|
Accelerator:
An additive to polyester resin that reacts with catalyst to speed
up polymerization. This additive is required in room temperature
cured resins. See Promoter.
Acetone: A ketone
group solvent that is used to dissolve polyester resins. Used to
a large extent for clean up of tools in fiberglass operations.
Additive:
Any
number of materials used to modify the properties of polymer
resins. Categories of additives include reagents, fillers,
viscosity modifiers, pigments and others.
Adhesion: The state
in which two surfaces are held together at an interface by forces
or interlocking action or both.
Aging: The effect,
on materials, of exposure to an environment for an interval of
time; the process of exposing materials to an environment for an
interval of time.
Air-bubble Void:
Air entrapment within and between the plies of reinforcement; non
interconnected, spherical in shape.
Air Vent: Small
outlet, to prevent entrapment of gases.
Alkyd Plastics:
Plastics based on resins composed principally of polymeric
esters, in which the recurring ester groups are an integral part
of the main polymer chain, and in which ester groups occur in
most cross links that may be present between chains.
Alligatoring: A
visible cosmetic defect in the exposed gel coat which looks like
wrinkled or alligator skin.
Ambient:
The
surrounding environmental conditions such as pressure or
temperature.
Amine Resins: A
synthetic resin derived from the reaction of urea, thiourea,
melamine or allied compounds with aldehydes, particularly
formaldehyde.
Anisotropy of Laminates:
The difference of the properties along the directions parallel to
the length or width into the lamination planes; or parallel to
the thickness into the planes perpendicular to the lamination.
Antimony Trioxide:
Fire retardant additive for use with resins.
Anti-static Agents:
Agents which, when added to the molding material or applied on
the surface of the molded object, make it less conducting (thus
hindering the fixation of dust).
Ash Content: The
solid residue remaining after a reinforcing substance has been
incinerated (or strongly heated).
Aspect Ratio: The
ratio of length to diameter of a fiber.
B-stage: An intermediate stage in the reaction of certain
thermosetting resins in which the material swells when in contact
with certain liquids and softens when heated, but may not
entirely dissolve or fuse; sometimes referred to as resistol. The
resin is an uncured prepreg or premix is usually in this stage.
Bag Molding:
An airtight film used to apply atmospheric force to a laminate.
See Vacuum and
Pressure.
Barcol Hardness:
A
measure of surface hardness made with a Barcol Impressor
instrument in accordance with ASTM D-2583. The hardness value can
be used as an indication of the degree of cure of FRP laminates.
Bare Glass: Glass
(yarns, rovings, fabrics) from which the sizing or finish has
been removed; also, such glass before the application of sizing
or finish.
Barrier Cream: A
cream used to protect the skin from contact with resins.
Benzoyl Peroxide (BPO):
An initiator for curing polyester resin. BPO is used with aniline
accelerators or where heat is used to cure the resin.
Biaxial Winding:
In
filament winding, a type of winding in which the helical band is
laid in sequence, side by side, with the crossover of the fibers
eliminated.
Bi-directional:
Reinforcing fibers that are arranged in two directions, usually
at right angles to each other.
Binder: A resin
soluble adhesive that secures the random fibers in chopped strand
mat or continuous strand roving.
Bisphenol A: A
condensation product formed by reaction of two (bis) molecules of
phenol with acetone (A). This polyhydric phenol is a standard
resin intermediate along with epichlorohydrin in the production
of epoxy resins.
Blister: A flaw
either between layers of laminate or between the gel coat film
and laminate.
Bond Strength: The
amount of adhesion between bonded surfaces; a measure of the
stress required to separate a layer of material from the base to
which it is bonded.
Burst Strength: (1)
Hydraulic pressure required to burst a vessel of given thickness.
Commonly used in testing filament-wound composite structures. (2)
Pressure required to break a fabric by expanding a flexible
diaphragm or pushing a smooth spherical surface against a
securely held circular area of fabric. The Mullen expanding
diaphragm and Scott ball burst machine are examples of equipment
used for this purpose.
Casting: The
process of pouring a mixture of resin, fillers and/or fibers into
a mold as opposed to building up layers through lamination. This
technique produces different physical properties from laminating.
Catalyst:
Technically considered an initiator, catalyst is the colloquial
name given to the substance added to the resin or gel coat to
initiate the cure.
Catastrophic Failures:
Failures of a mechanical and unpredictable nature.
Catenary:
A measure
of the difference in length of the strands in a specified length
of roving as a result of unequal tension; the tendency of some
strands in a taut horizontal roving to sag lower than the others.
Caulk: An elastic
material used to protect joints or connections from external
elements, particularly moisture.
Cavity: The space
between a male and female mold set in which the part is formed.
Sometimes used to refer to a female mold.
Centipoise: A unit
of measure used to describe the viscosity of a liquid. Viscosity
is measured with a Brookfield Viscometer for most polyester resin
applications.
Chalking:
A surface
phenomenon indicating degradation of a cosmetic surface. Chalking
is a powdery film which appears lighter than the original color.
Chopped
Strand Mat: A fiberglass reinforcement consisting
of short strands of fiber arranged in a random pattern and held
together with a binder. Mat is generally used in rolls consisting
of ¾ oz/ft2 material to 2 oz/ft2 material.
Cloth: A fiberglass
reinforcement made by weaving strands of glass fiber yarns. Cloth
is available in various weights measured in ounces per square
yard or kg/m2.
Color Stability:
The ability of a surface coating or pigment to resist degradation
due to environmental exposure.
Composite: A
reinforcing fiber in a resin matrix whose cumulative properties
are superior to the individual materials.
Compression Mold: A
closed mold, usually of steel, used to form a composite under
heat and pressure.
Compressive Modulus:
A mechanical property description which measures the compression
of a sample at a specified load. Described in ASTM D-695.
Compressive Strength:
The stress a given material can withstand when compressed.
Described in ASTM D-695.
Conductivity:
Reciprocal of volume resistivity; the conductance of a unit cube
of any material.
Connection:
Where
two panels are attached to each other or a panel is attached to
the building.
Contact Molding:
Refers to the use of a single or open mold onto which resin and
reinforcement materials can be applied. Contact molding is
characterized by one finished cosmetic side.
Continuous Filament Strand:
A fiber bundle composed of many glass filaments. Also when
referring to gun roving; a collection of string like glass fiber
or yarn, which is fed through a chopper gun in the spray up
process.
Continuous Strand Roving:
A bundle of glass filaments which are fed through a chopper gun
in the spray up process.
Continuous Laminating:
An automated process for forming panels and sheeting in which
fabric or mat is passed through a resin bath, brought together
between covering sheets, and passed through a heating zone for
cure. Squeeze rolls control thickness and resin content as the
various plies are brought together.
Core:
A low density
material used between two FRP skins. Examples of core materials
are end-grain balsa wood, urethane foam, PVC foam and various
honeycomb materials.
Coupling Agent:
Any
chemical substance designed to react with both the reinforcement
and matrix phases of a composite material to form or promote a
stronger bond at the interface; a bonding link.
Crazing: Cracking
of gel coat or resin due to stress.
Creel: A device for
holding the required number of roving balls or supply packages in
desired position for unwinding onto the next processing step.
Creep: The change
in dimension of a plastic under load over a period of time, not
including the initial instantaneous elastic deformation. (Creep
at room temperature is called 'cold flow.')
Cross-linking:
The
chemical bonding of molecules which in polymers occurs in the
curing transition from a liquid to a solid.
Cure: The
completion of the cross-linking process during which a composite
develops its full strength.
Cure Temperature:
Temperature at which a cast, molded, or extruded product, a
resin-impregnated reinforcement, an adhesive, etc., is subjected
to curing.
Cure Time: Time
between introduction of catalyst or initiator to a polymer and
final cure.
Curing Agent: A
catalytic or reactive agent which when added to a resin causes
polymerization; synonymous with hardener.
Cycle: The
complete, repeating sequence of operations in a process or part
of a process. In molding, the cycle time is the period (or
elapsed time) between a certain point in one cycle and the same
point in the next.
Delamination:
The separation of composite layers from each other.
Density:
A
comparison of weight per volume, measured in pounds per cubic
foot.
Dielectric Strength:
The value of a material as an electrical insulator or the
resistance to the flow of electric current.
Dimensional Stability:
A description of the change in size of an object during the
molding process or in varying temperature conditions or under
various loads.
Distortion:
A
change in shape form that which is intended.
Draft: The angle of
the vertical components of a mold which allow removal of the
part.
Drape: The ability
of pre impregnated broad goods to conform to an irregular shape;
textile conformity.
Dry Spot: Area of
incomplete surface film on laminated plastics; in laminated
glass, an area over which the interlayer and the glass have not
become bonded.
Back to Top
E-glass:
Originally formulated for use in electric circuitry, E-glass is
the most common glass formulation used in fiberglass
reinforcements.
Ejection/Demolding:
The process of removing a molding from the molding impression; by
mechanical means, by hand, or by the use of compressed air.
Ejection Plate: A
metal plate used to operate ejector pins; designed to apply a
uniform pressure to them in the process of ejection.
Elastic Limit: The
greatest stress which a material is capable of sustaining without
permanent strain remaining upon the complete release of the
stress. A material is said to have passed its elastic limit when
the load is sufficient to initiate plastic, or non recoverable,
deformation.
Elongation:
Standard measure for the amount a sample can stretch as a
percentage of original length before it fails or breaks.
Encapsulating:
Completely surrounding an object with resin or a fiber resin
composite.
End: A strand of
roving consisting of a given number of filaments gathered
together.
End Count: An exact
number of ends supplied on a ball or roving.
Epoxy Plastics:
Plastics based on resins made by the reaction of epoxides or
oxiranes with other materials such as amines, alcohols, phenols,
carboxylic acids, acid anhydrides and unsaturated compounds.
Epoxy Resin: A
polymer resin characterized by epoxide molecule groups.
Exothermic Heat:
Internally developed heat accompanying a chemical reaction, such
as might be created when curing a thermosetting resin.
Extenders: Low cost
materials used to dilute or extend high cost resins without much
lessening of properties.
Back to Top
Fabricator:
Manufacturer of reinforced plastic products.
Fatigue: The
failure or decay of mechanical properties after repeated
applications of stress.
Fatigue Life: The
number of cycles of deformation required to bring about failure
of the test specimen under a given set of oscillating conditions.
Fatigue Limit:
The
stress below which a material can be stressed cyclically for an
infinite number of times without failure.
Fatigue Strength:
The maximum cyclic stress a material can withstand for a given
number of cycles before failure occurs; the residual strength
after being subjected to fatigue.
Female Mold: A
concave mold used to precisely define the convex surface of a
molded part.
Fiber:
Reinforcement material which is a major component in a composite
matrix.
Fiber Diameter:
The
measurement (expressed in hundred-thousandths) of the diameter of
individual filaments.
Fiberglass:
Glass which has been extruded into extremely fine filaments.
These filaments vary in diameter, and are measured in microns.
Glass filaments are treated with special binders and processed
similar to textile fibers. These fibers come in many forms such
as roving, woven roving, mat and continuous strands.
Fiber Orientation:
Fiber alignment in a non-woven or a mat laminate where the
majority of fibers are in the same direction, resulting in a
higher strength in that direction.
Fiber Pattern:
Visible fibers on the surface of laminates or moldings; the
thread size and weave of glass cloth.
Filament: A single
thread-like fiber of extruded glass. Typically microns in
diameter.
Filament Winding:
A
process which involves winding a resin-saturated strand of glass
filament around a rotating mandrel.
Fill: yarn running
from selvage to selvage at right angles to the warp in a woven
fabric.
Fillers: Usually
inert organic or inorganic materials which are added to plastics,
resins or gel coats to vary the properties, extend volume, or
lower the cost of the article being produced.
Fillet: A rounded
filing of the internal angle between two surfaces of a plastic
molding.
Fire Retardants:
Compounds mixed with the resin to reduce flammability.
Fish Eye: The
effect of surface contamination which causes a circular
separation of a paint or gel coat.
Flame Retardant Resin:
A polyester resin which has been specifically formulated to
reduce the flame spread and/or smoke generation characteristics.
Flammability: A
measure of how fast a material will burn under controlled
conditions. ASTM D-635/UL E-84 tests.
Flange: An
extension around the perimeter of a mold or part for the purpose
of demolding, stiffening or connecting two components.
Flash Point: The
lowest temperature at which a substance gives off enough vapors
to form a flammable mixture.
Flexural Modulus:
An engineering measurement which determines how much a sample
will bend when a given load is applied. Described in ASTM D-790.
Flexural Strength:
The resistance of a material to being broken by bending stresses;
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 failure. (With plastics, this value is usually higher
than the straight tensile strength.)
Flow: The movement
of resin under pressure, allowing it to fill all parts of a mold;
flow or creep - the gradual but continuous distortion of a
material under continued load, usually at high temperature.
Flow Line:
A mark
on a molded piece made by the meeting of two flow fronts during
molding. (Also, 'striae', or 'weld-mark,' or 'weld-line.')
Foam: A
lightweight, cellular plastic material containing gas-filled
voids. Typical foams include urethane, PVC and polyester.
Foam-in-place:
The
process of creating a foam by the combination of two liquid
polymers. See In-Situ.
FRP:
Fiber Reinforced Plastics, also known as GFRP (Glass Fiber
Reinforced Plastic), GRP (Glass Reinforced Plastic), FRP
(Reinforced Plastic) and Composites.
Back to Top
Gel:
The irreversible point at which a polymer changes from a liquid
to a semi-solid. Sometimes called the "B" stage.
Gel Coat:
A surface
coat of a specialized polyester resin, either colored or clear,
providing a cosmetic enhancement and weatherability to a
fiberglass laminate.
Gel Time:
The length of time from catalyzation to gel or "B"
stage.
Gelation: The
formation of a gel.
Glint: A visual
defect in a fiber glass reinforced cured organic (usually
corrosion resistant resin) panel. The defect appears as many
small visible unwet or foreign substances - a salt and pepper
effect. The defect is not visible before cure but appears at
exotherm of the panel.
Good Side:
The side
of a molding in contact with a mold surface.
"Green":
Resin which has not completely cured and is still rather soft and
rubbery.
GRP: Glass
reinforced plastics. Generally based on polyester resin. See Fiberglass,
FRP.
Guide Pin: A pin
which guides mold halves into alignment on closing.
Hand Lay Up:
The process of manually building up layers of fiberglass and
resin using hand rollers, brushes and spray equipment.
Hardener: A
substance or mixture added to a plastic composition to promote or
control the curing action by taking part in it. Also, a substance
added to control the degree of hardness of the cured film.
Heat Distortion Point:
The temperature at which the strength of a material begins to
degrade.
HET-Acid Resin:
Polyester resin with exceptional fire qualities.
Honeycomb Core:
Strips of paper, plastic, metal, etc., joined together to form a
honeycomb pattern. Used as a lightweight core in sandwich
moldings.
Hydraulic Press: A
press in which the molding force is created by the pressure
exerted on a fluid.
Hygroscopic:
Capable of absorbing and retaining atmospheric moisture.
Ignition Loss: The difference in weight before and after
burning; as with glass, the burning off of the binder or size.
Impact Strength: The ability of a material to withstand shock
loading; the work done in fracturing a test specimen in a
specified manner under shock loading.
Impregnate:
To saturate with resin. The most common application is saturating
fiberglass with a catalyzed resin.
Inhibitor:
An
additive to polyester resin or styrene used to slow the chemical
reaction which leads to curing.
Insert: A piece of
material put into a laminate during or before molding to serve a
definite purpose.
Instron:
An
instrument utilized to determine the tensile and compressive
properties of materials.
Interface: The
junction point or surface between two different media; on glass
fibers, the contact area between glass and sizing or finish; in a
laminate, the contact area between the reinforcement and the
laminating resin.
Interlaminar Shear Strength:
The maximum shear stress existing between layers of a laminated
material.
Intumescent:
A
fire-retardant technology which causes an otherwise flammable
material to foam, forming an insulating barrier when exposed to
heat.
In-situ:
In the position which it will finally occupy, e.g. molding or
forming foam.
Isophthalic: A
polyester resin based on isophthalic acid, generally higher in
properties than a general purpose or orthothalic polyester resin.
Isotropic: The
description of equal strength properties in all orientation.
Isotropic composites are usually achieved by random fiber
orientation.
IZOD Impact Test: A
destructive test designed to determine the resistance of a
plastic to the impact of a suddenly applied force.
Back to Top
Jackstrawing:
A visual effect of glass fiber turning white in a cured laminate.
This usually does not effect the strength of a laminate, but
could be an indication of materials incompatibility.
Jig: Any fixture
for holding parts in position, while joining them together or to
maintain their shape.
Joint:
A line or distinction formed when two panels are connected. Also
referred to as a seam.
Back to Top
Laminant:
The product of lamination. A composite consisting of a layer or
layers of thermoset polymer and fiber reinforcement.
Laminate:
To place
into a mold a series of layers of polymer and reinforcement. The
process of applying FRP materials to a mold. To lay up.
Lamination:
Applying layers of glass and resin to a mold. Also used to
describe a single ply of laminate.
Lay: In glass
fiber, the spacing of the roving bands on the roving package
expressed in the number of bands per inch; in filament winding,
the orientation of the ribbon with some reference, usually the
axis of rotation.
Layer:
A single ply
of lay up or laminate.
Lay Up: The act of
building up successive layers of polymer and reinforcement.
Layers of catalyzed resin and fiberglass or other reinforcements
are applied to a mold in order to make a part.
L/D Ratio:
A term
used to define an extrusion screw, which denotes the ratio of the
screw length to the screw diameter.
Load-Deflection Curve:
A curve in which the increasing flexural loads are plotted on the
ordinate axis and the deflections caused by those loads are
plotted on the abscissa axis.
Loss on Ignition:
Weight loss, usually expressed as percent of total, after burning
off an organic sizing from glass fibers, or an organic resin from
a glass fiber laminate.
Low-pressure Laminates:
Laminated, molded and cured using pressures from 400 psi down to
and including the pressure obtained by the mere contact of the
plies.
Low-pressure Molding:
The distribution of relatively uniform low pressure (200 psi or
less) over a resin-bearing fibrous assembly of cellulose, glass,
asbestos, or other material, with or without application of heat
from external source, to form a structure possessing definite
physical properties.
Back to Top
Male Mold:
A convex mold where the concave surface of the part is precisely
defined by the mold surface.
Mandrel:
The core
around which paper-, fabric-, or resin-impregnated glass is wound
to form pipes, tubes, or vessels; in extrusion, the central
finger of a pipe or tubing die.
Master (plug): A
full scale representation of the intended part, usually retained
as a reference and the part from which production molds are made.
Mat: See
Chopped Strand Mat.
Mat Binder:
Resin applied to glass fiber and cured during
the manufacture of mat, to hold the fibers in place and maintain
the shape of the mat.
Matched Die Molding:
Technique for producing long runs of identical parts with two
finished sides.
Matched Molds: Two
or more tools arranged in a set as a male and female mold.
Normally used in a press.
Matrix:
The liquid
component of a composite or laminate.
MEK Peroxide (MEKP):
An initiator often referred to as catalyst and used to initiate
polymerization of a resin. Methyl Ethyl Ketone Peroxide.
MEK Solvent:
Methyl
Ethyl Ketone; a colorless, flammable liquid sometimes used in
clean up procedures.
Microballoons:
Microscopic bubbles of glass, ceramic or phenolic, used as a
filler or to create syntactic foam or putty mixtures.
Micron:
One micron
= .001 millimeter = .00003937 inch.
Mil (Mil Thickness):
The unit used in measuring film thickness. One mil equals one
thousandth of an inch. (l mil = .001 ").
Milled Fibers:
Glass fiber processed by a hammer mill into lengths of 1/32"
to 1/8". Commonly used as a reinforcement in polyester
putty.
Modulus of Elasticity:
An engineering term used to describe a material's ability to bend
without losing its ability to return to its original physical
properties.
Mold: The tool used
to fabricate the desired part shape. Also used to describe the
process of making a part in a mold.
Molding:
The
process of using a mold to form a part.
Mold
Release: A wax or polymer compound that is
applied to the mold surface which acts as a barrier between the
mold and the part, thus preventing the part from bonding to the
mold.
Mold Shrinkage:
The
immediate shrinkage which a molded part undergoes when it is
removed from a mold and cooled to room temperature; the
difference in dimensions, expressed in inches per inch between a
molding and the mold cavity in which it was molded (at normal
temperature measurement); the incremental difference between the
dimensions of the molding and the mold from which it was made,
expressed as a percentage of the dimensions of the mold.
Molding Compounds:
Plastics in a wide range of forms to meet specific processing
requirements. Granules or pellets are popular forms.
Molding Cycle: The
period of time occupied by the complete sequence of operations on
a molding press requisite for the production of one set of
moldings; the operations necessary to produce a set of moldings
without reference to the time taken.
Molding Pressure:
The pressure applied to the ram of an injection machine or press
to force the softened plastic completely to fill the mold
cavities.
Monomer: One of the
constituents of polyester resin.
Multiple-cavity Mold:
A mold with two or more mold impressions; that is, a mold which
produces more than one molding per molding cycle.
Back to Top
NOL Ring:
A parallel filament wound test specimen used for measuring
various mechanical strength properties of the material by testing
the entire ring, or segments of it.
NPG Gel Coat:
Neopentyl glycol gel coat has enhanced weatherability compared to
non-NPG gel coat.
Nesting:
In
reinforced plastics, the placing of plies of fabric so that the
yarns of one ply lie in the valleys between the yarns of the
adjacent ply (nested cloth).
Notch Sensitivity:
The extent to which the sensitivity of a material to fracture is
increased by the presence of a surface inhomogeneity such as a
notch, a sudden change in section, a crack or a scratch. Low
notch sensitivity is usually associated with ductile materials
and high notch sensitivity with brittle materials.
Back to Top
Orange Peel:
A gel coated or painted finish which is not smooth and is
patterned similar to an orange's skin.
Orthophthalic or Ortho Resin:
A polyester resin based on orthophthalic acid, also known as a
general purpose resin (GP).
Back to Top
Parting Agent:
See Mold Release and
PVA.
Parting Line: The
location on a molded product between different segments of the
mold used to produce the product.
Pattern:
The
initial model for making fiberglass molds. See Plug.
Pigment: A colorant
added to gel coat or resin.
Pigment Separation:
Occurs when the pigment is not thoroughly mixed into the gel coat
during formulation or the gel coat is improperly mixed prior to
use. It is characterized by a non-homogeneous surface color.
Pinholes: Small
holes on the exposed gel coated surface. They are about the
diameter of common pins and may be easily counted.
Pit: Small regular
or irregular crater in the surface of a plastic, usually with
width approximately of the same order of magnitude as its depth.
Plastics: Organic
chemical compounds called polymers which can be formulated to
produce a wide range of properties.
Plastic Deformation:
Change in dimensions of an object under load that is not
recovered when the load is removed; opposed to elastic
deformation.
Plastic Tooling:
Tools (mostly for the metal forming trades) constructed of
plastics, generally laminates or casting materials.
Plug: A composite industry term for a pattern or model.
Polyamide:
A
polymer in which the structural units are linked by amide or
thioamide groupings. Many polyamides are fiber-forming.
Polyester Resin (Unsaturated):
The product of an acid-glycol reaction commonly blended with a
monomer to create a polymer resin. In its thermosetting form it
is the most common resin used in the FRP industry.
Polymer: A chain
molecule composed of many identical groups, commonly found in
plastics.
Polymerization:
The
chemical bonding of polymer molecules during the curing reaction.
Polyvinyl Alcohol
(PVA): A parting film applied to a mold for part
releasing.
Porosity:
Entrapped
gas bubbles or voids in a gel coat film.
Positive Mold: A
mold designed to apply pressure to a piece being molded with no
escape of material.
Post-cure: To cure
by application of heat after the chemical exothermic reaction has
subsided.
Pot Life: The time
during which the catalyzed resin remains liquid or
"workable." See
Gel
Time.
Pregel:
An
unintentional extra layer of cured resin on part of the surface
of a reinforced plastic. (Not relating to 'gel coat.')
Premix:
Reinforcing
material mixed with resin, and usually with pigment, filler and
catalyst, before placing in the mold.
Prepreg:
Reinforcing material impregnated with resin prior to the molding
process and cured by the application of heat.
Pressure
Bag: A membrane which conforms to the inside of a
laminate laid up on a mold. The membrane or bag is then inflated
applying pressure which consolidates and densifies the laminate.
Print Through: A
distortion in the surface of a part which allows the pattern of
the core or fiberglass reinforcement to be visible through the
surface. Also known as print out, telegraphing or read through.
Promoter:
A reagent which speeds resin cure. See Accelerator.
Pultrusion:
Reversed "extrusion" of resin-impregnated roving in the
manufacture of rods, tubes and structural shapes of a permanent
cross-section. The roving, after passing through the resin dip
tank, is drawn through a die to form the desired cross-section.
Putty: A thickened
mixture of resin made by adding fillers, thixotrophs and
reinforcing fibers.
PVA: See
Polyvinyl Alcohol.
Back to Top
Reinforced
Molding Compound: Compound consisting of a
polymer and a reinforcement fiber or filler supplied by raw
material producer in the form of ready-to-use materials.
Reinforcement: A
fiber which when encapsulated in a polymer resin matrix forms a
composite or fiberglass laminate. Also refers to a structural
member designed to stiffen a molded part.
Release
Agent: A compound used to reduce surface tension
or adhesion between a mold and a part.
Resin: A liquid
polymer which when catalyzed cures to a solid state.
Resin Content: The
amount of resin in a laminate expressed as either a percent of
total weight or total volume.
Resin-Rich Area:
Space which is filled with resin and lacking reinforcing
material.
Resin-Starved Area:
Areas of insufficient resin, usually identified by low gloss, dry
spots or fiber show.
Resin Tearing:
Separation of pigments in a gel coat affecting cosmetic
appearance.
Rib: A reinforcing
member of a fabricated or molded part.
Room Temperature Curing Adhesives:
Adhesives that set (to handling strength) within an hour at
temperatures from 68 to 86 F, and later reach full strength
without heating.
Roving: A
collection of bundles of continuous filaments in untwisted
strands. Used in the spray-up (chopping) process.
Sandwich
Construction: A laminate with two composite skins
separated by, but bonded to, a structural core material. Used to
create stiff, lightweight structures.
Scrim: A low cost,
non woven open-weave reinforcing fabric made from continuous
filament yarn in an open mesh construction.
Seam: See
Joint.
Self Extinguishing:
Ceases to burn when the source of flame is removed.
Self-tapping Screws:
Hardened screws which cut their own thread as they are set.
Set-up: To harden,
as in curing.
Shear:
An
engineering term referring to forces applied normal to the
surface of a given material. The movement between plies of a
laminate is referred to as interlaminate shear.
Shear Edge: The
cut-off edge of the mold.
Shelf
Life: The allowable storage time before a product
must be used.
Ship Lap: Method of
joining two panels together by means of one panel having a
recessed shelf to receive the other panel on top of it leaving a
flush surface.
Shrinkage: The
relative change in dimension between the length measured on the
mold when it is cold and the length on the molded object 24 hours
after it has been taken out of the mold.
Sink Mark: A
shallow depression or dimple on the surface of an injection
molded part due to collapsing of the surface following local
internal shrinkage after the gate seals; an incipient short shot.
Skein:
A continuous
filament, strand, yarn, roving, etc., wound up to some measurable
length, and usually used to measure various physical properties.
Skin Coat: The
first layer of laminate next to the gel coat, generally, one ply
of chopped strand mat.
Solvent Resistance:
The non swelling of a material and, of course, the impossibility
for it to be dissolved by the solvent in question.
Specific Gravity:
The ratio between the density of a given substance and the
density of water.
Specimen:
An
individual piece or portion of a sample used to make a specific
test; of specific shape and dimensions.
Splice: The joining
of two ends of glass fiber yarn or strand, usually by means of an
air drying glue.
Split Mold:
An open
mold made in two or more pieces.
Spray Up: The
process of spraying glass fibers, resin and catalyst
simultaneously into a mold using a chopper gun.
Stiffness: The
relationship of load and deformation; a term often used when the
relationship of stress to strain does not conform to the
definition of Young's modulus.
Storage Life: The
period of time during which a liquid resin or packaged adhesive
can be stored under specified temperature conditions and remain
suitable for use. Also
Shelf
Life.
Strands: A primary
bundle of continuous filaments (or slivers) combined in a single
compact unit without twist. These filaments (usually 51, 102 or
204) are gathered together in the forming operations.
Strand Count: The
number of strands in a plied yarn; the number of strands in a
roving.
Strand Integrity:
The degree to which the individual filaments making up the strand
or end are held together by the sizing applied.
Stress-Strain Curve:
Simultaneous readings of load and deformation, converted to
stress and strain, are plotted as ordinates and abscissas,
respectively, to obtain a stress-strain diagram.
Styrene Monomer:
A
component of polyester resin that provides crosslinking sites and
reduces the polyester to a workable viscosity.
Surfacing Mat: A
lightweight tissue (10-30 mils thick) of glass or synthetic fiber
used to provide a resin-rich surface. See Veil.
Surfactant:
Chemicals used to modify or change the surface of a layer of
resin or polymer. Usually used to form a film on a curing resin,
producing a tack-free surface.
Syntatic Foam:
A
foam made by mixing microspheres with a resin.
Back to Top
Tack:
Surface stickiness.
Tack Free:
A
surface which is not sticky after cure.
Tangent Modulus:
The slope of the line at any point on a static stress-strain
curve expressed in psi per unit strain. This is the tangent
modulus at that point in shear, extension, or compression as the
case may be.
Tape: A narrow
width reinforcing fabric or mat.
Tenacity: The term
generally used in yarn manufacture and textile engineering to
denote the strength of a yarn or of a filament of a given size.
Numerically it is the grams of breaking force per denier unit of
yarn or filament size; grams per denier, gpd. The yarn is usually
pulled at the rate of 12 inches per minute. Tenacity equals
breaking strength (grams) divided by denier.
Tensile Load:
A
dulling load applied to opposite ends of a given sample.
Tensile Elongation:
An engineering term referring to the amount of stretch a sample
experiences during tensile strain. ASTM D-638.
Tensile Strength: A
measurement of the tensile load a sample can withstand. ASTM
D-638.
Thermal Coefficient of Expansion:
Measures dimensional change of a material when heated or cooled.
Measured in inches per inch per degree.
Thermal Conductivity:
Measures the transfer of heat through a material.
Thermoplastics: A
group of plastic materials that become elastic or melt when
heated, and return to their rigid state at room temperature.
Examples are PVC, ABS, polystyrene, polycarbonates, nylon, etc.
Thermosets:
Materials that undergo a chemical crosslinking reaction going
from liquid to solid or semi-solid. This reaction is
irreversible. Typical thermosets are polyesters, acrylics,
epoxies, and phenolics.
Thixotropic: A term
describing the rehology (or flow characteristics) of a liquid
that resists flowing or drainage during application.
Thixotropic Index (T.I.):
A measure of thixotropy using a Brookfield Viscometer. The low
speed viscosity divided by the high speed viscosity.
Tooling Get Coat:
A
gel coat formulated for mold surfaces.
Translucent:
Permits a percentage of light to pass but not optically clear
like window glass.
Back to Top
Ultimate Tensile
Strength: The ultimate or
final stress sustained by a specimen in a tension test; the
stress at moment of rupture.
Under Cut:
An area of a part or mold that has an acute angle between two
surfaces. If a part has an undercut a split mold is necessary.
Unidirectional:
Strength lying mainly in one direction. A glass reinforcement in
which the fiber is oriented in one direction.
UV Stabilizer: A
chemical compound which improves resistance to degradation from
ultraviolet radiation.
Back to Top
Vacuum
Bag Molding: Process for eliminating voids and
forcing out entrapped air and excess resin from lay ups by
drawing a vacuum from a plastic film which blankets a laminate.
Veil:
An ultra thin mat similar to a surface mat, often composed of
organic fibers as well as glass fibers.
Viscosity: The
liquid properties of a material. Resistance to flow.
Void Content: The
percentage of voids in a laminate.
Void Free: A
molding containing no entrapped air cavities, blisters, or voids.
Back to Top
Water
Absorption: The amount of water which a laminate
will absorb.
Wax: A compound
used as a release agent. See
Release
Agent.
Weave:
The
particular manner in which a fabric is formed by interlacing
yarns, and usually assigned a style number.
Wet Lay-up: The
reinforced plastic which has liquid resin applied at the
reinforcement is laid up. The opposite of "dry lay-up",
"prepreg".
"Wet-out":
The action of saturating a glass fabric with resin. Also a
measure of the speed with which a fabric soaks up resin.
Wet-out Rate: The
time required for a plastic to fill the interstices of a
reinforcement material and wet the surface of the reinforcement
fibers; usually determined by optical or light transmission
means.
Wet Strength:
The
strength of paper when saturated with water, especially used in
discussions of processes whereby the strength of paper is
increased by the addition, in manufacture, or plastic resins; the
strength of an adhesive joint determined immediately after
removal from a liquid in which it has been immersed under
specified conditions of time, temperature and pressure.
Woven Roving Fabric:
Heavy fabrics woven from continuous filament in roving form.
Usually in weights between 18-30 oz. per square yard.
Back to Top
Yarn:
Twisted strands of roving, used to weave textile reinforcements.
Yield Strength: The
stress at which a material exhibits a specified limiting
deviation from the proportionality of stress to strain; the
lowest stress at which a material undergoes plastic deformation.
Below this stress, the material is elastic; above it, viscous.
Young's Modulus:
The ratio of tensile stress to tensile strain below the
proportional limit.
Back to Top
|
