The role of the applied processing equipment shear history on the rheological properties of low-density polyethylene was studied in detail. It was found that the shear history depresses the melt strength and the oscillatory shear modulus, especially the storage modulus in low frequency region. This phenomenon is not caused by lowering of the molecular weight, which remained the same as the original, for all shear history samples, indicating absence of mechanical/thermal degradation during processing. Furthermore, annealing the melt processed samples enhances both the melt strength and the oscillatory modulus to the values of the original, unsheared sample. Finally we applied shear history in a cone-and-plate rheometer and found that the growth curve of the storage modulus, which can be expressed by a simple equation, is determined by both the duration of the flow and the magnitude of the applied shear stress.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Organic Chemistry
- Polymers and Plastics