Achieving High Thermal Conductivity in Epoxy Composites: Effect of Boron Nitride Particle Size and Matrix-Filler Interface

Moradi, Sasan; Calventus, Yolanda; Román, Frida; Hutchinson, John M.

doi:10.3390/polym11071156

Cited by 59 publications

(77 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Most noticeably, the shift is much greater for the smallest (2 µm) particles, with rather similar shifts for the other particles. This effect, which has been reported in earlier work and occurs also for epoxy-thiol composites filled with aluminium nitride particles, appears to be peculiar to epoxy systems cross-linked with thiol [21,29,30].…”

Section: Differential Scanning Calorimetrysupporting

confidence: 80%

“…In addition, although the BN particles are inert and hence would not a priori be expected to influence the chemical cure reaction, we have observed earlier that, for this epoxy-thiol system, there are some systematic effects of BN content on the reaction kinetics [21,29,30]. These effects were correlated to some extent with the thermal conductivity measurements, suggesting that the matrix-filler interface, so crucial to the thermal conductivity and dependent on SSA and filler particle shape and/or size, plays an important role also in the cure kinetics.…”

Section: Introductionmentioning

confidence: 88%

See 1 more Smart Citation

Epoxy composites filled with boron nitride: cure kinetics and the effect of particle shape on the thermal conductivity

Moradi

Calventus

Román

et al. 2020

J Therm Anal Calorim

Self Cite

View full text Add to dashboard Cite

Thermally conducting and electrically insulating materials have been prepared by filling an epoxy-thiol system with boron nitride (BN) particles of different shapes (platelets and agglomerates) and sizes (from 2 to 180 μm), and hence with different specific surface areas. The cure kinetics has been studied by differential scanning calorimetry in both non-isothermal and isothermal modes, and it has been shown that there is a systematic dependence of the cure kinetics on the BN content, the cure reaction generally being retarded by the addition of the BN particles. For filler loadings greater than about 30 vol%, the retardation of the cure, in both isothermal and non-isothermal mode, appears also to decrease as the specific surface area decreases. For the smallest (2 μm) platelets, which have a significantly higher specific surface area (10 m 2 g −1), the retardation is particularly pronounced, and this aspect is rationalized in terms of the activation energy and frequency factor of the reaction. The thermal conductivity of the cured epoxy-thiol-BN composites has been measured using the transient hot bridge method and is found to increase in the usual way with increasing BN content for all the particle types and sizes. For the platelets, the thermal conductivity increases with increasing particle size, mirroring the effect of BN content on the cure kinetics. The agglomerates, though, give the highest values of thermal conductivity, contrary to what might be expected in the light of their specific surface areas. Scanning electron microscopy of the fracture surfaces of the cured composites has been used to show that the interface between epoxy matrix and filler particles is better for the agglomerates. This, together with the reduced interfacial area, explains their higher thermal conductivity.

show abstract

Section: Differential Scanning Calorimetrysupporting

confidence: 80%

Section: Introductionmentioning

confidence: 88%

Epoxy composites filled with boron nitride: cure kinetics and the effect of particle shape on the thermal conductivity

Moradi

Calventus

Román

et al. 2020

J Therm Anal Calorim

Self Cite

View full text Add to dashboard Cite

show abstract

“…This is also illustrated in Figure 8, for the case of the BN particles not treated with silane; the same trend was reported for the silane-treated particles, for which higher thermal conductivities were observed, but for clarity these are not included in Figure 8. show a trend of increasing thermal conductivity as the BN particle size decreases, which contrasts with the usual observed effect of particle size [64,65]. This is also illustrated in Figure 8, for the case of the BN particles not treated with silane; the same trend was reported for the silane-treated particles, for which higher thermal conductivities were observed, but for clarity these are not included in Figure 8.…”

Section: Effect Of Bn Contentmentioning

confidence: 71%

“…These authors suggested that the Lewis acid-base interaction between the sulphur in the thiol and the boron in the filler leads to an improved matrix-filler interface, which was the reason for the enhanced thermal conductivity. In support of this hypothesis, they reported that the same epoxy-BN system cured with a diamine does not give such high thermal conductivities, for example only 1.7 W/mK at 53 wt.% BN [65]. They also noted that the cure kinetics of the epoxy-thiol system and the epoxy-diamine system are quite different in their dependence on the BN content, as discussed in Section 2, and consider this to be further evidence of the favourable matrix-filler interaction in the epoxy-thiol-BN composite system.…”

Section: Effect Of Surface Treatments and Coupling Agentsmentioning

confidence: 92%

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

Hutchinson

Moradi

2020

Materials

Self Cite

View full text Add to dashboard Cite

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.

show abstract

“…While this work focuses its attention on 12 µm diameter W particles, it is well known that size parameters can affect mixture properties. For a fixed volume fraction of filler particles, the thermal conductivity decreases and the viscosity increases as the particle diameter decreases . Although larger particle diameters should increase thermal conductivity, we note that paste‐like TIMs are quite thin and this places an upper limit on particle diameter (see Section S7 in the Supporting Information).…”

mentioning

confidence: 90%

Oxide‐Mediated Formation of Chemically Stable Tungsten–Liquid Metal Mixtures for Enhanced Thermal Interfaces

et al. 2019

View full text Add to dashboard Cite

Modern microelectronics and emerging technologies such as wearable devices and soft robotics require conformable and thermally conductive thermal interface materials to improve their performance and longevity. Gallium‐based liquid metals (LMs) are promising candidates for these applications yet are limited by their moderate thermal conductivity, difficulty in surface‐spreading, and pump‐out issues. Incorporation of metallic particles into the LM can address these problems, but observed alloying processes shift the LM melting point and lead to undesirable formation of additional surface roughness. Here, these problems are addressed by introducing a mixture of tungsten microparticles dispersed within a LM matrix (LM‐W) that exhibits two‐ to threefold enhanced thermal conductivity (62 ± 2.28 W m−1 K−1 for gallium and 57 ± 2.08 W m−1 K−1 for EGaInSn at a 40% filler volume mixing ratio) and liquid‐to‐paste transition for better surface application. It is shown that the formation of a nanometer‐scale LM oxide in oxygen‐rich environments allows highly nonwetting tungsten particles to mix into LMs. Using in situ imaging and particle dipping experimentation within a focused ion beam and scanning electron microscopy system, the oxide‐assisted mechanism behind this wetting process is revealed. Furthermore, since tungsten does not undergo room‐temperature alloying with gallium, it is shown that LM‐W remains a chemically stable mixture.

show abstract

Achieving High Thermal Conductivity in Epoxy Composites: Effect of Boron Nitride Particle Size and Matrix-Filler Interface

Cited by 59 publications

References 23 publications

Epoxy composites filled with boron nitride: cure kinetics and the effect of particle shape on the thermal conductivity

Epoxy composites filled with boron nitride: cure kinetics and the effect of particle shape on the thermal conductivity

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

Oxide‐Mediated Formation of Chemically Stable Tungsten–Liquid Metal Mixtures for Enhanced Thermal Interfaces

Contact Info

Product

Resources

About