Plastic Strapping Quality Terms

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Gauge:

The thickness of the strapping material expressed in inches.
"Nominal" refers to the target thickness.
The "maximum" and "minimum" establish the tolerance or "leeway for variation from a standard."
Example: 0.016" + or - 0.002"

Polypropylene Strap and Polyester Strap Width:

Break Strength:

The level of strength in which a strap will fail when pulled apart (expressed in pounds).
"Tensile Strength" is the resistance of a material to a force tending to tear it apart.
This value is properly determined using a tensile tester
Break strengths vary according to product gauge and widths.

Slip (Surface Friction):

Proper lubrication enables the poly strap to slide easily around an object, corner, or on the strap itself.
Strap surface friction (or slip) is expressed in Newton or Meters.
Polypropylene Strapping Sheet Products: Maximum 10 NM, Minimum 3 NM.
Polyester Sheet Products: Maximum 10NM, Minimum 4 NM.
A lower number means a more slippery strap surface.

Slip (Surface Friction): Referring to Polypropylene Strapping

A slip additive is mixed with virgin PP pellets in the extruder. Finished coils of PP strap dwell in a chamber heated to 120 degrees for 48 hours. This causes the additive to "bloom" thereby providing proper surface friction.

Slip (Surface Friction): Referring to Polyester Strapping

Polyester surface friction is achieved by applying a coating of wax to the sheet. After annealing the polyester sheet is immersed into a wax/water mixture just before it is and wound onto a "slip spool."

Flame Treatment: Polypropylene Strap

Both sides of the sheet are exposed to flame treatment which "de-orients" the surface of the strapping material. This is needed to assure a good friction weld seal by reducing hairs and filaments that would otherwise interfere with the welding process.

Split:

Characteristics that enable a strap to resist lengthwise splitting.
Spit sensitive strap can get hung up in chutes, jam feed wheels, or not weld properly.
Polyester strap sheet specification: 1 of 10 split samples will be no more than 1 inch in length.
Polypropylene sheet specification: varies according to the width of the strap.

Elongation:

The increase in length of a poly strap stressed in tension.
The Signode test uses a tensile testing machine that stretches the strap until it breaks.
Elongation is expressed as a percentage at break.
Polypropylene sheet elongation specification is 20% to 40% with a nominal of 30%
Polyester sheet products have lower nominal elongation compared to Signode polypropylene. Depending on the strapping product, the elongation range is 10% to 25% with a nominal of 14%.

Camber:

Camber is the characteristic of strap that, when laying on a flat surface, curves continuously to one side.
Excessive camber can cause miss-feads, and improper welds.
Polypropylene strapping should not exhibit camber of more than 6 inches in an 8 foot sample.
The specification for "Thin Strap" polypropylene products is 10 inches in an 8 foot sample.

Curl:

Curl is the characteristic of strap that, when laying on a flat surface, curves upward.
Polyester sheet strap has a curl specification of 0.5 to 7.0 inches of curl in a 4 foot sample.
Polypropylene sheet specifications vary by product.

Edge Condition:

Sheet strap is slit into the finished width. A slit strap that is rough, ragged, or has "hair-like" filaments may cause miss-feeds and excessive dusting.

Weld or Joint Strength:

The level of strength that a weld will fail when pulled apart.
Sheet strap weld or joint strength values are expressed in pounds
Signode specifications satisfy A.S.T.M. minimum requirement for strapping material (at least 45% of the minimum break strength of the strap).

Pulldowns:

Pulldowns refers to straps that have "pulled down" between the side of the coil and the dispenser wall. This may be caused by improper winding tensions, a "saddled" or otherwise miss-wound coil, or improper setup of the coil on the dispenser.

Miss-Wound:

Miss-wound refers to coils that do not have a uniform winding pattern.
There are a number of examples of miss-wound coils that may cause pull-downs, short feeds, miss-feeds

Crushed Cores:

Crushed cores is the result of miss-handling of strapping materials. Dropping strapping coils or tipping over full skids of material will cause the paper cores to crush, making it impossible to set the coil up on a dispenser.

Delamination:

Delamination is a condition that occurs in polypropylene strapping products whereby the strap peels apart.
Delamination is more likely to occur when black concentrate is added or when exceedingly high levels or "regrind" are included in the mix.

Scuff:

Scuff is a defect caused by insufficient flame depth that becomes evident when strap passes through the feed-wheel system of a power strapping machine.