When polypropylene POY yarn is subjected to stretch treatment, the total breakage rate? The problem might lie in these two indicators. 

polypropylene POY yarn (pre-tensioned yarn) is a semi-finished product of polypropylene filament yarn. It needs to undergo filament drawing or stretching processing to achieve the final performance. Many purchasers often encounter confusion when selecting types: for the same POY yarn, some have more broken ends during filament drawing, while others have uneven fineness after stretching. Below, starting from two common problems, we will help you clarify your thinking. 

1. Fineness and elongation: Where does the root cause of the broken ends of the yarn lie? 

The uniformity of yarn structure and the CV value of elongation are two key indicators for evaluating the quality of POY yarns, which directly affect the smoothness of the subsequent drawing process and the quality of the finished DTY. 

Evenness of yarn (CV value): Uneven yarn can cause significant tension fluctuations during the subsequent drawing process, leading to the generation of fuzz or uneven dyeing. The smaller the CV value, the more uniform the thickness of the yarn in the length direction, and the lower the breakage rate during drawing. When purchasing, you can request the supplier to provide a yarn evenness test report and pay attention to the control level of the CV value. 

Elongation and its CV value: The elongation of POY filament is usually around 120% - 150%. Excessive or insufficient elongation will affect the matching of subsequent stretching processes. The CV value of elongation reflects the amplitude of elongation fluctuations within the same batch. The smaller the value, the more stable it is, and the smaller the tension fluctuation during subsequent processing, the fewer lint and breakage will be. Ningbo Dazhong Industrial Fibre Co., Ltd. was founded in 1984. It produces 15,000 tons of polypropylene POY filament, polypropylene FDY filament, polypropylene strong filament, and polypropylene colored filament annually. It has routine testing capabilities for properties such as yarn fineness and elongation. 

II. Coiling Forming and Uncoiling Properties: A Guarantee for Smooth Production 

The winding quality of POY filament directly affects the smoothness of unwinding on the drawing machine. It is an aspect that is often overlooked but is actually very important. 

Roll hardness and end face flatness: If the POY filament rolls are too hard, the tension of the filament during unwinding will fluctuate greatly; if they are too soft, they are prone to sagging or coming off the reel. Rolls with poor end face flatness are likely to have filament cross-over or layering during high-speed unwinding, resulting in breakage. When purchasing, it is recommended to request samples for on-machine trial use to observe whether the unwinding is smooth, and whether there is any sagging or tension fluctuation. 

Oil content and static electricity resistance: The oil content on the surface of POY filament affects its bunching property and static electricity resistance. A too low oil content is likely to cause static hairiness, while an excessively high oil content may cause smoke and coking during the subsequent drawing process. The supplier can adjust the oil formulation and content according to your drawing process. 

Summary and Selection Suggestions 

When purchasing polypropylene POY yarn, it is recommended to follow the steps below for confirmation: 

Let's first look at the yarn fineness and elongation data: The supplier is required to provide the CV values for yarn uniformity and elongation for the test report. These are the core references for evaluating the processability of POY yarn. 

Re-examine the winding and forming quality: Check whether the end face of the roll is smooth and whether the hardness is appropriate. If possible, conduct on-machine trial to verify the unwinding performance. 

Finally, conduct a sample trial run: Use it on a small scale on your beam forming machine or stretching equipment to observe the breakage rate, tension fluctuations, as well as the appearance and feel of the finished silk. 

Ningbo Dazhong Industrial Fibre Co., Ltd. was founded in 1984. It produces 15,000 tons of products annually, including polypropylene POY yarn, polypropylene FDY yarn, polypropylene stretching yarn, and polypropylene coloured yarn. The fibre fineness ranges from 68D to 1800D. Please feel free to send samples for testing and discuss the requirements for subsequent processes. 

Official website: http://www.dzfibre.cn