Imperfection Index of Yarns

IPI (Imperfection Index)
Engr. Monirul Islam Shaikat
Dept. of Textile Engineering
Ahsanullah University of Science & Technology (AUST), Bangladesh
Email: shaikat6163@gmail.com





Imperfection Index:
IPI stands for Imperfection Index of yarns , Imperfections is the description for thin, thick places and neps in 1000m of yarn . Evenness Tester is required to calculate the IPI of yarns with the results of different yarn evenness parameters.It is a fault of yarn.
Imperfection Index of Yarns
For ring spun yarn imperfections in the yarn refer to the total number of thin places (-50%), thick places (+50%) and neps (+200%) present per 1000 metre of yarn.

For rotor spun yarns the number of (+280%) neps per 1000 meters of the tested yarns is considered instead of +200% neps.
  • A thin place of -50% mean the cross-section of the yarn at the thick place is only 50% of its mean cross section or less.
  • A thick place of +50% means the cross-section of the yarn at the thick place is 150% of its mean cross section or more.
  • +200%Neps indicates the cross-section at the nep is 240% of the mean cross-section of the yarn or more.
  • +280%Neps indicates the cross-section at the nep is 280% of the mean cross-section of the yarn or more.
Imperfections can both be the cause of ends down in downstream processing and also make a disturbing appearance in the fabric.The less imperfections in the yarn, the better the appearance of the fabric.

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