# K value according to Fikentscher

The K value , also known as intrinsic viscosity, is determined by measuring the viscosity of polymer solutions and is often used in the technical field to determine the molar mass of polymers such as PVC . Under constant measurement conditions, with regard to solvent, solvent concentration and temperature , the K value is only dependent on the mean molar mass of the polymers examined. It is calculated using the relationship K value = 1000 · k according to the Fikentscher equation, in which: = relative viscosity (dynamic viscosity of the solution / dynamic viscosity of the solvent) and c = mass concentration of polymer in the solution in g / cm³ . ${\ displaystyle {\ eta} _ {r}}$ ${\ displaystyle K = 1000 \ cdot k = 1000 \ cdot {\ frac {1 {,} 5 \ lg {\ eta} _ {r} -1 + {\ sqrt {1 + ({\ frac {2} {c }} + 2 + 1 {,} 5 \ lg {\ eta} _ {r}) \ cdot 1 {,} 5 \ lg {\ eta} _ {r}}}} {150 + 300c}}}$ ## literature

1. DIN EN ISO 1628-1; Plastics - Determination of the viscosity of polymers in dilute solution using a capillary viscometer - Part 1: General principles
2. Batzer 1 , 16; 3, 83f.
3. Houben-Weyl 14/1 , 83
4. Ullmann (4th) 19 , 347