Constructing Hierarchical Polymer Nanocomposites with Strongly Enhanced Thermal Conductivity

Highly Thermally Conductive and Flame-Retardant Waterborne Polyurethane Composites with 3D BNNS Bridging Structures via Magnetic Field Assistance

The microstructure design for thermal conduction pathways in polymeric electrical encapsulation materials is essential to meet the stringent requirements for efficient thermal management and thermal runaway safety in modern electronic devices. Hence, a composite with three-dimensional network (Ho/U-BNNS/WPU) is developed by simultaneously incorporating magnetically modified boron nitride nanosheets (M@BNNS) and non-magnetic organo-grafted BNNS (U-BNNS) into waterborne polyurethane (WPU) to synchronous molding under a horizontal magnetic field. The results indicate that the continuous in-plane pathways formed by M@BNNS aligned along the magnetic field direction, combined with the bridging structure established by U-BNNS, enable Ho/U-BNNS/WPU to exhibit exceptional in-plane (λ//) and through-plane thermal conductivities (λ⊥). In particular, with the addition of 30 wt% M@BNNS and 5 wt% U-BNNS, the λ// and λ⊥ of composites reach 11.47 and 2.88 W m-1 K-1, respectively, which representing a 194.2% improvement in λ⊥ compared to the composites with a single orientation of M@BNNS. Meanwhile, Ho/U-BNNS/WPU exhibits distinguished thermal management capabilities as thermal interface materials for LED and chips. The composites also demonstrate excellent flame retardancy, with a peak heat release and total heat release reduced by 58.9% and 36.9%, respectively, compared to WPU. Thus, this work offers new insights into the thermally conductive structural design and efficient flame-retardant systems of polymer composites, presenting broad application potential in electronic packaging fields.

Two-directions mechanical strength and high-barrier mechanisms of cellulose nanocrystal- based hybrids reinforced packaging with nacre-mimetic structure

This work represents a new composite film with a nacre-mimetic structure through the alignment of hybrids comprising cellulose nanocrystals and ball-milled boron nitride (CNC-BNNS), within polypropylene carbonate (PPC) endowed with various properties. The impact of CNC-BNNS hybrids on mechanical strength mechanisms was evaluated under two-directional forces, marking the first such assessment. Using a solution casting approach, incorporating 5 % CNC-BNNS improved tensile strength by 67.6 % longitudinally and 4 % in the cross-sectional direction of the prepared PPC composite. Adding 5 %, CNC-BNNS increased the maximum degradation temperature by 12.1 °C and the glass transition temperature by 6.8 °C, as anticipated. Through synergies between CNC-BNNS and PPC, composite film with 15 % CNC-BNNS displayed enhanced barrier properties, notably reducing oxygen permeability (OP) and water vapor permeability (WVP) by 26.1 % and 90.9 %. Consequently, strawberries and blueberries packaged with these films saw extended shelf lives of up to 6 days. Furthermore, the degradation mechanisms of the composite in natural soil were investigated to assure the environmental issue, revealing a fast degradation rate of 44.5 % over 90 days. This study proposes a sustainable method for producing high-performance composite materials with antioxidant, liquid leakage resistance, and UV resistance, making them ideal for food packaging.

Advancing high thermal conductivity: novel theories, innovative materials, and applications in thermal management technologies

Effective thermal management is crucial for the performance and stability of modern electronics, emphasizing the demand for high thermal conductivity (κ). This review summarizes the latest development in highκ, discussing the emerging theories, innovative materials and practical applications for interfacial heat dissipation. Unique phononic thermal transport behaviors are discussed, including four phonon-phonon scattering, hydrodynamic phonons, surface phonon-polaritons, and more. The review also highlights innovative materials with highκ, such as two-dimensional pentagonal structures, boron carbon nitrogen structures, hexagonal boron arsenide andθ-phase tantalum nitride. In addition, the potential of polymer composites reinforced with highκfillers and surface engineering for advanced electronic applications are also discussed. By integrating these theoretical approaches and material innovations, this review offers comprehensive strategies for enhancing thermal management in modern electronic devices.

Polymeric Nanocomposites of Boron Nitride Nanosheets for Enhanced Directional or Isotropic Thermal Transport Performance

Polymeric composites with boron nitride nanosheets (BNNs), which are thermally conductive yet electrically insulating, have been pursued for a variety of technological applications, especially those for thermal management in electronic devices and systems. Highlighted in this review are recent advances in the effort to improve in-plane thermal transport performance in polymer/BNNs composites and also the growing research activities aimed at composites of enhanced cross-plane or isotropic thermal conductivity, for which various filler alignment strategies during composite fabrication have been explored. Also highlighted and discussed are some significant challenges and major opportunities for further advances in the development of thermally conductive composite materials and their mechanistic understandings.

SPI-Modified h-BN Nanosheets-Based Thermal Interface Materials for Thermal Management Applications

The rising concern over the usage of electronic devices and the operating environment requires efficient thermal interface materials (TIMs) to take away the excess heat generated from hotspots. TIMs are crucial in dissipating undesired heat by transferring energy from the source to the heat sink. Silicone oil (SO)-based composites are the most used TIMs due to their strong bonding and oxidation resistance. However, thermal grease performance is unreliable due to aging effects, toxic chemicals, and a higher percentage of fillers. In this work, TIMs are prepared using exfoliated hexagonal boron nitride nanosheets (h-BNNS) as a nanofiller, and they were functionalized by ecofriendly natural biopolymer soy protein isolate (SPI). The exfoliated h-BNNS has an average lateral size of ∼266 nm. The functionalized h-BNNS/SPI are used as fillers in the SO matrix, and composites are prepared using solution mixing. Hydrogen bonding is present between the organic chain/oxygen in silicone polymer, and the functionalized h-BNNS are evident from the FTIR measurements. The thermal conductivity of h-BNNS/SPI/SO was measured using the modified transient plane source (MTPS) method. At room temperature, the maximum thermal conductivity is 1.162 Wm-1K-1 (833% enhancement) at 50 wt % of 3:1 ratio of h-BNNS:SPI, and the thermal resistance (TR) of the composite is 5.249 × 106 K/W which is calculated using the Foygel nonlinear model. The heat management application was demonstrated by applying TIM on a 10 W LED bulb. It was found that during heating, the 50 wt % TIM decreases the surface temperature of LED by ∼6 °C compared with the pure SO-based TIM after 10 min of ON condition. During cooling, the modified TIM reduces the surface temperature by ∼8 °C under OFF conditions within 1 min. The results indicate that natural polymers can effectively stabilize and link layered materials, enhancing the efficiency of TIMs for cooling electronics and LEDs.

Rapid Thermochromic and Highly Thermally Conductive Nanocomposite Based on Silicone Rubber for Temperature Visualization Thermal Management in Electronic Devices

Effective heat dissipation and real-time temperature monitoring are crucial for ensuring the long-term stable operation of modern, high-performance electronic products. This study proposes a silicon rubber polydimethylsiloxane (PDMS)-based nanocomposite with a rapid thermal response and high thermal conductivity. This nanocomposite enables both rapid heat dissipation and real-time temperature monitoring for high-performance electronic products. The reported material primarily consists of a thermally conductive layer (Al2O3/PDMS composites) and a reversible thermochromic layer (organic thermochromic material, graphene oxide, and PDMS nanocoating; OTM-GO/PDMS). The thermal conductivity of OTM-GO/Al2O3/PDMS nanocomposites reached 4.14 W m-1 K-1, reflecting an increase of 2200% relative to that of pure PDMS. When the operating temperature reached 35, 45, and 65 °C, the surface of OTM-GO/Al2O3/PDMS nanocomposites turned green, yellow, and red, respectively, and the thermal response time was only 30 s. The OTM-GO/Al2O3/PDMS nanocomposites also exhibited outstanding repeatability and maintained excellent color stability over 20 repeated applications.

Dry-Contact Thermal Interface Material with the Desired Bond Line Thickness and Ultralow Applied Thermal Resistance

Efforts to directly utilize thixotropic polymer composites for out-of-plane thermal transport applications, known as thermal interface materials (TIMs), have been impeded by their mediocre applied thermal resistance (Reff) in a sandwiched structure. Different from traditional attempts at enhancing thermal conductivity, this study proposes a low-bond line thickness (BLT) path for mitigating the sandwiched thermal impedance. Taking the most common TIM, polydimethylsiloxane/aluminum oxide/zinc oxide (PDMS/Al2O3/ZnO), as an example, liquid metal is designed to on-demand localize at the Al2O3-polymer and Al2O3-filler interface regions, breaking rheological challenges for lowering the BLT. Specifically, during the sandwiched compression process, interfacial LM is just like the lubricant, dexterously promoting the relaxation of immobilized PDMS chains and helping fillers to flow through mitigating the internal friction between Al2O3 and adjacent filler. As a result, this TIM first time exhibits a boundary BLT (4.28 μm) that almost approaches the diameter of the maximum filler and performs an ultralow dry-contact Reff of 4.05 mm2 K/W at 40 psi, outperforming most reported and commercial dry-contact TIMs. This study of the low-BLT direction is believed to point to a new path for future research on high-performance TIMs.