| Abstract: | The breakdown of primary particle structure in PVC is intimately related to the mechanical properties of the material. This article addresses the measurement of primary particle breakdown through microscopic observation, torque bowl rheometry, penetration impact, yield stress determinations, and zero length capillary rheometry. It is found that each method gives information which identifies certain stages in the breakdown process and complements information obtained from the other methods. Characterization via penetration impact identifies the melt conditions at which both the onset of a continuous network on the microscopic scale and primary particle breakdown occurs. Yield stress determined as a function of melt temperature identifies the completion of primary particle breakdown. The onset of primary particle breakdown, as well as the breakdown of other structural units, such as grains, are readily determined by torque bowl rheometry. However, the results from zero-length capillary rheometry cannot, as yet, be readily generalized in terms of the particulate breakdown process. |
