Palletizing - A process
of producing pellets.
Parison - The hollow plastic
tube from which a container, toy, etc. is blow molded.
Parison Swell - In blow
molding the ratio of the cross-sectional area of the
parison to the cross-sectional area of the die opening.
Parting Agent - A lubricant,
often wax, used to coat a mold cavity to prevent the
molded piece from sticking to it, and thus to facilitate
its removal from the mold. Also called Release Agent.
Parting Line - Mark on a
molding or casting where halves of mold met in closing.
Partitioned Mold Cooling - A large diameter hole drilled into the mold (usually
the core) and partitioned by a metal plate extending
to near the bottom end of the channel. Water is introduced
near the top of one side of the partition and removed
on the other side.
Pellet - A small ball or
spherical shape.
Permanent Set - The increase
in length, expressed in a percentage of the original
length, by which an elastic material fails to return
to original length after being stressed for a standard
period of time.
Permeability - (1) The passage
or diffusion of a gas, vapor, liquid, or solid through
a barrier without physically or chemically affecting
it. (2) The rate of such passage.
PH - An expression of the
degree of acidity or alkalinity of a substance. Neutrality
is pH -acid solutions being under 7 and alkaline solution
over 7. pH meters are commercially available for accurate
readings.
Phenolic Resin - A synthetic
resin produced by the condensation of an aromatic alcohol
with an aldehyde, particularly of phenol with formaldehyde.
Phenolic resins from the basis of thermosetting molding
materials, laminated sheet, and varnishes. They are
also used as impregnating agents and as components of
paint, varnishes, lacquers, and adhesives.
Pigment - Any colorant,
usually an insoluble powdered substance used to produce
a desired color of hue.
Pinpoint Gate - A restricted
orifice of 0.030 inches or less in diameter through
which molten resin flows into a mold cavity.
Pitch - The distance from
any point on the flight of a screw line to the corresponding
point on an adjacent flight, measured parallel to the
axis of the screw line or threading.
Plastic Deformation - A
change in dimensions of an object under load that is
not recovered when the load is removed; opposed to elastic
deformation.
Plastic Memory - A phenomenon
of plastic to return to its original molded form. Different
plastics possess varying degrees of this characteristic.
Plasticity - The quality
of being able to be shaped by plastic flow.
Plasticize - To soften a
material and make it plastic or moldable, either by
means of a plasticizer or the application of heat.
Plasticizer - Chemical agent
added to plastic compositions to make them softer and
more flexible.
Plastics Wood Composites - a range of materials that resemble wood. It combines the advantages of wood with those of plastics.
Plastisols - Mixtures of
resins and plasticizers which can be molded, cast, or
converted to continuous films by the application of
heat. If the mixtures contain volatile thinners also,
they are known as Organosols.
Plate Dispersion Plug -
Two perforated plates held together with a connecting
rod which are placed in the nozzle of an injection molding
machine to aid in dispersing a colorant in a resin as
it flows through the orifices in the plates.
Plate-mark - Any imperfection
in a pressed plastic sheet resulting from the surface
of the pressing plate.
Platens - The mounting plates
of a press to which the entire mold assembly is bolted.
Platform Blowing - A special
technique for blowing large parts. To prevent excessive
sag of the heavy parison the machine employs a table
which after rising to meet the parison at the die descends
with the parison but at a slightly lower rate than the
parison extrusion speed.
Plug Forming - A thermoforming
process in which a plug or male mold is used to partially
preform the part before forming is completed using vacuum
or pressure.
Plug-and-ring - Method of
sheet forming in which a plug, functioning as a male
mold, is forced into a heated plastic sheet held in
place by a clamping ring.
Plunger - See Force Plug.
Pneumatic - A system in
which energy is transferred by compression, flow and
expansion of air.
Poise - The unit of viscosity
expressed as one dyne per second per square centimeter.
Polyamide - A polymer in
which the structural units are linked by amide or thioamide
groupings. Many polyamides are fiber-forming.
Polybutylene - A polymer
prepared by the polymerization of butene as the sole
monomer.
Polyester - A resin formed
by the reaction between a dibasic acid and a dihydroxy
alcohol, both organic. Modification with multi-functional
acids and/or bases and some unsaturated reactants permit
cross-linking to thermosetting resins. Polyesters modified
with fatty acids are called Alkyds.
Polyethylene - A thermoplastic
material composed by polymers of ethylene. It is normally
a translucent, tough, waxy solid which is unaffected
by water and by a large range of chemicals.
Polyimide Resins - A new
group of resins recently introduced in the United States.
The material is an aromatic polyimide made by reacting
pyromellitic dianhydride with aromatic diamines. The
polymer is characterized by the fact that it has rings
of four carbon atoms tightly bound together, and the
manufacturers claim that the new resin has greater resistance
to heat than any other unfilled organic material yet
discovered. Suggested applications include components
for internal combustion engines.
Polyisobutylene - The polymerization
product of isobutylene. It varies in consistency from
a viscous liquid to a rubber-like solid with corresponding
variation in molecular weight from 1,000 to 400,000.
Polyliner - A perforated
longitudinally ribbed sleeve that fits inside the cylinder
of an injection molding machine; used as a replacement
for conventional injection cylinder torpedoes.
Polymer - A high-molecular-weight
organic compound, natural or synthetic, whose structure
can be represented by a repeated small unit, the mer;
e.g., polyethylene, rubber, cellulose. Synthetic polymers
are formed by addition or condensation polymerization
of monomers. If two or more monomers are involved, a
copolymer is obtained. Some polymers are elastomers,
some plastics.
Polymerization - A chemical
reaction in which the molecules of a monomer are linked
together to form large molecules whose molecular weight
is a multiple of that of the original substance. When
two or more monomers are involved, the process is called
copolymerization or heteropolymerization. See also Degree
of, Condensation, and Polymer.
Polymethyl Methacrylate - A thermoplastic material composed of polymers of methyl
methacrylate. It is a transparent solid with exceptional
optical properties and good resistance to water. It
is obtainable in the form of sheets, granules, solutions,
and emulsions. It is extensively used for aircraft domes,
lighting, fixtures, decorative articles, etc.; it is
also used in optical instruments and surgical appliances.
Polyolefin - A polymer prepared
by the polymerization of an Olefin(s) as the sole Monomer(s).
Polyoxymethylene - A polymer
in which the repeated structural unit in the chain is
oxymethylene.
Polypropylene - A tough,
lightweight rigid plastic made by the polymerization
of high-purity propylene gas in the presence of an organometallic
catalyst at relatively low pressures and temperatures.
Polystyrene - A water-white
thermoplastic produced by the polymerization of styrene
(vinyl benzene). The electrical insulating properties
of polystyrene are outstandingly good and the material
is relatively unaffected by moisture.
Polytetrafluoroethylene (PTFE) Resins - Members of the fluorocarbons family
of plastics made by the polymerization of tetrafluoroethylene.
PTFE is characterized by its extreme inertness to chemicals,
very high thermal stability and low frictional properties.
Among the applications for these materials are bearings,
fuel hoses, gaskets and tapes, and coatings for metal
and fabric.
Polyurethane Resins - A
family of resins produced by reacting diisocyanate with
organic compounds containing two or more active hydrogens
to form polymers having free isocyanate groups. These
groups, under the influence of heat or certain catalysts,
will react with each other, or with water, glycols,
etc., to form a thermosetting material.
Polyvinyl Acetal - A member
of the family of vinyl plastics. Polyvinyl acetal is
the general name for resins produced from a condensation
of polyvinyl alcohol with an aldehyde. There are three
main groups: polyvinyl acetal itself; polyvinyl butyl,
and polyvinyl formal. Polyvinyl acetal resins are thermoplastics
which can be processed by casting, extruding, molding
and coating, but their main uses are in adhesives, lacquers,
coatings and films.
Polyvinyl Acetate - A thermoplastic
material composed of polymers of vinyl acetate in the
form of a colorless solid. It is obtainable in the form
of granules, solutions, lattices, and pastes, and is
used extensively in adhesives, for paper and fabric
coatings, and in bases for inks and lacquers.
Polyvinyl Carbazole - A
thermoplastic resin, brown in color, obtained by reacting
acetylene with carbazole. The resin has excellent electrical
properties and good heat and chemical resistance. It
is used as an impregnate for paper capacitors.
Polyvinyl Chloride (PVC) - A thermoplastic material composed of polymers of vinyl
chloride; a colorless solid with outstanding resistance
to water, alcohols, and concentrated acids and alkalies.
It is obtainable in the form of granules, solutions,
lattices, and pastes. Compounded with plasticizers it
yields a flexible material superior to rubber in ageing
properties. It is widely used for cable and wire coverings,
in chemical plants, and in the manufacture of protective
garments.
Polyvinyl Chloride Acetate - A thermoplastic material composed of copolymers of
vinyl chloride and vinyl acetate; a colorless solid
with good resistance to water, and concentrated acids
and alkalies. It is obtainable in the form of granules,
solutions, and emulsions. Compounded with plasticizers
it yields a flexible material superior to rubber in
aging properties. It is widely used for cable and wire
coverings, in chemical plants, and in protective garments.
POM - The chemical abbreviation for Acetal, also known as Polyoxymethylene.
Postcure - Those additional
operations to which a cured thermosetting plastic or
rubber composition are subjected to enhance the level
of one or more properties.
Postforming - The forming,
bending, or shaping of fully cured, C-stage thermoset
laminates that have been heated to make them flexible.
On cooling, the formed laminate retains the contours
and shape of the mold over which it has been formed.
Powder Molding - General
term used to denote several techniques for producing
objects of varying sizes and shapes by melting polyethylene
powder, usually against the inside of a mold. The techniques
vary as to whether the molds are stationary (e.g., as
in variations on slush molding techniques) or rotating
(e.g., as in variations on rotational molding).
Power Factor - 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, throws the 90 degree relationship
out according to the proportion of current absorbed
by the dielectric. The power factor is the cosine of
the angle between voltage applied and the current resulting.
Preform - (n.) A compressed
tablet or biscuit of plastic composition used for efficiency
in handling and accuracy in weighing materials. (v.)
To make plastic molding powder into pellets or tablets.
Preheat Roll - In extrusion
coating, a heated roll installed between the pressure
roll and unwind roll whose purpose is to heat the substrate
before it is coated.
Preheating - The heating
of a compound prior to molding or casting in order to
facilitate the operation or to reduce the molding cycle.
Preimpregnation - The practice
of mixing resin and reinforcement before shipping it
to the molder.
Prepreg - A term generally
used in reinforced plastics to mean the reinforcing
material containing or combined with the full complement
of resin before molding.
Pressure Forming - A thermoforming
process wherein pressure is used to push the sheet to
be formed against the mold surface as opposed to using
a vacuum to suck the sheet against the mold.
Pressure Pads - Reinforcements
or hardened steel distributed around the dead areas
in the faces of a mold to help the land absorb the final
pressure of closing without collapsing.
Pressure Roll - In extrusion
coating, the roll which with the chill roll applies
pressure to the substrate and the molten extruded web.
Prototype Mold - A simplified
mold construction often made from a light metal casting
alloy or from an epoxy resin in order to obtain information
for the final mold and/or part design.
Pulp - A form of cellulose
obtained from wood or other vegetable matter by prolonged
cooking with chemicals.
Pulp Molding - Process by
which a resin-impregnated pulp material is preformed
by application of a vacuum and subsequently oven cured
or molded.
Purging - Cleaning one color
or type of material from the cylinder of an injection
molding machine or extruder by forcing it out with the
new color or material to be used in subsequent production.
Purging materials are also available.
Push Up - The bottom contor
of a plastic container designed in such a manner as
to allow an even bearing surface on the outside edge
and to prevent the bottle from rocking. |