POY polyester yarn, or Pre-Oriented Yarn, is a professional term in the textile field, used to describe a yarn made of polyester fiber. The following is a detailed explanation:

Definition and characteristics
Definition: POY is a semi-finished form of polyester yarn (Polyester Yarn), the full name is Pre-Oriented Yarn, that is, pre-oriented yarn. It is obtained by high-speed spinning process, and is a kind of chemical fiber filament with an orientation degree between unoriented yarn (UDY) and fully drawn yarn (such as FDY).
Characteristics: POY has a certain degree of orientation and stability, but it has not been fully stretched, so its residual elongation is high, usually above 50%. This characteristic makes POY have high plasticity in subsequent processing and is suitable as a raw material for further stretching or false twisting.

Uses and processing
Uses: POY is widely used in the textile industry and is an important raw material for making textured yarns such as polyester low-elastic yarn (DTY). At the same time, although POY itself is rarely used directly in final products such as knitting due to its unstable shrinkage, it plays an important role as an intermediate link in the textile industry chain.
Processing: POY can be made into polyester low-elastic yarn (DTY) with specific elasticity and shrinkage after further stretching and false twisting. This processing not only improves the performance of the yarn, but also broadens its application field.

Comparison with other yarns
Compared with FDY: FDY (fully stretched yarn) is another form of polyester yarn. Its fibers have been fully stretched, with low residual elongation and good stability. It is suitable for direct use in textile warping processing. In contrast, POY has a higher residual elongation and requires further processing to meet certain application requirements.
Compared with UDY: UDY (unoriented yarn) is the initial product of the spinning process, with low orientation and poor stability. POY is a semi-finished product with a certain degree of orientation obtained by high-speed spinning on this basis.

As a semi-finished form of polyester yarn, POY polyester yarn has an important position and role in the textile industry. Its unique physical properties and processing performance make it an important raw material for making textured yarns such as polyester low-elastic yarn.