Spin finish is actually a molecular layer that is applied on the surface of the fibers in order to increase the antistatic properties and create adhesion between the filaments. It is one of the most important parameters affecting the quality of yarn.
Determining the percentage of spin finish on the yarn (Oil Pick-Up) (OPU)
The percentage of spin finish on the yarn has a definite limit and should not be less or more than a certain amount. For example, according to Iranian National Standard No. 925, the acceptable range of oil percentage for FDY yarn, is between 0.7-1.3%.
Therefore, due to the importance of the allowable amount of oil in the yarn, it is necessary to provide a method to determine the percentage of spin finish oil in the yarn.
Video of the steps of performing this test in laboratory of Sirang Company
Following the national standard of Iran, number 925, to determine the percentage of FDY yarn spin finish oil, one can act according to the international standard ASTM D2257.
To determine the spin finish oil percentage, an oil extractor and an appropriate solvent for oil extraction, an Analytical Balance sensitive to 0.1 mg for weighing, and an oven and desiccator to dry samples are used.
Solvents used in this test can be alcohols, halogenated hydrocarbons, as well as substances such as chloroform, tetrachloroethane, ethanol, etc.
In this method, three samples of yarn with a specific weight (about 2 grams) are weighed exactly with an accuracy of 0.001 using an Analytical Balance and placed inside the tube of the machine. Then, using a measuring pipette, 10 cc ethanol is added to each sample in the tube and the oil on the yarn is allowed to dissolve in the ethanol. After that, using a compression rod, the solvent containing the oil is removed from the tube and let be poured on a small aluminum container whose weight has already been recorded and is being heated. This temperature is adjustable and actually causes the solvent to evaporate. The last to remain in the container will be oil.
These steps are repeated by pouring the other two series of ethanol, and at the end, after cooling the container, the remaining oil is weighed.
The yarn sample is also dried in the oven and having the weight of oil and dry yarn, the percentage of oil can be calculated.
The allowable range for the percentage of POY and DTY yarn oil according to the national standard of Iran is 0.25-1% and 1-3%, respectively.