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INJECTION-COMPRESSION AND CO-INJECTION MOLDINGS OF AMORPHOUS POLYMERS: VISCOELASTIC SIMULATION AND EXPERIMENT

Kim, Nam Hyung
http://rave.ohiolink.edu/etdc/view?acc_num=akron1230065091

Abstract Details

2009, Doctor of Philosophy, University of Akron, Polymer Engineering.
Injection-compression molding (ICM) and co-injection molding have gained increasing importance in manufacturing of polymer products. Scientific understanding of these processes is presently limited and no attempts have been made to simulate co-injection molding using a viscoelastic model. In addressing this issue, the present study provides results of comprehensive viscoelastic simulations and experimental investigations of the residual stresses and birefringence in center-gated disk moldings of amorphous polymers obtained by ICM and sequential co-injection molding (SCIM) at various processing conditions. The governing equations for viscoelastic simulation of ICM and SCIM processes were derived using a nonlinear viscoelastic model. The equations were solved using a hybrid control volume/finite element/finite difference method. In general, residual stresses and birefringence in moldings arise from the flow- and thermally-induced contributions. To consider the thermal contribution, simulations and experimental study of birefringence in freely quenched multi-layered plates were carried out. The flow- and thermally-induced stresses were simulated using nonlinear and linear viscoelastic theories, respectively. The overall residual birefringence in moldings was obtained by summation of the flow- and thermally-induced birefringence contributions calculated using the stress-optical rule and photoviscoelastic constitutive equation, respectively. The numerical results were found to be in fair agreement with experimental data on the distribution of residual birefringence and average transverse birefringence of the ICM made from polycarbonate (PC) and polystyrene (PS). It was found that the melt temperature and compression stroke strongly affected the residual birefringence in ICM, while the mold temperature had less effect. The numerical and experimental results of the gapwise distribution of the residual birefringence and interface of the SCIM were obtained at various processing conditions and various combinations of multi-layers of PC, PS and PMMA. It was found that the melt temperature strongly affected the birefringence and interface distribution, while the mold temperature had less effect. In addition, the interface was strongly affected by the volume of injected skin melt. Numerical results were found to be in a fair agreement with experimental data.
Avraam I. Isayev (Advisor)
417 p.
Polymers
Viscoelastic simulation; Sequential co-injection molding; Injection-compression molding; Quenching; Flow birefringence; Thermal birefringence

Recommended Citations

Citations

  • Kim, N. H. (2009). INJECTION-COMPRESSION AND CO-INJECTION MOLDINGS OF AMORPHOUS POLYMERS: VISCOELASTIC SIMULATION AND EXPERIMENT [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1230065091

    APA Style (7th edition)

  • Kim, Nam Hyung. INJECTION-COMPRESSION AND CO-INJECTION MOLDINGS OF AMORPHOUS POLYMERS: VISCOELASTIC SIMULATION AND EXPERIMENT. 2009. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1230065091.

    MLA Style (8th edition)

  • Kim, Nam Hyung. "INJECTION-COMPRESSION AND CO-INJECTION MOLDINGS OF AMORPHOUS POLYMERS: VISCOELASTIC SIMULATION AND EXPERIMENT." Doctoral dissertation, University of Akron, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1230065091

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Akron and OhioLINK.