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 value 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 “B” 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.
