Any fabric can be expected to shrink about 1 to 3 percent. Manufactured fibers will shrink the least, and natural fibers the most. When buying RTW, the shrinkage of natural fibers is often controlled during the manufacturing process, by washing and preshrinking the fabric before it is made into a garment.
Knit fabrics in particular tend to shrink more than woven fabrics do. I tend to launder these twice before cutting out a pattern.
Natural fibers which are not preshrunk, and some manufactured fibers such as rayon and acetate (both of which are made using natural plant matter as part of their ingredients) can shrink significantly...even several sizes.
Generally, preshrink your fabric in the same way that you expect to launder the finished garment. Laundering it once should be plenty as 90% of its shrinkage takes place in the first laundry (washer/dryer) cycle. (With the exception of knits -especially cotton or rayon knits - which should be laundered twice.
If you are unsure of the fibres in a fabric, you can do a burn test. Generally, synthetic fibers ( like polyester) melt whereas natural ones burn and leave ashes. Combinations of fibers can act like one type, the other, or neither. There's an excellent burn test chart here.
The table given below shows the comparison of only the characteristics of few fabrics. For example, water retention is very high in cotton and the lowest in polypropylene. Same with the drying time, it's very long in cotton and vice versa in polypropylene. Cotton and wool shrinks more than polyester and nylon.
|Heat Conduction (Wet)||High||Low||Low||Low||Medium|
|Comfort Level (Dry)||High||Medium||High||Medium||Medium|