You ll need to use a heat transfer that applies at a low temperature so that the polyester won t scorch.
Heat transfer vinyl on polyester bag.
Because i own the cricut easypress i like to reference their user guide for all of my projects.
These go over the heat transfer during the heat printing transfer and carry out the function of stopping the fabric from scorching of melting.
Then you ll need to order your transfer type or vinyl material in something that applies that low.
Generally around 300 degrees you should be fine but you ll need to see how heat sensitive your polyester is.
What heat settings do you use for a polyester bag.
This means that it is a good idea to use a cover sheet as it will protect your polyester garment.
In this video zoe will demonstrate how to heat press transfers onto bags including a laptop case hydration pack and duffle bag.
Siser heat transfer vinyl can be applied to 600 denier polyester with the lower temperature method explained in this post 280 f for 15 20 seconds and you ll likely want to use a heat transfer pillow or rolled up towel to achieve even pressure.
Another issue to look at is around the cover sheet that you use.