Dependence of the polycarbonate mechanical performances on boron nitride flakes morphology
Dependence of the polycarbonate mechanical performances on boron nitride flakes morphology
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DOI：
10.1088/2515-7639/ac0ac0
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发表时间：
2021-10-01
影响因子：
4.8
通讯作者：
Bonaccorso, Francesco
中科院分区：
文献类型：
--
作者：
Lago, Emanuele;Toth, Peter S.;Bonaccorso, Francesco
在复合材料领域开发二维 (2D) 晶体的一个关键要求依赖于其大规模生产。在这方面，层状晶体的液相剥离正在成为大规模生产高质量二维晶体的最有前途的方法之一。然而，二维晶体薄片形态（即厚度和横向尺寸）对聚合物复合材料机械性能的依赖性尚未完全了解。在此，我们通过设计一种环保方法来解决这个问题，该方法基于块状六方氮化硼（h-BN）的剥离，该方法因其高固有刚度而广泛用作聚合物复合材料中的填料，即接近1 TPa，在水/表面活性剂溶液中通过级联超速离心控制厚度和横向尺寸。我们的方法使我们能够获得两个长宽比（即横向尺寸除以厚度）分别等于 250 和 350 的薄片群体。随后，通过在 1,3-二氧戊环（汉森溶解度参数与 h-BN 的溶解度参数相匹配的溶剂）中进行溶液混合，将具有调整长径比的 h-BN 薄片用作聚碳酸酯 (PC) 基体中的填料，从而增强填料在基体内的分散性（通过拉曼图谱评估）。我们测试了复合材料的机械性能，发现具有较高长径比的薄片与较低长径比的薄片相比，在极限拉伸强度和杨氏模量方面表现出优异的增强效果。例如，在负载量为 0.1 wt% 时，杨氏模量的增强差异为 56 MPa，与原始 PC 相比，对于使用较高长径比填料生产的复合材料而言，增量约为 22%，而对于较低长径比填料而言，增量仅为 17%。
A key requirement for the exploitation of two-dimensional (2D)-crystals in the field of composites relies on their large-scale production. In this respect, liquid phase exfoliation of layered-crystals is emerging as one of the most promising approaches for the scalable production of high-quality 2D-crystals. However, the dependence of the 2D crystal flakes morphology, i.e. thickness and lateral size, on the mechanical properties of the polymer composites is not fully understood yet. Herein, we tackle this issue by designing an environmentally friendly approach, based on the exfoliation of bulk hexagonal-boron nitride (h-BN), widely used as filler in polymer composites for its high intrinsic stiffness, i.e. approaching 1 TPa, in a water/surfactant solution with controlled thickness and lateral size by using cascade ultra-centrifugation. Our approach allows us to obtain two populations of flakes with aspect ratio, i.e. lateral size over thickness, equal to 250 and 350, respectively. The h-BN flakes with tuned aspect ratio are subsequently used as filler in a polycarbonate (PC) matrix by exploiting solution blending in 1,3-dioxolane, a solvent with Hansen's solubility parameters matching the ones of h-BN, thus enhancing the dispersion of the filler inside the matrix, as evaluated by Raman mapping. We tested the composite mechanical properties finding that flakes with higher aspect ratio show superior reinforcements in terms of both ultimate tensile strength and Young's modulus, compared with their lower aspect ratio counterparts. As example, at 0.1 wt% of loading, the difference in reinforcement in terms of Young's Modulus is of 56 MPa, being the increment, compared to pristine PC, of similar to 22% for composites produced with higher aspect ratio fillers, whereas it is instead of only similar to 17% for lower aspect ratio fillers.