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.