Elastic Recovery of Immscible Polymer Blends
Interfacially active species, called compatibilizers, are often added when blending immiscible polymers to promote blending and improve product properties. The effects of compatibilizer on the rheological properties of polymer blends are considered here.
Blends of immiscible Polyisobutylene (PIB) and Polydimethyl siloxane (PDMS) compatibilized by a diblock copolymer of PIB and PDMS were studied. Blends had droplet matrix morphologies contained up to 30 wt. % of PIB and up to 1 wt. % of compatibilizer. The ratio of viscosity of the PIB to that of the PDMS was varied from 0.29 to 1.7.
In blends without compatibilizer, the recovery was a single-retardation time process. The ultimate recovery and retardation time were found to increase with wt. fraction of the dispersed phase and with the capillary number; and decrease with increasing viscosity ratio. A previously developed model by Vinckier et al. was found to predict the retardation time well, but overpredicted the ultimate recovery.
In blends with compatibilizer, recovery was no longer a single retardation time process. Compatibilizer was found to increase ultimate recovery and retardation time under all conditions studied. The largest increase occurred at the lowest viscosity ratio. Moreover, under certain flow conditions, a weak but very slow recovery process was observed. The results may be explained by a coupling between flow and compatibilizer concentration on the interface, however, the phenomena are too complex to draw a firm conclusion based on the available data.
Advisor:Joseph J. McCarthy; Sachin Velankar; Lynn M. Walker
School:University of Pittsburgh
School Location:USA - Pennsylvania
Source Type:Master's Thesis
Date of Publication:01/28/2005