Fig. 1: In-plane thermal characterization of disentangled UHMWPE films using TG.

A Schematic illustration of transient grating formation and temperature profile. Pump laser pulses impulsively generate a spatial grating on the sample from which probe beams diffract. B Optical image of disentangled UHMWPE film (DR = 196). C SEM image of the disentangled UHMWPE film. Extended fibers over tens of μm are visible. D Representative TG signal versus time for grating period L = 9.8 μm at 300 K. The signal is an average of 3 × 10⁴ repetitions at a single location on the sample. The measurement was conducted at multiple locations (see Supplementary Material Section 1 for additional data). The thermal diffusivity is obtained as the time constant of the exponential decay. E Thermal conductivity versus angle between draw direction and thermal gradient defined by the grating L = 9.8 μm. The 0° (90°) indicates heat flow direction parallel (perpendicular) to the draw direction. The maximum thermal conductivity is around 40 W m⁻¹ K⁻¹ along the chain, while the perpendicular value is comparable to that of unoriented PE.