pneumatic to Poleyster
Pneumatic. (Engin.) Pertaining to, or operated by, air pressure.
Pneumatic brakes. (Auto.) Brakes operated either by air pressure or vacuum, the pressure being on a large piston to get the proper force.
Penumatic tire. (Auto.) A tire usually consisting of an outer casing or shoe and an inner tube which, when inflated to pro pert pressure, enables the tire to retain its shape uneder load.
Pneumatic tools. (Engin.) Tools operated by air pressure.
Pocket rot. (Wood) Decay which appears in the form of a hole, pocket, or area of soft rot, usually surrounded by apparently sound wood.
Pock marks. (Paint and Lacquer) Air bubbles that are trapped in a porous surfacer coat, and which show up as pock marks when the surfacer is sanded. In spraying, too much surfacer is applied or too much air pressure employed, or the combination of two result in this condition.
Point. (Print.) The unit on which type sizes are based. One point is .013837 of an inch.
Pointing. (Arch.) The finishing of joints in a brick or masonry wall.
Pointing trowel. (Masonry) A small trowel used by bricklayers for pointing and striking up joints and for removing mortar from the face of the wall.
Point line. (Print.) Type is said to be "point line" when the faces of various sizes may be made to align with the aid of point-size spacing materials.
Points. (Print.) Punctuation marks in type.
Point system. (Print.) The unit of size in the casting of type bodies.
Poke or push welding. A spotwelding process where pressure is applied manually to one electrode only.
Polarity. (Elec.) A means of designating the poles of a magnet or magnetic circuit, the kind of charge of static electricity, or the positive or negative. terminal of a d.c. electrical circuit.
Polarization. (Elec.) In a primary cell, the collection of hydrogen bubbles on the positive plate, which increases the internal resistance, and diminishes the current strength.
Polarized light. (Plast.) That phenomenon whereby light rays are limited to one plane of vibration.
Poles. (Elec.) The positive and negative terminals of an electric circuit.
Pole shoes. (Elec.) The outer part of the pole pieces curved concentrically with the armature.
Polish. To make smooth or bright by friction.
Polychrome (Furn.) A form of painted ornamentation, originating in Egypt and much used in Italy during the sixteenth century.
Polyester (Plast.) A plastic family of many types. It has grown rapidly to 'great importance in the industry. The unsaturated
polythylene to ploystyrence polyesters, whose two basic ingredients are dihydric alcohols and dibasic acids are cross linked with the monomer Styrene and others. They are easily. handled in liquired form and cure easily with no 'liquid or gasous byproduct, They have goods weathering, heat corrosion, electrical and physical properties, and they are dimensionally stable, They are usd extensively for laminating such products as huge boat hulls, truck tanks, hampers, radomes, swimming pools,. chairs, auto bodies, small electrical components, and architectural panels, Much polyester is also used in foamed plastics, (See Foamed Plastics.) Polyesters are highly recommended for school use because of their versatility, and ease of use. The resin comes in liquid form, and by adding a hardener, it solidifies in simple molds or on glass surfaces at room temperatures, and without pressure. Other forms of polyesters used for fibers (Dacron) and film (Mylar), the latter, very strong, was used in the now famous earth-circling "Ecco. (See Plastics.)
Polyethylene. (P/asL) A thermoplastic, composed of poly-mers of ethylene: tough, waxy, and uneffected by water. It is commonly seen in flexible bottles, and in builders, agriculturalists', and manufacturers' protective, weather proof sheets. (See Plastics.)
Polygon. A plane figure of many sides and angles, especially more than four.
Polygon of forces. An expansion of the triangle of forces. If any number of forces are represented in magnitude and direction by tbe sides of (l polygon taken in order, they are in -equilibrium.
Polymer. (Plast.) A chemical compound of high molecular weight formed by the combining of simpler compounds having the same chemical elements in the same proportion. Polymers may be made by condensation or by successive addition of numbers of relatively small monomers.
Polymerization. (Chem.) Union of two or more molecules of the same substance to .form a different substance without loss of anything from the original substance; e.g., change of 6 formaldehyde molecules (CHP) into 1 of sugar (C6H.P6) by chlorophyll (green' colouring matter in plants) during photosynthesis.
Polymers. (Chern. Plast.) The products of reaction in polymerization.
Polyphase. (Elec.) Two or more phases or circuits associated electrically with each other.
Polystyrence (Chern. Plast.) An acidresisting thennoplastic resin easily molded by the injection process producing a high gloss and luster on molded pieces. Used for acid containers, refrigerator parts, instrument panels, novelties, etc.
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