Terms in this guide:

PPY=Polypropylene Strapping-normally has a textured surface but Signode makes their PPY smooth. PPY can be tested by attempting to crack it lengthwise. If it cracks it is PPY.

PET=Polyester Strapping=smooth surface and a hard material. cannot be cracked lengthwise.

Joint=Joint efficiency. Expressed as a percentage of the available strap strength. IE 50& means that the joint will be 500 pounds on 1000 pound break strapping.  A joint is always the weakest point in a strap.

Smooth sealer=My term for a poly strap sealer designed to be used on strapping seals that are smooth inside. Sealer will close the seal tightly and make a series of points or indentations into the top of the seal. The textured surfaces of the PPY strap tend to nest together making a good joint.

Offset sealer=A sealer designed to be used with the serrated seals. Called offset because the jaws are longer on one side of the sealer than the other which is necessary due to the shape of the serrated seals. Sealer will tightly close the seal and make a series of lines across the seal. More importantly it causes the teeth inside the serrated seal to bite into the strap.

Facts:

1. Using smooth seals with PPY strap and a smooth sealer will yield seal joint averages of 50%.

2. Using serrated seals with PPY and the offset sealer will yield seal joint averages of 65%.

3. Using serrrated seals with PET and the offset sealer will also yield seal joint averages of 65%.

4. Using smooth seals with PET strap and a smooth sealer will yield seal joint averages of about only 25%. The culprit is PET straps hardness.  PET's "harder" surface does not permit the diamond points of the smooth sealer to really bite into the surface of the strap under the seal. The smooth slippery surface on PET also contributes to the problem.

5. Using serrated seals and the offset sealer on PPY strap will yield a seal joint in the 65% area. This could result in a money savings by using serrated seals on PPY. As an example, a customer using 600# PPY and smooth seals would have a joint efficiency of 50% or 300#.  Using 500# PPY strap sealed with the serrated seal yields a seal joint efficiency of 65% or 325#. The savings of going to the 500# PPY strap could more than offset the cost of a new offset sealer and serrated seals and still gave a better joint efficiency.

6. Seal joint efficiency remains fairly constant for these two systems.  The PPY seal system would yield 50% of the strap break strength on 1/2 x 300# strap or 50% on 3/4 x 1050# strap. The same would hold true on PET strap using the serrated seal system. You would get 65% on 1/2 x 600# strap as well as 65% on 5/8 x 1400# strap.

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