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Hot pressing-induced alignment of hexagonal boron nitride in SEBS elastomer for superior thermally conductive composites.

ABSTRACT: Styrene-ethylene-butylene-styrene (SEBS) composite films containing well-dispersed and highly aligned hexagonal boron nitride (hBN) platelets were achieved by a ball milling process followed by hot-pressing treatment. An ultrahigh in-plane thermal conductivity of 45 W m^-1 K^-1 was achievable in the SEBS composite film with 95 wt% hBN. The corresponding out-of-plane thermal conductivity was also as high as 4.4 W m^-1 K^-1. The hBN/SEBS composite film was further used to cool a CPU connected to a computer, resulting in a decrease by about 4 °C in the stable temperature. Percolation thresholds over 40 wt% and 60 wt% in the hBN/SEBS composites were obtained in the in-plane and out-of-plane directions, respectively. This phenomenon has rarely been reported in polymer composites. Molecular dynamics simulations were also conducted to support this percolation threshold. The linear coefficients of the thermal expansion value of the hBN/SEBS composite with 95 wt% hBN was as low as 16 ppm K^-1. This was a significant decrease compared to that of pure SEBS (149 ppm K^-1). The proposed strategy provides valuable advice about the heat-transfer mechanism in polymer composites containing oriented two-dimensional materials.

SUBMITTER: Yu C

PROVIDER: S-EPMC9082571 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

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Hot pressing-induced alignment of hexagonal boron nitride in SEBS elastomer for superior thermally conductive composites.

Yu Cuiping C Gong Wenbin W Zhang Jun J Lv Weibang W Tian Wei W Fan Xiaodong X Yao Yagang Y

RSC advances 20180718 45

Styrene-ethylene-butylene-styrene (SEBS) composite films containing well-dispersed and highly aligned hexagonal boron nitride (hBN) platelets were achieved by a ball milling process followed by hot-pressing treatment. An ultrahigh in-plane thermal conductivity of 45 W m-1 K-1 was achievable in the SEBS composite film with 95 wt% hBN. The corresponding out-of-plane thermal conductivity was also as high as 4.4 W m-1 K-1. The hBN/SEBS composite film was f ...[more]

PMID: 35539796

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Project description:Two-dimensional hexagonal boron nitride (hBN) has attracted tremendous attention over the last few years, thanks to its stable structure and its outstanding properties, such as mechanical strength, thermal conductivity, electrical insulation, and lubricant behavior. This work demonstrates that hBN can also improve the rheological and mechanical properties of elastomer composites when used to partially replace silica. In this work, commercially available pristine hBN (hBN-p) was exfoliated and ball-mill treated in air for different durations (2.5, 5, and 10 h milling). Functionalization occurred with the -NH and -OH groups (hBN-OH). The functional groups were detected using Fourier-Transform Infrared pectroscopy (FT-IR) and were estimated to be up to about 7% through thermogravimetric analysis. The presence of an increased amount of oxygen in hBN-OH was confirmed using Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy. (SEM-EDS). The number of stacked layers, estimated using WAXD analysis, decreased to 8-9 in hBN-OH (10 h milling) from about 130 in hBN-p. High-resolution transmission electron microscopy (HR-TEM) and SEM-EDS revealed the increase in disorder in hBN-OH. hBN-p and hBN-OH were used to partially replace silica by 15% and 30%, respectively, by volume, in elastomer composites based on poly(styrene-co-butadiene) from solution anionic polymerization (S-SBR) and poly(1,4-cis-isoprene) from Hevea Brasiliensis (natural rubber, NR) as the elastomers (volume (mm3) of composites released by the instrument). The use of both hBNs in substitution of 30% of silica led to a lower Payne effect, a higher dynamic rigidity, and an increase in E' of up to about 15% at 70 °C, with similar/lower hysteresis. Indeed, the composites with hBN-OH revealed a better balance of tan delta (higher at low temperatures and lower at high temperatures) and better ultimate properties. The functional groups reasonably promote the interaction of hBN with silica and with the silica's coupling agent, sulfur-based silane, and thus promoted the interaction with the elastomer chains. The volume of the composite, measured using a high-pressure capillary viscometer, increased by about 500% and 400% after one week of storage in the presence of hBN-p and hBN-OH. Hence, both hBNs improved the processability and the shelf life of the composites. Composites obtained using hBN-OH had even filler dispersion without the detachments of the filler from the elastomer matrix, as shown through TEM micrographs. These results pave the way for substantial improvements in the important properties of silica-based composites for tire compounds, used to reduce rolling resistance and thus the improve environmental impacts.

Dataset Information

Hot pressing-induced alignment of hexagonal boron nitride in SEBS elastomer for superior thermally conductive composites.

Publications

Hot pressing-induced alignment of hexagonal boron nitride in SEBS elastomer for superior thermally conductive composites.

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