Melt rheology and morphology of thermoplastic elastomers from polyethylene/nitrile-rubber blends: The effect of blend ratio, reactive compatibilization, and dynamic vulcanization

A study of the melt-theological behavior of thermoplastic elastomers from h igh-density polyethylene and acrylonitrile butadiene rubber (NBR) blends wa s carried out in a capillary rheometer. The effect of the blend ratio and s hear rate on the melt viscosity reveals that the viscosity decreases with t he shear rate but increases with NBR content. Compatibilization by maleic a nhydride modified polyethylene has no significant effect on the blend visco sity, but a finer dispersion of the rubber is obtained, as is evident from scanning electron micrographs. The melt-elasticity parameters, such as the die swell, principal normal stress difference, recoverable shear strain, an d elastic shear modulus of the blends, were also evaluated. The effect of a nnealing on the morphology of the extrudate reveals that annealing in the e xtruder barrel results in the coalescence of rubber particles in the case o f the incompatible blends, whereas the tendency toward agglomeration is som ewhat suppressed in the compatibilized blends. (C) 2000 John Wiley & Sons, Inc.