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