reduction of the deforming stress to or below its yield stress.

Plasticizer - A substance that softens or plasticizes another substance through its solvent action.

Plunger Pump Seals - Packing seal rings used to seal the plunger of a reciprocating pump.

Plunger Seals - Sealing rings used on a plunger.

Plugs - A cone shaped rubber part used to be forced into a tube end or hole to make a complete seal.

Pneumatic Seals - Any seal or packing ring, usually flexible rubber, used to seal against compressed air instead of hydraulic fluid or other liquid.

Pock marks - Uneven blister-like elevations, depressions, or pimpled appearance.

Poisson's Ratio - The ratio of lateral concentration per unit of diameter to longitudinal extension per unit of length in a bar of material longitudinally stressed. For a body which does not change its volume on deformation, it is 0.5. For metals, the ratio is usually considerably less than 0.5. In the case of vulcanized rubber, pure gum, having practically no volume change on extension, shows a ratio of approximately 0.5 for small deformations; compounded rubber may increase in volume on extension, consequently the ratio drops below 0.5. For rubber the ratio is constant only for small extensions.

Polymer (a) - A material formed by the joining together of many (poly) individual units (mar) of a monomer.

Polymer (b) - A polymer is a very long chain of units of monomers prepared by means of an addition and/or a condensation polymerization. The units may be the same or different. There are copolymers, dipolymers, tri- or terpolymers, quadripolymers, high polymers, etc...

Porosity - The presence of numer- ous small holes or voids.

Post cure - Heat or radiation treatment, or both, to which a cured or partially cured thermosetting plastic or rubber composition is subjected to enhanced the level of one or more properties.

Preliminary Bill of Material - An initial Bill of Material completed prior to design and print release.

Preliminary Process Flow Chart - An early depiction of the anticipated manufacturing process for a product.

Press-in Wipers - A wiper or scraper ring for a hydraulic cylinder which has a metal outside diameter so that it can be press-fitted into a housing.

Pressure - (No, Low, Poor) - May refer to inadequate pressure in mold/press, oven heater or autoclave during Cure. Symptoms may be porosity, unfills, blister, low adhesions, etc...

Process Failure Mode and Effects Analysis (PFMEA) - An analytical technique used by a manufacturing responsible engineer/ team as a means to assure that, to the extent possible, potential failure modes and their associated causes/mechanisms have been considered and addressed.

Processing Aids - Waxes, low molecular weight polyethylene, metal soaps, petroleum oils, and other agents which dissolve or lubricate rubbers, soften them and act as processing aids.

Product Assurance Plan - A part of the Product Quality Plan. It is a prevention-oriented management tool that addresses product design, process design, and when applicable software design.

Production Trial Run - Product made using all production tools, processes, equipment, environment, facility; and cycle time.

Protectors - A rubber or plastic cap or cup shaped ring used to protect threads or fragile items during shipping or assembly.

Proto-Types - A part that is made during the design process to determine the feasibilty or suitability of a project.

Proto Types - See proto-types

Pusher Rings - A ring that fits against another sealing device to push it in order to activate it or enegize it in the absence of pressure or in low pressure applications.