Paper Number
SM27 

Session
Polymers Solutions, Melts and Blends

Title
"Tying the knot", ultra-fast entangling across ultra-high molecular weight polyethylene interfaces

Presentation Date and Time
October 11, 2022 (Tuesday) 2:30

Track / Room
Track 2 / Sheraton 3

Authors (Click on name to view author profile)

  1. Christakopoulos, Fotis (ETH Zürich, Department of Materials)
  2. Troisi, Enrico M. (SABIC Technology & Innovation)
  3. Friederichs, Nic (SABIC Technology & Innovation)
  4. Vermant, Jan (ETH Zürich, Materials)
  5. Tervoort, Theo A. (ETH Zurich, Department of Materials)

Author and Affiliation Lines (in printed abstract book)
Fotis Christakopoulos1, Enrico M. Troisi2, Nic Friederichs2, Jan Vermant1 and Theo A. Tervoort1
1Department of Materials, ETH Zürich, Zurich, Zurich 8093, Switzerland; 2SABIC Technology & Innovation, Geleen, The Netherlands

Speaker / Presenter 
Christakopoulos, Fotis

Keywords
experimental methods; polymer melts; polymer sustainability

Text of Abstract
Joining of two solid polymer interfaces of identical monomeric composition has important practical applications, as it directly controls the quality of welding and plays a key role in determining properties of mechanical recycled products. It also has interesting theoretical aspects, e.g. related to adhesion and self-diffusion of macromolecular chains. Ultra-high molecular weight polyethylene (UHMWPE) is a high-end engineering polymer and is the material of choice in numerous applications ranging from high-performance fibers and bulletproof panels to medical implants. It combines a low friction coefficient and excellent chemical resistance and in its isotropic form, UHMWPE possesses among the highest values of impact strength and wear resistance of all polymers. However, the very features that lead to its exceptional properties, i.e. ultra-long macromolecular chains, render joining two surfaces of this material a tedious and slow process, leading to long welding times and impeding mechanical recycling of UHMWPE. A special feature of UHMWPE is that it can be produced through dedicated polymerization protocols in a disentangled state. The possibility of accelerating diffusion using these fully disentangled chains is explored and exploited in the present work. An anomalous fast joining of UHMWPE interfaces, by simply depositing small amounts of nascent disentangled UHMWPE powder at the interface, is observed. The time evolution of build-up of adhesive fracture energy in the molten state and the reduction in interfacial slip between two molten UHMWPE layers, reveal an order of magnitude increase of the rate of interpenetration compared to the dynamics of a regular UHMWPE-melt interface. This ultra-fast self-diffusion mechanism is insensitive to molecular weight, in contrast to reptation-driven diffusion, and provides a direct indication of the entropy-driven “chain explosion” upon melting of nascent disentangled UHMWPE. The usefulness of fast molecular stitching is demonstrated for enhanced recycling of UHMWPE.