tear away backing for poly blend polos

With simple tear away backing we had bad experiences on light weight dry fit polos. We use Filmoplast (self-adhesive tear away) from Gunhold for lower stitch counts and a cut away for higher. An Iron-On Tear away should work too (on lower stitch counts).
It is important that these stretchy fabrics are not moving on the backing. You need to bond backing and fabric together. You can use spray adhesive + normal backing, self-adhesive backing or head adhesive backing. If the fabric is hooped and you can rub with your finger on the fabric without moving it on the backing, it should be ok. But try to avoid large fills and high stitch counts if you use tear away.

If possible, we always try to use an applique for larger areas. It adds stability and reduces the amount of stitch.

The problem with most tear-away backing is that the emphasis is on the tear-away, rather than the backing!

In other words, it helps with speed of production but is almost useless for providing stability as the stitches destroy the material with the first pass of stitching. If you have a filled area and then an outline (almost 100% then!) there is nothing keeping the first embroidery in place.

Often you will see embroiderers using mulitple sheets in different orientations (most tear-away has a tendency to rip in one direction), just to overcome the limitations, but this becomes expensive and self defeating.

The truth is that there isn't a great deal of research done into such things. Most backing is simply standard interlining used to stiffen fabric for tailoring and has been adapted for use in embroidery.

Ideally, you need to get a lot of samples from these companies and to test for stability, whether to tear or cut, and laundering. The last one is particularly important and often overlooked as it's no good producing fabulous embroidery if the first time the garment goes in the wash it is all distorted by the backing shrinking!

Finally, the quality of the digitizing has a bearing too, as many digitizers have no idea how to correctly sew a design. The backing stitches serve many purposes and one of the most important is to secure the cloth to the backing. This needs to be done first, rather than a section at a time, otherwise it is almost useless. Unfortunately, a good number of computer programs don't do this automatically and digitizers become lazy relying on the automatic fill. Have a word with your digitizer and get them to punch your designs properly!