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W/O Emulsions Water-in-oil emulsion in which the water is the
internal phase and the oil is the external or continuous phase. The W/O
emulsion may be diluted by the addition of an oil and retain its
homogeneity (see definition of Unstable Emulsions). Warpage The
distortion caused by non-uniform shrinkage within a part. This
non-uniform shrinkage is caused by some kind of stress induced during
filling, packing, or cooling. Warp is a complex phenomenon and is often
caused by the combination of many forces, a few of which are dominant.
Do not confuse with distortion; a physical deformation of the article.
Warping A change in the shape of the part after ejection.
Water Absorption The amount of water absorbed by a plastic
article when immersed in water for a stipulated period of time. All
plastics will absorb moisture to some extent.
Water manifolds A single distribution device that connects
many smaller water fittings, thus allowing the molding technician to use
only two hose connections for the mold cooling water.
Water White A colloquial term used to describe the appearance
of a transparent polymer which has no tint or color.
Wax Distillates Neutral petroleum distillates that contain
paraffin.
Weathering, artificial The exposure of plastics to accelerated
laboratory-produced environmental conditions.
Weathering A broad term encompassing exposure of plastics to
solar or ultraviolet light, temperature, oxygen, humidity, rain, snow'
wind, and air-borne biological and chemical agents.
Weber Number Dimensionless parameter concerning surfaces or
interfacional tension forces.
Weld lines The marks visible on a finished part made by two
flow fronts, traveling in opposite directions, meeting during molding.
Areas in the part where two different fronts of molten plastic have come
together at a "meeting" angle less than 135°F.
Welding Joining thermoplastic pieces by one of several
heat-softening processes.
Wetting Agent Surface-active agent that is widely used in the
textile industry to aid dyeing and sizing operations by making the
textile absorbent and thus easier to "wet" with the dye or size.
Whisker A very short fiber form of reinforcement, usually of
crystalline material.
Wisps These are similar to stringing but smaller in size.
These may also occur as slight flashing when the mold is overpacked,
forced open slightly or due to mold parting line wear or misalignment. |
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