Metallic-like thermal conductivity in a lightweight insulator: Solid-state processed Ultra High Molecular Weight Polyethylene tapes and films

For disentangled UHMWPE of draw ratio ≳150, the thermal conductivity is observed to increase on average by a factor of about 20% despite a lack of detectable change in crystallinity or chain orientation.

“For disentangled UHMWPE of DR ≳ 150, the increase in thermal conductivity is difficult to interpret using the above models because the thermal conductivity is observed to increase on average by factor of ∼20% despite a lack of detectable change in crystallinity or chain orientation11–13,23,24.”

The introduction of disentangled UHMWPE films with higher crystallinities and less entangled amorphous regions compared to prior samples has led to reports of high thermal conductivities exceeding 60 W m−1 K−1.

“In macroscopic samples, the introduction of disentangled ultra-high molecular weight polyethylene (UHMWPE) films21,22 with higher crystallinities and less entangled amorphous regions compared to prior samples has led to reports of high thermal conductivities exceeding 60 Wm−1 K−1 (refs. 23,24).”

Recent studies have provided conflicting explanations for the high thermal conductivity in disentangled UHMWPE, with Xu et al. attributing it to the high thermal conductivity of the amorphous phase and Ronca et al. attributing it to increased extended crystal dimensions.

“Recent studies have provided conflicting explanations for the high thermal conductivity, with Xu et al. 24 attributing it to the high thermal conductivity of the amorphous phase58 but Ronca et al. 23 attributing it to increased extended crystal dimensions.”

The authors' results support the hypothesis of ref. 23 that high thermal conductivity is attributed to the enlargement of extended crystal dimensions.

“Our results therefore support the hypothesis of ref. 23 in which the high thermal conductivity compared to the prediction including only crystallinity and anisotropy factors for DR ≳ 180 (Fig. 7 in ref. 23) was attributed to the enlargement of extended crystal dimensions.”

High thermal conductivities of about 50 W m−1 K−1 or more have recently been reported in disentangled ultra-high molecular weight polyethylene (UHMWPE) films, considerably exceeding prior reported values for oriented films.

“High thermal conductivities ( ≳ 50 Wm−1K−1) have recently been reported in disentangled ultra-high molecular weight polyethylene (UHMWPE) films, considerably exceeding prior reported values for oriented films.”

The value of κ∥ is in reasonable agreement with that obtained on a sample without Au nanoparticles using the laser flash method, indicating that 1 wt% Au nanoparticles does not measurably affect the thermal transport properties of the present sample.

“The value along the draw direction is in reasonable agreement with that obtained on a sample without Au nanoparticles using the laser flash method in ref. 23, indicating that the 1 wt% of AuNPs does not measurably affect the thermal transport properties of the present sample.”