Lim Donghwan, Kim Kwanhoon, Hong Jin, Cha Sung Woon
Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea.
Polymers (Basel). 2025 Jun 27;17(13):1780. doi: 10.3390/polym17131780.
Traditionally, the microcellular foaming process has aimed to generate uniform cell structures by applying heat uniformly to all surfaces of a polymer. Homogeneous cell distribution is known to enhance the mechanical properties and durability of the final product. However, the ability to engineer a gradient in cell density offers potential advantages for specific functional applications, such as improved sound absorption and thermal insulation. In this study, a controlled thermal gradient was introduced by heating only one side of a fully CO-saturated poly(methyl methacrylate) (PMMA) specimen. This approach allowed for the formation of a cell density gradient across the sample thickness. The entire process was conducted using a solid-state batch foaming technique, commonly referred to as the microcellular foaming process. A one-sided heating strategy successfully induced a spatial variation in cell morphology. Furthermore, a coalescence function was developed to account for cell merging behavior, enabling the construction of a predictive model for local cell density. The proposed model accurately captured the evolution of cell density gradients under asymmetric thermal conditions and was validated through experimental observations, demonstrating its potential for precise control over foam structure in saturated PMMA systems.
传统上，微孔发泡工艺旨在通过对聚合物的所有表面均匀施热来生成均匀的泡孔结构。众所周知，均匀的泡孔分布可提高最终产品的机械性能和耐久性。然而，设计泡孔密度梯度的能力对于特定的功能应用具有潜在优势，例如改善吸声和隔热性能。在本研究中，通过仅加热完全CO饱和的聚甲基丙烯酸甲酯（PMMA）试样的一侧引入可控的热梯度。这种方法使得在样品厚度方向上形成泡孔密度梯度。整个过程采用固态间歇发泡技术进行，通常称为微孔发泡工艺。单侧加热策略成功地诱导了泡孔形态的空间变化。此外，还开发了一种聚并函数来解释泡孔合并行为，从而构建了局部泡孔密度的预测模型。所提出的模型准确地捕捉了非对称热条件下泡孔密度梯度的演变，并通过实验观察得到验证，证明了其在饱和PMMA体系中精确控制泡沫结构的潜力。
