Glossary

Plastics Glossary - F

Falling - Body Viscometer A device that utilizes a sphere, falling through a mass of the test fluid inside a cylindrical tube. The time for the sphere to fall a certain distance is measured and correlated with viscosity.

False Body Reversible work-softening that causes a high apparent viscosity of a material.

False Gel Unstabilized gel that breaks down upon standing.

Family mold Designed to produce several different and often unrelated parts. It is most often used when a processor needs to make only a small amount of different parts for a particular application, and all parts are made of the same material. Specific core/cavity inserts can be dropped into the mold base, and they can be easily changed without long production stoppage.

Fan gate Opening between the mold runner and the mold cavity which has the shape of a fan. This shape helps reduce stress concentrations in the gate area by spreading the opening over a wider area.

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 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.

FDA Abbreviation for Food and Drup Administration, the U.S. agency under the Department of Health, Education and Welfare which is concerned with the safety of products marketed for consumer use.

Feed section of screw First section or zone of an extruder screw which is fed from the hopper. Picks up pellets and carries them forward.

Feed throat opening The hole in the back of the barrel where the end of the screw will be exposed when the hopper is removed.

Feed throat The opening in the back of the barrel where the plastic enters.

Fiber orientation Fiber alignment in a nonwoven or a mat laminate where the majority of fibers are in the same direction, resulting in a higher strength in that direction.

Fiberglass reinforcement Major material used to reinforce plastics. Available as mat, roving, fabric, etc. It is incorporated into both thermosets and thermoplastics. The glass increases mechanical strength, impact resistance, stiffness, and dimensional stability of the matrix.

Fill time Time to fill a cavity or cavities. Does not include packing or static pressurization of the mold.

Fill Filling a cavity or cavities. Does not include pack or pressurization of the mold.

Filler A material added to plastics to make it less costly. Fillers can be inert or can alter various properties of the plastic. Fill time In injection molding, the elapsed time from the start of forward movement of the injection screw or ram until the machine switches to the packing phase of injection. The preferred method for switchover from fill to pack is cavity pressure or screw position. Switchover by time is a distant third option. Switchover by hydraulic pressure is NOT recommended.

Fillet Rounded interior corner of a part that makes the part stronger.

Film Films are distinguished from sheets in the plastics industry only according to their thickness. In general, films have thicknesses less than

Fin The web of material remaining in holes or openings in a molded part that must be removed for final assembly.

Fines In the classification of powdered or granular materials such as molding compounds according to particle size, fines are the portion of the material composed of particles which are smaller than a specified size.

Finish The surface texture of a finished article.

Fire Point Lowest temperature of an oil at which it will ignite and continue to burn for at least 5 seconds.

First stage pressure The pressure used to inject and fill the cavity with plastic.

First stage timer The cycle timer that controls the time that the high volume pump is used to inject plastic into the mold cavity.

Fish eye Small globular mass that has not blended completely into the surrounding material resulting as a fault in film, sheet, or molded part.

Fitzsimmons Viscometer Device that determines the kinematic viscosities of transparent Newtonian liquids in the 0.6-1200 cS range.

Flame retardant Reactive compounds and additive compounds that render a polymer fire retardant. Reactive compounds become an integral part of the polymer structure, while additive chemicals are physically dispersed in the polymer.

Flame retardant Reactive compounds and additive compounds to render a polymer fire retardant. Reactive compounds become an integral part of the polymer structure, while additive chemicals are physically dispersed in the polymer.

Flammability The measure of the extent to which a material will support combustion.

Flash Point (Cleveland Open-Cup Test) Lowest temperature of an oil at which it gives off vapors that will ignite when a small flame is passed over the surface of the oil.

Flash The thin, surplus of material which if forced into crevices between mating mold surfaces during a molding operation remains attached to the molded article.

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 The maximum stress in the outer fiber at the moment of crack or break. In the case of plastics, this value is usually higher than the tensile strength.

Flight depth The distance from the edge of a flight to the core of the screw. The flight depth of an injection molding screw is greater at the narrower feed section than at the wider metering section.

Flight The outer surface of the helical ridge of metal on an extruder or injection molding screw.

Floating plate In a 3-plate injection mold, plate which, upon mold opening, has a parting line on each side which open sequentially. The first parting line acts to degate the parts and the second acts to release the runner. Also referred to as a pin plate.

Floating platen Moveable platen(s) between the stationary platen and actuated platen on a vertically operating compression press.

Flocculation Process in which the disperse particles in a liquid medium display a tendency for mutual adhesion.

Flock Short fibers of cotton, wood, or glass used as a filler for resins.

Flotation Ore-dressing method in which surface-active additives cause one of the constituents to float to the surface in the froth produced by aeration and agitation.

Flow During processing by injection, compression, or transfer molding, the flow of a plastic is a measurement of fluidity.

Flow line The area of a molded part where multiple masses of plastic meet and weld together during molding. Ripples or lines on the part surface that follow the direction of the melt into the cavity.

Flow marks Distinctive surface marks caused when two flow fronts meet and weld together during molding.

Flow During processing by injection, compression, or transfer molding, the flow of a plastic is a measurement of fluidity.

Fluid Substance that cannot sustain shear forces when in static equilibrium. Real fluids in motion sustain shear forces because of the property of viscosity.

Fluidity Reciprocal of viscosity, expressed in inverse poise.

Fluorescent pigments Pigments which appear to glow. They absorb light at one frequency and remit it at another frequency.

Fluoroplastics Polyolefin polymers in which fluorine, fluorinated alkyl groups, or other halogens replace hydrogen atoms in the carbon chain. This structure has outstanding electrical properties, excellent resistance to chemical attack, low coefficient of friction, excellent fire resistance, exceptionally good performance at high and low temperatures, low moisture absorption, and outstanding weatherability.

Fluxing Thinning of heavy oil by the addition of a more fluid oil.

Foam Process for producing plastic sheet of cellular construction. Either a chemical or a gaseous blowing agent is introduced into the polymer melt while the melt is being prepared in the extruder barrel. As the plastic melt exits the die, it expands a predetermined amount forming a cellular wall.

Foamed plastics Process by foam molding or extrusion to achieve lower material densities for high rigidity, especially in large structural parts. Most processes for producing structural parts correspond to injection molding. To produce the foamed product, inert gas is dispersed through the polymer melt by blowing gas directly into the melt or by preblending with a chemical blowing agent, which releases inert as in the presence of processing heat.

Foaming Agent Any substance which alone or in combination with other substances is capable or producing a cellular structure in a plastic mass.

Foil, hot stamping A laminate consisting of a carrier film to which a series of coatings have been applied: a release coat, a decorative coat, and an adhesive coat.

Force Defined as pressure multiplied by the area.

Force-Type Viscometer Instrument that measure force at constant shear rate. Units of force can be converted directly into viscosity units.

Forming A general term encompassing processes in which the shape of plastic pieces such as sheets, rods or tubes is changed to a desired configuration.

Formula Weight Sum of the atomic weights of all the atoms in an empirical formula.

Fracture A material's failure to absorb impact.

Fracture The separation of a body, usually characterized as either brittle or ductile.

Free shrinkage Allowing a part with no critical dimensions to shrink freely during post mold crystallization.

Friction Factor Used in the Fanning equation to compute the friction loss through length of tube and is a function of Reynolds number.

Frothing Agent Surface-active material that is used specifically to stabilize the dispersion of a gas in a liquid or solid medium.

FRP Fiberglass reinforced plastic; a general term covering plastic which is reinforced with cloth, mat, strands, or any other form of fibrous glass.