Extension-Induced Crystallization of Poly(ethylene oxide) Bidisperse Blends: An Entanglement Network Perspective

Abstract

The role of long chains in extension flow-induced crystallization was studied with a combination of extension rheological and in situ small-angle X-ray scattering (SAXS) measurements at 52 °C. To elucidate the effects of long chains, bidisperse blends of poly(ethylene oxide) (PEO) with the long-chain concentration above the overlap concentration were prepared, constructing long-chain entanglement network in short-chain matrix. Rheological data of step extension on PEO melt are divided into two regions with fracture strain of pure short-chain sample as a boundary. Distinctly different features of crystallization kinetics and crystal morphologies are observed in these two regions, exactly corresponding to rheological behavior. A new mechanism based on entanglement network perspective is proposed, in which the second entanglement network constructed by long chains has three effects: (i) helping flow to change the free energy of polymer melt more effectively; (ii) ensuring the specific work can impose on the system; (iii) favoring the formation of precursors. This mechanism captures both rheological observation and crystallization behavior successfully and offers a new viewpoint for FIC study.

Two‐stage drawing process to prepare high‐strength and porous ultrahigh‐molecular‐weight polyethylene fibers: Cold drawing and hot drawing

“…For all of the hot‐drawn fibers, equatorial (vertical direction) streaks across the beam stop were observed; this indicated the existence of microfibrils or void structures in the fibers . The meridional (horizontal direction) rodlike maxima along the drawing direction on both sides of beam stop were associated with the presence of well‐defined lamellar stacks . As hot drawing proceeded at a constant T2, the equatorial streak became more slender with increasing DR2; this was accompanied by a pair of weaker meridional maxima.…”

The Entanglements of Macromolecules and Their Influence on the Properties of Polymers

“…The reduction of entanglements was deduced from the longer reptation times of fully relaxed melts (proportional to higher entangling), evaluated from the crossing point between G ′(ω) and G ″(ω), when compared to the reptation times of melts sheared up to a steady state. The orientation of macromolecules supports not only faster crystallization, but also the growth of specific, oriented structures, like shish–kebabs …”

Probing of polymer to carbon nanotube surface interactions within highly aligned electrospun nanofibers for advanced composites

“…The measured corresponding Young's Moduli were found to be 60 ± 2 MPa, 182 ± 5 MPa and 257 ± 8 MPa, respectively. The slight inflection point, found just after the elastic region (arrowed as A), corresponds to polymer heating as a result of extension-induced crystallisation [33]. The two-stage failure found just before the end of the 0.7% CNT loading test (arrowed as B), corresponds to many fibers in the rope failing, but with the remaining fibers briefly continuing to hold before failing themselves.…”