Rayon has most properties of silk and hence it is called artifitial silk. It is similar to silk by both texture and look.
Rayon is an organic fibre ( made from wood pulp ) where as nylon is sompletely synthetic
Rayon is soft, breathable, comfortable and moisture absorbent. This moisture absorbance and softness of the fabric make it ideal for summer wear. This fabric also drapes well.
Nylon is not a natural fiber; it is a synthetic fiber that is made from chemical by-products of petroleum, coal, and agricultural products. It has a low moisture absorbancy rate.
Nylon is often used in stockings, swimwear, sportswear, tents, tires, parachutes, etc. , not the kind of clothing in which one would use natural silk.
Nylon is far too synthetic to resemble silk which is soft and comfortable.