After the material and type of yarn, another characteristic that actually expresses its delicacy and in other words determines the thickness of yarn is linear density.
Determining the linear density of polyester yarn
The existing practical standards in determining the linear density of yarn in the form of skein are the international standard ASTM D1907, ISO 2060, and the national standard of Iran No. 28.
Video of the steps of performing this test in the laboratory of Sirang Co.
The devices used to determine the linear density of yarn include a wrap reel machine and a digital balance with a sensitivity of one milligram.
To determine the linear density of yarn, it is necessary to have a certain length of yarn, which is obtained using a wrap reel machine.
This machine consists of a regular metal hexagon with a circumference of 1000 mm or 1 m. It also has a mechanism that prevents the layers of yarn from becoming entangled. The number of turns of the wrap reel machine is also adjustable, so the prepared skein with a certain length is weighed with a digital balance, and having the length and weight of the yarn and the existing relations, the linear density can be calculated. For example, a skein with length and weight of 100 m and 0.831 g, respectively, has a linear density of 83.1 dtex.
According to the national standard of Iran, the allowable range of the linear density for FDY and POY yarns with <99 and ≥99 deniers is up to ±2.5% and ±2%, respectively. While it is ±2.6% and ±3% for dope-dyed DTY yarn with <100 and ≥100 deniers, respectively.