Tab Gated - A small removable
tab of approximately the same thickness as the mold
item, usually located perpendicular to the item. The
tab is used as a site for edge gate location, usually
on items with large flat areas.
Tack - Stickiness of an
adhesive, measurable as the force required to separate
an adherent from it by viscous or plastic flow of the
adhesive.
Tapered Cylinder - Refers
to a particular shape of a container in which the circular
cross section at the top is smaller in diameter than
that at the bottom, or vice versa.
Tenacity (gpd) - The term
generally used in yarn manufacture and textile engineering
to denote the strength of a yarn or of a filament for
its given size. Numerically it is the grams of breaking
force per denier unit of yarn or filament size; grams
per denier, gpd. The yarn is usually pulled at the rate
of 12 in./min. Tenacity equals breaking strength (grams)
divided by denier.
Tensile Bar (specimen) -
A compression or injection molded specimen of specified
dimensions which is used to determine the tensile properties
of a material.
Tensile Strength - The pulling
stress, in psi, required to break a given specimen.
Area used in computing strength is usually the original,
rather than the necked-down area.
Therimage - A trademark
for a decorating process for plastic which transfers
the image of a label or decoration to the object under
the influence of heat and light pressure.
Thermal Conductivity - Ability
of a material to conduct heat; physical constant for
quantity of heat that passes through a unit cube of
a substance in a unit of time when difference in temperature
of two faces is 1 degree.
Thermal Degradation - Deterioration
by heat.
Thermal Expansion Coefficient - The fractional change in length (sometimes volume,
specified) of a material for a unit change in temperature.
Values for plastics range from 0.01 to 0.2 mils/in.,
degrees C.
Thermal Stress Cracking (TSC) - Crazing and cracking of some thermoplastic resins
which results from over-exposure to elevated temperatures.
Thermoforming - Any process
of forming thermoplastic sheet which consists of heating
the sheet and pulling it down onto a mold surface.
Thermoforms - The product
which results from a thermoforming operation.
Thermoplastic - Capable
of being repeatedly softened by heat and hardened by
cooling (n.) - A material that will repeatedly soften
when heated and harden when cooled. Typical of the thermoplastics
family are the styrene polymers and copolymers, acrylics,
cellulosics, polyethylenes, vinyls, nylons, and the
various fluorocarbons materials.
Thermoset - A material that
will undergo or has undergone a chemical reaction by
the action of heat, catalysts, ultra-violet light, etc.,
leading to a relatively infusible state. Typical of
the plastics in the thermosetting family are the aminos
(melamine and urea), most polyesters, alkyds, epoxies,
and phenolics.
Tie Bars - Bars which provide
structural rigidity to the clamping mechanism often
used to guide platen movement.
Tolerance - A specified
allowance for deviations in weighing, measuring, etc.,
or for deviations from the standard dimensions or weight.
Top Blow - A specific type
of blow molding machine forms hollow articles by injecting
the blowing into the parison at the top of the mold.
Torsion - Stress caused
by twisting a material.
Tracking - A phenomenon
wherein a high voltage source current creates a leakage
or fault path across the surface of an insulating material
by slowly but steadily forming a carbonized path.
Transfer Molding - A method
of forming articles by fusing a plastic material in
a chamber and then forcing essentially the whole mass
into a hot mold where it solidifies.
Translucent - Descriptive
of a material or substance capable of transmitting some
light, but not clear enough to be seen through.
Transparent - Descriptive
of a material or substance capable of a high degree
of light transmission e.g., glass. Some polypropylene
films and acrylic moldings are outstanding in this respect.
Tumbling - Finishing operation
for small plastic articles by which gates, flash, and
fins are removed and/or surfaces are polished by rotating
them in a barrel together with wooden pegs, sawdust,
and polishing compounds. |