Improvement of thermal conductivities and simulation model for glass fabrics reinforced epoxy laminated composites via introducing hetero-structured BNN-30@BNNS fillers

Hetero-structured thermally conductive spherical boron nitride and boron nitride nanosheets(BNN-30@BNNS)fillers were prepared via electro static self-assembly method.And the corresponding thermally conductive&electrically insulating BNN-30@BNNS/Si-GFs/E-44 laminated composites were then fabricated via hot compression.BNN-30@BNNS-Ⅲ(fBNN-30/fBNNS,1/2,wt/wt)fillers presented the optimal synergistic improvement effects on the thermal conductivities of epoxy composites.When the mass fraction of BNN-30@BNNS-Ⅲwas 15 wt%,λvalue of the BNN-30@BNNS-Ⅲ/E-44 composites was up to0.61 W m^(-1)K^(-1),increased by 2.8 times compared with pure E-44(λ=0.22 W m^(-1)K^(-1)),also higher than that of the 15 wt%BNN-30/E-44(0.56 W m^(-1)K^(-1)),15 wt%BNNS/E-44(0.42 W m^(-1)K^(-1)),and 15 wt%(BNN-30/BNNS)/E-44(direct blending BNN-30/BNNS hybrid fillers,1/2,wt/wt,0.49 W m^(-1)K^(-1))composites.Theλin-plane(λ//)andλcross-plane(λ_(⊥))of 15 wt%BNN-30@BNNS-Ⅲ/Si-GFs/E-44 laminated composites significantly reached 2.75 W m^(-1)K^(-1)and 1.32 W m^(-1)K^(-1),186.5%and 187.0%higher than those of Si-GFs/E-44 laminated composites(λ//=0.96 W m^(-1)K^(-1)andλ_(⊥)=0.46 W m^(-1)K^(-1)).Established models can well simulate heat transfer efficiency in the BNN-30@BNNS-Ⅲ/Si-GFs/E-44 laminated composites.Under the condition of point heat source,the introduction of BNN-30@BNNS-Ⅲfillers were conducive to accelerating heat flow trans fe r.BNN-30@BNNS-Ⅲ/Si-GFs/E-44 laminated composites also demonstrated outstanding electrical insulating properties(cross-plane withstanding voltage,breakdown strength,surface&volume resistivity of 51.3 kV,23.8 kV mm^(-1),3.7×10^(14)Ω&3.4×10^(14)Ω·cm,favorable mechanical properties(flexural strength of 401.0 MPa and ILSS of 22.3 MPa),excellent dielectric properties(εof 4.92 and tanδof 0.008)and terrific thermal properties(T_(g )of 167.3℃and T_(HRI) of 199.2℃).

Significant Reduction of Interfacial Thermal Resistance and Phonon Scattering in Graphene/Polyimide Thermally Conductive Composite Films for Thermal Management

The developing flexible electronic equipment are greatly affected by the rapid accumulation of heat,which is urgent to be solved by thermally conductive polymer composite films.However,the interfacial thermal resistance(ITR)and the phonon scattering at the interfaces are the main bottlenecks limiting the rapid and efficient improvement of thermal conductivity coefficients(λ)of the polymer composite films.Moreover,few researches were focused on characterizing ITR and phonon scattering in thermally conductive polymer composite films.In this paper,graphene oxide(GO)was aminated(NH_(2)-GO)and reduced(NH_(2)-rGO),then NH_(2)-rGO/polyimide(NH_(2)-rGO/PI)thermally conductive composite films were fabricated.Raman spectroscopy was utilized to innovatively characterize phonon scattering and ITR at the interfaces in NH_(2)-rGO/PI thermally conductive composite films,revealing the interfacial thermal conduction mechanism,proving that the amination optimized the interfaces between NH_(2)-rGO and PI,reduced phonon scattering and ITR,and ultimately improved the interfacial thermal conduction.The in-planeλ(λ∥)and through-planeλ(λ_(⊥))of 15 wt%NH_(2)-rGO/PI thermally conductive composite films at room temperature were,respectively,7.13 W/mK and 0.74 W/mK,8.2 timesλ∥(0.87 W/mK)and 3.5 timesλ_(⊥)(0.21 W/mK)of pure PI film,also significantly higher thanλ∥(5.50 W/mK)andλ_(⊥)(0.62 W/mK)of 15 wt%rGO/PI thermally conductive composite films.Calculation based on the effective medium theory model proved that ITR was reduced via the amination of rGO.Infrared thermal imaging and finite element simulation showed that NH_(2)-rGO/PI thermally conductive composite films obtained excellent heat dissipation and efficient thermal management capabilities on the light-emitting diodes bulbs,5G high-power chips,and other electronic equipment,which are easy to generate heat severely.

Advances in 3D printing for polymer composites:A review

The potential of three-dimensional(3D)printing technology in the fabrication of advanced polymer composites is becoming increasingly evident.This review discusses the latest research developments and applications of 3D printing in polymer composites.First,it focuses on the optimization of 3D printing technology,that is,by upgrading the equipment or components or adjusting the printing parameters,to make them more adaptable to the processing characteristics of polymer composites and to improve the comprehensive performance of the products.Second,it focuses on the 3D printable novel consumables for polymer composites,which mainly include the new printing filaments,printing inks,photosensitive resins,and printing powders,introducing the unique properties of the new consumables and different ways to apply them to 3D printing.Finally,the applications of 3D printing technology in the preparation of functional polymer composites(such as thermal conductivity,electromagnetic interference shielding,biomedicine,self-healing,and environmental responsiveness)are explored,with a focus on the distribution of the functional fillers and the influence of the topological shapes on the properties and functional characteristics of the 3D printed products.The aim of this review is to deepen the understanding of the convergence between 3D printing technology and polymer composites and to anticipate future trends and applications.

3D打印调控铜线/聚乳酸复合材料的导热通路长度和数量

导热通路对理解导热高分子复合材料的导热行为至关重要,但目前有关导热通路属性(长度、数量)对高分子复合材料导热系数的影响机制缺乏深入研究.本文采用3D打印技术制备了铜线(Cw)导热通路长度和数量可控的一维铜线/聚乳酸(1D-Cw/PLA)导热复合材料,建立了针对一维导热通路的高分子复合材料的导热模型,明晰了其导热通路属性与其导热性能的定量关系.相同Cw用量下,1D-Cw/PLA导热复合材料的面内导热系数与导热通路的数量和长度呈正相关.采用本文构建的导热模型和经验方程对1D-Cw/PLA复合材料的导热系数进行预测,95%的置信度表明预测值与实测值无显著差异.