Real‐time in situ light scattering and X‐ray scattering studies of polyethylene blown film deformation

Abstract

A series of linear low-density polyethylene blown films were studied using the techniques of time-resolved, small-angle X-ray scattering (SAXS) using a synchrotron source and a time-resolved, small-angle light scattering. Scattering patterns and the load-extension curve were obtained simultaneously during deformation. It was found that the initial orientation of the film, with respect to the tensile axis, was important in determining the operative elastic deformation modes. Films drawn parallel to the machine direction (MD) showed evidence for lamellar separation, whereas interlamellar shear occurred in films drawn parallel to the transverse direction. In films drawn at 45Њ to MD, lamellar stack rotation was observed via SAXS. In all cases, the yield point corresponded to the activation of crystallographic deformation and the onset of the disruption of crystalline lamellae. In films drawn parallel to MD, the SAXS showed a distinct 4-point pattern upon macroscopic yield, indicating lamellar corrugation. Regardless of the initial orientation, a fibrillar morphology was achieved at some strain after yield that coexisted with the fragmenting lamellar morphology.Comparison of results from deformed spherulitic bulk samples showed that the study of oriented blown film containing a stacked lamellar morphology may be used, to a first approximation, as a model for the deformation of different regions of spherulites in unoriented spherulitic samples.

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“…Over the same strain region, both orthorhombic peaks decrease and attain an approximately constant value at lower strain values. The drop in the monoclinic phase content is believed to be due to the local stress relaxations caused by microvoid formation 11, 30, 31, 43. Although not shown here PE and PENC3 exhibit similar trends to PENC6 with decrease of orthorhombic peaks with increasing strains at both strain rates.…”

“…For samples measured at RT, the SAXS data also shows increased scattering at low q (<∼0.09 nm −1 ) with increasing deformation. This scattering results from structures with dimensions of >70 nm and could result from void formation 14, 30–32. The total amount of scattering can be quantified by determining the scattering invariant, Q ∝ ∫ l ( q ) dq 33…”

Changes in Arrangement of Lamella and Fine Crystallite in Fluorinated “Crystalline” Transparent Fibers with Drawing

“…This feature of the long periods corresponded well with that of PE, polypropylene (PP), and polyester. [30][31][32][33][34][35][36][37] From the viewpoint of enhancing transparency by using the drawing process, EFA fibers exhibited the elongation of the amorphous region with an increase in density in this region and indicated a resultant increase in the long period upon drawing. Figure 5 shows the change in SAXS patterns upon drawing.…”

Structure–Property–Process Relationship for Blown Films of Bimodal HDPE and Its LLDPE Blend

“…Based on experimental results, he proposed the concept of “row‐nucleated crystallization,” where the high‐MW chains are oriented along the machine direction (MD) in the format of fibrils that can subsequently nucleate the lamellae. This concept has been extensively supported and proven by several other groups later . In 1967, Keller and Machin further proposed a morphological model to explain the development of oriented morphology of PE that is strongly dependent on the stress.…”