Classical Nucleation Theory Applied to Homogeneous Bubble Nucleation in the Continuous Microcellular Foaming of the Polystyrene−CO2System

2009 ◽  
Vol 48 (16) ◽  
pp. 7603-7615 ◽  
Author(s):  
Shunahshep Shukla ◽  
Kurt W. Koelling
Keyword(s):  
Bubble Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Microcellular Foaming

Ultrasonic Bubble Nucleation in Reaction Injection Moulding of Polyurethane

1994 ◽  
Vol 208 (2) ◽  
pp. 121-128 ◽  
Author(s):  
W J Cho ◽  
H Park ◽  
J R Youn
Keyword(s):  
Injection Moulding ◽  
Saturation Pressure ◽  
Bubble Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Ultrasonic Activation ◽  
Cluster Theory ◽  
Foam Structure ◽  
Ultrasonic Effect

Ultrasonic foam processing of polyurethane for reaction injection moulding (RIM) was studied experimentally to investigate feasibility of ultrasonic bubble nucleation in polyurethane. Bubble nucleation was also studied theoretically to predict the rate of nucleation. Classical nucleation theory and cluster theory have been employed for explanation of the nucleation phenomena. A polyol resin was saturated with nitrogen at various pressures and the pressure was released slowly in order to generate supersaturated resin. Other components of the selected polyurethane system were added to the supersaturated resin and ultrasonic disruption was applied to the system producing enhanced nucleation. The ultrasonic excitation created a good foam structure even at a low saturation pressure around 0.15 MPa (1.5 atm). The effect of the ultrasonic activation on the bubble nucleation was considered and included in the nucleation theories. The cluster nucleation theory along with consideration of the ultrasonic effect predicted a higher rate of nucleation than the classical nucleation theory for the same condition.

Analytical Investigation on the Homogeneous Nucleation in a Mono-Component and Bi-Component Droplet

2019 ◽  
Author(s):  
Xi Xi ◽  
Hong Liu ◽  
Chang Cai ◽  
Ming Jia ◽  
Weilong Zhang
Keyword(s):  
Nucleation Rate ◽  
Homogeneous Nucleation ◽  
Ambient Pressure ◽  
Analytical Investigation ◽  
Bubble Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Liquid Temperature ◽  
Wide Range ◽  
Good Agreement

Abstract The work attempts to analyze the performance of homogeneous nucleation by using the non-equilibrium thermodynamics theory and the classical nucleation theory. A nucleation rate graph was constructed under a wide range of operating temperature conditions. The results indicate that the superheat limit temperature (SLT) estimated by the modified homogeneous nucleation sub-model is in good agreement with the experimental results. The nucleation rate increases exponentially with the liquid temperature rise when the liquid temperature exceeds the SLT under atmospheric pressure. The superheated temperature needed to trigger the bubble nucleation decreases with the elevated ambient pressure.

Processing of Cellular Polyurethane by Ultrasonic Excitation

1992 ◽  
Vol 114 (3) ◽  
pp. 323-328 ◽  
Author(s):  
H. Park ◽  
J. R. Youn
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Negative Pressure ◽  
Bubble Nucleation ◽  
High Rate ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Foam Structure ◽  
Pressure Equilibrium ◽  
Theoretical Results

Processing of cellular polyurethane was investigated experimentally and theoretically to examine the possibility of ultrasonic foaming. Polyol resin was supersaturated with nitrogen and ultrasonic excitation was applied for copious bubble nucleation. The ultrasonic excitation resulted in good foam structure whose size distribution was uniform and less than 100 μm. The ultrasonic excitation was modelled by utilizing the classical nucleation theory to predict the rate of nucleation. Theoretical results suggest that a high rate of nucleation will be obtained if the ultrasonic excitation generates large enough negative pressure. Final bubble size was calculated by considering the pressure equilibrium between inside and outside of the bubble.

Homogeneous Bubble Nucleation Predicted by a Molecular Interaction Model

1991 ◽  
Vol 113 (3) ◽  
pp. 714-721 ◽  
Author(s):  
Ho-Young Kwak ◽  
Sangbum Lee
Keyword(s):  
Bubble Formation ◽  
Interaction Model ◽  
Bubble Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Good Prediction ◽  
Evaporation Time ◽  
Modified Model ◽  
Superheat Limit ◽  
Good Agreement

The homogeneous bubble nucleation of various hydrocarbons was estimated by the modified classical nucleation theory. In this modification, the kinetic formalism of the classical theory is retained while the surface energy needed for the bubble formation is calculated from the interaction energy between molecules. With a nucleation rate value of Jnc =1022 nuclei/cm3s, this modified model gives a very good prediction of the superheat limit of liquids. In another test of the model the complete evaporation time of a butane droplet at its superheat limit is compared with experiments and found to be in good agreement.

Production of Microcellular Polycarbonate Using Carbon Dioxide for Bubble Nucleation

1994 ◽  
Vol 116 (4) ◽  
pp. 413-420 ◽  
Author(s):  
V. Kumar ◽  
J. Weller
Keyword(s):  
Carbon Dioxide ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Bubble Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Homogeneous Microstructure ◽  
Wide Range ◽  
Nucleation Phenomenon

A process to produce a family of novel materials from polycarbonate, having a microcellular structure, is described. The process utilizes the high solubility of carbon dioxide in polycarbonate to nucleate a very large number of bubbles, on the order of 1 to 10 × 109 bubbles/cm3, at temperatures well below the glass transition temperature of the original, unsaturated polycarbonate. Microcellular polycarbonate foams with homogeneous microstructure and a wide range of densities have been produced. In this paper experimental results on solubility, bubble nucleation, and bubble growth in the polycarbonate-carbon dioxide system are presented, and the critical ranges of the key process parameters are established. It is shown that the bubble nucleation phenomenon in polycarbonate near the glass transition temperature is not described by classical nucleation theory.

scholarly journals Classical Nucleation and Lattice Model Unite

2020 ◽  
pp. 32-36
Author(s):  
John H. Jennings
Keyword(s):  
Molecular Weight ◽  
Surface Tension ◽  
Nucleation Rate ◽  
Lattice Model ◽  
Polymer Solutions ◽  
Bubble Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Molecular Weight Polymer ◽  
To Come

Classical nucleation theory predicts the limit of superheat of liquids quite well. To come up with an equation for the limit of superheat of polymer solutions, the lattice model for polymer solutions was used to give the surface tension of polymer solutions. A formula for bubble nucleation in polymer solutions was derived by Jennings with the precursor equation dlnA/dK=1/(6K) where J=AexpK gives the nucleation rate for liquids. The aim of this paper was to show that the precursor equation holds for monomer in the polystyrene-cyclohexane system. Thus, the precursor equation is true for all molecular weight polymer. This happens because the surface tension of polystyrene is significantly more than cyclohexane and the influence of the surface tension dominates.

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