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Due to the rapid development of the miniaturization and portability of electronic devices, the demand for polymer composites with high thermal conductivity and mechanical flexibility has significantly increased. A carbon nanotube (CNT)-graphene (Gr)/polydimethylsiloxane (PDMS) composite with excellent thermal conductivity and mechanical flexibility is prepared by ultrasonic-assisted forced infiltration (UAFI). When the mass ratio of CNT and Gr reaches 3:1, the thermal conductivity of the CNT-Gr(3:1)/PDMS composite is 4.641 W/(m·K), which is 1619% higher than that of a pure PDMS matrix. In addition, the CNT-Gr(3:1)/PDMS composite also has excellent mechanical properties. The tensile strength and elongation at break of CNT-Gr(3:1)/PDMS composites are 3.29 MPa and 29.40%, respectively. The CNT-Gr/PDMS composite also shows good performance in terms of electromagnetic shielding and thermal stability. The PDMS composites have great potential in the thermal management of electronic devices. [ABSTRACT FROM AUTHOR]

For the better operation of future electronic devices in complex situations, higher requirements of mechanical performance, especially bearing capacity, were put forward to functional composites. Therefore, the mechanical performance enhancement of functional composites had important practical application value. In this work, we reported a short carbon fiber-graphene nanoplatelets-polydimethylsiloxane (SGP)/epoxy acrylic resin (EA resin) composites with integrated thermal conductivity, electromagnetic interference (EMI) shielding, and mechanical performances using a combination method of 3D printing and vacuum impregnation. In the SGP/EA resin composite, EA resin skeleton with different cell shapes was responsible for the bearing capacity of composite samples, while the thermal conductivity and EMI shielding performance were provided by the SGP compound. When the cell shape of skeleton was circular and the filling contents in SGP compound was 15 wt% SCF and 6 wt% GNP, the SGP/EA resin composite presented best combination properties of 323.5 kPa compressive modulus, 2.13 W/(m·K) thermal conductivity, and 45.93 dB EMI shielding performance at 12.4 GHz. This work provided a facile, low-cost, and scalable method to fabricate composite samples with integrated thermal conductivity, EMI shielding, and mechanical performances. These multifunctional composites are highly promising for applications concerning heat dissipation, EMI shielding, and load-bearing devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) printing is a layered additive manufacturing technology. In common 3D printing methods, direct ink writing (DIW) and fused deposition modeling (FDM) are new extrusion-based technologies. FDM works by melting a hot-melt material and squeezing it out through a tiny nozzle. Conversely, DIW, accurately deposit accurate amount of paste at different distances through the conveying system (extruder). As a unique approach, this technology introduces design freedom, versatility and stability into the printing structure at the same time. In addition, DIW technology is suitable for thermoset 3D printing. The influences of filler orientation in polymer matrix and printing paths on the thermal conductivity (λ) of thermoset 3D printing products are worth studying. Therefore, we built a thermoset 3D printer, and optimized the structure of the nozzle device, effectively improved the printing accuracy. Polydimethylsiloxane (PDMS) and hexagonal boron nitride (h BN) are selected as polymer matrix and thermally conductive filler, respectively. Compared with pure PDMS, the λ value of h BN/PDMS composites increases obviously with increasing h BN content. Meanwhile, the mechanical properties of composites with different printing paths are systematically studied. This designable orientation provides opportunities and challenges for other functional structure design such as hollow structure. [Display omitted] [ABSTRACT FROM AUTHOR]