Decreased Thermal Conductivity of Polyethylene Chain Influenced by Short Chain Branching

Luo, Danchen; Huang, Congliang; Huang, Zhifeng

doi:10.1115/1.4038003

Cited by 40 publications

(37 citation statements)

References 53 publications

(69 reference statements)

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“…Side-chains are functional groups branching out of the backbones [ 38]. Since side-chains change the topology of the polymer chains, the vibrational dynamics and the thermal conductivity are both expected to change when different types of side chains are introduced.…”

Section: Side-chainsmentioning

confidence: 99%

“…12(b). The mechanism of the reduced thermal conductivity caused by the side-chains could be understood as a result of phonon localization and phonon scatterings [38][39]. In bulk polymers, side chains are also found to decrease the thermal conductivity, because the crystallinity are found to decrease dramatically when side chains are introduced [39].…”

Section: Side-chainsmentioning

confidence: 99%

“…In bulk polymers, side chains are also found to decrease the thermal conductivity, because the crystallinity are found to decrease dramatically when side chains are introduced [39]. [38]. copyright 2017 American Society of Mechanical Engineers; (b) a single bottlebrush chain with different side-chain length.…”

Section: Side-chainsmentioning

confidence: 99%

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Thermal conductivity of polymers and polymer nanocomposites

Huang

Qian

Yang

2018

Materials Science and Engineering: R: Reports

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596

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Polymers are widely used in industry and in our daily life because of their diverse functionality, light weight, low cost and excellent chemical stability. However, on some applications such as heat exchangers and electronic packaging, the low thermal conductivity of polymers is one of the major technological barriers. Enhancing the thermal conductivity of polymers is important for these applications and has become a very active research topic over the past two decades. In this review article, we aim to: 1). systematically summarize the molecular level understanding on the thermal transport mechanisms in polymers in terms of polymer morphology, chain structure and inter-chain coupling; 2). highlight the rationales in the recent efforts in enhancing the thermal conductivity of nanostructured polymers and polymer nanocomposites. Finally, we outline the main advances, challenges and outlooks for highly thermal-conductive polymer and polymer nanocomposites. the inter-chain coupling. Fig. 1 Schematic diagrams of a polymer: (a) the morphology of a polymer consisting of crystalline and amorphous domains; (b) structure of a polymer chain.In addition to engineering the morphology of polymer chains, another common method to enhance the thermal conductivity of polymers is to blend polymers with highly thermal conductive fillers. The progress of nanotechnology over the last two decades not only provides more diverse high thermal conductivity fillers of different material types and topological shapes but also advances the understanding at the nanoscale. Fig. 2 shows a sketch of a polymer nanocomposite to illustrate the thermal transport mechanisms. In general, there are two types of polymer nanocomposites depending on whether nano-fillers form a network or not. When the filler concentration is low, no inter-filler networks could be formed, as shown in Fig. 2(a). The thermal conductivity is essentially determined by the filler-matrix coupling, i.e, interfacial thermal resistance, and the concentration and the geometric shapes of fillers. When the filler concentration is large enough, high conductivity fillers might form thermally conductive networks, as shown in Fig. 2(b). Although nanocomposites with filler network could possess a higher thermal conductivity than that without a network, their thermal conductivity could still be low due to the large inter-filler thermal contact resistance. Recently, three-dimensional fillers, such as carbon and graphene foams, have drawn a lot of attention. The fundamental thermal transport mechanisms and recent synthesis efforts in both types of nanocomposites are reviewed.This review article is organized as follows. In Section 2, we introduce the experimental progress on the enhancement of thermal conductivity by aligning polymer chains, and then review the methods to further tune the thermal conductivity by engineering chain structure and inter-chain coupling, as illustrated in Fig. 3(a). In Section 3, we discuss the thermal conductivity of polymer nanocomposites both with and without inter...

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Section: Side-chainsmentioning

confidence: 99%

Section: Side-chainsmentioning

confidence: 99%

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Thermal conductivity of polymers and polymer nanocomposites

Huang

Qian

Yang

2018

Materials Science and Engineering: R: Reports

Self Cite

596

391

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“…Studies show that by the introduction of side-chains into polymer backbones, thermal conductivity would decrease. [19] This is believed due to the change in morphology and thus affecting heat carrier propagation lengths. [20] In some cases, the reduction of crystallinity level was also observed.…”

Section: Polymer Chains Structurementioning

confidence: 99%

“…However, one of the main challenges is to avoid nanoparticle agglomeration during the dispersion process. Based on this, many works selected thermally conductive nanofillers 42.4 [54] 14.5 [58] 12.27 [60] 21.39 [56] 30.25 [55] 12.4 [57] 6.88 [59] F I G U R E 8 K eff of randomly oriented nano filled composites versus their filler content in wt% [86, F I G U R E 6 A schematic diagram of the preparation of graphene oxide microspheres/epoxy resin composites (reprinted with permission from Reference( [67]) copyright 2019 Elsevier) 0.96 [18] 3.5 [19] 19.5 [15] 13.41 [17] 21.1 [16] 6.4 F I G U R E 7 K eff of randomly oriented micro filled composites versus their filler content in wt%, [55, to create thermally conductive polymeric composites, some of which will be reviewed here. Figure 8 presents the maximum achieved thermal conductivity of nano-filled composites with respect to their filler loading wt%.…”

Section: Nano Filled Compositesmentioning

confidence: 99%

A review on high thermally conductive polymeric composites

Ghaffari‐Mosanenzadeh

Tafreshi

Dammen‐Brower

et al. 2021

Polymer Composites

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Polymers are known as thermally insulated materials with reported effective thermal conductivity (K eff ) in the range of 0.1 to 0.5 Wm À1 K À1 . However, increasing demand for smaller and more powerful electronics has created the need for thermally conductive polymers for use in heat exchangers and electronic packaging applications. Given this background, much research has been done over the past two decades to increase the K eff of polymers. Based on the strategy involved, those works can be divided into two main categories:(i) increasing the K eff of the neat polymer by aligning its chains orientation; and (ii) increasing polymer K eff by fabrication of polymeric composites with thermally conductive filler networks. Among these two strategies, the former is limited to nanoscale laboratory research and is difficult to scale up for mass production. Therefore, this work is mainly focused on the latter category, thermally conductive polymeric composites, which has a higher potential for large-scale production. This work aims to summarize, evaluate, and highlight the successful strategies of the recent efforts in enhancing the thermal conductivity of polymer composites. The major achievements, future challenges, and the outlooks of high thermally conductive polymeric composites are presented by analyzing the results of about 300 works.

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Tropocollagen‐Inspired Hierarchical Spiral Structure of Organic Fibers in Epoxy Bulk for 3D High Thermal Conductivity

Chen

Zhang

et al. 2022

Advanced Materials

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Their intrinsically high k is due to high electrical conductivity or harmonic crystal lattices. [10][11][12] Organic polymers are considered poor thermal conductors due to their randomly coiled covalent backbone and poor electrical conductivity, with low thermal conductivities on the order of 0.1 W m −1 K −1 . [13] However, early studies achieved orders of magnitude increases in k in oriented single chains, crystals, and anisotropic polymers, such as polyethylene (PE), poly(p-phenylene benzobisoxazole) (PBO), polythiophene, and Kevlar. [14][15][16] This creates opportunities to synthesize inexpensive, lightweight and electrically insulating thermal conductors to replace traditional metals and ceramics in specific applications.Taking the simplest polymer, PE, as an example, the milestone work was carried out by Choy et al., [17,18] where PE crystallites with a folded carbon-carbon backbone were restructured via extrusion to perform a large anisotropy in k. Since then, a variety of high-k products have been reported, including fibers, films, and bulks. [19][20][21][22][23][24][25] For instance, a high-k PE mat containing a large number of needle crystals was prepared that exhibited an axial k of 41.8 W m −1 K −1 , [26] about three times higher than steel; recently, this value has been further extended to 62 W m −1 K −1 in a PE thin-film through a typical disentanglement-extrusion-freezing process. [25] Shen et al. converted ultra-drawn PE objects into ideal single-crystalline nanofibers, achieving a record-high k of 104 W m −1 K −1 in the fiber direction. [19] Our lab previously took advantage of high-k PE microfibers to design an entirely organic and large-thickness bulk, exhibiting a k as high as 38.27 W m −1 K −1 in the through-plane direction. [27] Two conflicting explanations have been postulated for the efficient thermal transport in oriented polymers: one theorizes that content increment and/or dimension enlargement of the fibrillar crystal cause the remarkable thermal conduction; [23] the other attributes this to the evolving high k in the amorphous phase during the orientation process, for example, a classic 1D model calculated the k of amorphous domain in an ultra-drawn PE film to be as high as 16 W m −1 K −1 . [25] The high-k nature of polymers requires further experimental support and mechanistic explanations. Additionally, the highly thermal conductive characteristic for current polymer samples is still limited to only one specific direction, e.g., the axial direction for fibers and in-plane direction for films. 3D high thermal Polymers are usually considered thermal insulators; however, significant enhancements in thermal conductivity (k) have been observed in oriented fibers and films. Despite being advantageous in real-world applications, extending the linear thermal-transport advantage of polymers into the 3D space in bulk materials is still limited due to the spatially interfacial phononconduction barriers. Herein, inspired by the structure of tropocollagen, it is discovered that weaving hierarchi...

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Decreased Thermal Conductivity of Polyethylene Chain Influenced by Short Chain Branching

Cited by 40 publications

References 53 publications

Thermal conductivity of polymers and polymer nanocomposites

Thermal conductivity of polymers and polymer nanocomposites

A review on high thermally conductive polymeric composites

Tropocollagen‐Inspired Hierarchical Spiral Structure of Organic Fibers in Epoxy Bulk for 3D High Thermal Conductivity

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