Dilute Solution Viscosity of Polymers
ASTM D 1243 Test Method for Dilute Solution Viscosity of Vinyl Chloride Polymers
ASTM D 2857 Test Method for Standard Practice for Dilute Solution Viscosity of Polymers
ASTM D 4603 Test Method for Determining Inherent Viscosity of Poly(Ethylene Terephthalate) (PET) by Glass Capillary Viscometer
Dilute Solution Viscosity is used as an indication of the molecular weight of polymers. The results of the test are expressed as Relative Viscosity, Inherent Viscosity, or Intrinsic Viscosity. It is used for polymers that dissolve completely without chemical reaction or degradation and can provide an excellent determination of lot-to-lot consistency or be used to compare molded parts to original resin for determinations of degradation from molding.
The polymer is first weighed and then dissolved in an appropriate solvent. The solution and viscometer are placed in a constant temperature water bath. Thermal equilibrium is obtained within the solution. The liquid is then brought above the upper graduation mark on the viscometer. The time for the solution to flow from the upper to lower graduation marks is recorded.
Commonly a sample size of 40-50 mg. of polymer and 10 ml of solvent is utilized to determine solvent, specify material type. If the material is filled, it is important to specify percent filler.
Common solvents include chloroform, cyclohexanone, and phenol/trichloroethylene mixture.
Relative Viscosity, Inherent Viscosity or Intrinsic Viscosity is calculated.
Viscosity: The property of resistance of flow exhibited within the body of a material.
Relative Viscosity: The ratio of the viscosity of the solution to the viscosity of the solvent.
Relative Viscosity Increment: The ratio of the difference between the viscosities of solution and solvent to the viscosity of the solvent.
Reduced Viscosity: The ratio of the relative viscosity increment to the mass concentration of the polymer.
Inherent Viscosity: The ratio of the natural logarithm of the relative viscosity to the mass concentration of the polymer.
Intrinsic Viscosity: The limiting value of the reduced viscosity or the inherent viscosity at infinite dilution of the polymer.
Equipment used at Plastics Technology Laboratories, Inc:
Schott-Gerate model AVS/G/PA Automatic Viscometer Balance
Ubbelohde calibrated viscometer tube
Constant temperature water bath