Terminology

Shrink Films
Orientation is employed in the films manufacturing process that make the films shrink significantly with application of heat.


Film Types

Polyolefin (POF)

POF is a general term to describe films which is Polyethylene and / or Polypropylene based films. By a special manufacturing process, co-extrusion, a POF films could consist different materials (PP or PE) layers.


Polyethylene (PE)

PE is a simple thermoplastic polymer of ethylene. Each molecule consists of thousand of carbon atoms. The characteristics of the film is determined by the length of molecules and the amount of side branching, i.e. LDPE, LLDPE, HDPE, etc.


Polypropylene (PP)

PP is a thermoplastic polymer of propylene. PP materials are generally oriented, heat-set (OPP) materials which do not shrink.


Polyvinyl Chloride (PVC)

PVC is a thermoplastic material composed of vinyl chloride. Vinyl chloride is a colorless solid material which is resistance to water, alcohol and concentrated acids and alkalis. With the help of plasticizers, PVC is famous film widely used in the packaging.


Single wound Film

A single layer of film wound around a core is called single wound film. It is generally used on automatic form-fill-seal equipment.


Centerfold Film

A film folded in half lengthwise then wound around a core is called centerfold film. Product is inserted between the folded film and then a heat seal the 3 edges. This kind of film usually used in semi-automatic or automatic and manual packaging equipment.


Core

A tube made by paper and the film is wound around it. Normally the core inner diameter is 3”. 


Gauge

Gauge is a thickness measuring unit term. One mil is equal to 0.001 inch and 100 gauges are equal to 1 mil thick. Therefore, 1 gauge is equal to 0.00001inch.


Monolayer Film

Several raw materials (resins) are used to form a single layer of film by extrusion.


Multilayer Film

A film formed by a multilayer of polymers. The multilayer film obtains different properties depending on which polymers (similar or different) are used to compose the film.


Ballooning

When the shrink film exposed to hot air, a pillowing effect created. Air trapped by the film expands when heated and slowly escapes through the air evacuation holes. An even shrink achieve. 


Pin-perforated Air Evacuation Holes

Pins are installed on a rotating roller on the machine. When the film is passed through the roller, the pins will perforate the film to form the air evacuation holes.


Machinability

A term that indicate the ability of the film to form, fill and seal on wrapping equipment.


Co-extrusion

Two or more polymers extruded and combined in a die, each forming a distinct layer in the final film.


Cross-linking

The polymers chains form into a network which significantly increases the strength of the film. Processes that allow the polymers chains to form a network is called “Electronic Beam Cross-linking”. 


L-sealer

A general term which describe any automatic, semi-automatic, or manual trim-sealing equipment with the seal bars are arranged in an “L” shape. 


Sealing Wire

A sealing wire is used to melting or fusing two layers of a shrink-packaging film together.
Normally, sealing wire is a circular wire heated by its resistance to electrical current. Nickel chrome is commonly used to compos the seal wires and with a diameter from 0.018 to 0.3 inches.


The following terms is used to describe the packaging problems 


Dog Ears

Triangular projections of shrink film at the corners of the bag. It is caused by too large shrink film bag or incomplete shrink of the shrink films.


Fish Eyes

  Scalloped surfaces occur on the shrink-film package. It is caused by incomplete shrink of the shrink films.


Crow’s Feet

  Series of wrinkles radiating out from the corner of an over wrapped package. It is caused by incomplete shrink of the shrink films.


Angel Hair

  Some very thin stands of film appearing between the cut end of the film and the packaged item.


Burn Through

  A cloudy appearance or burns through of the shrink film after passing though the shrink tunnel. 

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