(245e) Effect of CO2-Philic Additives and Co-Blow Agents on CO2 Diffusion in Polystyrene Microcellular Foaming | AIChE

(245e) Effect of CO2-Philic Additives and Co-Blow Agents on CO2 Diffusion in Polystyrene Microcellular Foaming

Authors 

Qiang, W. - Presenter, East University of Science and Technology

Effect of CO2-philic
additives and co-blow agents on CO2 Diffusion in Polystyrene
Microcellular Foaming

Wei Qiang, Dong-dong Hu*, Tao Liu, Ling Zhao*

State Key Laboratory of Chemical Engineering,
East China University of Science and Technology, Shanghai 200237, China

* Corresponding author.
Tel.: +86 21 64253175; E-mail:
hudd@ecust.edu.cn, zhaoling@ecust.edu.cn

ABSTRACT

The
solubility and diffusivity of gas in polymer matrix play crucial roles in
controlling the CO2 foaming process and foam structure. The low
solubility and the high diffusion coefficient (D) of CO2 in
polymers lead to the difficulty of controlling the CO2 foaming [1-3].
In this work, the synergetic effect of molecular weight (Mw) of polydimethylsiloxane
(PDMS) and co-blow agents on the diffusion of supercritical CO2 into
and out of polystyrene (PS) and foam structures were investigated via DPD
simulations and experiments.

Fig.1 CO2
diffusion coefficient in PS with PDMS and co-blow agents from DPD simulations and
experiments: the solid dots are the simulation results and the hollow dots are
the experiment results

Fig.2 Desorption curves of CO2
in PS with PDMS and co-blow agents (the number behind represents the molecular
weight): (a) PS/PDMS (b) PS/PDMS/ethanol (c) PS/PDMS/pentane (d)
PS/PDMS/acetone

The
PDMS with low Mw increased the D of CO2 in PS,
while the D decreased with the increase of Mw of CO2-philic
additives. The relation between Mw of PDMS and the D of CO2
in PS was calculated via DPD simulation, showing a similar variation with
diffusion measurements. From the DPD results, the co-blow agents increased the D
dramatically and the system with acetone showed the highest CO2
diffusion.

The
desorption test demonstrated the CO2 desorption rates were smaller
in PS with low Mw PDMS than that in PS with high Mw additives. As for co-blow
agents, ethanol and acetone accelerated the CO2 desorption rates
while n-pentane lowered the CO2 desorption rate. However, when the
impregnated with co-blow agents, the desorption rates were larger in PS with
low Mw PDMS than that in PS with high Mw PDMS.

Fig.3 PS foams with additives
and co-blow agents: 1-PS; 2-PS/PDMS2258; 3-PS/PDMS6097; 4-PS/PDMS/16097

The
saturation time of foams was shortened indicated by the DPD simulations as low
Mw PDMS and co-blow agents increased the D of CO2 in PS. The
cell nucleation was favored as low Mw PDMS increased the solubility of CO2
in PS. The slow CO2 desorption rate in PS with low Mw PDMS enabled
higher amount of CO2 retained in the PS. Hence, PS with low Mw PDMS
foams presented smaller cell size and larger cell density. Moreover, all
co-blow agents had plastication effects on PS, n-pentane slowed the CO2
desorption and yielded larger cells. PS foamed with low Mw PDMS and acetone
showed bi-modal cell structure due to the strong interactions between low Mw
PDMS and acetone.

REFERENCES

[1] Srinivas S, J. M. DeSimone, Saad A. Khan, and Richard J. S., Controlled Foaming of Polymer Films through Restricted Surface
Diffusion and the Addition of Nanosilica Particles or CO2-philic
Surfactants[J]. Macromolecules, 2005, 38(6):2271-2280.

[2] Sun Y, Ueda Y, Suganaga H, Haruki M, Kihara S, Takishima S.
Pressure drop threshold in the foaming of low-density polyethylene,
polystyrene, and polypropylene using CO2, and N2, as foaming
agents.[J].Journal of Supercritical Fluids, 2015,103(2): 38-47.

[3] Spitael P, And C W M, Mcclurg R B. Block Copolymer Micelles
for Nucleation of Microcellular Thermoplastic Foams.[J]. Macromolecules, 2004, 37(18):
6874-6882.