CHANGES IN THE VISCOSITY, RELAXATION SPECTRA AND THE MOLECULAR WEIGHT DISTRIBUTION OF POLYPROPYLENE RESINS DUE TO THE ADDITION OF PEROXIDE DURING EXTRUSION

摘要

The oscillatory response of controlled rheology polypropylene (CRPP) resins and their respective starting resins was determined using a strain controlled rheometer. The complex viscosity and the relaxation spectra ( H(λ)) were obtained from the loss and storage moduli. Viscosity density functions (VDF= λ H(λ)) were then obtained and fitted with log-normal distribution functions. The viscosity, relaxation spectra and VDF were in good agreement with published data. The ratios of the moments of the viscosity function were found to be related to the peroxide levels and to the changes in the polydispersity index obtained from Gel Permeation Chromatography (GPC).