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Stretch Film Terminology

39 common stretch film terminology mistakes by crawfordpackaging.com graphic.

39 Common Stretch Film Terminology Mistakes

Banding

Applying multiple wraps of stretch film to reinforce a specific area of a pallet or to band together multiple units.

Blown Film

Stretch films manufactured by the blown film extrusion process are called blown films. Stretch film extruded by the blown method typically produces greater puncture resistance but less aesthetic values than cast films.

Bottom Wraps

The rotations a stretch wrap machine makes applying stretch film to the lower portion of a unitized load. Bottom wraps of more than one rotation help pallet stability.

Cast Film

Stretch films manufactured by the cast film extrusion process are called cast films. Stretch film extruded by the cast method typically have greater tear resistance, greater aesthetic values and are quiet to unwind, which is not typically found in film manufactured by the blown method.

Cling

Cling provides the sticking to self but not to the product attribute. Films will be designed as a single-sided cling or a two-sided cling. The cling bonding agent is typically added in as a single-sided or two-sided layer in the co-extrusion process.

Co-extrusion

Co-extrusion is the process of taking materials that are; fed, melted and or pumped in through other extruders, which are then merged to create a multi-layer film.

Dart Drop

A technique used to measure the impact strength or sturdiness of a film; this is tested by dropping a crescent shaped weight (aka dart) onto a film.

Elastic Recovery

When the stretch film is stretched, strained and / or deformed; its ability to recover and return to its original form indicates its elastic recovery capacity.

Elmendorf Tear

A testing means for measuring a material’s ability to resist tearing forces. This method creates a tear in a sample material, then measures the amount of force needed to tear the sample apart. Test result value is referred to as the tear value.

Extruder

A piece of equipment that uses mechanical and thermal actions to change solid polymer into a molten polymer.

Extrusion

A manufacturing process that takes materials from one or more extruders, the resulting extrudates are then configured to the fabrication of the end product.

Film Feed

The speed at which the film is supplied to the load is the film feed. Film feed rate adjusts as needed on load corners to maintain consistent film tension.

Film Force

As the film is applied the rate of tension in the film is called the film force or film tension. The rate is usually measured in pounds.

Film Memory

Is the memory of the stretch film trying to return to its original un-stretched form and in the process makes the load tighter and more consistently secure. This prevents loosening of the load that can occur later as the load settles. To achieve optimal film memory and film efficiency, proper film and application settings are essential.

Film Tail

The film tail refers to the start and end pieces of stretch film that are initially applied and then later cut off from a pallet in the stretch wrapping process.

Gauge

An imperial measurement used to measure stretch film thickness or caliper. An example value would read as: 70 gauge, 80 gauge or 100 gauge. Also note: Often used as a synonym for film thickness.

Gloss

Refers to a surface’s shine or sparkle. In LDPE stretch films, it refers to the amount of light that is reflected from the stretch film’s surface. High gloss attributes are typically found in cast stretch films.

Hand Film

Hand stretch film that’s used for manual stretch wrap packaging application. Designed for hand wrapping application, hand film rolls are lighter and smaller than machine film rolls to make application easier. Also known as hand wrap, hand stretch wrap and hand stretch film.

Haze

Refers to lack of clarity or the inability to see through a film. It is measured by the percentage of light not transmitted through a film sample. It is a typical characteristic of blown stretch films.

Impact Strength

The capability of a stretch film or other material to defy rapidly applied destructive forces.

LDPE Stretch Film

Stands for Low Density Polyethylene Stretch Film.

LLDPE Stretch Film

Stands for Linear Low Density Polyethylene Stretch Film.

Machine Direction

Refers to the direction perpendicular to the film width. Acronym: MD.

Machine Films

Is stretch film designed specifically for stretch film equipment.

Metallocene

New polyethylene resins developed using “Metallocene” change the polyethylene chain structures resulting in a new breed of stretch films. Metallocene stretch films can achieve increased puncture resistance and clarity while blends offer balanced film properties and universal stretch percentage applications (ex. machine film, hand film).

Microns

Microns is a metric measurement used for measuring film thickness. One micron is equal to one millionth of a meter.

Neckdown

Neckdown is when a film loses its dispensing roll width / breadth and narrows down while being stretched. Neckdown reduces the coverage each wrap provides, thereby making it likely that more wrap rotations and more film will be needed to wrap a load or pallet.

Overwrap

Refers to the amount of stretch film applied over the top of load. Overwrap provides a downward force on a pallet load and is often used to secure a pallet top sheet or corrugated top cap in place.

Pallet Covers

Poly film covers commonly used to protect pallets from dirt, dust and/or conceal pallet contents.

Poststretch

Poststretching is stretching a film by using the load to pull the film out at the same time as it applies film. Although this allows for the benefit of film tension, the tension levels are inconsistent and, as such, can damage many load types. Attempts to attain higher tension stretch can be done but can increase risk of damaging some load types and increase chances of stretch film breakage.

Prestretch

Prestretching is stretching the film prior to application. The process can increase film strength, improve load integrity, reduce amount of stretch wrap film needed, and save on stretch film packaging costs. Today many stretch films are designed to achieve optimal prestretching values that can be attained with leading-edge high performance stretch wrap machines as well as prestretched films for manual application operations.

Roping

The process of bunching the stretch films full width to create a rope. Stretch film roping is extremely strong and is often used to further secure a pallet to its load. Bunching stretch film is a feature function of many stretch wrap machines (ex: turntable stretch wrappers).

Tackifiers

Additives used in the material fabrication process to increase the “tack” of the film or material. Also see: Cling Tear.

Resistance

Refers to the resistance of the film to tear. This attribute is quantified by measuring the force needed to propagate an initiated tear.

Tensile Strength

Tensile strength is a measurement of the maximum amount of force a material can take without breaking. The greater the tensile stretch measurement, the stronger the material.

Tension Stretch

Tension stretch is a pulling force that stretches materials. For example: stretching a rubber band will make it longer because, as it gets longer, its tension increases. Also referred to as poststretch.

Transverse Direction

Refers to the direction across the stretch film web. Also referred to as TD.

Wide Web

A specialty sized large film roll designed for equipment that wrap using larger widths.

Yield Strength

The amount of stress a material can withstand without permanently having plastic deformation. Prior to reaching the yield point a material will elastically deform but will return to original shape once the stress is removed.

Zippering

Refers to the lack of resistance to of an initiated TD tear or cut. Once initiated, the tear will rapidly spread.

 

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