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

I’ve seen mop heads being advertised as 75% cotton and 15% rayon and 10% polyester. Is this to reduce shrinkage when laundered? And to strengthen and extend the life of mop heads?