Definitions /Dictionary/Glossary - nptel

Plastic Tooling: Tools (mostly for metal forming trades) constructed of plastics, generally
laminates or casting materials.
Platens: Mounting plates of a press to which the entire mold assembly is bolted.
Plied Yarn: It is yarn formed by twisting two or more single yarns together in one operation.
(Synonyms: folded yarn, formed yarn)
Plug: A composite industry term for a pattern or model.
Ply: The number of single yarns twisted together to form a plied yarn; also the number of plied
yarns twisted together to form a cord. It is the individual yarn in a plied yarn or in a cord. It is
one of several layers of fabric.
Poisson's Ratio: The ratio of transverse strain to axial strain during axial load.
Polyamide: A polymer in which the structural units are linked by amide or thioamide groupings.
Many polyamides are fiber-forming.
Polyester Combination Yarn: A polyester/fiber glass hybrid yarn.
Polyester (Unsaturated): Product of an acid-glycol reaction commonly blended with a
monomer to create a polymer resin. In its thermosetting form it is the most common resin used in
the FRP industry.
Polymer: Chain molecule composed of many identical groups, commonly found in plastics.
Polymerization: Chemical bonding of polymer molecules during the curing reaction.
Porosity: Entrapped gas bubbles or voids in a gel coat film.
Positive Mold: Mold that applies pressure to the piece being molded without material escaping.
Post Bake: see Post Cure
Post Cure: Heat cycle that a roving doffs goes through after fabrication. Generally used to help
"set" the ribbon on the outside of doff, improving doff's stability and resistance to package
collapse.
Pot Life: The length of time that catalyzed resin retains a viscosity low enough to be used in
processing.
PPO: Polyphenylene Oxide (Thermoplastic Resin).
PPS: Polyphenylene Sulfide (Thermoplastic Resin).