Abstract In this work, we introduce the use of selective microwave heating to solve the problems of conventional heating systems, such as non-uniformity and thickness restriction, in classical thermoplastic foaming methods. To do so, carbon nanotubes (CNTs) are used as microwave absorbers in a transparent polymer media. When irradiated, CNTs are responsible for a local temperature increase in the polymer/gas solution, allowing local polymer softening and increased blowing agent super-saturation, in turn inducing bubble nucleation and growth. The huge number of active sites (CNTs) for both heating and bubble nucleation and the possibility to fine-tune the heating energy provide large uniformity and an extra control over the bubble growth, to generate well-expanded, fine-celled, uniform, relatively thick foams. As a model system, we successfully foamed 1 cm-thick polystyrene/CNT nanocomposites with CO2, and achieved uniform morphologies and large expansion ratios (over 22 folds). For proper comparison, we also utilized conventional foaming methods such as water bath and fast pressure drop, both resulting in denser and less uniform foams. Here, for the first time, a single particle type, CNTs, is used as a “nucleating agent”, a “heating agent” and, as it will be seen in the following, a “collapse-preventing agent”.

中文翻译：

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碳纳米管在热塑性塑料微波发泡中的应用

摘要 在这项工作中，我们介绍了使用选择性微波加热来解决传统加热系统在经典热塑性发泡方法中存在的不均匀性和厚度限制等问题。为此，碳纳米管 (CNT) 被用作透明聚合物介质中的微波吸收剂。当受到照射时，碳纳米管会导致聚合物/气体溶液的局部温度升高，从而使聚合物局部软化并增加发泡剂过饱和度，进而导致气泡成核和生长。用于加热和气泡成核的大量活性位点 (CNT) 以及微调加热能量的可能性提供了大的均匀性和对气泡生长的额外控制，以产生膨胀良好、细孔、均匀、相对厚厚的泡沫。作为模型系统，我们成功地用 CO2 发泡了 1 cm 厚的聚苯乙烯/CNT 纳米复合材料，并实现了均匀的形态和大的膨胀率（超过 22 倍）。为了进行适当的比较，我们还使用了传统的发泡方法，例如水浴和快速压降，两者都会产生更密集且不太均匀的泡沫。在这里，单颗粒类型的 CNT 首次被用作“成核剂”、“加热剂”，以及在下文中将看到的“防坍塌剂”。