In this work, a novel method for regulating cellular structure of polypropylene (PP) foam under CO₂ batch foaming with water as disperse medium was established by addition of hydrophilic fillers (Such as NaCl). The presence of NaCl increased adsorption amount of water in PP/NaCl composites. As a result, both CO₂ and adsorbed water acts as blowing agents during CO₂ batch foaming. Thus the dispersed state and size of NaCl particles directly affect the mixed state of two blowing agents (water and CO₂) and the competition between two types of heterogeneous nucleation from NaCl particles and PP crystals during foaming, which are the fundamental reasons for the formation of the foamed materials with different cellular structures, such as isolated large cell surrounded by uniform small cell structure, bimodal cell structure and homogeneous cell structure. Another unexpected finding was that the water absorption of PP/NaCl composites increased with the decrease of NaCl particle size, which is beneficial to play the in-situ cooling effect and co-blowing agent of absorbed water to control the foaming behavior of PP, and avoid the damage of foam mechanical properties due to the high content of filler.

在这项工作中，通过添加亲水性填料（如NaCl），建立了一种在以水为分散介质的CO ₂间歇发泡条件下调节聚丙烯（PP）泡沫孔结构的新方法。NaCl的存在增加了PP / NaCl复合材料中水的吸附量。结果，在CO ₂分批发泡期间，CO ₂和吸附的水均充当发泡剂。因此，NaCl颗粒的分散状态和尺寸直接影响两种发泡剂（水和CO ₂）以及NaCl颗粒和PP晶体在发泡过程中两种非均相成核之间的竞争，这是形成具有不同泡孔结构的发泡材料的根本原因，例如孤立的大泡孔被均匀的小泡孔结构包围，双峰泡孔结构和均质的细胞结构。另一个出乎意料的发现是PP / NaCl复合材料的吸水率随着NaCl粒径的减小而增加，这有利于发挥原位冷却作用和吸收水的共发泡剂来控制PP的发泡行为，以及避免由于填料含量高而损坏泡沫机械性能。