Triexta: Dupont 3GT Sorona is a renewably sourced polymer (contains 37% corn sugar) that offers durability, softness and advanced stain protection built into the carpet fiber. Sorona has softness and stain resistance of PET with the durability of nylon.
Nylon: The strongest of all synthetic fibers, nylon usually lasts the longest and has great resilience. It has great yarn memory and bounces back after being crushed or stepped on. Nylon is very easy to clean and hides soil very well. It is water resistant, so it resists mold and mildew. It also is solution dyed, causing the color to last longer. There are two types - type 6 and type 6,6. Type 6,6 does not fuzz like a type 6 will. Nylon is the most versatile fiber in the carpet industry today.
PET Polyester: This is not the same fiber of 30 years ago. It is less expensive, so the quality is not as good as Nylon or Olefin, but the fibers are soft. Polyester is naturally an dpermanently stain resistant, but is susceptible to wear, matting, and traffic patterns. It repels dust mites, which is good for allergy sufferers. It is easy to clean and won't shrink. Polyester can be recycled over and over, but is best for short term carpet.
Olefin or Polypropylene: The most color fast and natyurally stain resistant fiber on the market. It is naturally water resistant because it wicks moisture. Olefin or Polypropylene is often used for outdoor carpet and in basements. Like nylon, it is solution dyed, so the color lasts extremely long making it good in areas exposed to sunlight. It is not as strong as nylon and does not bounce back as readily, so it may mat where it is repeatedly walked on. This fiber performs best in a very tight or small loop.
Wool: The most expensive and luxurious fiber on the market. Wool is naturally resilient and has excellent yarn memory. It can last 60+ years if it is properly cared for. It is very high-maintenance and needs to be professionally cleaned often. Wool has a resistance to fire, so it will char instead of burn. It absorbs and releases moisture, making it a natural humidifier. It is good for allergy sufferers because it resists dust mites. Because it is so expensive, wool is more popularly used for rugs.
*Disclaimer: some people are allergic to wool.