If we know the and values for a given polymer solution the intrinsic viscosity and molecular weight can be calculate using the above equation. Where is the intrinsic viscosity, is Molecular weight, and are constants for a particular polymer solvent system. The molecular weight of the polymer solution is very high so the viscosity of polymer solution is very high compared to that of pure solvent.įrom the Mark-Houwink equation the relationship among the molecular weight and viscosity are given below The molecular weight of the polymer is measured by using viscometer and the molecular weight obtained by this technique is called viscosity average molecular weight. The unknown composition can be determined by plotting a graph for the time of flow and compositions. In this method the flow times are measured for different known compositions and a graph is plot for time of flow and compositions. The time of flow of liquid depends on the viscosity and composition. Various mixtures of two non-interacting liquids viscosities will lie among the viscosities of those pure components. And η 1 is the coefficient of viscosity of water.įor a given liquid η has a specific value at the same temperature. Here t 1 and t 2 are the time of flow of the liquids and ρ 1 and ρ 2 are the respective densities. Then the coefficient of viscosity of liquid (η 2) is given by equation In this method viscosity of liquid is measured by comparing the flow times of two liquids of equal volumes using same viscometer.Ĭonsider two liquids are passing through a capillary of same viscometer. The Ostwald method is a simple method for the measurement of viscosity, in which viscosity of liquid is measured by comparing the viscosity of an unknown liquid with that of liquid whose viscosity is known. Many methods are available for measuring viscosity of polymer solution. It is due to the internal friction of molecules and mainly depends on the nature & temperature of the liquid. Viscosity is an internal property of a fluid that offers resistance to flow. Determine the viscosity average molecular weight of a polymer.This form also follows the general trend shown in literature for the inverse relationship between intrinsic viscosity and overlap concentration c, as per the MarkHouwink equation 52, 53, 54. Determine the absolute viscosity of Polymer solutions of different concentrations (14) and (15) are of the same general form, and the intrinsic viscosity is expressed as: (16) 1, 2 R T (R h R g) a 1 c.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |