Glossary
Abrasion |
The wearing away of a surface by rubbing or scraping. | ||||
Adhesion |
The state in which two surfaces are held together by interfacial forces which may consist of valence forces, or interlocking action, or both. | ||||
Air Locks |
Surface depressions on molded part caused by trapped air between the mold surface and the plastics material. | ||||
Autoclave |
A device for applying pressure and heat to a tool. (Might be compared to a modern pressure cooker.) | ||||
Bag-Molding |
Application of fluid pressure, usually air or vacuum, to a flexible membrane or bag enclosing the material to be molded. | ||||
Blending |
Mixing of various ingredients of a molding composition, or of several batches of the same type, to ensure uniform distribution of all particles. Called dry blending or wet blending depending on condition. | ||||
Bubble |
A globule of air or other gas trapped within a plastic. | ||||
Cast |
To form a plastic material into a definite shape by pouring it into a mold and letting it harden without applying external pressure. Can be accomplished with or without application of external heat either before or after pouring. | ||||
Casting |
The finished product of a casting operation. (Should not be used as synonym for molding.) | ||||
Cross-laminated |
A laminate in which some, usually alternate, layers of material are oriented at right angles to the strongest direction in tension. | ||||
Cure |
To change the physical properties of a material by chemical reaction, which may be condensation, polymerization or vulcanization: usually accomplished by the action of heat and catalysts, alone or in combination with or without pressure. | ||||
Curing Agent |
A reactive chemical which causes a resin to cure. Also called hardener. | ||||
Delamination |
An area over which initial adhesion between I materials has been lost. | ||||
Diluent |
Any material which reduces the concentration of the fundamental resin; usually a liquid added to the resin to afford lower viscosity in order to facilitate working with the system. | ||||
Dimensional Stability |
Ability of a product to retain its exact shape and dimensions under ordinary conditions of use. | ||||
Draw |
To stretch a sheet of plastic material to fit a mold, to cup. |
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Elongation |
The increase in length of a material under tension. | ||||
Endothermic |
Indicating a reaction which absorbs heat. | ||||
Exothermic |
Indicating a reaction which liberates heat. | ||||
F.R.P. |
Fiberglass reinforced plastic. | ||||
Fiber Pattern |
Denotes the thread size and weave of glass cloth. | ||||
Filler |
Inert material added to a plastic composition for purposes of reducing cost, modifying mechanical properties, to serve as a base for color effects, or to serve as a heat sink. | ||||
Flexible Molds |
Molds that can be stretched to remove cured plastics. | ||||
Flexural Strength |
The strength of a material in bending. | ||||
Gel |
1. The name given to any gelatinous solid mass produced from a solution of a colloid body. 2. The "stage" at which a polymerizing resin composition thickens to a semi-solid state. |
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Gel Time |
The time in minutes required for a specific quantity of mixed resin and hardener to become unworkable (gelled). | ||||
Heat Distortion Point |
The temperature at which a test bar deflects under a given flexural load and a prescribed amount of heat. | ||||
Hygroscopic |
The ability to absorb and retain atmospheric moisture. | ||||
Inert |
Not chemically reactive. | ||||
Impregnate |
To saturate reinforcement with plastic. | ||||
Laminate |
To unite sheets of material by a bonding material. Normally used in reference to flat sheets. | ||||
Lay-Up |
The arrangement of reinforcing material (glass cloth) and the resin in its uncured state. |
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Mil |
.001 inch. | ||||
Mold |
The cavity or matrix into or on which the plastic composition is placed and from which it takes its form. | ||||
Mold Release |
An agent used to prevent a plastic from sticking to the mold. | ||||
Mold Shrinkage |
The immediate shrinkage a molded part undergoes when removed from a mold and cooled to room temperature. | ||||
Parallel laminated |
A laminate in which all the layers of material are oriented parallel with respect to the strongest direction in tension. | ||||
Plastic |
Anyone of a large and varied group of materials which consists of or contains as an essential ingredient an organic substance of large molecular weight and which, while solid in the finished state, at some stage in its manufacture has been or can be formed (cast, calendered, extruded, molded, etc.) into various shapes by flow usually through the application singly or together of heat and pressure. | ||||
Post-Cure |
In certain resins complete cure and ultimate mechanical properties are attained only by exposure of the cured resin to higher temperatures. This second stage is the post-cure and is necessitated by the fact that the higher temperatures would resul1 in excessive reaction if used throughout the entire cure. | ||||
Polyurethane |
Thermosetting plastics used for flexible molds, protective coatings and abrasion resistant casting applications. | ||||
Pot Life |
Regarding a resin mix, the time period between complete catalyzation and initial gelation, during which time the mix is said to be usable. Also called "working life". | ||||
Reinforcement |
Material used primarily for strengthening a plastic product, i.e., fibrous glass, cotton, etc., which is impregnated with the plastics mixture. (Should not be used synonymous with filler.) | ||||
Room Temperature |
25° C (77° F) | ||||
Resin |
A class of solid or semi-solid organic products of natural or synthetic origin, generally of high molecular weight with no definite melting point. (Resins are generally water-insoluble and have little or no tendency to crystallize. However, certain resins such as some polyvinyl alcohols and polyacrylates are readily dispersible in water; and others such as polyamides and polyvinylidene chloride are readily crystallized.) |
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Spline |
To prepare a surface to its desired contour by working a paste material with a flat-edged tool. The procedure is similar to screeding of concrete. | ||||
Spray Up |
The technique of using a spray gun to prepare a reinforced plastic article. | ||||
Sprue |
The main opening into a mold cavity through which a plastic material is introduced into the mold. | ||||
Starved Area |
The area in a reinforced plastic part that did not have sufficient plastic to wet the reinforcement completely. | ||||
Tack |
Stickiness. | ||||
Thermal Conductivity |
The ability of a material to conduct heat. | ||||
Thermoforming |
Shaping a plastic material by heating it to its softening point and cooling it on a mold. | ||||
Thermoset |
A plastic which when cured changes into a substantially infusible or insoluble product. | ||||
Thixotropic Liquids |
Liquids which reduce their viscosity as the agitation is increased, i.e., ketchup, latex paint. | ||||
Thixotrophy |
The property by which some compositions become semi-solid at rest and liquefy again on agitation. | ||||
Viscosity |
The resistance of a liquid to flow. Thickness. | ||||
Voids |
Gas or air pockets trapped within a material. | ||||
Working Life |
Same as "gel time", but may also be defined for other sizes of resin-hardener mixtures. That is, the working life of a one-pint unit is usually longer than the working life of a one-quart unit. | ||||
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