
Processing
 Injection
Pressure: The pressure (on the face of the
injection ram) at which molding material is injected into a mold.
 Injection
Cylinder Temperature: The injection molding
machine's barrel temperature.
 Mold
Temperature: The temperature of the mold's
surface.
Permanence
 Specific
Gravity: The density (mass per unit volume) of any
material divided by that of water at a standard temperature (usually 4
degrees C).
 Molding
Shrinkage: The difference in dimension between a
molded part and the cavity in which it was molded. Both are measured at room
temperature.
 Water
Absorption: The percentage of water absorbed by a
material when immersed in water for 24 hours.
Mechanical
 Impact
Strength: (IZOD) Notched— The energy
required to break specimens in which there is a vnotch to create an initial
stress point.
 Tensile
Strength: Yield— the maximum
stress that a material can withstand (up to 10% of bar length) without
yielding when subject to a stretching load. Break— The
maximum stress that a material can withstand without breaking when subjected
to a stretching load.
 Tensile
Elongation: Yield— the increase in
distance (up to 10% of bar length) between two gauge marks at a yield point
divided by the original distance between the marks. Break—
the increase in distance between two gauge marks at the break point divided
by the original distance between the marks.
 Tensile
Modulus: The ratio of stress to strain in a
material that is elastically deformed.
 Flexural
Strength: The strength of a material in bending,
expressed as the tensile stress of the outermost fibers of a bent test
sample at the instant of the failure. With plastics, this value is usually
higher than the straight tensile strength.
 Flexural
Modulus: The ratio, within the elastic limit, of
the applied stress on a test specimen in flexure to the corresponding strain
in the outermost fibers of the specimen.
 Tear
Strength: (Die C) In a tensile test, the force
required to tear an elastomer, divided by the sample thickness.
 Compressive
Strength: Crushing load at the failure of a
specimen divided by the original sectional area of the specimen.
 Hardness:
The resistance of a plastic material to compression and indentation. Among
the most important methods of testing are Rockwell Hardness and Shore
Hardness.
Electrical
 Dielectric
Strength: The electric voltage gradient at which
an insulating material is broken down or "arced through" in volts
per millimeter of thickness.
 Dielectric
Constant: The ratio of the capacity of a condenser
(made with a dielectric material) to the capacity of the same condenser
(with air as the dielectric). Measured at a frequency of 10E6 cycles per
second.
 Dissipation
Factor: The cosine of the angle between applied
voltage and the resulting current. Measurements are usually made in
millioncycle frequencies. (In a perfect condenser, the current leads the
voltage by 90 degrees. When a loss takes place in the insulation, the
absorbed current, which produces heat, changes this relationship according
to the proportion of current absorbed by the dielectric.)
 Arc
Resistance: Time required for an electrical
current to render the surface of a material conductive due to carbonization
by the arc flame.
 Volume
Resistivity: The electrical resistance between the
opposite faces of a solid volume of insulating material. It is measured
under prescribed conditions using a direct current potential after a
specified time of electrification. Commonly expressed in ohmcm.
 Surface
Resistivity: The electrical resistance between
opposite edges of a unit square on the surface of an insulating material.
Commonly expressed in ohm/sq.
 Static
Decay: The time required (in seconds) for a charge
placed on the surface of an insulating material to decay to a percentage of
the original charge. The test is performed at a specified relative humidity
condition.
Thermal
 Deflection
Temperature (HDT): The temperature at which a
standard test bar deflects 0.010 in (0.25 mm) under a stated load of either
66 psi (0.45 MPa) or 264 psi (1.82 MPa).
 Flammability:
The extent to which a material will support combustion using standardized
methods.
 Coefficient
of Expansion: The fractional change in length (or
volume) of a material divided by the change in temperature.
 Thermal
Conductivity: For steadstate heat flow, the
proportionality constant between the heat flux and the temperature gradient.
Also, a parameter characterizing the ability of a material to conduct heat.
