Definitions /Dictionary/Glossary - nptel
Definitions /Dictionary/Glossary - nptel
Definitions /Dictionary/Glossary - nptel
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Pregel: An unintentional extra layer of cured resin on part of the surface of a reinforced plastic.<br />
(Not relating to "gel coat.")<br />
Preheating: The heating of compound prior to molding or casting in order to facilitate the<br />
operation or to reduce the molding cycle.<br />
Premix: A molding compound prepared prior to and apart from the molding operations and<br />
containing all components required for molding: resin, reinforcement, fillers, catalysts, release<br />
agents, and other compounds.<br />
Pre-ply: Layers of prepreg material, which have been assembled according to a user specified<br />
stacking sequence.<br />
Prepreg: Ready to mold or cure material in sheet form which may be tow, tape, cloth, or mat<br />
impregnated with resin. It may be stored before use. The resin is partially cured to a "B" stage<br />
and supplied to the fabricator who lays up the finished shape and completes the cure with heat<br />
and pressure.<br />
Pre-Release: The premature release of the gel coat or laminate from the mold. Pre-release<br />
causes cosmetic or dimensional problems.<br />
Pressure Bag: A membrane which conforms to the inside of a laminate laid up on a mold. The<br />
membrane or bag is then inflated applying pressure, which consolidates and densifies the<br />
laminate.<br />
Pressure: The force or load per unit area.<br />
Pressure-Bag Molding: A molding technique in which a flexible bag is placed over the contact<br />
layup in the mold, sealed, and clamped in place, and pressure applied by compressed air, which<br />
forces the bag against the part while the part cures.<br />
Primary Laminate: Laminate applied after the skin coat has cured. Generally thicker than the<br />
skin coat.<br />
Print Through: "Telegraphing" of the image of glass strands through the gel coat film.<br />
Promoter: See Accelerator.<br />
Proportional Limit: The maximum stress that a material is capable of sustaining without any<br />
deviation from the proportionality of stress to strain (also known as Hooke's law).<br />
Prototype: Process of creating a test part not intended for commercial release that establishes<br />
design, material and fabrication parameters for a new product. May entail multiple iterations to<br />
arrive at final/commercial part design.