How to Measure Molecular Weight

The polymer problem is to measure the weight of molecule because the polymer may content of molecular chain so the weight of molecule may vary on certain polymer solution. The usefulness of solution viscosity as a measure of polymer molecular weight has been recognize ever since the early work of Staudinger (1930). Solution viscosity is basically a measure of the size or extension in space of polymer molecules. It is empirically related to molecular weight for linear polymers; the simplicity of the measurement and the usefulness of the viscosity molecular weight correlation are so great that viscosity measurement constitute an extremely valuable tool for the molecular characterization polymers.

Measurements of solution viscosity are usually made by comparing the effux time t required for a specific volume of polymer solution to flow through a capillary tube with the correspond effux time t_o  and the solute concentration are derived several quantities whose defining equation and names. Two sets of nomenclature are in use for these quantities; one (Cragg 1946) has had and widespread application, the other (International Union 1952) was proposed for greater clarify and prescision.

To measure viscosity of polymer solution commonly use capillary viscometers, but in industrial application using viscometer may need long time and not enough time if the viscosity check need often time in an hours or should check other process parameter in one hours so viscosity method than modify with the fastest test by ball fall method. The time need through certain height of metal ball in the measurement cylinder calibrate with the polymer molecular weight that already measure.