Subdivision of protective film products

I remember tireless (N) materials are divided into PE, PET and D categories. Polyester tire (PY) materials are divided into PE, S and D categories. What does this mean?
First, look at the tireless (N) category. The PE and PET in this material are both single-sided adhesive materials, that is, the lower surface is a removable silicone-coated isolation film, and the upper surface is made of PE film or PET film. Among them, PE The performance index of the film will be slightly higher than that of PET film, while the D type is double-sided without tire lining, and the top and bottom are coated with silicone isolation films.
What about PE, S and D types of polyester tires (PY)?
The principle is similar. PE and S are both single-sided adhesive materials. Similarly, the lower surface is a silicone-coated isolation film that can be peeled off, and the upper surface is PE film or fine sand (S). Type D is also double-sided adhesive, that is, the upper and lower surfaces are both sticky. It is a silicone-coated isolation film.