Browse
Submit Data
Databases
API
Help

Dataset Information

17 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Thermal Diffusivity and Conductivity of Polyolefins by Thermal Lens Technique.

ABSTRACT: A mode-mismatched thermal lens spectrometry (TLS) technique, in a pump-probe two-laser-beam configuration, was employed for the experimental determination of the thermal properties of four selected well-characterized polyolefin homopolymer films. We investigated the thermal diffusivity (D) and thermal conductivity (κ) of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and polypropylene. We also measured the structural properties (i.e., average molecular weight, polydispersity index, branching number), along with the rheological and thermal properties (i.e., melting point, specific heat capacity Cp, degree of crystallinity) of samples by high-temperature gel permeation chromatography (HT-GPC), rheometric mechanical spectrometry (RMS), differential scanning calorimetry (DSC), and densitometry. The relationship between microstructural properties such as degree of crystallinity, D, and κ was investigated. The results show that there is good correlation between the degree of crystallinity and D. The TL technique enables measurement of D in semitransparent thin films within an uncertainty of 4%.

SUBMITTER: Abbasgholi-Na B

PROVIDER: S-EPMC9269369 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Conductivity-limiting bipolar thermal conductivity in semiconductors.

Project description:Intriguing experimental results raised the question about the fundamental mechanisms governing the electron-hole coupling induced bipolar thermal conduction in semiconductors. Our combined theoretical analysis and experimental measurements show that in semiconductors bipolar thermal transport is in general a "conductivity-limiting" phenomenon, and it is thus controlled by the carrier mobility ratio and by the minority carrier partial electrical conductivity for the intrinsic and extrinsic cases, respectively. Our numerical method quantifies the role of electronic band structure and carrier scattering mechanisms. We have successfully demonstrated bipolar thermal conductivity reduction in doped semiconductors via electronic band structure modulation and/or preferential minority carrier scatterings. We expect this study to be beneficial to the current interests in optimizing thermoelectric properties of narrow gap semiconductors.

| S-EPMC4650813 | biostudies-other

First-in-human clinical study of novel technique to diagnose malignant melanoma via thermal conductivity measurements.

Project description:Melanoma is an aggressive skin cancer that originates from melanocytes and, especially in the case of early-stage melanoma, is distributed adjacent to the epidermis and superficial dermis. Although early-stage melanoma can be distinguished from benign nevus via a dermoscopy, it is difficult to distinguish invasive melanoma in its early stages from in situ melanoma. Because invasive melanoma must undergo a sentinel lymph node biopsy to be diagnosed, a non-invasive method to detect the micro-invasion of early-stage melanoma is needed for dermato-oncologists. This paper proposes a novel quantitative melanoma identification method based on accurate measurements of thermal conductivity using a pen-shaped device. This method requires skin temperature data for one minute to determine the effective thermal conductivity of the skin, allowing it to distinguish melanoma lesions from healthy skin. Results suggest that effective thermal conductivity was negative for in situ melanoma. However, in accordance with tumour progression, effective thermal conductivity was larger in invasive melanoma. The proposed thermal conductivity measurement is a novel tool that detects the micro-invasion of melanoma.

| S-EPMC6405870 | biostudies-other

Filamentous Virus-based Assembly: Their Oriented Structures and Thermal Diffusivity.

Project description:Organic polymers are generally regarded as thermal insulators because amorphous arrangement of molecular chains reduces the mean free path of heat-conducting phonons. However, recent studies indicated that single chains of polymers with highly oriented structures could have high thermal conductivity than bulk polymers because stretched polymer chains effectively conduct phonons through polymeric covalent bonds. Here, we demonstrated the possibility of non-covalent virus assembly prepared by simple flow-induced methods toward high thermal conductive polymeric materials. Films with high thermal diffusivity composed of non-covalent bond-based assemblies of liquid crystalline filamentous viruses were prepared using a simple flow-induced orientation method. Structural and thermal characterization demonstrated that highly oriented structures of the viruses in the film were attributed to the high thermal diffusivity. Our results will open attractive opportunities for biomolecular-based thermally conductive soft materials even though the assemblies are based on non-covalent bonds.

| S-EPMC5883014 | biostudies-literature

Thermal conductivity in porous silicon nanowire arrays.

Project description:The nanoscale features in silicon nanowires (SiNWs) can suppress phonon propagation and strongly reduce their thermal conductivities compared to the bulk value. This work measures the thermal conductivity along the axial direction of SiNW arrays with varying nanowire diameters, doping concentrations, surface roughness, and internal porosities using nanosecond transient thermoreflectance. For SiNWs with diameters larger than the phonon mean free path, porosity substantially reduces the thermal conductivity, yielding thermal conductivities as low as 1 W/m/K in highly porous SiNWs. However, when the SiNW diameter is below the phonon mean free path, both the internal porosity and the diameter significantly contribute to phonon scattering and lead to reduced thermal conductivity of the SiNWs.

| S-EPMC3494563 | biostudies-literature

Study of the Viscosity and Thermal Characteristics of Polyolefins/Solvent Mixtures: Applications for Plastic Pyrolysis.

Project description:Plastic pollution is one of the biggest environmental problems that the world is currently facing. Pyrolysis is a frontier technique aimed at converting plastic waste back into virgin-quality resin. However, the transfer of the waste plastic feed into the pyrolysis reactor must be optimized before the process can be upscaled to a continuous process. In this study, a new solvent that reduces the viscosity of molten plastic was introduced and characterized. The results revealed that the polymers are soluble in the ratio of up to 75 wt % plastic and 25 wt % solvent at 240 °C. The viscosity of pure low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP) in the solvent was measured in different weight percentages of polymer in solvent (30-80 wt %) and at 160, 180, 200, 220, 240, and 260 °C. The viscosity decreased with the decreasing polymer-weight percentage and with increasing temperature. The viscosity of LDPE/solvent and PPs(isotactic)/solvent is much lower than for HDPE/solvent and PPp(polypropylene impact copolymer)/solvent. Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) were applied to characterize the thermal behavior of LDPE, HDPE, and PP in the solvent in three different weight percentages (25, 50, and 75 wt %). The DSC results indicate that in the mixture of PPs/solvent and LDPE/solvent the melting point of PP and LDPE decreases as the amount of solvent increases. Overall, these results indicate that the selected solvent is an effective agent to prepare waste plastics for pyrolysis.

| S-EPMC8655911 | biostudies-literature

Thermal conductivity of Fe-Si alloys and thermal stratification in Earth's core.

Project description:Light elements in Earth's core play a key role in driving convection and influencing geodynamics, both of which are crucial to the geodynamo. However, the thermal transport properties of iron alloys at high-pressure and -temperature conditions remain uncertain. Here we investigate the transport properties of solid hexagonal close-packed and liquid Fe-Si alloys with 4.3 and 9.0 wt % Si at high pressure and temperature using laser-heated diamond anvil cell experiments and first-principles molecular dynamics and dynamical mean field theory calculations. In contrast to the case of Fe, Si impurity scattering gradually dominates the total scattering in Fe-Si alloys with increasing Si concentration, leading to temperature independence of the resistivity and less electron-electron contribution to the conductivity in Fe-9Si. Our results show a thermal conductivity of ∼100 to 110 W⋅m-1⋅K-1 for liquid Fe-9Si near the topmost outer core. If Earth's core consists of a large amount of silicon (e.g., > 4.3 wt %) with such a high thermal conductivity, a subadiabatic heat flow across the core-mantle boundary is likely, leaving a 400- to 500-km-deep thermally stratified layer below the core-mantle boundary, and challenges proposed thermal convection in Fe-Si liquid outer core.

| S-EPMC8740763 | biostudies-literature

Fully Organic Bulk Polymer with Metallic Thermal Conductivity and Tunable Thermal Pathways.

Project description:Electrically insulating polymers are indispensable for electronic and energy applications, but their poor thermal conduction has increasingly become a bottleneck for high-performance devices. Highly drawn low-dimensional polymeric fibers and thin films can exhibit metallic conductivity. Extending this to bulk materials required by real world applications is prohibitive due to the additional interfacial thermal conduction barriers. It is demonstrated that highly aligned ultrahigh molecular weight polyethylene microfibers can be incorporated into a silicone matrix to yield a fully organic bulk polymer composite with a continuous vertical phonon pathway. This leads to a perpendicular thermal conductivity of 38.27 W m-1 K-1 , at par with metals and two orders of magnitude higher than other bulk organic polymers. Taking further advantage of the mechanical flexibility of the microfibers, the processing method offers the freedom to tailor heat transfer pathways in a macroscopic 3D space. The material/process opens up opportunities for efficient thermal management in high-performance devices.

| S-EPMC8292902 | biostudies-literature

Non-Contact Measurement of Thermal Diffusivity in Ion-Implanted Nuclear Materials.

Project description:Knowledge of mechanical and physical property evolution due to irradiation damage is essential for the development of future fission and fusion reactors. Ion-irradiation provides an excellent proxy for studying irradiation damage, allowing high damage doses without sample activation. Limited ion-penetration-depth means that only few-micron-thick damaged layers are produced. Substantial effort has been devoted to probing the mechanical properties of these thin implanted layers. Yet, whilst key to reactor design, their thermal transport properties remain largely unexplored due to a lack of suitable measurement techniques. Here we demonstrate non-contact thermal diffusivity measurements in ion-implanted tungsten for nuclear fusion armour. Alloying with transmutation elements and the interaction of retained gas with implantation-induced defects both lead to dramatic reductions in thermal diffusivity. These changes are well captured by our modelling approaches. Our observations have important implications for the design of future fusion power plants.

| S-EPMC4630606 | biostudies-literature

Light-triggered thermal conductivity switching in azobenzene polymers.

Project description:Materials that can be switched between low and high thermal conductivity states would advance the control and conversion of thermal energy. Employing in situ time-domain thermoreflectance (TDTR) and in situ synchrotron X-ray scattering, we report a reversible, light-responsive azobenzene polymer that switches between high (0.35 W m-1 K-1) and low thermal conductivity (0.10 W m-1 K-1) states. This threefold change in the thermal conductivity is achieved by modulation of chain alignment resulted from the conformational transition between planar (trans) and nonplanar (cis) azobenzene groups under UV and green light illumination. This conformational transition leads to changes in the ?-? stacking geometry and drives the crystal-to-liquid transition, which is fully reversible and occurs on a time scale of tens of seconds at room temperature. This result demonstrates an effective control of the thermophysical properties of polymers by modulating interchain ?-? networks by light.

| S-EPMC6442584 | biostudies-literature

Strain-controlled thermal conductivity in ferroic twinned films.

Project description:Large reversible changes of thermal conductivity are induced by mechanical stress, and the corresponding device is a key element for phononics applications. We show that the thermal conductivity ? of ferroic twinned thin films can be reversibly controlled by strain. Nonequilibrium molecular dynamics simulations reveal that thermal conductivity decreases linearly with the number of twin boundaries perpendicular to the direction of heat flow. Our demonstration of large and reversible changes in thermal conductivity driven by strain may inspire the design of controllable thermal switches for thermal logic gates and all-solid-state cooling devices.

| S-EPMC4165272 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data