Definitions /Dictionary/Glossary - nptel

Organic: Matter originating in plant or animal life, or composed of chemicals of hydrocarbon
origin, either natural or synthetic.
Orientation: Position with relation to flow of polymer in the mold.
Orthophthalic Resin: Polyester resin based on Orthophthalic acid, also known as a general
purpose resin (GP).
Overlay Sheet: Non-woven fibrous mat (of glass, synthetic fiber or other material) used as the
top layer in a cloth or mat lay-up to provide a smoother finish, minimize the appearance of a
fibrous pattern, or permit machining or grinding to a precise dimension. It is also called surfacing
mat.
Overspray: A specially formulated binder applied to texturized yarn that helps retain the yarn
bulk after texturizing.
Parting Line: It is a mark on a molded piece where mold sections have met in closing.
PBT: Polybuthlene Therephthalate (Thermoplastic Polyester Resin).
PET: Polyethylene Terephthalate (Thermoplastic Polyester Resin).
Phenolic Resin: Thermosetting resin produced by the condensation of an aromatic alcohol with
an aldehyde, particularly of phenol with formaldehyde. Used in high-temperature applications
with various fillers and reinforcements.
Pigment: Colorant added to gel coat or resin.
Pinholes: Small holes on the exposed gel coated surface that are about the diameter of common
pins and may be easily counted.
Pit: Small regular or irregular crater in the surface of a plastic, usually of equal width and depth.
Plastic: Material of which an essential ingredient is an organic polymer of large molecular
weight and also contains hardeners, fillers and reinforcements; is solid in its finished state; and
has been shaped by flow during some stage of its manufacture or processing. It is made of
plastic. A plastic may be either thermoplastic or thermoset.
Plastic Deformation: Change in dimensions of an object under load that is not recovered when
the load is removed; opposed to elastic deformation.
Plasticizers: Material added to increase a plastic’s workability and flexibility. These are
normally used in thermoplastics. Also a lower molecular weight material added to epoxy to
reduce stiffness and brittleness, thereby resulting in a lower glass transition temperature for the
polymer.