Do Nu Bich Duyen, Imenes Kristin, Aasmundtveit Knut E, Nguyen Hoang-Vu, Andreassen Erik
Department of Microsystems, University of South-Eastern Norway, 3184 Borre, Norway.
SINTEF Industry, 0373 Oslo, Norway.
Polymers (Basel). 2023 Mar 21;15(6):1552. doi: 10.3390/polym15061552.
Materials providing heat dissipation and electrical insulation are required for many electronic and medical devices. Polymer composites with hexagonal boron nitride (hBN) may fulfil such requirements. The focus of this study is to compare composites with hBN fabricated by injection moulding (IM), powder bed fusion (PBF) and casting. The specimens were characterised by measuring thermal conductivity, tensile properties, hardness and hBN particle orientation. A thermoplastic polyurethane (TPU) was selected as the matrix for IM and PBF, and an epoxy was the matrix for casting. The maximum filler weight fractions were 65%, 55% and 40% for IM, casting and PBF, respectively. The highest thermal conductivity (2.1 W/m∙K) was measured for an IM specimen with 65 wt% hBN. However, cast specimens had the highest thermal conductivity for a given hBN fraction. The orientation of hBN platelets in the specimens was characterised by X-ray diffraction and compared with numerical simulations. The measured thermal conductivities were discussed by comparing them with four models from the literature (the effective medium approximation model, the Ordóñez-Miranda model, the Sun model, and the Lewis-Nielsen model). These models predicted quite different thermal conductivities vs. filler fraction. Adding hBN increased the hardness and tensile modulus, and the tensile strength at high hBN fractions. The strength had a minimum as the function of filler fraction, while the strain at break decreased. These trends can be explained by two mechanisms which occur when adding hBN: reinforcement and embrittlement.
许多电子和医疗设备都需要具备散热和电绝缘性能的材料。含有六方氮化硼（hBN）的聚合物复合材料可能满足此类要求。本研究的重点是比较通过注塑成型（IM）、粉末床熔融（PBF）和浇铸制备的含hBN的复合材料。通过测量热导率、拉伸性能、硬度和hBN颗粒取向对试样进行表征。选择热塑性聚氨酯（TPU）作为IM和PBF的基体，环氧树脂作为浇铸的基体。IM、浇铸和PBF的最大填料重量分数分别为65%、55%和40%。对于含65 wt% hBN的IM试样，测得的最高热导率为2.1 W/m∙K。然而，对于给定的hBN分数，浇铸试样具有最高的热导率。通过X射线衍射对试样中hBN片晶的取向进行表征，并与数值模拟结果进行比较。通过将测得的热导率与文献中的四种模型（有效介质近似模型、奥尔多涅斯 - 米兰达模型、孙模型和刘易斯 - 尼尔森模型）进行比较来讨论这些热导率。这些模型预测的热导率与填料分数的关系差异很大。添加hBN提高了硬度和拉伸模量，在高hBN分数时还提高了拉伸强度。强度随填料分数的增加呈现最小值，而断裂应变降低。这些趋势可以通过添加hBN时发生的两种机制来解释：增强和脆化。
