Abstract The bimodal cellular structure of foam is known to provide unique physical properties. In addition, it may help reduce foam density. This study proposes a simple method of creating a bimodal microcellular/nanocellular structure by blending PMMAs of different molecular weights using CO2 as the blowing agent. Nanofoam, with its low relative density, is the right candidate for thermal insulation, but obtaining it is challenging. Introducing micron-sized bubbles into homogeneous nanocellular structures may be one way to reduce the foam density and potentially not affect some of the properties. Beyond the bimodal structure, a transition from an ultramicrocellular to a nanocellular structure and from a closed-cell to an open-cell structure was observed. These transitions may be related to the relaxation time and weight percentage of non-entangled PMMA content. Formation of the bimodal nanocellular or open-cell structure may be predicted by the viscoelastic properties such as the relaxation time.

中文翻译：

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通过混合不同分子量来控制 PMMA 双峰纳米泡沫的结构和密度

摘要 众所周知，泡沫的双峰蜂窝结构可提供独特的物理特性。此外，它可能有助于降低泡沫密度。本研究提出了一种通过使用 CO2 作为发泡剂混合不同分子量的 PMMA 来创建双峰微孔/纳米孔结构的简单方法。纳米泡沫的相对密度较低，是隔热材料的合适选择，但获得它具有挑战性。将微米级气泡引入均匀的纳米孔结构可能是降低泡沫密度的一种方法，并且可能不会影响某些特性。除了双峰结构之外，还观察到从超微孔结构到纳米孔结构以及从闭孔结构到开孔结构的转变。这些转变可能与非缠结 PMMA 含量的弛豫时间和重量百分比有关。双峰纳米孔或开孔结构的形成可以通过粘弹性特性如弛豫时间来预测。