We suggest switching to poly strap, with a couple exceptions:

1. Don’t switch to poly strap if you are strapping a high temperature load.  Poly will normally take what nature can throw at it, including sitting in a black rail road car in the summer.  It will not take a round through an annealing furnace, or course.  If you can touch the area the strapping and not jerk your hand away, it is cool enough.  Poly strap can take up to 180 Degrees F, and we have seen some people use it to 200 or even 220 F.
2. Don’t switch to poly strap if the elongation is not acceptable.  Unlike steel strapping, poly strapping stretches fairly evenly along the tension curve.  So at 1/2 tension, you will see 1/2 of the elongation.  With steel strapping, at 1/2 tension, there is 0% elongation.  We notice the elongation on small diameter pipe loads that start as a hex, and will roll with PET strapping applied.  It rolls because the poly will stretch.
3. The simplest reason not to use poly strapping, is if your customer’s packaging spec tells you to use steel strapping.  We expect more companies will require poly strap, but there are still some stuck in old school packaging.  A good website to see all the available strapping and tools is Allstrap (click to link).