Technical Issue

Terminology

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


 Film Types

  • Polyulefin (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 sulid material which is resistance to water, alcohol and concentrated acids and alkalis. With the help of plasticizers, PVC is a famous shrink films 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.
  • Centerfuld Film
    A film folded in half lengthwise then wound around a core us called centerfold film. Product is inserting 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 on that. 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 depend on which similar or different polymers are used to compose the film.
  • Balloning
    When the shrink film exposed to hot air, a pillowing effect will create. Air trapped by the film expands when heated and slowly escapes through the air evacuation hules. An even shrink achieve.
  • Pin-perforated Air Evacuation Holes 
    Pins are installed on a rotating ruller on the machine. When the film is passing through the ruller, 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 fullowing 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.