Stretching-Induced Thermal Conductivity Change in Shape-Memory Polymer Composites

2020 ◽  
Author(s):  
Stephen Hostler ◽  
Mohnish Peswani ◽  
Han Yang ◽  
Harrison Paul ◽  
Stuart J. Rowan ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Shape Memory ◽  
Thermal Management ◽  
Energy Savings ◽  
Thermal State ◽  
Shape Memory Polymer ◽  
Applied Strain ◽  
Proof Of Concept ◽  
Conductivity Change ◽  
The Matrix

Abstract Active thermal materials like thermal diodes, regulators, and switches have the potential to revolutionize thermal management, creating an opportunity for significant energy savings. We present results on a thermal switching composite that changes its thermal conductivity based on applied strain. The composite is constructed of highly-crystalline, high aspect ratio cellulose nanocrystal (CNC) nanorods embedded in a shape-memory polymer matrix. The properties of the matrix allow for changes to the thermal state to be indefinitely retained and also for the state to be reversed. A switching ratio of two is achieved for this proof-of-concept composite. By comparing the measured results to a Maxwell mixing model, the primary drivers of the thermal conductivity change are traced to changes in crystallinity of the matrix and CNC alignment.

Characristics of Shape Memory Composites Combined with Shape Memory Alloy and Shape Memory Polymer

2013 ◽  
Vol 705 ◽  
pp. 169-172
Author(s):  
Xue Feng ◽  
Li Min Zhao ◽  
Xu Jun Mi
Keyword(s):  
Shape Memory ◽  
Room Temperature ◽  
Shape Recovery ◽  
Volume Fraction ◽  
Shape Memory Polymer ◽  
Young Modulus ◽  
Thermomechanical Properties ◽  
The Matrix ◽  
Shape Memory Composites ◽  
Shape Fixity

In order to develop high functionality of shape memory materials, the shape memory composites combined with TiNi wire and shape memory epoxy were prepared, and the mechanical and thermomechanical properties were studied. The results showed the addition of TiNi wire increased the Young modulus and breaking strength both at room temperature and at elevated temperature. The composites maintained the rates of shape fixity and shape recovery close to 100%. The maximum recovery stress increased with increasing TiNi wire volume fraction, and obtained almost 3 times of the matrix by adding 1vol% TiNi wire.

scholarly journals Thermal Conductivity and Cure Kinetics of Epoxy-Boron Nitride Composites—A Review

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3634
Author(s):  
John M. Hutchinson ◽  
Sasan Moradi
Keyword(s):  
Thermal Conductivity ◽  
Boron Nitride ◽  
Thermal Management ◽  
Filler Content ◽  
Electronic Devices ◽  
Cure Kinetics ◽  
The Matrix ◽  
Thermally Conductive ◽  
Filler Particles ◽  
Kinetics Of

Epoxy resin composites filled with thermally conductive but electrically insulating particles play an important role in the thermal management of modern electronic devices. Although many types of particles are used for this purpose, including oxides, carbides and nitrides, one of the most widely used fillers is boron nitride (BN). In this review we concentrate specifically on epoxy-BN composites for high thermal conductivity applications. First, the cure kinetics of epoxy composites in general, and of epoxy-BN composites in particular, are discussed separately in terms of the effects of the filler particles on cure parameters and the cured composite. Then, several fundamental aspects of epoxy-BN composites are discussed in terms of their effect on thermal conductivity. These aspects include the following: the filler content; the type of epoxy system used for the matrix; the morphology of the filler particles (platelets, agglomerates) and their size and concentration; the use of surface treatments of the filler particles or of coupling agents; and the composite preparation procedures, for example whether or not solvents are used for dispersion of the filler in the matrix. The dependence of thermal conductivity on filler content, obtained from over one hundred reports in the literature, is examined in detail, and an attempt is made to categorise the effects of the variables and to compare the results obtained by different procedures.

A Shape Memory Polymer with Improved Shape Recovery

2004 ◽  
Vol 855 ◽  
Author(s):  
Changdeng Liu ◽  
Patrick T. Mather
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Shape Memory ◽  
Shape Memory Polymer ◽  
Model Fit ◽  
Mechanical Reinforcement ◽  
Conducting Filler ◽  
Thermal Conducting ◽  
Thermally Actuated ◽  
Triggering Process

ABSTRACTThermally actuated shape memory polymers (SMPs) interest, both academically and industrially, due to their ability to memorize a permanent shape that is set during processing and a temporary shape that is later programmed by manipulation above a critical temperature, either Tg or Tm. However, the thermal triggering process for SMPs is usually retarded compared to that of shape memory alloys, because the thermal conductivity of polymers is much lower (<0.30 W/m.K). In the present study, we incorporated a highly thermal conducting filler into a shape memory matrix to increase its thermal conductivity and therefore, shorten the heat transfer progress. A mathematical was worked out that quantitatively relates the material's thermal conductivity with the heat transfer time, τ, also defined as a shape memory induction time. The model fit nicely with our experimental data. In addition, mechanical reinforcement was observed with the addition of this rigid thermal conducting filler.

scholarly journals Micro-buckling of carbon fibers in shape memory polymer composites under bending in the glass transition temperature region

2021 ◽  
Vol 8 (1) ◽  
pp. 96-108
Author(s):  
Nilesh Tiwari ◽  
AbdulHafiz A. Shaikh
Keyword(s):  
Glass Transition ◽  
Shape Memory ◽  
Polymer Composites ◽  
Volume Fraction ◽  
Shape Memory Polymer ◽  
Minimum Energy ◽  
Three Dimensional ◽  
Fiber Volume ◽  
Half Wavelength ◽  
The Matrix

Abstract The influence of a wide temperature range in the glass transition region of a shape memory polymer (SMP) matrix on micro-buckling of the fiber reinforcements in shape memory polymer composites (SMPC) under large bending deformation is described. Analytical expressions to estimate the strain energy, neutral strain surface, critical buckling surface and half wavelength of the buckled fibers in the SMPC are presented based on the minimum energy method. This study considers the reinforced fibers as three-dimensional elastic bodies and the matrix as a temperature stimulated flat plate. A comprehensive study was performed to understand the dynamic temperature behavior of the micro-buckled fibers and corresponding results were validated by previous works in the literature. The effects of fiber volume fraction and thickness of the SMPC plates on the half wavelength are also discussed along with the simultaneous influence of temperature on the parameters computed in the minimum energy analysis.

scholarly journals Thermomechanical performance and shape recovery behaviour of shape memory polymer nanocomposite incorporated with hexagonal boron nitride

2017 ◽  
Vol 46 (1) ◽  
pp. 79-83 ◽  
Author(s):  
Zhenghong Li ◽  
Haibao Lu ◽  
Yongtao Yao ◽  
Long Lin
Keyword(s):  
Thermal Conductivity ◽  
Shape Memory ◽  
Shape Recovery ◽  
Hexagonal Boron Nitride ◽  
Shape Memory Polymer ◽  
Polymer Nanocomposite ◽  
Thermomechanical Properties ◽  
Content Type ◽  
Thermally Responsive ◽  
Thermally Actuated

Purpose The purpose of this paper is to develop an effective approach to significantly improve the thermomechanical properties of shape memory polymer (SMP) nanocomposites that show fast thermally responsive shape recovery. Design/methodology/approach Hexagonal boron nitrides (h-BNs) were incorporated into polymer matrix in an attempt to improve the thermal conductivity and thermally responsive shape recovery behaviour of SMP, respectively. Thermally actuated shape recovery behaviour was recorded and monitored instrumentally. Findings The results show that both glass transition temperature (Tg) and thermomechanical properties of the SMP nanocomposites have been progressively improved with increasing concentration of h-BNs. Analytical results also suggest that the fast-responsive recovery behaviour of the SMP nanocomposite incorporated with h-BNs was due to the increased thermal conductivity. Research limitations/implications A simple way for fabricating SMP nanocomposites with enhanced thermally responsive shape recovery based on the incorporation of h-BNs was developed. Originality/value The outcome of this study may help fabrication of SMP nanocomposites with fast responsive recovery behaviour.

Thermal Properties of Polyurethane Shape Memory Polymer Filled With Magnetite Particles

2011 ◽  
Author(s):  
Bernd Weidenfeller ◽  
Mathias Anhalt ◽  
Hauke Marquardt ◽  
Frank R. Schilling ◽  
Muhammad Y. Razzaq ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Shape Memory ◽  
Specific Heat Capacity ◽  
Shape Memory Polymer ◽  
Particle Sizes ◽  
Magnetite Particles ◽  
Increasing Temperature

Temperature dependent thermal diffusivity (295K ≤ T ≤ 375K), specific heat capacity (290K ≤ T ≤ 380K) and thermal conductivity (300K ≤ T ≤ 340K) were measured on extrusion compounded and injection molded polyurethane shape memory polymers filled with different volume fractions (0%, 10%, 20%, 30%, 40%) of magnetite particles (10μm, 50μm and 150μm). With increasing particle content thermal diffusivity arises from α(PU + 0% Fe3O4) ≈ 0.13mm2/s to α(PU + 40% Fe3O4) ≈ 0.31mm2/s whereas d = 10μm particle sizes lead to higher values than larger particle sizes. Values measured for 150μm large particles are lying between values of composites with 10μm and 50μm particle sizes in the whole investigated temperature range. For higher filler contents differences in thermal diffusivity between composites of different particle sizes disappear. Thermal diffusivity decreases with increasing temperature, while thermal conductivity is increasing from λ(PU+0% Fe3O4) ≈ 0.2W/mK to λ(PU+40% Fe3O4) ≈ 0.6W/mK. Corresponding to glass transition temperatures of the polymer, the specific heat capacity shows a rise between 300K and 320K and a decrease between 350K and 370K.

Cross-linked ethylene-vinyl acetate – poly(urethane) temperature-memory composite actuator

2020 ◽  
Vol 54 (28) ◽  
pp. 4441-4455
Author(s):  
JE Rodriguez ◽  
DH Giraldo ◽  
JC Restrepo ◽  
HA Colorado
Keyword(s):  
Shape Memory ◽  
Vinyl Acetate ◽  
Shape Memory Polymer ◽  
Ethylene Vinyl Acetate ◽  
Mechanical Analysis ◽  
Scanning Calorimetry ◽  
Polymeric Systems ◽  
Responsive Polymers ◽  
The Matrix ◽  
The Relationship

Semicrystalline polymeric systems are a type of Shape Memory Polymer (SMP), which are more straightforward to synthesize in comparison with other class of stimulus-responsive polymers. On these systems, the shape memory is triggered by temperature and partially driven by crystallization-induced elongation, heating-induced contraction, and elastic entropy. However, a stable temporary and permanent shape through cycling is not easy to achieve. For that reason, a laminar composite made based in the encapsulation of ethylene vinyl acetate (EVA) inside a PU matrix was developed, with the aim of obtaining an actuator with a preferred deformation direction and stable change of shape. In this study, chemically cross-linked ethylene vinyl acetate copolymer (cEVA) as SMP was synthesized and functionalized as a reinforcing strip. A temperature-memory actuator composite was manufactured by the encapsulation of a shape memory programmed strip in an elastomer matrix. The shape memory properties and thermocycling assessment were evaluated using differential scanning calorimetry and dynamic mechanical analysis. Results show the ability of the actuator to bend and unbend, following multiple consecutive heating-cooling cycles. The relationship between the strip, the matrix, and the interface is critical in the bending and shape memory maintenance.

scholarly journals Thermally Conductive Shape Memory Polymer Composites Filled with Boron Nitride for Heat Management in Electrical Insulation

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2191
Author(s):  
Andrzej Rybak ◽  
Lukasz Malinowski ◽  
Agnieszka Adamus-Wlodarczyk ◽  
Piotr Ulanski
Keyword(s):  
Thermal Conductivity ◽  
Boron Nitride ◽  
Shape Memory ◽  
Polymer Composites ◽  
Heat Dissipation ◽  
Shape Memory Polymer ◽  
Electrical Insulation ◽  
Heat Management ◽  
Crosslinked Polymer ◽  
Thermally Conductive

The evaluation of a possible application of functional shrinkable materials in thermally conductive electrical insulation elements was investigated. The effectiveness of an electron beam and gamma radiation on the crosslinking of a selected high density polyethylene grade was analyzed, both qualitatively and quantitatively. The crosslinked polymer composites filled with ceramic particles were successfully fabricated and tested. On the basis of the performed investigation, it was concluded that the selected filler, namely a boron nitride powder, is suitable for the preparation of the crosslinked polymer composites with enhanced thermal conductivity. The shape memory effect was fully observed in the crosslinked samples with a recovery factor reaching nearly 99%. There was no significant influence of the crosslinking, stretching, and recovery of the polymer composite during shape memory phenomenon on the value of thermal conductivity. The proposed boron nitride filled polyethylene composite subjected to crosslinking is a promising candidate for fabrication of thermally shrinkable material with enhanced heat dissipation functionality for application as electrically insulating components.

scholarly journals Effect of Liquid Phase Additions on Microstructure and Thermal Properties in Copper and Copper-Diamond Composites

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
A. Rape ◽  
X. Liu ◽  
A. Kulkarni ◽  
J. Singh
Keyword(s):  
Thermal Conductivity ◽  
Liquid Phase ◽  
Thermal Management ◽  
Diamond Particle ◽  
Two Phase ◽  
New Approach ◽  
The Matrix ◽  
Reactive Liquid ◽  
Field Assisted Sintering ◽  
Solid Liquid

This study details a new approach to creating copper-diamond composite materials for thermal management applications by using a two-phase (solid-liquid) approach in powder metallurgy using Field Assisted Sintering Technology (FAST). Silver-copper alloyed powder at eutectic compositions was used as a nonreactive liquid phase while Cu5Si was used as a reactive liquid phase. Microstructure results are reported favorably comparing the additions of a small amount of liquid phase to pure solid state sintering. Additionally, EDX results indicate that the liquid phase material fills gaps at the interface of the matrix and diamond particle resulting in improved microstructure and density. Thermal conductivity results show that liquid phase additions improve the thermal conductivity of composites compared to composites without any liquid phase, but Si additions cause a severe drop in baseline conductivity.

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