A Comparison of CO2 and N2 Foaming Behaviors of PP in a Visualization System

Abstract Understanding of polypropylene (PP) foaming is critically important to reduce the weight of automotive parts. In this study, we used a batch foaming simulation system with visualization cell, to observe the foaming behaviors of PP that is blown with CO2 and N2 under various experimental conditions. We found that the nucleating agent content, initial temperature, pressure (i. e., gas content), and pressure drop rate during foaming have a significant effect on cell nucleation and cell growth. The cell density and the void fraction of PP foamed with CO2 and N2, respectively, were separately observed and compared. It was found that under the same experimental conditions, the maximum cell density of PP foamed with CO2 was higher than that of PP foamed with N2. However, the maximum cell density of PP foamed with CO2 was determined to be lower than that of PP foamed with N2, when the same gas mole numbers were employed. Based on the experimental results, optimum foaming conditions and effective processing strategies for PP-CO2 system are suggested.

[1]  Chul B. Park,et al.  Solubility and diffusivity of CO2 and N2 in TPU and their effects on cell nucleation in batch foaming , 2019 .

[2]  Yi-Chun Chang,et al.  Foam extrusion of polypropylene–rice husk composites using CO2 as the blowing agent , 2019, Journal of Cellular Plastics.

[3]  H. Yano,et al.  Cell morphologies and mechanical properties of cellulose nanofiber reinforced polypropylene foams , 2019, Journal of Cellular Plastics.

[4]  A. Ghosh,et al.  Evaluation of polypropylene/clay nanocomposite foamability based on their morphological and rheological aspects , 2018 .

[5]  M. Wilhelm,et al.  Influence of molecular structure on the foamability of polypropylene: Linear and extensional rheological fingerprint , 2017 .

[6]  K. Kreger,et al.  Improved compression properties of polypropylene extrusion foams by supramolecular additives , 2017 .

[7]  Chul B. Park,et al.  Mechanisms of nanoclay-enhanced plastic foaming processes: effects of nanoclay intercalation and exfoliation , 2013, Journal of Nanoparticle Research.

[8]  Chul B. Park,et al.  A batch foaming visualization system with extensional stress-inducing ability , 2011 .

[9]  Chul Park,et al.  Determination of Solubilities of CO2 in Linear and Branched Polypropylene Using a Magnetic Suspension Balance and a PVT Apparatus , 2010 .

[10]  Chul B. Park,et al.  Change in the critical nucleation radius and its impact on cell stability during polymeric foaming processes , 2009 .

[11]  Chul B. Park,et al.  Measurement of gas solubility in linear/branched PP melts , 2007 .

[12]  P. Carreau,et al.  Cell structure and dynamic properties of injection molded polypropylene foams , 2007 .

[13]  Chul B. Park,et al.  Solubility measurements of N2 and CO2 in polypropylene and ethene/octene copolymer , 2007 .

[14]  Chul B. Park,et al.  A Microcellular Foaming Simulation System with a High Pressure-Drop Rate , 2006 .

[15]  Chul B. Park,et al.  Numerical simulation of polymeric foaming processes using modified nucleation theory , 2006 .

[16]  C. B. Park,et al.  Finite Element Analysis of Cell Coarsening in Plastic Foaming , 2005 .

[17]  Chul B. Park,et al.  Fundamental foaming mechanisms governing the volume expansion of extruded polypropylene foams , 2004 .

[18]  Chul B. Park,et al.  Rotational foam molding of polypropylene with control of melt strength , 2003 .

[19]  Chul B. Park,et al.  Effect of Talc Content on the Volume Expansion Ratio of Extruded PP Foams , 2003 .

[20]  Chul B. Park,et al.  PP-Blends with Tailored Foamability and Mechanical Properties , 2003 .

[21]  Chul B. Park,et al.  Processing of Polypropylene Foams in Melt Compounding Based Rotational Foam Molding , 2002 .

[22]  Chul B. Park,et al.  Strategies for achieving ultra low‐density polypropylene foams , 2002 .

[23]  M. Xanthos,et al.  Parameters Affecting the In-Line Measurement of Gas Solubility in Thermoplastic Melts during Foam Extrusion , 2001 .

[24]  Chul B. Park,et al.  The effect of talc on cell nucleation in extrusion foam processing of polypropylene with CO2 and isopentane , 1998 .

[25]  Chul B. Park,et al.  A study of cell nucleation in the extrusion of polypropylene foams , 1997 .

[26]  C. Han,et al.  A study of bubble nucleation in a mixture of molten polymer and volatile liquid in a shear flow field , 1988 .

[27]  C. Han,et al.  Studies on structural foam processing II. Bubble dynamics in foam injection molding , 1978 .

[28]  C. Han,et al.  Studies on structural foam processing I. The rheology of foam extrusion , 1978 .

[29]  A. S. Tucker,et al.  Critical state of bubbles in liquid‐gas solutions , 1975 .