Morphology related bulk and surface mechanical properties of ultralow diameter VGCF–iPP monofilament nanocomposites under potential confinement conditions

Abstract

This study looks at the effects of imposed confinement on morphology related properties in vapor grown carbon nanofibers (VGCF) polypropylene nanocomposite filaments. Different levels of imposed confinement are achieved through varying the content of the VGCF and the dimensions of the nanocomposite filaments. The resulting molecular confinement is apparent through a sharp increase (termed the inversion point) in a number of properties at low filament diameters, which is associated with a formation of a 'shish kebab' structure and a transition from a skin/core morphology to an axially oriented lamellar structure.

Crystalline structure and thermodynamic analysis of ultra‐low diameter VGCF‐polypropylene nanocomposite monofilaments

“…It is noted that the crystallite size trend in Fig. 1b and c is identical to that found earlier for the yield strength and stiffness [12,13], which is discussed below. Figure 2 shows the 2-D WAXD diffraction patterns for the pristine and 10 wt% VGCF filaments.…”

“…The present study—in correspondence with our recent work on the same system —attempts to establish a relationship between the crystalline structure of the filament to its diameter and to the presence of the nanofibers. X‐ray diffraction and thermal analyses are conducted to determine the molecular orientation, crystallite size, melting temperature, and degree of crystallinity as functions of the filament diameter for both pristine and VGCF loaded fibers.…”

“…Increased spinline stress produces higher shear rates, and consequently longer and better oriented crystalline segments are produced of a highly ordered shish-kebab structure with higher parent lamellae content. This is now linked to the improvement of the mechanical properties, found in our earlier work [13]. Concomitantly, the low diameter extruded filaments-experiencing significantly higher in-process cooling rates and confinement conditions-exhibit lower degrees of crystallinity, fractions of daughter lamellae, and melting temperatures.…”

“…In our previous studies , we have shown that the orientation of the polymer chains and the confinement effect of CNT or VGCF affect the strength as well as the modulus of extruded monofilaments. As thinning of the monofilaments takes place, alignment of polymer chains along the drawing direction occurs and results in a higher degree of chain orientation and improved strength and stiffness.…”

Nanoclay assisted ultra-drawing of polypropylene tapes

“…However, the question remains in many of these studies if the improvements in mechanical performance came from true nanofiller reinforcement or from some kind of modification of the polymer matrix. For example, it is well known that the addition of nanoparticles can lead to confinement effects and changes in glass transition temperature [16][17][18] or nucleating effects and changes in crystallinity [19,20]. Wang et al for example studied in detail the influence of polymer morphology on the mechanical reinforcement of an oriented poly(vinyl alcohol) (PVA)/single-wall nanotube (SWNT) composites and could show that for their system the enhanced mechanical properties were a true reinforcement effect of the nanotubes [21].…”