Effect of Oscillatory Shear on Polystyrene Cell Morphology

Abstract

In the present study, a novel microcellular processing experimental setup is developed. With this setup, an oscillatory shear flow is superimposed perpendicular to a steady shear flow during microcellular processing. The effects of processing conditions such as processing pressure, shear rate, and vibration frequency on polystyrene (PS) cell morphology are investigated. The cell morphology is analyzed with a scanning electron microscope (SEM). The results show that the cell density increases and cell size decreases with the increase of processing pressure, shear rate, and vibration frequency. The effects of steady and oscillatory shear on PS cell morphology are further studied with lower melt flow index PS processed with a larger gap thickness. The results show that the final cell structure processed under simple steady shear flow shows an elongated oval shape, while those processed under combined shear flow show nearly spherical cell shape.

Keywords

microcellular processing supercritical CO2 polystyrene foam oscillatory shear orthogonal superposition

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References

Sato, Y. , Yurugi, M. , Fujiwara, K. , Takishima, S. and Masuoka, H. (1996). Solubilities of Carbon Dioxide and Nitrogen in Polystyrene under High Temperature and Pressure , Fluid Phase Equilib., 125(1–2): 129–138 .

Sato, Y. , Fujiwara, K. , Takikawa, T. , Sumarno , Takishima, S. and Masuoka, H. (1999). Solubilities and Diffusion Coefficients of Carbon Dioxide and Nitrogen in Polypropylene, High-density Polyethylene, and Polystyrene under High Pressures and Temperatures , Fluid Phase Equilib., 162(1–2): 261–276 .

Park, C.B. and Suh, N.P. (1996). Filamentary Extrusion of Microcellular Polymers using a Rapid Decompressive Element , Polym. Eng. Sci., 36(1): 34–48 .

Chen, L. , Sheth, H. and Kim, R. (2001). Gas Absorption with Filled Polymer Systems , Polym. Eng. Sci., 41(6): 990–997 .

Chen, L. , Sheth, H. and Wang, X. (2001). Effects of Shear Stress and Pressure Drop Rate on Microcellular Foaming Process , J. Cell. Plast., 37(4): 353–363 .

Chen, L. , Wang, X. , Straff, R. and Blizard, K. (2002). Shear Stress Nucleation in Microcellular Foaming Process , Polym. Eng. Sci., 42(6): 1151–1158 .

Park, C.B. and Suh, N.P. (1996). Rapid Polymer/Gas Solution Formation for Continuous Production of Microcellular Plastics , J. Manuf. Sci. E.-T. ASME, 118(4): 639–645 .

Park, H. and Youn, J.R. (1995). Study on Reaction Injection Molding of Polyurethane Microcellular Foam , Polym. Eng. Sci., 35(23): 1899–1906 .

Youn, J.R. and Park, H. (1999). Bubble Growth in Reaction Injection Molded Parts Foamed by Ultrasonic Excitation , Polym. Eng. Sci., 39(3): 457–468 .

10.

Koo, M.S. , Chung, K. and Youn, J.R. (2001). Reaction Injection Molding of Polyurethane Foam for Improved Thermal Insulation , Polym. Eng. Sci., 41(7): 1177–1186 .

11.

Qu, J.P. (1993) Method and Equipment for Electromagnetic Dynamic Plasticating Extrusion of Polymer Materials, US Patent No. 5,217,302.

12.

Qu, J.P. , Xu, B.P. , Jin, G. , He, H.Z. and Peng, X.F. (2002). Performance of Filled Polymer Systems under Novel Dynamic Extrusion Processing Conditions , Plast. Rubber Compos., 31(10): 432–435 .

13.

Liu, Y.J. , Qu, J.P. , Xu, B.P. and Peng, X.F. (2004). Studies on Viscoelastic Behaviors of Polymer Melt under the Vibration Force Field , Polym. Mat. Sci. Eng., 20(1): 18–21 .

14.

Qu, J.P. (2002). Study on the Pulsating Extrusion Characteristics of Polymer Melt through Round Sectioned Die , Polym.-Plast. Technol., 41(1): 115–132 .

15.

Qu, J. , He, G. , He, H. , Yu, G. and Liu, G. (2004). Effect of the Vibration Shear Flow Field in Capillary Dynamic Rheometer on the Crystallization Behavior of Polypropylene , Eur. Polym. J., 40(8): 1849–1855 .

16.

Qu, J.P. and Zhang, J. (2002). Transient Network Structural Model of Polymer Melts for Extrusion Flow in Vibration Force Field , J. South China Univ. Technol. (Nat. Sci.), 30(11): 21–26 .

17.

Liu, Y.J. , Qu, J.P. , Fan, S.H. and Cao, X.W. (2004). Relationship between Shear Stress and Shear Strain of Polymer Melt under Vibrating Force Field , Plast. Rubber Compos., 33(2–3): 120–124 .

18.

Qu, J. , Peng, X. and Zhou, N. (1998). Research on Elastic Behaviors of LDPE Melt during Capillary Dynamic Extrusion , J. South China Univ. Technol. (Nat. Sci.), 26(11): 1–7 .

19.

Baldwin, D.F. , Park, C.B. and Suh, N.P. (1996). Microcellular Processing Study of Poly (ethylene terephthalate) in the Amorphous and Semicrystalline States. Part I: Microcell Nucleation , Polym. Eng. Sci., 36(11): 1437–1445 .

20.

Matuana, L.M. , Park, C.B. and Balatinecz, J.J. (1997). Processing and Cell Morphology Relationships for Microcellular Foamed PVC/Wood-fiber Composites , Polym. Eng. Sci., 37(7): 1137–1147 .

21.

Putta, S. and Nemat-Nasser, S. (2001). Molecularly-based Numerical Evaluation of Free Volume in Amorphous Polymers , Mat. Sci. Eng. A-Struct., 317(1–2): 70–76 .