scholarly journals Enhancement of the Thermal Performance of the Paraffin-Based Microcapsules Intended for Textile Applications

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1120
Author(s):  
Virginija Skurkyte-Papieviene ◽  
Ausra Abraitiene ◽  
Audrone Sankauskaite ◽  
Vitalija Rubeziene ◽  
Julija Baltusnikaite-Guzaitiene
Keyword(s):  
Thermal Conductivity ◽  
Thermal Performance ◽  
Comparative Method ◽  
Multiwall Carbon Nanotubes ◽  
Acrylic Resin ◽  
Positive Influence ◽  
Outer Shell ◽  
Ir Camera ◽  
Spacer Fabric ◽  
Thermally Conductive

Phase changing materials (PCMs) microcapsules MPCM32D, consisting of a polymeric melamine-formaldehyde (MF) resin shell surrounding a paraffin core (melting point: 30–32 °C), have been modified by introducing thermally conductive additives on their outer shell surface. As additives, multiwall carbon nanotubes (MWCNTs) and poly (3,4-ethylenedioxyoxythiophene) poly (styrene sulphonate) (PEDOT: PSS) were used in different parts by weight (1 wt.%, 5 wt.%, and 10 wt.%). The main aim of this modification—to enhance the thermal performance of the microencapsulated PCMs intended for textile applications. The morphologic analysis of the newly formed coating of MWCNTs or PEDOT: PSS microcapsules shell was observed by SEM. The heat storage and release capacity were evaluated by changing microcapsules MPCM32D shell modification. In order to evaluate the influence of the modified MF outer shell on the thermal properties of paraffin PCM, a thermal conductivity coefficient (λ) of these unmodified and shell-modified microcapsules was also measured by the comparative method. Based on the identified optimal parameters of the thermal performance of the tested PCM microcapsules, a 3D warp-knitted spacer fabric from PET was treated with a composition containing 5 wt.% MWCNTs or 5 wt.% PEDOT: PSS shell-modified microcapsules MPCM32D and acrylic resin binder. To assess the dynamic thermal behaviour of the treated fabric samples, an IR heating source and IR camera were used. The fabric with 5 wt.% MWCNTs or 5 wt.% PEDOT: PSS in shell-modified paraffin microcapsules MPCM32D revealed much faster heating and significantly slower cooling compared to the fabric treated with the unmodified ones. The thermal conductivity of the investigated fabric samples with modified microcapsules MPCM32D has been improved in comparison to the fabric samples with unmodified ones. That confirms the positive influence of using thermally conductive enhancing additives for the heat transfer rate within the textile sample containing these modified paraffin PCM microcapsules.

Buckling of Magnetically Formed Filler Fiber Columns Under Compression Increases Thermal Resistance of Soft Polymer Composites

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Matthew Ralphs ◽  
Chandler Scheitlin ◽  
Robert Y. Wang ◽  
Konrad Rykaczewski
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Volume Fraction ◽  
Potential Method ◽  
Nickel Particles ◽  
Thermal Management Of Electronics ◽  
Thermally Conductive ◽  
Soft Polymer ◽  
Magnetically Aligned

Thermally conductive soft composites are in high demand, and aligning the fill material is a potential method of enhancing their thermal performance. In particular, magnetic alignment of nickel particles has previously been demonstrated as an easy and effective way to improve directional thermal conductivity of such composites. However, the effect of compression on the thermal performance of these materials has not yet been investigated. This work investigates the thermal performance of magnetically aligned nickel fibers in a soft polymer matrix under compression. The fibers orient themselves in the direction of the applied magnetic field and align into columns, resulting in a 3× increase in directional thermal conductivity over unaligned composites at a volume fraction of 0.15. Nevertheless, these aligned fiber columns buckle under strain resulting in an increase in the composite thermal resistance. These results highlight potential pitfalls of magnetic filler alignment when designing soft composites for applications where strain is expected such as thermal management of electronics.

scholarly journals Enhancement of thermal properties of bio-based microcapsules intended for textile applications

2020 ◽  
Vol 18 (1) ◽  
pp. 669-680
Author(s):  
Virginija Skurkytė-Papievienė ◽  
Aušra Abraitienė ◽  
Audronė Sankauskaitė ◽  
Vitalija Rubežienė ◽  
Kristina Dubinskaitė
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Phase Change ◽  
Multiwall Carbon Nanotubes ◽  
Capric Acid ◽  
Test Method ◽  
Supplementary Information ◽  
Scanning Calorimetry ◽  
Ir Camera ◽  
The Core

AbstractThe thermal properties of bio-based phase change material (PCM) microcapsules and their separate components, core and shell, were investigated considering the influence of used thermal enhancer. As a core, bio-based PCM, capric acid (CA), was used. Biodegradable material, such as polylactic acid (PLA), was used as a shell. To improve the thermal conductivity of PLA/CA microcapsules, the multiwall carbon nanotubes (MWCNTs) were used as a thermal enhancer. Composites of PCM with different concentrations of MWCNT as well as composites of PLA with these carbon compounds were prepared and investigated to assess how MWCNT influences the thermal conductivity of the core and the shell. The heat storage and release capacity, as well as the phase change temperatures of CA/MWCNT composites and manufactured PCM microcapsules, were determined using differential scanning calorimetry. To evaluate the thermal conductivity of prepared composites and to compare it with the conductivity of pure materials (without MWCNT), their thermal resistance was measured using the guarded-hotplate test method. To obtain the supplementary information and to assess the dynamic behavior of used PCM during the temperature changes, another technique, such as monitoring of a cold/hot plate with an IR camera, was used. The results of these measurements showed that introduced MWCNT increases the thermal conductivity of PCM used for the core and the conductivity of films prepared from PLA. Consequently, with reference to the results obtained, it could be stated that the introduction of MWCNT into PLA/CA microcapsules improved the thermal properties of these microcapsules. However, it was determined that too large concentration of MWCNT reduces an enthalpy of melting and crystallization of tested PCM and PCM microcapsules. Therefore, during the investigation, an optimal concentration of MWCNT additives has been determined.

Thermally Conductive (TC) Plastics in LED Lamps

2010 ◽  
Vol 2010 (DPC) ◽  
pp. 001514-001539
Author(s):  
Rob Janssen ◽  
Ir. L. Douven ◽  
H. K. van Dijk
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Thermal Performance ◽  
Heat Sinks ◽  
Complex Case ◽  
Ideal Case ◽  
General Validity ◽  
Trade Off ◽  
Thermally Conductive ◽  
The Ideal

In section 1, an assessment is made of the typical thermal conductivities attainable in a TC-plastic followed by an examination of the trade-off between increased thermal conductivity and decreased toughness caused by increasing filler load of such a TC-plastic. Having established that currently there is a ceiling conductivity of around 25 W/mK for TC-plastics, i.e., well below the 100 W/mK TC level of metals, subsequently a basic analysis is provided on the suitability of materials with such moderate TC-levels in metal replacement. For this purpose, the ideal case of a unidirectional (1D) heat flow is considered in section 2, in section 3, a more complex case of a bidirectional heat flow is analyzed. Finally, section 4 considers the thermal performance of TC-plastics in a real 3D part, i.e., the heat sink housing of an LED lamp. More specifically, a comparison is made between the thermal performance of the housing molded in a heat conductive plastic and that of an all-aluminum housing. This comparison clearly demonstrates general validity and practical value of the conclusions drawn in sections 2 and 3 and highlights the outstanding suitability of TC-plastics for heat sinks in lighting applications. High performances STANYL TC in particular.

Highly thermally conductive UHMWPE/NG composites with the segregated structure and their application for heat spreader

2020 ◽  
pp. 089270572096564
Author(s):  
Xiao Wang ◽  
Hui Lu ◽  
Jun Chen
Keyword(s):  
Thermal Conductivity ◽  
Laser Flash ◽  
Heating Process ◽  
X Ray Diffraction ◽  
Heat Spreader ◽  
Conductive Composites ◽  
Compression Direction ◽  
Thermal Analyzer ◽  
Thermally Conductive ◽  
Plane Direction

In this work, ultra-high molecular weight polyethylene (UHMWPE)/natural flake graphite (NG) polymer composites with the extraordinary high thermal conductivity were prepared by a facile mixed-heating powder method. Morphology observation and X-ray diffraction (XRD) tests revealed that the NG flakes could be more tightly coated on the surface of UHMWPE granules by mixed-heating process and align horizontally (perpendicular to the hot compression direction of composites). Laser flash thermal analyzer (LFA) demonstrated that the thermal conductivity (TC) of composites with 21.6 vol% of NG reached 19.87 W/(m·K) and 10.67 W/(m·K) in the in-plane and through-plane direction, respectively. Application experiment further demonstrated that UHMWPE/NG composites had strong capability to dissipate the heat as heat spreader. The obtained results provided a valuable basis for fabricating high thermal conductive composites which can act as advanced thermal management materials.

Maximizing Heat Transfer Through Joint Fin Systems

2005 ◽  
Vol 128 (2) ◽  
pp. 203-206 ◽  
Author(s):  
A.-R. A. Khaled
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Performance ◽  
Critical Length ◽  
The Other ◽  
Rigid Fixation ◽  
Convection Coefficient ◽  
Heat Transfer Characteristics ◽  
Cold Side ◽  
Transfer Characteristics

Heat transfer through joint fins is modeled and analyzed analytically in this work. The terminology “joint fin systems” is used to refer to extending surfaces that are exposed to two different convective media from its both ends. It is found that heat transfer through joint fins is maximized at certain critical lengths of each portion (the receiver fin portion which faces the hot side and the sender fin portion that faces the cold side of the convective media). The critical length of each portion of joint fins is increased as the convection coefficient of the other fin portion increases. At a certain value of the thermal conductivity of the sender fin portion, the critical length for the receiver fin portion may be reduced while heat transfer is maximized. This value depends on the convection coefficient for both fin portions. Thermal performance of joint fins is increased as both thermal conductivity of the sender fin portion or its convection coefficient increases. This work shows that the design of machine components such as bolts, screws, and others can be improved to achieve favorable heat transfer characteristics in addition to its main functions such as rigid fixation properties.

scholarly journals Advances in Liquid Crystalline Epoxy Resins for High Thermal Conductivity

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1302
Author(s):  
Younggi Hong ◽  
Munju Goh
Keyword(s):  
Thermal Conductivity ◽  
Network Structure ◽  
Epoxy Resins ◽  
Liquid Crystalline ◽  
Random Network ◽  
Three Dimensional ◽  
Heat Insulator ◽  
Liquid Crystalline Epoxy ◽  
Thermally Conductive ◽  
Substantial Interest

Epoxy resin (EP) is one of the most famous thermoset materials. In general, because EP has a three-dimensional random network, it possesses thermal properties similar to those of a typical heat insulator. Recently, there has been substantial interest in controlling the network structure of EP to create new functionalities. Indeed, the modified EP, represented as liquid crystalline epoxy (LCE), is considered promising for producing novel functionalities, which cannot be obtained from conventional EPs, by replacing the random network structure with an oriented one. In this paper, we review the current progress in the field of LCEs and their application to highly thermally conductive composite materials.

scholarly journals Improving the Actuation Speed and Multi-Cyclic Actuation Characteristics of Silicone/Ethanol Soft Actuators

Actuators ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 62 ◽  
Author(s):  
Boxi Xia ◽  
Aslan Miriyev ◽  
Cesar Trujillo ◽  
Neil Chen ◽  
Mark Cartolano ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Short Term Memory ◽  
Conductive Filler ◽  
Thermally Driven ◽  
Thermally Conductive ◽  
Ethanol Evaporation ◽  
Long Short Term Memory ◽  
Soft Actuators ◽  
Robotic Applications ◽  
Soft Composite

The actuation of silicone/ethanol soft composite material-actuators is based on the phase change of ethanol upon heating, followed by the expansion of the whole composite, exhibiting high actuation stress and strain. However, the low thermal conductivity of silicone rubber hinders uniform heating throughout the material, creating overheated damaged areas in the silicone matrix and accelerating ethanol evaporation. This limits the actuation speed and the total number of operation cycles of these thermally-driven soft actuators. In this paper, we showed that adding 8 wt.% of diamond nanoparticle-based thermally conductive filler increases the thermal conductivity (from 0.190 W/mK to 0.212 W/mK), actuation speed and amount of operation cycles of silicone/ethanol actuators, while not affecting the mechanical properties. We performed multi-cyclic actuation tests and showed that the faster and longer operation of 8 wt.% filler material-actuators allows collecting enough reliable data for computational methods to model further actuation behavior. We successfully implemented a long short-term memory (LSTM) neural network model to predict the actuation force exerted in a uniform multi-cyclic actuation experiment. This work paves the way for a broader implementation of soft thermally-driven actuators in various robotic applications.

scholarly journals Polycrystalline SnSe with a thermoelectric figure of merit greater than the single crystal

2021 ◽  
Author(s):  
Chongjian Zhou ◽  
Yong Kyu Lee ◽  
Yuan Yu ◽  
Sejin Byun ◽  
Zhong-Zhen Luo ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Single Crystal ◽  
High Performance ◽  
Figure Of Merit ◽  
Waste Heat ◽  
Electric Energy ◽  
Cost Effective ◽  
Tin Selenide ◽  
Tin Oxides ◽  
Thermally Conductive

AbstractThermoelectric materials generate electric energy from waste heat, with conversion efficiency governed by the dimensionless figure of merit, ZT. Single-crystal tin selenide (SnSe) was discovered to exhibit a high ZT of roughly 2.2–2.6 at 913 K, but more practical and deployable polycrystal versions of the same compound suffer from much poorer overall ZT, thereby thwarting prospects for cost-effective lead-free thermoelectrics. The poor polycrystal bulk performance is attributed to traces of tin oxides covering the surface of SnSe powders, which increases thermal conductivity, reduces electrical conductivity and thereby reduces ZT. Here, we report that hole-doped SnSe polycrystalline samples with reagents carefully purified and tin oxides removed exhibit an ZT of roughly 3.1 at 783 K. Its lattice thermal conductivity is ultralow at roughly 0.07 W m–1 K–1 at 783 K, lower than the single crystals. The path to ultrahigh thermoelectric performance in polycrystalline samples is the proper removal of the deleterious thermally conductive oxides from the surface of SnSe grains. These results could open an era of high-performance practical thermoelectrics from this high-performance material.

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