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Tensile Strength
The amount of force required to elongate the plastic by a defined amount. The higher the value, the stronger the material. Or the maximum stress sustained by a material before failure in tension. When the maximum stress occurs at the yield point, it is called tensile strength at yield. When maximum stress at break: tensile strength at break.

Thermal Conductivity
The measure of the ability of a material to conduct heat along its length or through its thickness. Or the rate of heat flow under steady conditions through unit area, per unit temperature gradient in the direction perpendicular to the area. The higher the value, the more conductive: a material with a low value for thermal conductivity acts like an insulator

Rubber-like elasticity exhibited by a rigid plastic resulting from an increase in temperature.

The process of forming a thermoplastic sheet into a three-dimensional shape by clamping the sheet in a frame, heating it to tender it soft and flowable. Then applying differential pressure to make the sheet conform to the shape of a mold or die positioned below the frame.

Materials that become soft when heated and solid when cooled to room temperature. This softening and setting may be repeated many times.

Thermoplastic Isomers
The family of polymers that resemble elastomers in that they can be repeatedly stretched without distortion of the unstressed part shape, but are true thermoplastics and thus do not require curing.

Thermoplastics vs. Thermosets
A thermoplastic is a polymeric material or plastic which becomes soft and formable when heated and rigid when cooled. This process may be repeated a number of times without chemically altering the material. A thermoset is a polymeric material which undergoes irreversible chemical changes when cured through heat, catalysts or ultraviolet light: cross-linking prevents movement of molecular chains after curing. Once cured, the structure cannot be changed.

Materials that may not be reheated and softened again. Once the structural framework is set, these plastics cannot be reformed.

Depth of the material and contributory to pressure requirements; thickening reduces the pressure required to fill the part.

Titanium dioxide
A white pigment available in two crystalline forms, rutile and anatase, the former being the most widely used white and opacifying pigment in thermoplastics, printing inks and paints

A protuberance or indentation that impedes withdrawal from a mold.

The dominant flow of two confronting flows, over the other. The lesser flow reverses direction giving poor surface appearance and structural strength. Underflow should be avoided by positioning gates so that the flow fronts meet at the end of filling.

Uniform Cooling Time
Cooling time the same throughout the part to avoid warping.

UV absorber
An additive which protects materials by absorbing UV radiation.

UV stabiliser
Additive which stabilises organic materials against UV radiation.

Vacuum Forming
A method of forming plastic sheets or films into three-dimensional shapes, in which the plastic sheet is clamped in a frame suspended above a mold, heated until it becomes softened, drawn down into contact with the mold by means of a vacuum, and cooled while in contact with the mold. Often used interchangeably with thermoforming.

Vicat Softening Temperature Undercut
Vicat Softening Temperature, is a measure of the temperature at which a plastic starts to soften at specified test conditions according to ISO 306. It is determined with a standard indenter (a flat-ended needle of 1 mm 2 circular cross section) penetrating into the surface of a test specimen under a predefined load. The temperature at 1 mm penetration is quoted as the VST in Co. VST gives an indication of a material’s ability to withstand limited short-term contact with a heated object. For material comparisons only.

Virgin Material
Any plastic compound or resin that has not been subjected to use or processing other than that required for its original manufacture.

Viscosity, MFR, MVI, and MV
Viscosity is the resistance to steady flow shown within the body of a material. It is internal friction or the measure of a polymer melt’s resistance to flow. In testing: the ratio of the shearing stress to the rate of shear of a fluid. Which ‘Newtonian viscosity’, the ratio of shearing stress to rate of shearing strain is constant. In non-Newtonian behavior – which is the usual case with plastics – the ratio is not constant but varies with the shearing stress. Such a ratio is often called the apparent viscosity at the corresponding shearing stress. It represents one point on the flow curve. MFR, or melt flow rate, is the mass of thermoplastic material extruded in a given time through a defined orifice under specified conditions. Also called "flow rate." The expression MVI, or melt volume index, equals MVR. MV, or melt viscosity, is a measure of a polymer at a given temperature at which the molecular chains can move relative to each other. It is expressed as the quotient of the real shear stress t and the real rate of shear y. Melt viscosity is considerably dependent on the molecular weight: the higher the molecular weight the greater the entanglements and the greater the melt viscosity.

To twist or deform from a desired shape. Often caused by molded in stress or shrinkage.

Dimensional distortion of a plastic part due to strain resulting from injection molding or other conversion methods.

Sections of the barrel which are controlled individually by temperature controllers.




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