Rheology–Structure Relationship of Polymer/Layered Silicate Hybrids

Abstract

Linear and non-linear rheology of polymer/layered silicate hybrids(nanocomposites) of organically modified smectite clay in poly(methylmethacrylate) (PMMA) were studied in oscillatory shear and elongationflow for understanding the relation between rheology and structure inthe lights of time-dependent phenomena. Various rules for the linearviscoelastic response were proved by a comparison of the theoreticalpredictions with the experimental data at the low amplitude oscillatoryshear. Time-temperature superposition principal, as well as the relationbetween the relaxation time spectrum and the linear functions, asrelaxation modulus G(t) and elongation viscosity η E (t) were verified.Relaxation spectrum is shifted towards the longer relaxation time scalesfor 10 and 15 wt% SPN/PMMA hybrids, if compared with that of thematrix PMMA. Both the large-amplitude oscillatory shear and the fastelongation produced much stronger non-linear effects of hybrids than thatof pure PMMA. It is proposed that, the non-linear damping of hybridsunder step strain is a result of the strain-induced alignment of themultilayered clay domains in a shear flow field. Moreover, theretardation of the polymer relaxation of hybrids probably gives rise tothe strain-hardening properties under fast elongation. Highly orientedand elongated multilayered domain structure of hybrids in an elongationflow field has been proposed as a microstructural origin of both strainhardening and birefringence.