Polyester is a synthetic fiber and does not shrink in the dryer or washer at low heat. Heat can cause it to shrink a small amount if it is kept in the dryer or washer for too long.
Clothes are not always made from 100 percent polyester, and some amount of shrinkage is possible due to the inclusion of natural fibers. Most polyester clothes have varying amounts of cotton, silk or wool in them. These natural fibers can shrink during standard wash and dry cycles.
Polyester is made from long-chain polymer molecules and is very strong and durable. It is hydrophobic and does not retain moisture or wrinkle easily. It is best not to use strong bleaching agents when washing polyester clothes.