Glossary of Terms

Additive Top of Page
A compound or substance added to polymer, such as pigments and antistats, to alter or improve its characteristics.
An additive used in film production that prevents undesired adhesion between film layers during unwinding.
An additive that prevents a film’s degradation and oxidation during processing.
An additive, which prevents the build up of static electricity.
Average Molecular Weight
The molecular weight of a polymer is determined by the viscosity of the material in solution at a specific temperature. Because polymer molecules, even if of the same type, come in different sizes, average molecular weight is a way of describing the molecular weight of a polymer.
Backside Treat Top of Page
Film defect when areas of the untreated/lamination side of film test positive for corona treatment.
A resin or film containing no additives.
Barrier Resins
Polymers, which have very low permeability to gases. Examples include polyamide and EVOH.
The mixing of polymers with other polymers, copolymers, or additives to achieve desired physical properties.
An undesirable adhesion between layers of film or sheeting which may develop during processing or storage.
A thin greasy film on the surface of a plastic film usually caused by an additive being exuded. Additives are designed to rise, or bloom, to the surface of the film over time.
Blown Film
Extrusion of a continuous thin walled tube of plastic through a round die and inflating it to form a bubble. The bubble is then collapsed flat between rollers and slit into layflat film which is wound onto rolls.
Blow Up Ratio
In blown film extrusion, the ratio of the diameter of the bubble to the diameter of the die.
Calcium Carbonate Top of Page
A filler and extender used in thermoplastics. It’s found naturally in minerals such as calcite, chalk and limestone.
Center Fold
Folding a film along its length to create a two layered product with half the width.
Coefficient of Friction (COF)
The ratio of the force required to slide an object over a frictionless surface to the force required to slide the same object over the actual surface being tested. It’s used to determine how slippery or tacky a film is.
Fabrication of a multi-layer film by pumping materials through two or more extruders then merging them into a common die assembly. The die assemblies are constructed to maintain distinct material layers. Fusion occurs at the boundaries due to the pressures and temperature of the extruded materials. Coextrusion allows resin combinations to be used to produce films having properties not obtainable through blending in a single layer extrusion.
Color Concentrate
A plastics compound which contains a high percentage of color pigment blended with a base resin. Sometimes referred to as a masterbatch.
A polymer resulting from the polymerization reaction between two chemically different monomers.
Rigid cardboard tube onto which film is wound. Typical cores have either 3 inch or 6 inch inside diameters.
Corona Treat
A process that increases the surface energy of plastic film to allow inks, coatings or adhesives to attach to the film.
Density Top of Page
Weight per unit volume of a substance usually reported in g/cm3 or lb/ft3.
Dart Drop
Measurement of the puncture resistance/impact strength of film and its ability to withstand the shock of a falling "dart" without breaking. Expressed as gram weight of the heaviest dart which doesn't break the film when dropped from a specified height.
Weight per unit volume of a substance, usually expressed in grams per cubic centimeter. Polyethylene resins often range between .890 - .965.
A circular steel block made up of an inner and outer ring through which plastic is extruded and inflated into a large tube.
Die Gap
Distance between the metal surfaces which form the die opening.
Die Lines
Lines in the machine direction of film caused by buildup of oxidized materials on the die.
Differential Scanning Calorimetry (DSC)
Method used to determine thermal histories of polymers such as melting temperatures and glass transition points.
Double Wound Sheeting (DWS)
Two layers of plastic film wound onto the same core.
The process of pulling extruded material away from the die at a linear speed higher than that at which the melt is emerging from the die. The result reduces the cross-sectional dimensions of the extruded material.
Unit of measure for surface tension (treat level).
Edge Wrinkles Top of Page
Rough cut, or jagged edge followed by a wrinkle extending into the roll.
The property of plastic materials which allows them to recover their original size and shape after being stretched.
A material, which at room temperature, can be stretched under low stress to at least twice its original length and when released will return – with force – to its original shape.
Usually expressed as a percentage, it is the increase in length of a test specimen when a tensile load is placed on the sample. Such test data is often obtained by equipment such as an Instron during tensile testing.
Erucamide Slip
A fatty acid based additive commonly used in polyolefin resins to increase slip.
Ethylene Vinyl Acetate (EVA)
Part of the polyolefin family created from random copolymerization of vinyl acetate and ethylene.
Ethylene Vinyl Alcohol (EVOH)
Copolymer exhibiting outstanding barrier to many chemicals and gasses.
Compressing and melting a plastic material and forcing it continuously through a die.
Film Top of Page
Plastic sheet material usually having a thickness of 10 mil or less.
Flame Retardant
Additive compounds used to make a polymer fire resistant.
Gauge Top of Page
Thickness measurement of plastic film, often expressed in mils. One mil equals one thousandth of an inch (0.001" or 0.001in.).
Gauge Bands
Raised regions in the machine direction around the circumference of a roll, produced by winding areas of thicker film in the same place on a roll.
Small globular mass of unmelted polymer or degraded material, which creates a defect in plastic film.
A measurement of a film's surface reflectivity of light shone from a given angle, commonly 45 degrees for blown film. Expressed as a percentage, the higher the number, the shinier the film.
Haze Top of Page
Cloudiness of plastic film. Anything measurement below five percent is considered high clarity.
Heat Seal
The process of bonding two or more thermoplastic films or sheets by using heat and pressure to create fusion at their contact points.
High-Density Polyethylene (HDPE)
Polyethylene resins/films ranging in density from approximately 0.940 to 0.965.
The result of the polymerization of a single monomer, a homopolymer consists of a single type of repeating unit.
Hot Tack
Hot tack is a measure of the strength of a heat seal before the seal has cooled completely.
J Sheet Top of Page
Similar to center fold, j-sheet is folded on one edge of the roll and slit in the machine direction on the other side allowing the film to be unfolded. The difference is that the fold is not directly in the center of the film, so the width of the film on either side of the fold is asymmetrical when opened.
Lamination Top of Page
Bonding of a polymeric or non-polymeric substrate to a polymeric film using heat and pressure.
Measurement of the transverse/cross direction of film, also known as film width.
Light Transmission
Measurement of the amount of light that color pigmented films allow to pass through them. Values range from 100% for clear film to 0% for opaque films.
Linear Polymer
A polymer in which the monomeric units are linked together in linear fashion with little or no long chain branching.
Linear Low-Density Polyethylene
A process variation of low density polyethylene. It allows for higher draw down-gauging in extrusion and increased film strength.
Low-Density Polyethylene
A partially crystalline, lightweight thermoplastic with density ranging from 0.910 - 0.929 g/cm3 that is relatively soft, flexible, and will withstand moderate heat.
Machine Direction (MD) Top of Page
Direction of the film corresponding to the way it exited the die.
A concentrated blend of slip, additives, or color pigment in a base polymer carrier resin. Sometimes referred to as color concentrate.
Melt Fracture
Extrudate or film having a surface that appears rough and wavy. Melt fracture may be evenly distributed throughout the film or concentrated in some areas only.
Melt Index
Grams of a thermoplastic resin which can be forced through a 0.0825 inch orifice by 2160 grams of force in 10 minutes at 190°C.
Melt Temperature
The temperature at which a resin changes from a solid to a liquid.
Gauge measurement commonly used in film manufacturing. One mil equals one thousandth of an inch (0.001" or 0.001in.).
Molecular Weight Distribution
The relative amounts of polymers of different molecular weights that form a specific polymer.
Mono layer
Film comprised of a homogeneous mixture of one or more polymers blended together in a molten state and extruded through a die assembly to form a film or sheet.
Nip Top of Page
The "V" shaped gap between a pair of calendar rolls where incoming material is nipped and drawn between the rolls.
Octene Top of Page
A comonomer used in the production of linear low density polyethylenes.
A powder used as slip additive in polyolefins.
The amount of light that is blocked by a pigmented film.
Orange Peel
An uneven surface texture of a plastic article or its finished coating somewhat resembling the surface of an orange.
Pellets Top of Page
Small pieces of unmixed resins or resins mixed with compounding additives that have been prepared for molding operations by being cut to a uniform size.
A process by which holes are deliberately punched into film or sheeting, from very large holes to those that are nearly invisible, depending on the machine use to create the perforations.
The degree to which a film allows gasses, vapors, liquids or solids through a barrier without changing it physically or chemically.
Polyamide (PA)
Also known as nylon, a thermoplastic used for high strength, puncture resistance, heat resistance, and barrier to certain gasses.
The process by which light causes film to breakdown and lose some of its characteristics.
Polyethylene (PE)
Resins of various densities produced by polymerizing ethylene gas. Examples are Low Density (LDPE), Linear Low Density (LLDPE) and High Density (HDPE).
Polypropylene (PP)
A tough, lightweight, rigid plastic made by the polymerization of high-purity propylene gas in the presence of an organometallic catalyst at relatively low pressures and temperatures.
Process Aid
Additives used in the production of plastics to improve extrusion performance and reduce surface defects of film.
A chemical reaction in which the molecules of a simple substance (monomer) are linked together to form large molecules whose molecular weight is a multiple of that of the monomer.
Class of polymers made by polymerizing relatively simple olefins, including ethylene, propylene, butene, isoprene, and pentene.
Resin Top of Page
An organic substance of natural or synthetic origin characterized by being polymeric. Usually comes in the form of pellets.
Sheeting Top of Page
A term often used in the film industry as an abbreviation for single wound sheeting. Actually, a web under 10 mils (.010 inch) thick is usually called a film, whereas a web 10 mils and over in thickness is usually called a sheet.
Shelf life
The length of time over which a product will remain fit for use when properly stored.
A measurement of the percent of film shrinkage in the machine direction or transverse direction at a specified temperature and time.
Single Wound Sheeting (SWS)
A single layer of plastic film that is wound on a roll.
Slip Agent
Additive which lowers the coefficient of friction of film to make the sliding action easier on processing and filling equipment.
Ingredient used in the formulation of some polymers to assist in maintaining their physical and chemical properties.
A slip additive used in polyolefins.
The ratio of the elongation to the gauge length of the test specimen.
The force producing or tending to produce deformation divided by the area over which the force is applied.
Tack Top of Page
The stickiness of an adhesive. It is measured as the force required to separate an adherent from it by viscous or plastic flow of the adhesive.
Additive composed of hydrous magnesium silicate, used frequently as a filler or antiblock agent.
Roll phenomenon characterized by layers of film sliding laterally in the transverse direction, causing the edge of the roll to have a conical shaped appearance resembling that of a telescope.
Tensile Strength
The maximum tensile stress sustained by the specimen before failure in a tension test.
Tin Canning
Roll defect appearing as raised ridges around the circumference of the roll resembling a tin can.
Titanium Dioxide
A white powder available in two crystalline forms, the anatase and rutile types.
Transition Temperature
The temperature at which a polymer changes between a viscous condition and a solid one.
Transverse Direction (TD)
Film direction which is at a right angle to the direction of extrusion, also called cross direction (CD).
Blown film is extruded through a circular die which creates a tube of film. When the tube of film is collapsed and rolled onto a core, the finished product is called tubing.
Ultra Violet Inhibitor (UVI) Top of Page
Additive used to prevent degradation of plastic materials from prolonged exposure to sunlight.
Vapor Barrier Top of Page
A layer of material through which water vapor will not pass.
Vicat Softening Point
The temperature at which a flat ended needle of 1 square millimeter circular or a square cross section will penetrate a thermoplastic specimen to a depth of 1 millimeter under a specific load using a uniform rate of temperature rise.
The measure of resistance of a fluid to flow.
Wrinkle Top of Page
An imperfection in plastic films that has the appearance of a crease, fold, or wave.
Yellowness Index Top of Page
A measure of the tendency of plastics to turn yellow upon long-term exposure to light or heat.
The area of film of a given thickness per unit of weight. Common units used are square inches of film per pound.