FAQ Glossary

Vision Plastics Glossary

Additives-Materials added to the basic resin to add a specific property. Examples are UVI, color pigment, slip and anti-stat.

A-Frame- Mechanical device for folding film on bag machine or extruder.

Air Ring- Mechanical device used to cool tube of film after it leaves extruder die. Vast technical differences in older designs compared to newest. Design affects both quality and rate of cooling.

Anti-Block- An additive allowing the bag to open easily, or film to unwind without blocking. Acts to roughen film surface. Anti-Stat Additive to dissipate static charge. Works at or above 50% humidity all the time, between 25% and 50% humidity, less effective.

Autoclave Process- Batch type resin making process. Used to produce high pressure low density PE.

A-Wind- A specification pertaining to type of winding of center fold film.

Back Flip- Used as a method for bag closing. (Sandwich bag).

Back Seal-Machine direction seal. Typically on form/fill/seal machinery.

Barrier-Film layer used to block the passage of a vapor, liquid or odor.

Bio-Degradable- Readily decomposed by bacteria, fungi or algae action.

Blends- A mixture of two or more resin to achieve specific film properties in a single layer of film.

Blown Film- The process employed to biaxially orientate a polymer (LLDPE). Physical strength test results in machine direction (MD) and transverse (TD) closer than those gained from other processes (ex: Cast film).

Bottom Gusset-Refers to material tucked into bottom of a side weld bag.

Bottom Seal- Heat seal made across the machine direction (MD)of a tube of film.

Branched Polyethylene- High pressure low density polyethylene (HPLDPE)

Butene- A co-monomer used in gas phase reactors for making linear low
density polyethylene.

B-Wind- A specification pertaining to type of winding of center fold film.

Caliper- Film thickness.

Cast Film- A one direction oriented film. Transverse direction (TD) tear resistance much greater than machine direction (MD). Process employs casting rolls to impart higher clarity than blown film process.

Center Fold- Tubing slit on one edge allowing web to open, doubling its size.

Clarity Film-Usually HPLDPE. Haze values of 3.0 to 10.0.

Cling- Ability of film to adhere to another object. Cling is enhanced with an additive.

Coextrusion- A blown film process with two or more layers of film. Combined during extrusion to achieve special film characteristics.

Color Units- Physical measure of light passing through a color specimen.(opacity)

Co-monomer- Two Polymer resin. (ex: LLDPE, EVA-HPLDPE).

Copolymirization- Process by which two polymers are linked chemically into one polymer chain.

Corn Starch- An additive used in the manufacture of bio-degradable film.

Corona Treatment- Process by which the bonding of ink or adhesives to film is strengthened.

Dart Impact- See impact resistance.

Density-Specific gravity of a molecule compared to water (value = 1.0)
Ex: LLDPE specific gravity = .88 to .930.

Dynes- Measurement of surface tension. Printing and laminating films are generally corona treated to a specified dyne level.

DWS- Double wound sheeting.

EVA- Ethylene Vinyl Acetate. Commonomer used in some HPLDPE resins. Adds strength
and "softens" to help prevent stress cracking.

Extrudate- Molten or plasticized resin.

Extruder- A machine that converts plastic resin pellets by melting, pumping and homogenizing into a molten material. When material passes through a die, a tube or sheet of film is formed.

FDA/USDA Approved-Requirement for food contact packaging.

Flat Bag-No gusset. Uses raised type rubber plates with fast drying liquid inks.

Fractional Melt- Resin with melt index less than 1.0. Used primarily for shrink and skin packaging applications.

Gauge- A measure of film thickness; normally in thousandths of an inch. "2 mil equal .002".

Gravure Printing- Use of an etched metal cylinder to deposit liquid ink on film.

Gusset- See film construction section.

Half Tones- Sometimes referred to as process printing versus line printing. Imparts shades of
color as opposed to solid ink coverage.

H.D.P.E.- High density P.E. made from high pressure or low pressure resin. Stiff and not
very transparent.

Hexene- Co-monomer used in gas phase reactors for making LLDPE resins. Superior physical
properties to butane LLDPE.

HMW-HDPE- High molecular weight low pressure HDPE. Has superior properties to regular high
density P.E. like H.D., has paper "crinkle" feel.

Impact Resistance- Physical strength of film as measured by a dull dart dropped onto a firmly held
specimen of film.

Ink Coverage-Square inches of ink per unit (ex: foot, impression etc.).

J-Sheet- Folded film with unequal sides (legs).

LDPE-Low density polyethylene resin. Refer to tutorial section.

LLDPE- Linear low density polyethylene. Refer to tutorial section.

Machine Direction- (MD) Refers to length-wise direction of film as it is rewound from extruder.

Melt Index- A measurement of resin heat-resistant properties.

Microns- 25.4 microns = .001 inch.

Mils-Thousandths of an inch film thickness.

Monoextrusions-Single layer film.

Monomer- Singular chemical component of resin raw material.

Multi-layer- Film manufactured with more than one layer of material.

Non-abrasive Film- No antibloc used. Requires a dependence on slip to get bags open or film to unwind.

Octene- Co-monomer combined with ethylene to produce some LLDPE products (Dowlex & Attane)

Off Grade Resin- A material with properties not meeting prime specifications. Will not give uniform results lot-to-lot.

Pantone Matching Systems (PMS)- A swatch method of specifying ink colors.

Photo-degradable Film- A degradable plastic in which the degradation results from the action of natural daylight.

Pigment-Additive blended with resin to achieve color.

Polymer- A combination of more than one monomer.

Polymerization- The process of combining monomers.

P.O.R.-Perforated on roll.

Prime Resin- Highest level of resin consistency. FDA Approved.

Random Print- Print copy on film not requiring specific location.

Reactor- The machine in which a monomer is polymerized.

Registered Print- Print copy reproduced in same location on each bag.

Repro- Resin made from repellatized film scraps.

Reprocessed Film- Film manufactured from reprocessed resin.

Resin- Product of a reactor. Raw material used in extrusion process,
Example: HPLDPE, LLDPE, etc.

Shrink Film- Manufactured with a specific resin to react to heat.

Side Weld- A seal running perpendicular to the bottom. Accomplished the same time the bag is cut to length.

Single Wound Sheet (SWS)- A single layer of film wound on a roll.

Skirt- The material below the bottom seal.

Sleeve- A continuous tube cut or perforated at a specific length.

Slip- A fatty like additive that migrates to the surface of the film reducing the coefficient of friction. The ability of the film to "slide" aids in subsequent processing.

Star Seal- A seal across multi folds of film which would produce a narrow gathered bottom when bag is opened.

Stretch Film- Manufactured to elongate and then retreat to cling to one or both sides. No heat required.

Tear Resistance- An industry test to determine film strength.

Tensile Strength- The ultimate force in square inches it takes to break a sample.

TD- Transverse direction (perpendicular to web or machine direction)

Thermo Plastics- Resins which melt under heat.

Thickness- See gauge.

Tint- A gradation of film color.

Treated Film- A process that enhances the film's surface to bond with ink or adhesives. See "Corona Treatment" definition.

Tri-extrusion- Three layers of film extruded and blended in one process.

Tubing- The most common form of film from blown extrusion.

U-film- Blown film tubing which is gusseted and cut in the gusset or otherwise manufactured to produce a flat face width of film with wings of the same or unequal width folded back.

ULDPE- Ultra low density polyethylene. Specific gravity of .880 to .915. High seal, tear and puncture strength. Excellent cold temperature performance.

UVI- Ultra-violet inhibitor. Additive designed to absorb ultra-violet light, preventing film strength degradation.

Vapor Barrier-A layer of film designed to retard or stop the passage of moisture.

VCI- Volatile corrosive inhibitor. A moisture absorbing additive not effective in all circumstances.

Viscosity- A measure of resistance to free flow.

VLDPE- See ultra low density polyethylene.

W-film- A specification pertaining to type of rewinding. A gusseted tube slit entirely through the center of the tube would yield two lanes of w-film sheeting.

Wicket- U-shaped wire holding 250 to 500 bags in a high speed packaging operation.