The best replacement for cotton is polyester.

The best alternatives to cotton are rated as following:
★★★★★  polyester
★★★  wool
★★  linen
★★  hemp
★★  egyptian cotton
★★  polyester sheets
★  wool suit
★  silica wick
★  sateen
★  polyester thread
★  linen canvas
★  polyester socks
★  nylon flag
★  ekowool
★  wool socks
★  nylon
★  organic cotton
★  microfiber
★  microfiber sheets
★  polyester hammock
  polyester warmer
  rayon
  pima cotton
  silica
  wool pants
  wool blazer
  silk
  cotton polyester blend
  polyester shirts
  pryor
  bamboo sheets
  sateen sheets
  nylon hammock
  fleece
  silk pocket square
  polyester comforters
  acrylic
  synthetic fibers
  bamboo
  cotton
  acrylic socks
  pima cotton sheets
  polyester comforter
  tobacco
  conrad
  regular cotton
  synthetic kt tape
  polyester clothing
  silk sleeping bag liner
  egyptian

Your alternative for cotton is not listed? Suggest!
Speaking about cotton, one probably shouldn't forget about lycra.

Other search terms related to cotton and their ratings are:
★★★★★ lycra
★★★★ polyester
★★ modal
★ linen
★ wool
You have in mind a companion for cotton and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of cotton in all years. Click on graph for more.
cotton
polyester
wool