Satin sheets are not always silk

Satin sheets are constructed using a fabric made by the satin weaving method, one of the three basic textile weaves, that has no strong diagonal line. The fabric is smooth-faced, with an unbroken surface made up of long floating warp yarns. Satins are susceptible to the wear caused by rubbing and snagging so they are luxury fabrics. The finish is achieved by heat treatment, resulting in fabric with a high sheen face and mat reverse side. Satin sheets are sometimes but not exclusively made from silk, modern alternatives include rayon.

Silk satin sheets go way way back

Silk was discovered in China before 2700 BC. James I of England introduced silk growing to American colonies around 1619, to discourage tobacco planting. World War II interrupted silk trade with Japan, silk prices went sky high and the US turned to synthetic substitutes, which lead to the use of synthetics like nylon.  Nylon and other synthetic fibers have replaced silk in many applications but silk remains an important luxury material for clothing and satin sheets. More than half of the world's silk is still produced in China.
Nylon & synthetics used in satin bed sheets production lowers cost

Nylon was developed by Du Pont in the 1930s and production of a useful fiber by chemical synthesis from compounds readily available from air, water, and coal or petroleum and lead to even more synthetics for satin sheet production and lower prices. This has produced the variety of satin fabrics used in the satin bed sheets that are available today.
Live it up try satin sheets

It is important to read the satin sheets specification closely as fabric type and weight vary from one satin bedding manufacturer to another. Satin sheets are appealing because they are different from "ordinary sheets". satin bedding like satin comforters, satin bedspreads, satin duvet covers all are smooth and sexy to the touch, so live a little try satin, you can treat satin bedding like grandma's china and use it for those special occasions!