Deformation of disentangled polypropylene crystalline grains into nanofibers

Abstract

It was shown that a solid‐state deformation of polypropylene (PP) being in the form of partially disentangled powder is possible by blending with another molten polymer. During mixing of disentangled polypropylene powder with polystyrene at the temperature below melting of polypropylene crystals the shear forces deform powder grains into nanofibers. All disentangled powder particles larger than 0.7 µm underwent deformation into nanofibers having the mean thickness between 100 and 200 nm. Polypropylene nanofibers got entangled during blending and form a network within polystyrene matrix, reinforcing it. Network of entangled nanofibers can be further deformed with pronounced strain hardening and strength reaching 70 MPa at 135 °C. Blending resulted in generation of PP nanofibers and formation of PP nanofibers entangled network, thus formation of “all‐polymer nanocomposites” in one step compounding. The crucial feature for ultra‐deformation of PP grains by shearing during mixing is disentanglement of macromolecules. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1983–1994

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

“…The disentangled polymers after solidification can be used for studies of crystallization from liquid state (melt, solution) or crystallization in the solid state (i.e., cold crystallization). The crystallization from disentangled melt was examined for iPP, sPP, PLA, iPS, PEO, and UHMWPE . Cold crystallization was examined for PC, PET, PEO, and iPS .…”

“…Most of the polymers used in these experiments were disentangled by using the freeze‐drying method. Partially disentangled iPP obtained by crystallization from diluted solution was also used for studies of isothermal crystallization from melt …”

“…Partially disentangled iPP obtained by crystallization from diluted solution was also used for studies of isothermal crystallization from melt. [115,117,150] Pandey et al [152] compared crystallization of commercial, entangled UHMWPE and synthesized, disentangled UHMWPE. It was found that for the entangled polymer the melting temperature increases with increasing of the heating rate and this dependence is linear when the heating rate is presented in a logarithmic scale.…”

The crystallization of polypropylene with reduced density of entanglements

“…Wang et al obtained isotactic polypropylene with “disentangled” chains through crystallization from hot mineral oil solution. Recently, we prepared a polypropylene powder with reduced density of entanglements using entangled commercial polymer and dissolving it in hot xylene or (similarly to Wang's method) in hot mineral oil …”

All-polymer composites - a new approach with the use of disentangled semi-crystalline polymers. Part I. Disentangling and properties of disentangled polylactide

“…This is due to the fact that large deformations can be achieved in a polymer with a limited density of entanglements. Galeski et al [16,17] proposed using such a polymer in the preparation of a nanocomposite by blending it with a second, molten polymer. In the mixing process carried out at high temperature, but below the melting temperature of the partially disentangled polymer, the forces are transmitted to it, resulting in the grain refinement and causing the plastic deformation, leading to the transformation of the lamellar structure into micro and nano-size fibers.…”