Why is polyester often added to cotton cloth, even if only in tiny few percentage quantities?

Question

I often see on clothes, bags, sheets, etc. a few % of polyester in the cotton cloth label. What does this mean and why do they do it? Are they weaving one out of every few strands out of polyester? Or is the fiber itself made of a few % polyester in composition? And what does it do for the cloth?

In: 1242

Answer 1

As an aside from this conversation, is there any way to re-stretch a cotton shirt that shrunk when it was washed in hot water, back to its original size?