In siturheo-x-ray investigation of flow-induced orientation in layered silicate–syndiotactic polypropylene nanocomposite melt

Stress relaxation in aging soft colloidal glasses

“…Clearly, owing to the large distribution of time scales that characterize these relaxation processes, a complete decay is not observed. However, at the highest strain values achieved in our experiments, B approaches unity, indicating the possible onset of ordering into a nematic phase [21]. At even higher strains beyond 12000%, the shape of the stress relaxation changes dramatically and cannot be modeled by the KWW function.…”

Infrared Spectroscopic Characterization of Polymer and Clay Platelet Orientation in Blown Films Based on Polypropylene‐Clay Nanocomposite

“…[20] However, values as high as þ0.85 have been reported for in situ X-ray measurements on a flowing melt of syndiotactic PP and layered silicate. [21] The mechanical, optical, and permeability properties of the films discussed here were briefly summarized in a recent publication [7] and will subsequently be reported in more detail. [22] Some improvements were observed, particularly when the compatibilizing agent used was PB3150 rather than E43.…”

Rheology of Polymers with Nanofillers

“…The stress responses have been controlled by hydrodynamics, while the fast disorientation was driven by stress relaxation and randomizing Brownian motion. A similar relaxation of orientation for PP-based CPNCs with PP-MA was reported by Lele et al [2002]. The authors presheared the system and then followed the disorientation with XRD.…”

“…However, it was unable to predict the effect ofγ on the overshoots (i.e., the growth of stress overshoot amplitude with increasingγ). The structure reorganization of particles was predicted qualitatively and the kinetics for the particle disorientation based on the Brownian motion was too slow in comparison with experimental results [Solomon et al, 2001;Lele et al, 2002;Ren et al, 2003a,b], which might imply that the matrix recovery affects the clay orientation. Sepehr et al [2008] are investigating the viscoelastic Giesekus model [Giesekus, 1982[Giesekus, , 1983Bird et al, 1987] coupled with Eq.…”

“…Bulk clays absorb a large volume of water, and under suitable conditions fully exfoliate in it. Two natural clays with CEC ≈ 1 meq/g are of special interest: montmorillonite (MMT) [Al l.67 During flow, their platelets orient with the major axis in the flow direction and surface usually parallel to the shear plane [Kojima et al, 1995;Varlot et al, 2001;Lele et al, 2002;Bafna et al, 2003;Galgali et al, 2004]. Upon cessation of flow in low-viscosity media, the Brownian motion leads to a randomization of the flow-imposed orientation.…”