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Ph. D. Candidate: Guangming Li Supervisor: Prof. Chul B. Park

Study of the Solubility of Gas in a Polymer Melt & Cell Nucleation in Die. Ph. D. Candidate: Guangming Li Supervisor: Prof. Chul B. Park. Microcellular Plastics Manufacturing Laboratory, University of Toronto. Outline. Introduction Objectives Background Approach Experiments

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Ph. D. Candidate: Guangming Li Supervisor: Prof. Chul B. Park

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  1. Study of the Solubility of Gas in a Polymer Melt & Cell Nucleation in Die Ph. D. Candidate: Guangming Li Supervisor: Prof. Chul B. Park Microcellular Plastics Manufacturing Laboratory,University of Toronto

  2. Outline • Introduction • Objectives • Background • Approach • Experiments • Contributions

  3. Introduction

  4. Plastic Foams • Plastic foams • Decreased density • Cellular structure • Advantages over non-foamed plastic • Insulating properties • Impact resistant characteristics • Buoyancy • Outstanding strength-to-weight ratios

  5. gas Gas injection Mixing & diffusion Diffusion + polymer Single-phase polymer/gas solution Two-phase polymer/gas mixture Two-phase polymer/gas mixture Two system Plastic Foam Processing Formation of single-phase polymer/gas solution Cell nucleation Cell growth Stabilization

  6. Plastic Foam Processing Formation of single-phase polymer/gas solution Cell nucleation Die Pressure Psolubility Distance Cell growth Stabilization

  7. Objectives

  8. To systematically investigate the gas solubility for different polymer/gas mixture systems To verify the solubility pressure inside the die during the continuous plastic foaming process

  9. Background

  10. Previous Study of Solubility • Pressure Decay+ SL-EOS • Y. Sato, etc., Fluid Phase Equilibria 162 (1999) 261; for N2 and CO2 in PP, HDPE and PS • Electrobalance + Partial Volume by Henrian Sorption Theory • B. Wong, etc., Journal of Polymer Science (Part B)36 (1998) 2025; • for PS + CO2 and PVC + CO2

  11. Application of Gas Solubility in an Extrusion Die Critical Isotherm Point PRESSURE Liquid Spinodal Saturated Vapor Saturated Vapor (Binodal) Liquid Spinodal VOLUME

  12. The minimum work to create a bubble (radius R) The bubble nucleation rate

  13. Approach

  14. The fundamental concept of this approach is that the chemical potential of a vapor is equal to the chemical potential of its condensate in the polymer melt, when the equilibrium condition is reached. Theoretical Prediction of Gas Solubility A: Gas B: Polymer G: Gas phase P : Polymer/Gas Solution phase A(G) Equal at equilibrium A(P) +B(P)

  15. Equation-of-State for the Multi-component System (Gas/Polymer Mixture) • Lattice-Fluid Model (Sanchez and Lacombe EOS) • Hole Model (Simha and Somcynsky EOS) Segment of Component A Segment of Component B Empty cell (hole)

  16. SL Model

  17. SS Model

  18. Experimental Measurement of the Solubility by MSB F(P,T) microbalance (High pressure gas) Solubility Initial Volume of pure polymer at P,T Volume of Swelling Volume of holder + ) F(P,T)- F(0,T)+ρgas× ( + Apparent Solubility Buoyancy Compensation F(0,T) F is Balance Reading microbalance (Vacuum) Polymer Sample

  19. Swollen volume contributed buoyancy effect is an outstanding factor on solubility measurement in high pressure conditions. Theoretical method (Equation-of-State) to predict the swollen volume. Volume of Swelling

  20. SL EOS: Theoretical Estimation of Volume of Swelling SS EOS:

  21. Actual Measurement of Volume of Swelling -Pendent Droplet Method Pendent drop in high temperature and pressure cell is currently utilized to do the PVT density measurement by examining the final volume after swelling. Rod High T and P cell Scale Polymer droplet gas

  22. Experiments

  23. Polystyrene (PS, Tg=381.4K, Mw=3.30×105, Mn= 1.07×105), A&M Styrene Corporation, (Kawasaki, Japan). Carbon dioxide (Coleman grade, 99.99% purity), BOC Canada. Comparison of SL EOS and SS EOS Materials: Equipment: • MSB

  24. Schematic of MSB Instrument c a f b e d MSB a: Microbalance b: Measuring cell c: Temperature control device d: Gas dosing system e: Control panel f: Data acquisition system

  25. Obtain set ofApparent Solubility (AS)experimentally. Set an initial value of EOSs interaction parameter(s). Obtain the corresponding set of the Theoretical Solubility (S)and the density of polymer/gas mixture based on SS or SL EOS. Obtain the Corrected Solubility (CS)using the SS-based or SL-based swollen volume. Calculate thedifference of the corrected solubility and theoretical solubility:(CSi- Si)2 Decide the optimum interaction parameter(s) by minimizing (CSi- Si)2 Proposed Procedure to Determine the Solubility

  26. (a) (b) • Volume Swelling effect prediction • SS-based and SL-based prediction at 110oC; • SS-based and SL-based prediction at 150 oC; • SS-based and SL-based prediction at 200 oC; (c)

  27. Solubility of CO2 in Polystyrene at 1100C

  28. Solubility of CO2 in Polystyrene at 1500C

  29. Solubility of CO2 in Polystyrene at 2000C

  30. Temperature Effect on Interaction Parameters of EOS K12 of SL-EOS δe and δv of SS-EOS δe =1.0638δv = 0.9568

  31. SL EOS and SS EOS predicted different swollen volumes. Below 1500 psi, corrected solubilities from SL and SS EOS are very close to each other. Above 1500 psi, there are significant difference between the SL EOS and SS EOS in terms of the solubility measurement. The interaction parameters for SL EOS and SS EOS show different temperature dependence. Sub-conclusion

  32. Investigation of the Solubility of CO2 in Branched –PP and Linear-PP

  33. Rheological Behavior Difference Between the Branched-PP and Linear PP Branched-PP Branched-PP Linear-PP Linear-PP This behavior of LCB-PP is beneficial to all the processes involving extensional flow, such as thermoforming, foaming and blow molding

  34. SL-EOS SS-EOS 5% CO2 content 10% CO2 content

  35. Solubility for linear PP/CO2 mixture and branched PP/CO2by SL EOS

  36. Solubility for linear PP/CO2 mixture and branched PP/CO2by SS EOS

  37. Investigation of the Solubility of CO2 in Polycarbonateand the Effect of Crystallinity on Solubility Material • Tough • Transparent • Crystallizable (regular chemical structure) • Extremely low crystallization rate (chain rigidity)

  38. Uptake curve for the sorption of CO2 in PC 200 oC 240 oC 160 oC

  39. Investigation of the Crystallization of PC induced by CO2 at 160 oC DSC PC treated with CO2 at 160oC for 24 hrs (crystallinity is 21.66%) Original PC Polarizing Light Microscope

  40. Solubility of CO2 in PC at 200oC and 240oC 200oC 240oC

  41. System Design for Study of Solubility Pressure inside the Die

  42. Upgrade the primary 1.5" extruder with 30:1 L/D ratio . • Upgrade gear pump (Zenith, PEP-II 10 cc/rev) for controlling the melt flow rate up to 100 g/min. • Secondary 1.5" extruder with a mixing screw of 24:1 L/D ratio attached after the gear pump. • Die design

  43. Contributions

  44. Solubility Study • Development of experimental approach to study the solubility of gas in a polymer at elevated temperature and pressure; • Development of a theoretical approach to predict the swollen volume for the polymer/gas mixture; • Investigation of the solubility of various gases in different polymer melts; Nucleation investigation • The investigation on the nucleation inside the die theory.

  45. Research Timetable Please see the attached Report

  46. Thank You!

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