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Molds: Glossary of Terms Print

Accelerator

An additive that reduces the gel and curing time of thermosetting plastics such as polyester gel coat and resin. Also called promoter or activator.

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Acetone

In an FRP context, acetone is primarily useful as a cleaning solvent for removal of uncured resin from applicator equipment and clothing. VERY FLAMMABLE LIQUID.

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Activator

See Accelerator.

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Additive

Substance added to the resin mix to impart special performance qualities, such as ultraviolet absorbers, flame retarding materials (antimony trioxide, chlorinated waxes).

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Air Dry

To cure at room temperature with the addition of catalyst but without the assistance of heat and pressure.

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Alligatoring

Wrinkling of the gel coat film resembling alligator hide.

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Backpour

The second pour or casting of cast polymer matrix into the female mold that creates the proper wall thickness of the product.

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Barcol Hardness

A determination of hardness of a polyester using a Barcol Impressor.

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Cast Polymer

A generic term referring to cast man-made material created by combining catalyzed polyester resin with inorganic fillers and color pigments.

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Catalyst Injection

Used with spray equipment to catalyze the polyester at the spray gun, therefore eliminating the need to clean the system within the gel time of the polyester. Internal mix guns do require a solvent for cleaning the gun head.

Injector: Atomizing air atomizes the catalyst at the injector unit itself.

Pot: Catalyst is supplied to the spray gun, then air is introduced to atomize the catalyst.

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Catalyst (Peroxide)

In FRP terms, a substance added to the resin or gel coat in controlled quantities to make it cure more rapidly. Usually it oxidizes an accelerator, creating free radicals, which in turn cures the resin or gel coat.

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Cavity

The space between matched molds (pressure molds) in which the laminate is formed. Also a term for a female molds.

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Centipoise

Measurement of viscosity as compared to water (1 centipoise).

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Cobalt

Used as the accelerator for Methyl Ethyl Ketone Peroxide catalyzed polyesters.

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Crazing

Cracking of the resin due to internal stress.

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Cross-Linking

The process of bridging two polymer chains, which converts a thermoplastic to a thermoset.

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Cure

The polymerization of the transforming from the liquid to the solid state with maximum physical properties, including hardness.

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Cure Time

The time required for the liquid resin to reach a polymerized state after the catalyst has been added.

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Cut-Out

The hole left in a flat deck or vanity top created by casting around a plug. The cut-out is used to accommodate either an undermount or drop-in bowl or bathtub.

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Delamination

The separation of a laminate into layers owing to the failure of adhesion of the binder or failure of cohesion of the filler.

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Density

Weight per unit of volume, usually expressed as pounds per cubic foot.

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Dimensions

(As measured from a position facing the front, leading edge of the product)

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Drop-In Bowl

Also referred to as a self-rimming lavatory. The Drop-In Bowl fits through a cut-out in the vanity top. It has a lip or flange that rests on the vanity top holding it in place.

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Exothermic Reaction

Internally developed heat accompanying a chemical reaction.

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Faucet Landing Area

The area on the backside of the bowl that accommodates the faucet fixtures.

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Fillers

Relatively inert organic or inorganic materials which are added to plastics resins or gel coats for special flow characteristics, to extend volume, and lower the cost of the article being produced.

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Finished Edge/End

The edge or end of a piece of cast polymer that is gelcoated and has been cast in contact with the mold surface to achieve a smooth, glossy finished surface.

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Flash Point

The lowest temperature at which a substance gives off enough vapors to form a flammable or ignitable mixture with air near the surface of the substance being tested.

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Flexural Strength

Determination of the load required to cause failure by flexing.

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Fumed Silica (Aerosil, Cabosil)

A very low weight thickening agent used in polyesters to increase thixotropic qualities.

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Gel

A partial cure stage of plastics resins in a viscous, jelly-like state where the liquid material starts to transform into a solid.

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Gel coat

The protective, transparent surface layer of polyester resin which is applied to the mold. The gel coat becomes the sanitary, glossy surface of the cast polymer product.

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Gel Time

The length of time that a catalyzed polyester remains workable--- starts to solidify.

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Gelation

The formation of a gel.

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Hot Pot

Catalyst is mixed with the gel coat or resin in the material container prior to spraying, as opposed to internal or external gun mixing.

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Humidity

Moisture content of the air.

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Inhibitor

A substance designed to slow down or prevent a chemical reaction.

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Integral Bowl

A bowl that is cast as one piece with the vanity top.

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Iso

Abbreviated terminology for isophthalic acid type resins and gel coats.

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Location of Bowl

As determined from the location of the integral bowl(s) in the finished product as seen from a position facing the front of the vanity top.

Right bowl: A bowl located on the right side of the vanity, the dimensions of which are given as the distance from the center of the drain to the right end of the vanity top.

Left bowl: A bowl located on the left side of the vanity, the dimensions of which are given as the distance between the center of the drain to the left end of the vanity top.

Double bowl: A vanity top with two bowls in which the dimensions are given as the distance between the center of the drain of each bowl.

No bowl: A vanity top mold without a bowl.

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Mass

The quantity of matter contained in a specified body. In reference to polyesters, mass is measured in mils or inches thickness of a film or casting.

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Master (Plug)

The permanent tool used to build molds for the manufacture of cast polymer parts.

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Matrix (Batch, Mix)

The combined mixture of resin, catalyst, and filler materials.

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MEK Peroxide (MEKP)

Abbreviation for Methy Ethyl Ketone Peroxide, a strong oxidizing agent (free radical source) commonly used as the catalyst for polyester in the FRP industry.

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MEK Solvent

Abbreviation for Methyl Ethyl Ketone, a colorless fammable liquid commonly used in gun clean up procedures.

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Mil

The unit used in measuring film thickness and the diameter of glass fiber strands, wire, etc. (one mil = .001”)

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Monomer

A relatively simple compound capable of polymerization with itself or with a compatible resin. It is also used to dilute polyester.

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Net Wt of Mold

 

The approximate weight of the mold prior to packaging for shipment. The weights of the same mold may vary slightly due to the weight differences of the wood substructure.

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Ortho

Abbreviation for orthophtalic acid type resins and gel coats.

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Parting Agent

See Mold Release.

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Pattern

The initial model for making fiberglass molds.

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Peroxides

Category of compounds containing an unstable O-O Group: Oxygen to Oxygen atoms.

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Pigment

The ingredient used in gel coats to impart color.

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Plug

See Master. Both terms used to imply the same meaning.

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Polyester (Unsaturated)

A resin formed by the reaction between dibasic acids and dihydroxy alcohols, one of which must be unsaturated (typically maleic anhydride) to permit cross-linking.

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Polymer

A large chemical chain composed of many identical groups, such as polystyrene.

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Polymerization

The chemical reaction of cross-linking the molecules in the resin (see also Cure).

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Polyvinyl Alcohol (PVA)

A liquid water soluble release agent for polyester.

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Porosity

Small air bubbles in the gel coat film, too numerous to count. Generally smaller in size than pinholes.

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Post-Cure

Exposure of the cured resin to higher temperatures than during curing, necessary in certain resins to attain complete cure and ultimate mechanical properties.

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Pot Life

See Gel Time.

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Promoter

See Accelerator.

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Release Agent

See Mold Release.

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Resin

Any of a class of solid or semisolid organic products of natural or synthetic origin, generally of high molecular weight having no definite melting point. Used in reinforced products to surround and hold fibers. Most resins are polymers.

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RTM (Resin Transfer Molding)

Intermediate process of using matched molds (similar to match metal die) at low pressure and heat.

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Shelf Life

The length of time an uncatalyzed polyester remains workable while stored in a tightly sealed container.

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Skin Coat

The first layer of laminate next to the gel coat. Generally only 1/16” thick to afford good roll-out and to reduce heat.

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Specific Gravity

The ratio of the weight of any volume of a substance to the weight of an equal volume of some substance taken as a standard unit, usually water for solids and liquids, and air or hydrogen for gasses.

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Styrene Monomer

An unsaturated hydrocarbon, used in plastics. In polyester, it is a co-reactant diluent.

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Surfacing Agent

A material that allows the surface of polyesters to cure. It limits adhesion of another coat of resin if the first is thoroughly cured. It may be removed by sanding or by rubbing with steel wool.

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Thermosets

Materials that will undergo or have undergone a chemical reaction by the action of heat, catalyst, ultra-violet light, etc., leading to a relatively infusible state. Typical materials are aminos (melamine and urea), most polyesters, alkyds, epoxies, and phenolics. They are not reformable.

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Thixotropic

A term describing materials more jelly-like at rest than when stirred or agitated. Agitation (shear) reduces the gel and increases the flow characteristics.

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Tooling Gel Coat/Laminating Resin

Special polyesters designed to give ultimate strengths and cure values for mold making.

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Undercut

Negative or reverse draft on the mold. Split molds are necessary to shape pieces that are undercut.

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Undermount Bowl

A separate bowl which is attached to the underside of the countertop.

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Viscosity

The internal resistance to flow of a fluid; thickness.

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Wet Out

The speed with which a reinforcing material can be completely saturated with resin. This rate is usually determined visually and measured in elapsed time.

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