Definitions /Dictionary/Glossary - nptel

Glass Transition: The reversible change in an amorphous polymer or in amorphous regions of a
partially crystalline polymer from (or to) a viscous or rubbery condition to (or from) a hard and
relatively brittle one.
Glass Transition Temperature ( T g ): The approximate midpoint of the temperature range over
which the glass transition takes place.
Glint: A visual defect in a fiberglass reinforced cured organic (usually corrosion resistant resin)
panel. The defect appears as many small visible unwet or foreign substances - a salt and pepper
effect. The defect is not visible before cure but appears at exotherm of the panel.
Graphite: A form of carbon. Structural graphite is used in composite structures due to its
strength and stiffness.
Graphite Fibers: See Carbon Fibers.
Graphitization: The process of pyrolization at very high temperatures (as high as 5400(F) that
converts carbon to its crystalline allotropic form.
Greige: Fabric that has received no finish.
GRP: Glass-reinforced plastic, polymer, polyester. this derivation is commonly used in Europe.
Guide Pin: A pin, which guides mold halves into alignment on closing.
Hand Lay-up: A process in which components are applied either to a mold or a working
surface, and the successive plies are built up and worked by hand.
Handling Life: The out of refrigeration time over which, a material retains its handleability.
Hard Tool: A tool made of metallics or any "hard" material that is generally impervious to
damage during normal use.
Hardener: A substance or mixture added to a plastic composition to promote or control the
curing action.
Hardness: Resistance to deformation; usually measured by indention. Types of standard tests
include Brinell, Rockwell, Knoop, and Vickers.
Heat Cleaned: It is a Glass or other fibers which have been exposed to elevated temperatures to
remove preliminary sizing or binders which are not compatible with the resin system to be
applied.