A
ACCELERATOR
An additive to polyester resin that speeds up the cure and is usually used in conjunction with a promoter. 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.
ADHESIVE
A bonding substance that creates a molecular attraction, holding two surfaces together.
AIR DRY
A resin or paint that dries through the loss of solvent or monomer.
AIR-INHIBITED RESIN
Resin that cures with a tacky surface due to their air inhibiting their cure in a thin surface layer.
ADDITIVE
Any number of materials used to modify the properties of polymer resins. Categories of additives include reagents, fillers, viscosity modifiers, pigments and others.
ALLIGATORING
A visible cosmetic defect in the exposed gel coat that looks like wrinkled or alligator skin.
ANTIMONY TRIOXIDE
Fire retardant additive for use with resins containing chloride or bromine.
ARAMID
Aromatic polyamide used to make high strength fibers, commonly known as Dupont KevlarTM.
ARCING
A spray gun stroke that moves the gun through an arc, thus changing the spray angle throughout the stroke. An arcing stroke should be avoided for proper spraying technique.
AUTOCLAVE MOLDING
Molding technique where a vacuum bagged composite lay-up is placed in a pressure chamber and heated to cure. A pressure of 50 to 100 psi consolidates the laminate.
AUTO-IGNITION TEMPERATURE
The temperature at which a substance experiences ignition in the absence of a spark or flame.
B
BAG MOLDING
An airtight film used to apply atmospheric force to a laminate. See Vacuum Bag Molding and Pressure bag.
BARCOL HARDNESS
A measure of surface hardness made with a Barcol Impressor instrument in accordance with ASTM D-2583. The harness ＆#118alue can be used as an indication of the degree of cure of FRP laminates.
BENZOYL PEROXIDE (BPO)
An initiator for curing polyester resin. BPO is used with aniline accelerators or where heat is used to cure the resin.
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.
BLEEDER PLY
Layer of porous material placed in a vacuum bag to absorb excess resin and allow air and gas to escape.
BOND STRENGTH
Stress required (as measured by load/bond area) to separate a layer of material from another material to which it is bonded. Also, amount of adhesion between bonded surfaces.
BREAKOUT
Separation or breakage of fibers when edges of a composite part are drilled or cut.
BRIDGING
Fabric reinforcement extended over a curved edge that does not come into contact with rest of the composite.
BUCKLING
Failure mode usually characterized by fiber deflection rather than breaking.
BULK MOLDING COMPOUND (BMC)
Premixed blend of thermosetting resin, reinforcements, catalysts and fillers for use in compression, transfer, or injection molding process.
BLISTER
A void formed within a composite that may be the result of either trapping air in a laminate, or chemical action within the laminate.
C
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.
CARBON FIBER
A high strength-reinforcing fiber used in lightweight structural composites. Produced by pyrolysis of an organic precursor fiber in an inert atmosphere at temperatures above 1800oF. Material can also be graphitized by heat treating above 3000oF. See Graphic fiber.
CAST POLYMER
Non-reinforced composite (resin used without reinforcing fibers). Combines polymers, fillers and additives as composites to meet specific applications requirements.
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. The most common catalyst used in the composites industry are MEKP and BPO.
CATALYST INJECTION
Plural components spray equipment that mixes catalyst and resin at the spray gun or applicator.
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.
CENTIPOISES
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 that 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 ?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 material made of distinct components. For example; a reinforcing fiber in a resin matrix where the combined 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 that 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.
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.
CRAZING
Cracking of gel coat or resin due to stress.
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.
CURING AGENT
An initiator or catalyst that initiates polymerization when added to a resin.
CURE TIME
Time between introduction of catalyst or initiator to a polymer and final cure.
D
DELAMINATE
An adhesion failure between layers of a laminate.
DE-MOLD
To remove a part from a tool, or a tool from an intermediate model.
DENSITY
A comparison of weight per volume, measured in pounds per cubic foot, grams per liter or pounds per gallon.
DIELECTRIC STRENGTH
The measurement ＆#118alue of a material as an electrical insulator or the resistance to the flow of electric current.
DIETHYL ANILINE (DEA)
Promoter used in conjunction with BPO initiator or as an accelerator for cobalt/MEKP systems.
DIMPLES
A gel coat surface effect that consists of small concave defects. They are caused by entrapped liquid, tiny air voids, or poorly cut chopped glass or excess binder in chopped strand mat.
DISTORTION
A change in shape from that which is intended.
DRAFT
The angle of the vertical components of a mold that allows removal of the part.
DRAPE
The conformance ability of reinforcement fabric to the geometry of a mold.
E
E-GLASS
Originally formulated for use in electric circuitry, e-glass is the most common glass formulation used in fiberglass reinforcements.
ELASTOMER
A polymeric material that has a high modulus of elasticity and toughness. Urethane elastomer is an example.
ELONGATION
Standard measure for the amount a sample can stretch as 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 is considered an end before twisting.
END COUNT
The number of filament strands contained in a roving.
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.
F
FABRIC, NON-WOVEN
Material formed from fibers or yarns without interlacing, e.g., stitched non-woven broad goods.
FABRIC, WOVEN
Material constructed of interlaced yarns, fibers, or filaments formed from fibers or yarns without interlacing, e.g., stitched woven broad goods.
FABRICATOR
Manufacturer of reinforced plastic products.
FADING
Degradation of color in gel coat or coatings.
FEMALE MOLD
A concave mold used to precisely define the convex surface of a molded part.
FIBER
Reinforcement material that is a major component in a composite matrix.
FIBER CONTENT
Amount of fiber in a composite compared to the amount of resin and/or filler.
FIBER GLASS
Glass that 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
The direction of fiber alignment in a laminate. Chopped strand mat has isotropic (all directions) orientation. Knitted and woven fabrics can have two or mover orientations such as 00/900 or +450/-450.
FIBER REINFORCED PLASTICS (FRP)
A common term for molded thermoset resin matrices reinforced with fiber.
FILAMENT
A single thread-like fiber of extruded glass, typically microns in diameter.
FILAMENT WINDING
A process that involves winding a resin-saturated strand of glass filament around a rotating mandrel.
FILLERS
Usually inert organic or inorganic materials that are added to plastics, resins or gel coats to vary the properties, extend volume or lower the cost of the article being produced.
FIRE RETARDANTS
Compounds mixed with the resin to reduce flammability.
FISH EYE
The effect of mold surface contamination that causes a circular separation of a paint or gel coat.
FLAME RETARDANT RESIN
A polyester resin that 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 purposes of demolding, stiffening, or connecting two components; or for containing over spray.
FLASH POINT
The lowest temperature at which a substance produces vapor that can create a flammable mixture.
FLEXURAL MODULUS
ASTM D-790. An engineering measurement that determines how much a sample will bend when a given load is applied.
FLEXURAL STRENGTH
Strength of a material in bending at the instant of failure; usually expressed in force per unit area.
FOAM
A lightweight, cellular plastic material containing gas-filled voids.
FOAM-IN-PLACE
The process of creating a foam by the combination of two liquid polymers. See In-Situ
FREE RADICALS
Highly reactive molecular fragments capable of initiating chemical reactions, such as polymerization of polyester resins.
FRP
Fiber Reinforced Plastics, also known as GFRP (Glass Reinforced Plastic), RP (Reinforced Plastic) and Composites.
G
GEL
The irreversible point at which a polymer changes from a liquid to a semi-solid.
GEL COAT
A surface coat of 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 揃?stage.
GELATION
The formation of a gel.
GLASS TRANSITION
Reversible change in an amorphous polymer between a viscous or rubbery condition and a hard, relatively brittle one.
GLASS TRANSITION TEMPERATURE (Tg)
Approximate temperature above which increased molecular mobility causes a material to become rubbery rather than brittle.
GRP
Glass reinforced plastics. Generally based on polyester resin. See fiberglass or FRP.
H
HAND LAY UP
The process of manually building up layers of fiberglass, with roll stock reinforcements and resin, using hand rollers, brushes and spray equipment.
HEAT DEFLECTION TEMPERATURE
The temperature at which the strength of a material begins to degrade as determined by ASTM D-2583. (Sometimes referred to as Heat Distortion Point).
HEAT-ACID RESIN
Polyester resin with exceptional fire qualities based chloridic acid.
HONEYCOMB CORE
Strips of paper, plastic, metal, etc., joined together to form a honeycomb pattern. Used as a lightweight core in sandwich moldings.
I
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 that leads to curing.
INSERT
A piece of material put into a laminate during or before molding to serve a definite purpose.
IN TUMESCENCE
A coating technology that causes the material to foam when exposed to heat, forming an insulating barrier to resist fire.
IN-SITU
In the position that 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 orthophthalic polyester resin.
ISOTROPIC
The description of equal strength properties in all orientation. Isotropic composites are usually achieved by random fiber orientation.
J
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.
L
LAMINATE (noun)
Layers of a composite consisting of a resin and a reinforcement, bonded together to form a single structure.
LAMINATE
The act of processing resin and reinforcement into a bonded structure. Saturating glass reinforcement and rolling out air voids is to laminate.
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.
LOW-PRESSURE
Laminated, molded and cured using pressures from 400 psi down to and including the pressure obtained by the mere contact of the plies.
LOW PROFILE RESINS
Low shrink resins, that reduce surface distortion.
M
MALE MOLD
A convex mold where the concave surface of the part is precisely defined by the mold surface.
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 Chapped Strand 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 polymer liquid component of a composite or laminate.
MATCHED-METAL MOLDING
A high volume molding method that uses two machined metal molds in a hydraulic press. Generally the process uses sheet molding compound or bulk molding compound.
MEK PEROXIDE (MEKP)
A peroxide initiator often referred to as catalyst and used initiate polymerization of a resin.
METHYL ETHYL KETONE PEROXIDE
(See above)
MEK SOLVENT
Methyl Ethyl Ketone; a colorless, flammable liquid sometimes used in clean up procedures. It is not a peroxide initiator.
MICRO CRACKING
Cracks formed in composites when thermal stresses locally exceed strength of the matrix.
MICROSPHERES
Microscopic bubbles of glass, ceramic or phenolic, used as filler or to create syntactic foam or putty mixtures.
MIL THICKNESS ?MILS
The unit used in measuring film thickness. One mil equals one thousandth of an inch (1 mil = .001?.
MILLED FIBERS
Glass fiber processed by a hammer mill into lengths of 1/32?to 1/8? Commonly used as reinforcement in polyester putty.
MODULUS OF ELASTICITY
An engineering term used to describe a material抯 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 surfaces acts as a barrier between the mold and the part, thus preventing the part from bonding to the mold.
MONOMER
A constituent of polyester or vinyl ester resin. Styrene monomer is most commonly used.
N
NET SHAPE
A fabricated part that comes out of the mold and does not require cutting, trimming or machining.
NON-DESTRUCTIVE TESTING
Methods of testing materials that involve tests that do not alter the properties of the material.
NPG GEL COAT
Neopentyl glycol gel coat has enhanced weatherability compared to non-NPG gel coat.
O
ONE-OFF
A custom fabrication process in which a single part is fabricated.
ORIFICE
An opening, generally referred to regarding spray tip size.
ORANGE PEEL
A gel coated or painted finish that is not smooth and is patterned similar to an orange抯 skin;
ORTHOPHTHALIC OR ORTHO RESIN
A polyester resin based on orhtophthalic acid, also known as a general purpose resin (GP).
P
PARTING AGENT
See Mold Release and PVA.
PARTING LINE
The location on a mold product between different segments of the mold used to produce the product.
PATTERN
The initial model for making fiberglass molds. See Plug.
PEEL PLY
A removable non-stick fabric applied to a lay-up surface that is removed from the cured laminate prior to bonding operations, in order to leave clean, resin-rich surface ready for bonding.
PEEL STRENGTH
The strength of the bond between laminate plies obtained by stress that is applied in a peeling mode.
PEROXIDES
Category of compounds containing oxygen groups that are used as initiators. (see MEK Peroxide)
PHENOLIC RESIN
Thermosetting resin produced by condensation of an aromatic alcohol with an aldehyde, particularly phenol with formaldehyde.
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.
PLASTICS
Organic chemical compounds called polymers that can be formulated to produce a wide range of properties.
PLUG
A composite industry term for a pattern of model.
PLY
A single layer within a laminate.
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 molecules during the curing reaction.
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POLYVINYL ALCOHOL (PVA)
A parting film applied to a mold for part releasing.
POROSITY
Entrapped gas bubbles or voids in a gel coat film
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 搘orkable?See Gel Time.
PRE-FORM
A fiber reinforcement reshaped to match the shape of the mold. There are several methods of making pre-forms including the directed fiber method and the use of thermo-formable mat.
PREMIX
Reinforcing material mixed with resin and usually with pigment, filler and catalyst, before placing in the mold.
PRE-PREG
Reinforcing material impregnated with resin prior to the molding process and cured by the application of heat.
PRE-RELEASE
The premature release of the gel coat or laminate from the mold. Pre-release causes cosmetic or dimensional problems.
PRESSURE BAG
A membrane that conforms to the inside of a laminate laid up on a mold. The membrane or bag is then inflated by applying pressure that consolidates and densifies the laminate.
PRINT THROUGH
A distortion in the surface of a part that 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
An additive to speed up the cure. This additive is required for room temperature resin cure. See Accelerator.
PROTOTYPE
The initial fabrication of a product that is used to develop and refine product specifications, design and process methods.
PULTRUSION
A continuous molding process for manufacturing composite profile shapes such as rods, tubes and structural shapes having a constant cross section. Roving and other reinforcements are saturated with rein and continuously pulled through a heated die, where the part is formed and cured.
PUTTY
A thickened mixture of resin made by adding fillers, thixotophs and reinforcing fibers.
PVA
See Polyvinyl Alcohol
R
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 that 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 apart.
RELEASE FILM
A non-stick film layer that does not bond to the composite during cure.
RESIN
A liquid polymer that when catalyzed cures to a solid state.
RESIN RICH
Excess resin in a laminate.
RESIN STARVED
Insufficient resin in a laminate.
RESIN TEARING
Separation of pigments in a gel coat effecting cosmetic appearance.
RESIN TRANSFER MOLDING (RTM)
Molding process in that catalyzed resin is pumped into a two-sided, matched mold where a fibrous reinforcement has been placed. The mold and/or resin may or may not be heated.
ROVING
A collection of bundles of continuous filaments in untwisted strands. Used in the spray-up (chopping) process.
S
SANDWICH CONSTRUCTION
A laminate with two composite skins separated by, but bonded to, a structural core material. Used to create, rigid, lightweight structures.
SECONDARY BONDING
Bonding to a previously cured laminate surface.
S-GLASS
High strength glass fiber, commonly used in high-performance parts. S-Glass has high compression strength.
SELF EXTINGUISHING
Ceases to burn when the source of flame is removed.
SHEAR
Stress resulting from applied forces. It is caused by two contiguous parts of a body sling, relative to each other, in a direction parallel to their plane of contact.
SHEET MOLDING COMPOUND (SMC)
A molding compound consisting of a B-staged resin and chopped glass fiber, used in compression molding.
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.
SKIN COAT
The first layer of laminate next to the gel coat, generally, one ply of chopped strand mat.
SLAVE PUMP
A catalyst pump that is driven by the resin pump through a pair of level arms.
SPECIFIC GRAVITY
The ratio between the density of a given substance and the density of water.
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 (RIGIDITY)
Material抯 ability to resist bending. Relationship of load to deformation for a particular material.
STRAIN
Deformation resulting from stress.
STRANDS
A primary bundle of continuous filaments combined in a single compact unit without twist.
STRESS
External force applied to an object, expressed in force per unit area.
STRESS CRACK
External or internal cracks in a composite caused by tensile stresses; cracking may be present internally, externally or in combination.
STYRENE MONOMER
SURFACING MAT
SURFACING VEIL
SURFACTANT
SYNTACTIC FOAM
T
TACK
Surface stickiness.
TACK FREE
A surface that is not sticky after cure.
TAPE
A narrow width reinforcing fabric or mat.
TENSILE LOAD
A pulling 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
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 cross-linking 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 thixotroy using a Brookfield Viscometer. The low speed viscosity divided by the high-speed viscosity.
TOOLING GEL COAT
A gel coat formulated for mold surfaces.
TRANSLUCENT
Permits a percentage of light to pass but not optically clear like a window glass.
U
UNDERCUT
An area of a part or mold that has 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 that improves resistance to degradation from ultraviolet radiation.
V
VACUUM INFUSION PROCESSING
A process where the reinforcement is laid-up in the mold dry, then vacuum bagged and the resin is pulled into the mold at lower then atmospheric pressure.
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 that blankets a laminate.
VISCOSITY
The liquid properties of a material. Resistance to flow.
VOIDS
Pockets of air that have been trapped in a laminate.
VOLATILE ORGANIC COMPOUNDS (VOC)
Carbon-containing chemical compounds (e.g., solvents or liquids) that evaporate readily at ambient or process temperatures. Environmental, safety and health regulations often limit exposure to these compounds, making low VOC content is preferable.
VOID FREE
A laminate containing no entrapped air cavities, blisters or voids.
W
WATER ABSORPTION
The amount of water that a laminate will absorb.
WAX
A compound used as a release agent. See Release Agent.
WEAVE
Pattern by which fabric is formed from woven yarns.
WEFT
Yarns running perpendicular to the warp in a woven fabric; also called 憌oof.?/font>
WET-OUT
The action of saturating a glass fabric with resin. Also a measure of the speed with that a fabric soaks up resin.
WETTING AGENT
Surface-active agent that promotes wetting by decreasing the cohesion within a liquid.
WHISKER
Short single crystal fiber or filament used as reinforcement in a matrix.
WOVEN ROVING FABRIC
Heavy fabrics woven from continuous filament in roving form. Usually in weights between 18-30 oz. Per square yard.
Y
YARN
Twisted strands of roving, used to weave textile reinforcements.
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