Linear Viscoelasticity of Blends ofPolybutadiene and Highly Hydrogenated Polybutadiene

GUILLERMO CASSANO; ENRIQUE M. VALLÉS; LIDIA MARÍA QUINZANI

JOURNAL OF RHEOLOGY

JOURNAL RHEOLOGY AMER INST PHYSICS

Lugar: Nueva York; Año: 2000 vol. 44 p. 47 - 63

0148-6055

The linear viscoelastic behavior of a series of partiallyhydrogenated polybutadienes (PHPB) obtained by catalytic hydrogenation of analmost monodisperse polybutadiene (PB) was studied experimentally at temperaturesabove 110°C.  The  molecular characterization of the polymersused in this study showed that the catalytic hydrogenation of PB producesmaterials with a bimodal distribution of polymer species for global conversionslower than approximately 90%.  All thePHPBs, even the less hydrogenated, are a mixture of a highly hydrogenated PB(with approximately 89% saturation) and unreacted PB.  The rheological behavior of the fluids wasstudied measuring the elastic and viscous moduli at different temperatures insmall-amplitude oscillatory shear flow. The two-phase polymer blends show thermo-rheological complex behaviorand an increase in elasticity at low frequencies which may be associated withlong relaxation time processes.  Thedynamic moduli of the pure components in the terminal region is modeled using asingle relaxation time while the blends are described by a minimum of threerelaxation modes.  The two smallerrelaxation times correspond to the relaxation of the blend components while thelargest comes from the geometric relaxation of the shape of the interface.  The zero-shear-rate viscosity of the PHPBsshows a positive deviation relative to log-additivity rule.  But when the predicted contribution of theinterface is subtracted, the resulting zero-shear-rate viscosity as a functionof the concentration follows this rule.