You can do a google search and find many different types of mylar. It is used in many different applications, including hydroponics, food packaging and gift wrap to name just a few.
DO NOT BE FOOLED
It is not, and never has been manufactured for the use of Embroidery Designs. I see all these sites offering Iridescent Embroidery Design Film, or Mylar Embroidery film – There is no such thing. You can call it what you like, but basically it is a type of polyethylene Terephthalate film commonly called PET film or mylar, which apart from food packaging and hydroponics is used a lot for gift wrap. Mylar is a brand name manufactured by Dupont. I was recently advised by a customer that the opal film I am selling is not the "true Mylar" but polypropylene. This is not the case. I have obtained the Material Safety Data Sheet from the manufacturer and it is a polyester film. Whatever it is, I know it works. The manufacturer I purchase from markets it as mylar and invoices me as mylar. To avoid any confusion and until I can prove or disprove this fact, I have removed the word Mylar from all my items in my webstore. I still stand by my product regardless, and am sure if you ask any of my customers they will attest to its suitability for embroidery designs, even though it was never intended for this purpose, but is in fact a gift wrap.
I have done quite a few test stitchouts and washed in the washing machine, dried in the dryer on low heat and ironed under a clean dishcloth and the film is not effected. I do not recommend high heat or dry cleaning. Do not iron directly on the film.
This is all the same sheet of opal film, just laid over different surfaces, the first two crinkled up over white and then black fabric, the third over a white tablecloth, the fourth over a red lace doily and the last over a hand. You can click on the pictures and it will take you to the photo gallery where you can see the images much larger