Sheer influences on polymer blends: experimental, theoretical approaches and technical implications

We examine the effects of shear on polymer blends consisting of partially m iscible components, i.e. systems close to the phase boundary. The eminent p henomenon is the shift of the phase boundary, either extending the homogene ous area (flow-induced mixing) or the opposite effect (flow-induced demixin g). The kinetics of the demixing process and concentration fluctuations are also influenced by flow fields, inducing anisotropy due to the flow direct ion. Experiments (scattering, rheology, in-situ flow-scattering, microscopy , DSC) are carried out with the academic model blend polystyrene/poly(vinyl methyl ether) and the industrial poly(styrene-co-maleic anhydride)/poly(me thyl methacrylate) blend. The experimental results are rationalised in term s of a generalised Gibbs energy of mixing by including the energy which is stored in the sheared fluids.