A tubular film extrusion of poly(vinylidene fluoride): structure/process/property behavior as a function of molecular weight

Isotactic Poly(propylene) Crystallization: Role of Small Fractions of High or Low Molecular Weight Polymer

“…Further studies of the strain effect are in progress. Similar observations were reported by Xu et al [16] on poly(vinylidene fluoride) using the Deborah number.…”

Stress-induced structural changes in electrospun polyvinylidene difluoride nanofibers collected using a modified rotating disk

“…A hypothetic mechanism for the formation of such a structure via the use of the modified rotating disk collector is that the fast solvent evaporation during the fanning may create a specific high-viscosity environment where a tensile stress could be effectively loaded onto polymer chains when the fibers are stretched between the two electrodes by the electric field and mechanical force, whereas the polymer chains could still pack to crystallize through ''sliding diffusion'' [22] to form extendedchain crystals. By tubular film extrusion and drawing, fibril crystals can be nucleated in PVDF [5] so that it is not surprising that they may also form in highly stressed electrospun fibers. Under the tensile stress, the slightly twisted zigzag conformation based on energy minimization without stress [1,2] may become a more perfect planar-zigzag, which may make slightly smaller lattice parameter(s) possible, as illustrated in Fig.…”

“…If the c-axis of the b-crystallites are oriented parallel to the film surface, the dipoles of the all-trans conformers will be in the b-axis direction of the orthorhombic lattice, which can be easily aligned along the normal of the thin film by the applied electric field. Preferred crystal orientation in PVDF can be achieved via melt spinning [4] or extrusion [5], mechanical drawing [6], Langmuir-Blodgett deposition [7] and poling [8,9]. An alternative route discovered recently is electrospinning, which promotes both the formation of the b-phase [10][11][12] and preferred crystal orientation [11].…”

Nanostructure Evolution in Poly(propylene) During Mechanical Testing

“…In this article, the last-mentioned method is demonstrated for poly(propylene) (PP) both after a continuous-straining experiment, and after a fatigue test. We study highly oriented, hardelastic [33][34][35][36][37] material, and strain in the normal direction of the crystalline lamellae. Thus, shear and the formation of micropores [38,39] are prevented [40] for the most part.…”