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Thermal Conductivit...
Thermal Conductivity of Cellulose Fibers in Different Size Scales and Densities
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- Antlauf, Mathis (author)
- Umeå universitet,Institutionen för fysik,Department of Physics, Umeå University, SE-90187 Umeå, Sweden
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- Boulanger, Nicolas (author)
- Umeå universitet,Institutionen för fysik,Department of Physics, Umeå̊ University, SE-90187 Umeå, Sweden
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- Berglund, Linn (author)
- Luleå tekniska universitet,Materialvetenskap,Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden
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- Oksman, Kristiina, 1959- (author)
- Luleå tekniska universitet,Materialvetenskap,Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden
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- Andersson, Ove (author)
- Umeå universitet,Institutionen för fysik,Department of Physics, Umeå University, SE-90187 Umeå, Sweden
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(creator_code:org_t)
- 2021-08-17
- 2021
- English.
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 22:9, s. 3800-3809
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Abstract
Subject headings
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- Considering the growing use of cellulose in various applications, knowledge and understanding of its physical properties become increasingly important. Thermal conductivity is a key property, but its variation with porosity and density is unknown, and it is not known if such a variation is affected by fiber size and temperature. Here, we determine the relationships by measurements of the thermal conductivity of cellulose fibers (CFs) and cellulose nanofibers (CNFs) derived from commercial birch pulp as a function of pressure and temperature. The results show that the thermal conductivity varies relatively weakly with density (ρsample = 1340–1560 kg m–3) and that its temperature dependence is independent of density, porosity, and fiber size for temperatures in the range 80–380 K. The universal temperature and density dependencies of the thermal conductivity of a random network of CNFs are described by a third-order polynomial function (SI-units): κCNF = (0.0787 + 2.73 × 10–3·T – 7.6749 × 10–6·T2 + 8.4637 × 10–9·T3)·(ρsample/ρ0)2, where ρ0 = 1340 kg m–3 and κCF = 1.065·κCNF. Despite a relatively high degree of crystallinity, both CF and CNF samples show amorphous-like thermal conductivity, that is, it increases with increasing temperature. This appears to be due to the nano-sized elementary fibrils of cellulose, which explains that the thermal conductivity of CNFs and CFs shows identical behavior and differs by only ca. 6%. The nano-sized fibrils effectively limit the phonon mean free path to a few nanometers for heat conduction across fibers, and it is only significantly longer for highly directed heat conduction along fibers. This feature of cellulose makes it easier to apply in applications that require low thermal conductivity combined with high strength; the weak density dependence of the thermal conductivity is a particularly useful property when the material is subjected to high loads. The results for thermal conductivity also suggest that the crystalline structures of cellulose remain stable up to at least 0.7 GPa.
Subject headings
- TEKNIK OCH TEKNOLOGIER -- Industriell bioteknik -- Biomaterial (hsv//swe)
- ENGINEERING AND TECHNOLOGY -- Industrial Biotechnology -- Bio Materials (hsv//eng)
- TEKNIK OCH TEKNOLOGIER -- Maskinteknik -- Energiteknik (hsv//swe)
- ENGINEERING AND TECHNOLOGY -- Mechanical Engineering -- Energy Engineering (hsv//eng)
- TEKNIK OCH TEKNOLOGIER -- Materialteknik -- Pappers-, massa- och fiberteknik (hsv//swe)
- ENGINEERING AND TECHNOLOGY -- Materials Engineering -- Paper, Pulp and Fiber Technology (hsv//eng)
Keyword
- Nanofibers
- Crystallinity
- Carbon nanomaterials
- Thermal conductivity
- Cellulose
- Trä och bionanokompositer
- Wood and Bionanocomposites
Publication and Content Type
- ref (subject category)
- art (subject category)
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