Preparation Of Open-cell Morphologies By Supercritical Carbon Dioxide Foaming Of LLDPE/Nanocomposites

It is a great extent determined by bubble pore morphology for polymer foam materials performance and application field. Open-cell foaming material is a kind of gas phase and matrix material phase continuous which substrate material existed in bubble wall. The 3D open pore structures have excellent absorption and penetration performance which applied in sound-absorbing materials, conductive materials, optical materials, filtration materials, especially in the biomedical materials(drug controlled release materials, bone tissue culture material, biological material of dialysis membrane). Opening foaming LLDPE in the sewage filtering processing and sound-absorbing material has a potential application prospect.In this work, we aim at preparing open-cell structure by scCO2 foaming of LLDPE with emphasis on the influence of processing parameters(foaming temperature, saturation pressure, and pressure drop rate) and the nature of polymers on the evolution of cell opening. We will discuss how to adjust the processing parameters to obtain the open-cell structures with high open content and tunable cell size. The underlying polymer physics will be discussed to conclude a few principles towards the open-cell structure materials. We will further explore new methods of LLDPE opening foam based on the experiment. What’s more, we prepared open-cell morphologies of LLDPE/CNT nanocomposites and LLDPE/UHMWPE blends. The influence of rheological properties and crystallization on foam structures of pure LLDPE and LLDPE/UHMWPE blend was investigated. Compared with puer LLDPE foams, the lower average cell size of LLDPE/UHMWPE blends foams and LLDPE/CNT blends foams were obtained indicating that not only the additon of UHMWPE had a obvious effect to induce heterogeneous nucleation, but also limited cell growth as a supporting structure during the foaming process. The results showed that the open-cell morphologies of LLDPE samples foamed at 23-28 MPa CO2 saturation pressure and 124-138 oC temperatures. The opening rate of LLDPE improved by “platelet-like” cell walls to “rod-like” cell walls.