Polyester will feel very differently depending how it is processed (and I am not even talking about the fabric, just the fiber or the yarn).polyester POY
The main difference in feel probably comes from whether it is textured or not. When it is spun, a polyester fiber is straight (or “flat”). The texturation process will make the fiber somewhat curly. Texture polyester will feel more like cotton while flat polyester will feel more like silk.
Another difference comes from the coarseness of the yarn, especially with textured polyester. With flat polyester, the coarseness of the yarn has less impact. Coarse polyester yarn will not feel cold to the touch, while thin polyester yarn will feel colder. Usually, when using thin yarn of textured polyester, the fiber is more textured to compensate. Flat yarn will feel even colder.
Finally, their is the coarseness of the fiber it self. A coarse fiber will feel more “plasticky”, in lack of a better word. On the other hand, thin fibers, especially highly textured microfibers, can feel so soft they will even make cotton feel plasticky in comparison.
Then, there is how you weave or knit it, the finishes, which all also affect how it feels.