Definitions /Dictionary/Glossary - nptel

shows how much one-inch of material will increase if its temperature is raised one degree
Fahrenheit. Units are expressed in inches per inch per degree Fahrenheit (in/in/°F) -
Meters/Meter/°C. Higher numbers mean that the material will expand or lengthen more for each
degree that its temperature increases. Smaller numbers indicate relative stability to changes in
temperature.
Thermal Conductivity (K factor): The amount of heat transferred by conduction; i.e., how
much heat is transferred from one side of a plate to the other. It is measured as BTUs (units of
heat in the English system) per hour per unit area (square feet) for a thickness of one inch and a
temperature difference of one degree Fahrenheit between both sides of the plate. Units are
expressed as BTU/hr/sq/°F/inch. - Watt/(Meter Deg Kelven) W/MK. Higher numbers mean that
the material will absorb more energy before it is broken by a moving weight.
Thermoplastic: Capable of being repeatedly softened by an increase of temperature and
hardened by a decrease in temperature. Applicable to those materials whose change upon heating
is substantially physical rather than chemical and that in the softened stage, they can be shaped
by flow into articles by molding or extrusion.
Thermoplastic Polyesters: Class of thermoplastic polymers in which the repeating units are
joined by ester groups. The two important types are:
(1) polyethylene terephthalate (PET), which is widely used as film, fiber and soda
bottles; and
(2) Polybutylene terephthalate (PBT), primarily a molding compound.
Thermoset: A material that undergoes a chemical reaction caused by heat, catalyst or other
condition, which results in the formation of a solid. Once it becomes a solid, it cannot be
reformed.
Thermosetting Polyesters: Class of resins produced by dissolving unsaturated, generally linear,
alkyd resins in a vinyl-type active monomer such as styrene, methyl styrene, or diallyl phthalate.
Cure is affected through vinyl polymerization using peroside catalysts and promoters or heat to
accelerate the reaction. The two important commercial types are:
(1) liquid resins that are cross-linked with styrene and used either as impregnants for glass
or carbon fiber reinforcements in laminates, filament-wound structures and other builtup
constructions, or as binders for chopped-fiber reinforcements in molding
compounds, such as sheet molding compound (SMC), bulk molding compound (BMC)
and thick molding compound (TMC); and
(2) liquid or solid resins cross-linked with other esters in chopped-fiber and mineral-filled
molding compounds (for example, alkyd and dially phthalate).
Theoretical End Count: The maximum number of bundles in a roving doff; for example, a
roving doff made with 18 forming cakes in the creel that were "split out" 4 ways in forming will
have 64 theoretical ends.
Thickeners: Material added to resin to thicken it or raise its viscosity index so that it will not
flow as readily.