Partially oriented yarn(POY): partially oriented yarn is a continuous straight multifilament yarn with no twist. Since yarn is wound on to the at a high speed, this orients the molecular chains. this is the reason it is called POY.
Partially oriented yarn is produced from the melting and extrusion (melt spinning) of the polyester chip or flake. During the spinning process the filaments are stretched or drawn as much as five times their original size to orient the polymer to meet the desired evenness, strength, shrinkage, and elongation properties. So the term partially oriented yarn refers to multi-filament that is only partially stretched