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[ B ]
B-stage
This
describes an intermediate stage of reaction where the
material will soften when heated and swells in the presence
of certain liquids, but may not completely fuse or dissolve.
The resin is usually supplied in this uncured state.
Bulk-molding compounds (BMC)
Bulk-molding compounds are used as a premix in composite
manufacturing. A BMC consists of a mixture of resin,
reinforcements, inert fillers, and other additives which
form a puttylike preformed shape, rope or sheet.
Binder
A resin
or other material used to hold particles together. The
binder is the continuous phase in a reinforced plastic which
provides mechanical strength or ensures uniform consistency,
solidification, or adhesion to a surface coating. Typical
binder materials include resin, glue, gum and casein.
Biocides
& Fungicides
These
additives act as pesticides and are used to inhibit the
growth of fungus and other pests.
Blocking
& Anticaking Agents
These
additives are used to prevent the adhesion of two touching
layers of film during fabrication and storage.
Blowing
& Foaming
Agents
Upon addition to plastics or rubbers and then heating, this
chemical generates inert gases which results in the resin
assuming a cellular structure.
Blow
Molding
Method
of fabrication in which a warm plastic parison (hollow
tube), is placed between the two halves of a mold cavity and
forced to assume the shape of that mold cavity by use of air
pressure.
Brighteners
Are used
to add smoother or brighter coatings.
Brittle
Temperature
A
measure for judging the relative merits of materials for low
temperature flexing or impact - i.e., the temperature at
which materials rupture by impact under specified
conditions.
Bulk
Density
ASTM
D1182-54 test method describes this measurement of mass per
unit volume of a molding powder (in large volume
determinations).
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[ C ]
C-stage
This
term describes the final stage of the reaction where the
material s relatively insoluble and infusible.
Calendering
A form
of extrusion using two or more counter rotating rolls in
which film and sheet is produced by squeezing a hot, viscous
material between them.
Cast
Film
A cast
film is made by depositing a layer of plastic onto a surface
then solidifying and removing the film from that surface.
The plastic layer can be in molten form, in a solution, or
in a dispersion.
Casting
The
process of forming solid or hollow articles from fluid
plastic mixtures or resins by pouring or injecting the fluid
into a mold or against a substrate with little or no
pressure, followed by solidification and removal of the
formed object.
Co-extrusion
The
process of combining two or more layers of extrudate to
produce a multiple layer product in a single step.
Cold
Flow or Creep
A
time-dependent strain of solids resulting from stress.
Cold
Molding
The
process of compression molding involving shaping an unheated
compound in a mold under pressure then heating the article
to cure it.
Colorants & Pigments
Are
additive used to change the color of the plastic. They can
be a powder or a resin/color premix.
Composite
A
structural material consisting of a combination of
materials. Typically, one of the materials is a
strengthening agent, the other being a thermoset or
thermoplastic resin.
Compound
These are chemical combinations of materials which include
all all the materials necessary for the finished product.
They include BMC (Bulk Molding Compounds), SMC (Sheet
Molding Compounds) and TMC (Thick Molding Compounds).
Compounding
The
process required to mix the polymer with all of the
materials that are necessary to provide the end user with a
finished product.
Compression Molding
The
process of molding a material in a confined shape by
applying pressure and usually heat.
Compressive Strength
The
ability of a material to resist a force that tends to crush
it.
Continuous Service Temperature
The
highest temperature at which a material can perform reliably
in long term application - long term being, however,
inconsistently defined by the manufacturers.
Copolymer
The
chemical reaction of two different monomers with each other,
result in a compound.
Coupling
Agents
A
material that is used to form a chemical bridge between the
resin and glass fiber or mineral fiber. By acting as an
interface, bonding is enhanced.
Crazing
Small
cracks near or on the surface of plastic materials.
Cross-linking
The
formation of chemical links between the molecular chains in
polymers. This process can be achieved by chemical reaction,
vulcanization, and electron bombardment.
Cure
The
process of changing properties of polymer into a more stable
and usable condition. This is accomplished by the use of
heat, radiation, or reaction with chemical additives.
Cure
Cycle
The time
periods at defined conditions to which a reacting
thermosetting material is processed to reach a desired
property level.
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[ D ]
Density
The
equivalent property to specific gravity; measured by
displacement.
Deflection Temperature (1)
The
measurement of temperature at which a specimen deflects 0.01
inches under a load of 66 lb/in2.
Deflection Temperature (2)
The
measure of temperature at which a specimen deflects 0.01
inches under a load of 264 lb/in2.
Dielectric Constant
The
ratio of the capacity of a condenser made with a particular
dielectric material to the capacity of the same condenser
with air as the dielectric. Measured at a frequency of 106
cycles per second.
Dielectric Strength
The
voltage that an insulating material can withstand before
dielectric breakdown occurs.
Dissipation Factor
The
ratio of the power dissipated in watts in an insulating
material to the product of the effective voltage and the
current. Measured at a frequency of 106 cycles per second.
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[ E ]
Effect
of Strong Acids
A
descriptive notation to indicate the material's performance.
Elongation, Break
The
increase in distance between two gauge marks at the break
point divided by the original distance between the marks. A
zero value in the field indicates that it measured less than
one.
Elongation, Yield
The
increase in distance between two gauge marks at a yield
point divided by the original distance between the marks. A
zero value indicates that it measured less than one.
Extender
A
material added to a plastic compound used to reduce the
amount of resin required per unit value.
Extrusion
The
process of forming a continuous piece of plastic by forcing
it through a shaping orifice with or without the presence of
heat.
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[ F ]
Fabricating
The
manufacture of plastic products by appropriate operations.
This includes plastics formed into molded parts, rods,
tubes, sheeting, extrusion and other forms by methods
including punching, cutting, drilling, tapping, fastening or
by using other mechanical devices.
Fillers
& Reinforcements
Fillers
are used to make a resin less costly. They can be inert or
they can alter some properties of the plastic.
Reinforcements are substances used to strengthen or give
dimensional stability to a material.
Film
Films
are flat materials that are extremely thin in comparison to
its length and breadth. Typically, a film has a maximum
nominal thickness of 0.25 millimeters.
Flame,
Fire & Smoke Retardants
These
additives are added to the resin to retard these undesirable
effects.
Flash
Gate
Wide
gate extending from a runner which runs parallel to an edge
of a molded part along the parting line of a mold.
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.
Flexural
Strength, Yield
The
measure of resistance of the material to fracture during
bending.
Flow
Line
A mark
on a molded piece made by the meeting of two flow fronts
during molding. Also called weld line.
Forming
The
process whereby the current shape of a plastic is
transformed to another desired configuration.
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[ G ]
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[ H ]
Hardener
A
substance or mixture of substance added to a material to
increase or control the curing reaction by taking part in
it.
Hardness
The
resistance of a material to compression, indentation and
scratching. There are several scales, and the data in the
book gives both the scale used and the value on it.
Haze
The
cloudy or turbid appearance of an otherwise transparent
material caused by light scattered from within the specimen
or from its surfaces.
Heat
Stabilizers
These
additives increase the ability of the material to withstand
the negative effects of heat exposure. They are used to
increase the overall service temperature of the material.
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[ I ]
Impact
Modifiers
These
additive used to enhance the material's ability to withstand
the force of impact.
Injection Blow Molding
Blow
molding process by which the plastic parison to be blown is
formed by injection molding.
Injection Molding
The
process of forming a material by forcing it from a heated
cylinder, under pressure, through a sprue into a cavity of a
confined mold.
Injection Molding Pressure
The
pressure applied to the cross-sectional area of the molding
cylinder.
Izod,
Notched, LT
The
energy required to break specimens in which there is a
v-notch to create an initial stress point but measured at
low temperature (minus 40°C).
Izod,
Notched, RT
The
energy required to break specimens in which there is a
v-notched to create an initial stress point.
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[ J ]
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[ K ]
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[ L ]
Laminar
Flow
Laminar
flow of thermoplastic resins in a mold is accomplished by
solidification of the layer in contact with the mold surface
that acts as an insulating shell through which molten
material flows to fill the remainder of the cavity.
Light,
UV Stabilizers & Absorbers
These
additives increase the ability of the material to withstand
the negative effects of light and UV exposure, thus
increasing the service life of the material.
Linear
Mold Shrinkage
The
difference between the size of the part and the size of the
mold cavity. Values given are often the average of a range.
Linear
Thermal Expansion
The
fractional change in length of a material for a unit change
in temperature.
Liquid
Injection Molding (LIM)
The
process that involves an integrated system for
proportioning, mixing, and dispensing two component liquid
resin formulations and directly injecting the resultant mix
into a mold which is clamped under pressure.
Lubricant Internal
Lubricants, without affecting the fusion properties of a
compound, promotes resin flow. External lubricants promote
release from metals which aids in the smooth flow of melt
over die surfaces.
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[ M ]
Machine
Shot Capacity
Refers
to the maximum weight of thermoplastic resin which can be
displaced or injected by the injection ram in a single
stroke.
Masterbatch
A
concentration of a substance (an additive, pigment, filler,
etc.) in a base polymer.
Melt
Flow
Rate of
extrusion of molten resin through a die of specified length
and diameter. The conditions of the test (e.g. temperature
and load) should be given. Frequently, however, the
manufacturer's data lists only the value, not the condition
as well.
Mold
Release Agent
A
lubricant used to coat a mold cavity to prevent adhesion of
the molded piece when removed.
Moldability
The
characteristics of being easy to mold without rupturing or
developing flaws due o movement of the polymer during
gelation.
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[ N ]
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[ O ]
Odorants
& Deodorants
Odorants
are used to add odor to materials, usually for safety
reasons.
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[ P ]
Plasticizer
These
additives are usually low-melting solids or high-boiling
organic liquids which, when added to hard plastics, impart
flexibility. They have varying degrees of softening action
and solvating ability resulting from a reduction of
intermolecular forces in the polymer.
Plastisol
Mixtures
of plasticizers and resins which can be converted to
continuous films by applying heat.
Polymer
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.
If two or more monomers are involved, a copolymer is
obtained.
Processing Aids
Some
processing aids include thixotropic agents, flatting agents,
and blocking and anticaking agents.
Processing Methods
The kind
of processing (extruding, molding, casting, etc.) techniques
recommended by the manufacturer.
Processing Temperature
An
average value is given rather than the temperature range
often specified by the manufacturer.
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[ Q ]
[ R ]
Reaction
Injection Molding (RIM)
A
process that involves the high pressure impingement mixing
of two or more reactive liquid components and injecting into
a closed mold at low pressure.
Refractive Index, Sodium D
The
ratio of the velocity and light in a vacuum to its velocity
in the material.
Regrind
Waste material from injection molding, blow molding and
extrusion operations, which has been reclaimed by shredding
or granulating.
Reinforced Plastics
A
plastic material with enhanced mechanical properties due to
the addition of high strength fillers imbedded in the
composition.
Resin A
pseudosolid or solid organic material often of high
molecular weight. It has a tendency to flow when subjected
to stress, usually has a softening or melting range, and
usually fractured conchoidally.
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[ S ]
Sheet
Sheets
are made of continuous phase plastic in a form in which the
thickness is very small in proportion to length and width.
The thickness is greater than 0.25 millimeters.
Slip
Agent
An
additive that provides surface lubrication during and
immediately following processing of the plastic material. It
acts as an internal lubricant which will eventually migrate
to the surfaces.
Spruce
The main
feed channel that connects the mold-filling orifice with the
runners leading to each gravity gate. Spruce is also the
piece of plastic material formed in this channel.
Spruce
Gate
The
passage through which molten resin flows from the nozzle to
the mold cavity.
Stabilizers & Surface Modifiers
Some
additives included in this category include antioxidants and
antizonants, antistats, biocides and fungicides, heat
stabilizers, light, and UV stabilizers and absorbers.
Stress
Crack
A crack,
either external or internal, in a plastic caused by tensile
stresses less than its short-time mechanical strength.
Structural Foam
The
process of molding thermoplastics articles with a cellular
core and integral solid skins in a single operation.
Surface
Resistivity
The
ratio of the potential gradient parallel to the current
along its surface to the current per unit width of the
surface.
Surfactants
The use
of these chemicals allows the formation of an emulsion or
intimate mixture of otherwise incompatible substances by
modifying the surface properties and influencing the wetting
and flowing properties of liquids.
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[ T ]
Tackifiers
Additives used to enhance the adhesiveness or bonding
ability of a material.
Tensile
Modulus (Also called modulus of elasticity).
The
ratio of nominal stress to the corresponding strain below
the proportional limit of a material.
Tensile
Strength, Break
The
maximum stress that a material can withstand without
breaking when subjected to a stretching load.
Tensile
Strength, Yield
The
maximum stress that a material can withstand without
yielding when subjected to a stretching load.
Thermal
Conductivity
The rate
of heat flow under steady state conditions through unit area
per unit temperature gradient in a direction perpendicular
to an isothermal surface.
Thermoplastics
Resins
capable of undergoing a chemical reaction leading to a
relative infusible and insolvable state.
Thermosets
Resins
or plastic compounds, which in their final state are
infusible and insoluble. After being fully cured, thermosets
cannot be resoftened by heat.
Transfer
Molding
A
process of forming articles by fusing a plastic material in
a chamber then forcing the whole mass into a hot mold to
solidify.
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[ U ]
UL
Temperature Index
The
maximum temperature below which a material maintains its
electrical and mechanical integrity over a reasonable
period.
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[ V ]
Vacuum
Forming
A
process whereby a heated plastic sheet is drawn against a
mold surface by evacuating the air between it and the mold.
Vicat
Softening Point
The
temperature at which a flat ended needle will penetrate a
specimen under a specific load using a uniform rate of
temperature rise.
Virgin
Material
A
plastic material that has not been subjected to use or
processing other than that required for its initial
manufacture. It can be in the form of pellets, granules,
powder, floc, or liquid.
Void
An
unfilled space in a cellular plastic which is substantially
larger than the individual cells. Can also be an empty space
in any material or medium.
Volume
Resistivity
The
measure of ratio of the potential gradient parallel to the
current in the material to the current in density.
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[ W ]
Warpage
A
nonuniform change in internal stresses resulting distortion
or warp of the material.
Water
Absorption, 24 hours
The
percentage of water absorbed by a material when immersed in
water for 24 hours; water absorbed in a material chiefly
affects its electrical properties.
Wet
Lay-up
A
reinforced plastic manufacturing process where the polymer
compound is applied as a liquid as the reinforcement is put
into place.
Wet
Winding
A fiber
reinforcement material is coated with a polymer compound as
a liquid prior to wrapping on a mandrel in the filament
wound manufacturing process.
Wetting
Agent
Wetting
is produced when this surface active agent decreases the
cohesion within a liquid. For wetting to occur, the adhesive
force between the two phases (solid and liquid) is greater
than the cohesive force within the liquid.
Whisker
A
single-crystal, short fiber.
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[ Z ]
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