Effect of processing parameters on the morphology development during extrusion of polyethylene tape: An in-line small-angle X-ray scattering (SAXS) study

Abstract

Ray scattering (SAXS). AbstractThe in-line development of crystalline morphology and orientation during melt extrusion of low density polyethylene (LDPE) tape at nil and low haul-off speeds has been investigated using Small-Angle X-Ray Scattering (SAXS). The processing parameters, namely haul-off speed and distance down the tape-line have been varied and the resulting crystalline morphology is described from detailed analysis of the SAXS data. Increasing haul-off speed increased orientation in the polymer tape and the resulting morphology could be described in terms of regular lamellar stacking perpendicular to the elongation direction. In contrast, under nil haul-off conditions the tape still showed some orientation down the tape-line, but a shish-kebab structure prevails. The final lamellae thickness (~50 Å) and bulk crystallinity (~20%), were low for all processing conditions investigated, which is attributed to the significant shortchain branching in the polymer acting as point defects limiting lamellae crystal growth.2

The formation of a nanohybrid shish-kebab (NHSK) structure in melt-processed composites of poly(ethylene terephthalate) (PET) and multi-walled carbon nanotubes (MWCNTs)

“…SAXS patterns of the extruded samples at 30 ºC prior to any further crystallization are given in Figure 1, including schematics of the associated polymer crystalline or amorphous structure. [12,42,48,49] The SAXS pattern for neat PET shows only diffuse scattering around the central beam stop, thus indicating no crystalline structure prevails from the extrusion process and the polymer is amorphous. In comparison, the PET1% composite shows increased scattering around the beam stop seen as a ring of intensity.…”

“…The 1D profiles of the azimuthal peaks were fitted using Gaussian functions to obtain the average full width at half maximum (FWHM) values. [12,38,42] Avrami plots [43,44], using the double logarithmic from of the Avrami equation, were obtained for the isothermal crystallization measurements from Qs:…”

Lamellae evolution of poly(butylene succinate-co-terephthalate) copolymer induced by uniaxial stretching and subsequent heating

“…1b, and some corresponding 2D SAXS patterns are presented in Fig. 44 Thus, from the transformation of these patterns, a general understanding about the lamellar changes during heating can be obtained. The two-bar-like patterns along the meridian gradually became noticeable, showing the lamellar structure again prevailed during the heating process.…”

Structure evolution in poly(ethylene terephthalate) (PET) – Multi-walled carbon nanotube (MWCNT) composite films during in-situ uniaxial deformation

“…period, L p , crystalline layer thickness L c , amorphous layer thickness L a and estimated bulk crystallinity X c [42,43].…”

“…This is mostly likely due to the presence of the MWCNT filler (as it is clearly absent in the neat PET sample) and imperfect PET crystallites. As the PET-MWCNT samples are annealed, the SAXS data showed the development of meridional arcs and diffuse spots, which can be interpreted as narrow lamellae or shish-kebab structures with a variety of orientations around the vertical draw direction [43,46,47].…”