Journal
CHEMICAL ENGINEERING SCIENCE
Volume 66, Issue 16, Pages 3656-3665Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ces.2011.04.035
Keywords
Foam; Long-chain branched polypropylene; Polymer processing; Rheology; Simulation; Supercritical fluid
Categories
Funding
- National Natural Science Foundation of China through NSFC [50390097, 50773069]
- Program for Changjiang Scholars and Innovative Research Team in University
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A mathematical model was established to simulate the bubble growth process during foaming of polypropylene (PP) by carbon dioxide, taking into account of a wide range of physical and rheological properties (solubility, diffusivity, surface tension, long-chain branching, zero shear viscosity, relaxation time, strain hardening), as well as processing conditions. By employing the Considere construction the possibility of grow thin stability and bubble rupture at later stage of bubble growth was predicted. The simulation revealed that the improvement of foamability of polypropylene by introducing long-chain branching was due to the well-defined viscoelastic characteristics of the melt. Rheological factors that impede bubble growth are beneficial in stabilizing the bubble growth. Stability during bubble growth is further facilitated by moderate strain hardening characteristics and elastics properties of the polymers. The diffusivity and solubility characteristics also have profound impact on the bubble growth stability, while the influence of the surface tension is negligible. (C) 2011 Elsevier Ltd. All rights reserved.
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