Continuous fabrication platform for highly aligned polymer films

Abstract

Superior mechanical and thermal properties in bulk polymers can be achieved by aligning the molecular chains through drawing-induced plastic deformation. Although highly aligned polymer films (HAPFs) are in demand, current fabrication methods are limited to manual, lab-scale batch processes. Here we report a continuous fabrication platform for HAPFs consisting of a three-step sol-gel extrusion, structure freezing and drying, and mechanical drawing process. First, a polymer-solvent solution is subjected to a high shear, high temperature, Couette flow extrusion into a thin film, resulting in initial chain disentanglement. Next, the extruded disentangled structure is frozen using a liquid N 2-cooled substrate, and then solvent is removed from polymer gel through ambient evaporation. Finally, dried films are mechanically drawn within a heated enclosure using a constant-force adaptive-thickness drawing system. The performance of this platform has been confirmed by fabricating polyethylene HAPFs with > 99% crystallinity and draw ratios up to 100× (creating continuous films > 15 m in length).

Nanostructured polymer films with metal-like thermal conductivity

“…1b) were mechanically pressed and drawn inside a heated enclosure using a continuous and scalable roll-to-roll system. 21 Heating allowed the disentangled polymer chains to move more freely and facilitated alignment along the draw direction( Fig. 1c, d).…”

An ode to polyethylene

“…8). [69][70][71][72][73][74] These properties of crystalline polyethylene films and fibers offer exciting opportunities in using them as transparent and electrically insulating heat exchangers for (opto-)electronics. Highly conductive polyethylene materials have already been successfully used in conduction cooling of superconducting magnets and can help in mitigating formation of hot spots in photovoltaic solar cells, which decrease the cells' lifetime and decrease their operational efficiency.…”

Strain-induced oriented crystallization of UHMWPE: Enhanced thermal conductivity through molecular chain alignment

“…This induced orientation increased peak intensity in the (200) plane, while decreased that in the (110) plane. 21 Increased the strain rate from 5.6 × 10 -4 s -1 to 0.067 s -1 enhanced the ratio of (200) to (100) peak intensities; however, further increased the strain rate to 0.508 s -1 would suppress this ratio. This trend was consistent with the dependence of the k // , χ c and T m on the strain rate.…”

“…With a draw ratio of ∼100×, UHMWPE film with thermal conductivity of ∼20 W·m -1 ·K -1 was achieved. 21 In this work, we investigate an industrially viable processing strategy with simplified and solventfree set-up to fabricate polymer films with enhanced thermal conductivity. A fabrication system based on a mechanical drawing process has been developed and an illustration of the system is shown in FIG.…”