Glossary of Blown Film Extrusion Terms

Additive

a compound or substance added to a base resin to improve or achieve a desired characteristic

Antiblock

additive blended into film to prevent sticking or adhesion (blocking) of layers of film during roll formation or end use

Antioxidant

additive, which limits the degradation and oxidation of film

Antistat

additive added to base resin to enable film to dissipate or reduce static

Barrel

tubular portion of extruder, which houses the rotating screw

Blend

the mixing of 2 or more polymers or copolymers to achieve a desired physical film property

Blocking

tackiness between layers of film causing an adhesion, preventable by adding antiblock additive and/or slip

Bloom

describes the migration of slip additive to the surface of the film

Blown Film

plastic resins melted and forced through a circular die, inflating the resulting tube. The tube stretches under pressure; increasing or decreasing diameter to achieve the desired lay flat tube. Increasing or decreasing line speed changes wall thickness of film to desired gauge. This is Blako Industries manufacturing process.

Cast Film

plastic resins are extruded through a slot die onto the surface of a water-cooled roll

Centerfold

film on a roll with a slit edge on the side opposite the folded edge

Co extrusion

multiple layers of film created by separate extruders, then merging the material through a single die

Color Concentrate

compounded plastic additive containing a high percentage of pigment that's blended with base resins

Corona Treat

the surface energy of films is intentionally increased by roughing up the surface microscopically to allow for better adhesion of inks and coatings

Degradation

breaking down of film properties usually creating discoloration caused by exposure to weathering, heat, light and oxygen.

Density

resin/film measurement of weight per unit volume, measured typically as g/cm2

Die

in blown film extrusion, it's the circular orifice where plastic resins are extruded

Die Gap

distance between the metal slits forming the die opening

Die Lines

usually machine direction visual marks on the film caused by contamination blocking a portion of the die opening

Double Wound Sheeting

a singular sheet of poly that is doubled on the roll

Elasticity

the ability of film to recover to its original size after being stressed or deformed

Elongation

the measured increase in length of a film stressed by tension

Erucamide

component of slip additive, which is a fatty acid

Ethylene Vinyl Acetate (EVA)

the random copolymer of vinyl acetate and ethylene

Extrusion

melting of plastic resins and continually pushing it through an orifice

FDA Compliance

In order to have contact with food or drugs, poly must be 100% virgin and meet US Government Specification LP378.

Film

type of tubing, sheeting, centerfold, double wound sheeting and "J" sheeting manufactured by Blako in a blown film process from 1 to 20 mils in thickness

Flame Retardant

additive to base resin that prevents a flame from spreading across the surface of a film. Usually measured by a "self-extinguishing" designation. Used in building and automotive applications.

Gauge

thickness of film measured in thousandths of an inch, known as a "mil"

Gel

small unmelted mass of resin that has not blended into the surrounding film

Gel Shower

several gels or clusters in a mass that are released from a "dirty die" or contaminated resin

Glass Transition Temperature

when a film is heated to a certain temperature and changes from it's cooled "hard" surface to a "softer", more flexible condition

Gloss

measurement of brightness, the result of a smooth surface

Gusset

pleats on both sides of a tube

Haze

measurement of degree of cloudiness of a film. Below 5% haze is considered high clarity.

High Density Polyethylene

any polyethylene ranging between 0.940 to 0.960 or above

Homopolymer

when a single monomer is used for polymerization

J-sheet film

film that wraps around the roll forming a lip on the slit tube edge

Lamination

bonding of two or more substrates using adhesive or heat and pressure

Lay Flat Tubing

continuous tube of film on a roll

Linear Low Density Polyethylene (LLDPE)

poly usually with less clarity but increased strength ranging in density from 0.915 to 0.935

Low Density Polyethylene (LDPE)

poly ranging from 0.915 to 0.925 in density. Monomers used to make LDPE make it relatively soft, flexible with better heat resistance than LLDPE.

Melt Fracture

upon exiting the die, the film appears rough or wavy

Melting Point

the temperature, which a resin changes from a solid to a liquid

Millage

the thickness of film measured in thousandths of an inch

Mono Layer

resin forced through a die from a single extruder

Octene

co monomer used in the production of certain linear low-density polyethylenes

Opaque

colored film that is more solid in color than "transparent" Industry standard letdown of 20

Oleamide

an off-white powder used in slip additives for polyolefin's

Orange Peel

an uneven surface texture of a film surface which looks like the surface of an orange

Pellets

form that resins or mixtures of resins come from the manufacturer, achieved in a reactor which turns a gas into a solid which is chopped into small segments or pellets

Perforated

film that can be torn off a roll easily as a result of a mechanical scoring or serration, process used to manufacture sheets and bags on a roll

Perforating

film that has tack holes or punch holes for surface air release

Photo degradation

the degradation of film due to its over exposure to light.

Polyethylene

a type of resin made from the polymerization of ethylene gas

Polypropylene

resin made from the polymerization of propylene gas, has stiffer and higher temperature properties than polyethylene.

Process Aid

additive used as a modifier to aid in the extrusion process.

Resin

synthetic or natural polymer that is melted and extruded, Blako utilizes only in the "blown film process"

Sheeting

one layer of poly film on a roll

Shelf Life

all poly products have a length of time that they will maintain physical properties before they begin to deteriorate, specific conditions of storage impact "shelf life"

Silica

used as antiblocking agents in resins or as an additive with resins, composed mostly of silicon dioxide

Slip

additive which makes the surface of film more lubricious, reduces the coefficient of friction, migratory properties enable the slip to "bloom" to the surface

Slitting

in "blown film extrusion", knives are inserted in line to reduce the width of a tube or sheet

Tear Resistance

the measurement of the resistance of a film when a force is initiated at the edge to create a failure

Tensile Strength

measurement of a film in a tension test measuring maximum tensile stress before failure occurs.

Titanium Dioxide

a white powder in crystalline form commonly in white color concentrate

Treater

in line equipment on blown film extruders that microscopically rough up the surface to make inks, coatings, and adhesives more receptive

Virgin Resin

any plastic resin that has not been previously used except for its original intent

Wrinkle

a folded crease in film, considered an imperfection