Question

Why do some fibres shrink after washing?

Answer 1

During washing, fibers materials (polymers) can react with water and detergent, causing swelling the fibers. The extent of swelling depends on the nature of fibers and the extend of their interaction with water. Natural fibers (e.g., cotton, wool, silk) absorb significant amounts of water and swell a lot, but the interaction of synthetic fibers (e.g., polyamides PA, polyester PET) with water is much less, so they swell much less than natural fibers. The outcome of swelling of fibers in threads is their shrinkage, leading to shrinkage of fabric and cloths.(That is when the fibres swells with water,the fabric shrinks.)