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Laminar Flow Streamline flow of a fluid. The mass of fluid
advances in separate sheets with simple shear existing at the surface of
contact of different layers if the layers move at different speeds.
Land (Gate Area) Gate dimension parallel to the direction of melt
flow.
Land Area The area of surfaces of a mold which contact each
other when the mold is closed.
Land The area on the surface of the mold about one inch around
the outside of the part.
Lantz- Zeitfuchs Viscometer Reverse-flow viscometer that permits the
measurement of kinematic viscosities of opaque Newtonian liquids of
60-120,000 cS.
Latent heat of fusion See Heat of fusion.
Latex Any stable dispersion of insoluble polymer particles in
a water system. Generally an emulsion of a high molecular weight polymer
in water, often formed by emulsion polymerization of the monomer(s).
LDR Let-down ratio used in coloring plastics with color
concentrates, etc. (e.g., 20:1 is 20 pounds of natural resin to 1 pound
of colorant).
Leaching Washing operation that removes a certain amount of
dissolved substance(s) from a material.
Leader pins Pins that align the two halves of the mold about
one inch around the outside of the part. See also guide pin.
Length/Diameter (L/D) ratio Describes the relationship between
the length of the screw and its diameter. An L/D of 20:1 is suggested to
ensure enough resistance time for thorough mixing without adding
excessive mechanical energy.
Levigation Grinding of a solid to a fine smooth powder while
in moist condition.
Light resistance The resistance of a plastic to change color,
fade, or other characteristics during exposure to sunlight.
Limit switch A position sensing device used to set stroke or
distances on the machine.
Limiting oxygen index (LOI) Method of testing the flammability
characteristics of a plastic by measuring the concentration of oxygen to
maintain burning.
Linear potentiometer An electromechanical component that
measures distances electrically and sends the signal to a
microprocessor.
Linkages The mechanical component arms that make up a toggle
clamp.
Lipophilic Attracted to oil; oil-soluble.
Liquid Substance that undergoes continuous deformation when
subjected to shearing stress.
Livering Coagulation of a paint or enamel into a viscous
rubbery mass.
Locating ring Device that aligns a mold with the center hole
in the stationary platen of an injection molding machine. It aligns the
sprue bushing with the nozzle tip.
Locator ring The ring that surrounds the sprue bushing to
align the mold and the nozzle.
Locking force The force exerted in the clamping system
(hydraulic, toggle, mechanical) of a molding machine to hold the mold
closed.
Log sheet An information sheet containing problems encountered
when using the mold, and molding solutions or parameter changes that
were used to correct them.
Lot A quantity of resin produced at one time. See batch.
Low Temperature Flexibility The ability of a plastic to be
bent without fracture at reduced temperatures.
Lubricant Additive compounded into a resin. Can be classified
into two areas: internal and external. Lubricants promote resin flow
and/or mold release.
Lubricant Bloom Irregular, cloudy, greasy exudation on the
surface of a plastic.
Lubricating Greases Solid or semifluid products of the
dispersion of a thickening agent in a liquid lubricant that may contain
ingredients to impart special properties.
Lyophilic Coilloid Reversible colloid; the dispersed phase
when removed from suspension returns to the colloidal state on remixing
with the dispersible medium. The suspension is a reversible sol.
Lyophilic Pertaining to a colloidal system of the emulsoid
type.
Lyophobic Colloid Irreversible colloid; the disperse phase
when removed from suspension does not return to the colloidal state upon
simple remixing.
Lyophobic Pertaining to a colloidal system of the suspensoid
type . |
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