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The cooling rate dependence of the specific volume in amorphous plastic injection molding

  • Kristjan Krebelj
  • Miroslav Halilovič
  • Nikolaj MoleEmail author
ORIGINAL ARTICLE
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Abstract

In numerical simulation of injection molding, the specific volume is important for the cavity pressure prediction, which governs the part properties, such as shrinkage and warpage. The specific volume is often considered as a function of pressure and temperature only. This neglects its cooling rate dependence. The related degradation of the cavity pressure prediction usually remains unknown. In this work, the cooling rate effect is modeled and the discrepancy is quantified for amorphous polystyrene. A rate equation is used to model the specific volume relaxation within the scope of three-dimensional computational fluid dynamics. The model incorporates the mold compliance to allow a comparison to the experimental results. The cavity pressure evolution and the final residual stresses are calculated for both the modeled and the neglected cooling rate effects. This provides argumentation for either neglecting or modeling the phenomenon.

Keywords

Injection molding Numerical simulation Specific volume relaxation Amorphous polymer Residual stresses 

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Notes

Acknowledgements

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

References

  1. 1.
    Delaunay D, Le Bot P, Fulchiron R et al (2000) Nature of contact between polymer and mold in injection molding. Part II: influence of mold deflection on pressure history and shrinkage. Polym Eng Sci 40:1692–1700.  https://doi.org/10.1002/pen.11301 CrossRefGoogle Scholar
  2. 2.
    Pantani R, Speranza V, Titomanlio G (2001) Relevance of mold-induced thermal boundary conditions and cavity deformation in the simulation of injection molding. Polym Eng Sci 41:2022–2035CrossRefGoogle Scholar
  3. 3.
    Bendada A, Derdouri A, Lamontagne M, Simard Y (2004) Analysis of thermal contact resistance between polymer and mold in injection molding. Appl Therm Eng 24:2029–2040.  https://doi.org/10.1016/j.applthermaleng.2003.12.027 CrossRefGoogle Scholar
  4. 4.
    Delaunay D, Le Bot P, Fulchiron R et al (2000) Nature of contact between polymer and mold in injection molding. Part I: influence of a non-perfect thermal contact. Polym Eng Sci 40:1682–1691.  https://doi.org/10.1002/pen.11300 CrossRefGoogle Scholar
  5. 5.
    Ferry JD (1980) Viscoelastic properties of polymers. John Wiley & Sons, IncGoogle Scholar
  6. 6.
    Knauss WG, Emri I (1987) Volume change and the nonlinearly thermo-viscoelastic constitution of polymers. Polym Eng Sci 27:86–100.  https://doi.org/10.1002/pen.760270113 CrossRefGoogle Scholar
  7. 7.
    Kennedy P, Zheng R (2013) Flow analysis of injection molds. Hanser Publishers, CincinnatiCrossRefGoogle Scholar
  8. 8.
    Baaijens FPT (1991) Calculation of residual stresses in injection molded products. Rheol Acta 30:284–299.  https://doi.org/10.1007/BF00366642 CrossRefGoogle Scholar
  9. 9.
    Chang R-Y, Chiou S-Y (1995) A unified K-BKZ model for residual stress analysis of injection molded three-dimensional thin shapes. Polym Eng Sci 35:1733–1747CrossRefGoogle Scholar
  10. 10.
    Chang R, Yang W (2001) Numerical simulation of mold filling in injection molding using a three-dimensional finite volume approach. Int J Numer Methods Fluids 37:125–148CrossRefzbMATHGoogle Scholar
  11. 11.
    Kamal MR, Lai-Fook RA, Hernandez-Aguilar JR (2002) Residual thermal stresses in injection moldings of thermoplastics: a theoretical and experimental study. Polym Eng Sci 42:1098–1114CrossRefGoogle Scholar
  12. 12.
    Guevara-Morales A, Figueroa-López U (2014) Residual stresses in injection molded products. J Mater Sci 49:4399–4415.  https://doi.org/10.1007/s10853-014-8170-y CrossRefGoogle Scholar
  13. 13.
    Schawe JEK (2015) Measurement of the thermal glass transition of polystyrene in a cooling rate range of more than six decades. Thermochim Acta 603:128–134.  https://doi.org/10.1016/j.tca.2014.05.025 CrossRefGoogle Scholar
  14. 14.
    Yu JS, Wagner AH, Kalyon DM (1992) Simulation of microstructure development in injection molding of engineering plastics. J Appl Polym Sci 44:477–489CrossRefGoogle Scholar
  15. 15.
    Yu JS, Kalyon DM (1991) Development of density distributions in injection molded amorphous engineering plastics. Part II. Polym Eng Sci 31:153–160.  https://doi.org/10.1002/pen.760310303 CrossRefGoogle Scholar
  16. 16.
    Ghoneim H, Hieber CA (1997) Incorporation of density relaxation in the analysis of residual stresses in molded parts. Polym Eng Sci 37:219–227CrossRefGoogle Scholar
  17. 17.
    Zheng R, Kennedy P, Phan-Thien N, Fan X-J (1999) Thermoviscoelastic simulation of thermally and pressure-induced stresses in injection moulding for the prediction of shrinkage and warpage for fibre-reinforced thermoplastics. J Non-Newton Fluid Mech 84:159–190.  https://doi.org/10.1016/S0377-0257(98)00148-7 CrossRefzbMATHGoogle Scholar
  18. 18.
    Lee YB, Kwon TH (2001) Modeling and numerical simulation of residual stresses and birefringence in injection molded center-gated disks. J Mater Process Technol 111:214–218CrossRefGoogle Scholar
  19. 19.
    Tool AQ (1946) Relation between inelastic deformability and thermal expansion of glass in its annealing range. J Am Ceram Soc 29:240–253.  https://doi.org/10.1111/j.1151-2916.1946.tb11592.x CrossRefGoogle Scholar
  20. 20.
    Kabanemi KK, Aït-Kadi A, Tanguy PA (1995) Prediction of residual flow and thermoviscoelastic stresses in injection molding. Rheol Acta 34:97–108CrossRefGoogle Scholar
  21. 21.
    Kabanemi KK, Vaillancourt H, Wang H, Salloum G (1998) Residual stresses, shrinkage, and warpage of complex injection molded products: numerical simulation and experimental validation. Polym Eng Sci 38:21–37.  https://doi.org/10.1002/pen.10162 CrossRefGoogle Scholar
  22. 22.
    Zhou H, Xi G, Liu F (2008) Residual stress simulation of injection molding. J Mater Eng Perform 17:422–427.  https://doi.org/10.1007/s11665-007-9156-6 CrossRefGoogle Scholar
  23. 23.
    Vietri U, Sorrentino A, Speranza V, Pantani R (2011) Improving the predictions of injection molding simulation software. Polym Eng Sci 51:2542–2551.  https://doi.org/10.1002/pen.22035 CrossRefGoogle Scholar
  24. 24.
    Jansen KMB, van Dijk DJ, Burgers EV (1998) Experimental validation of shrinkage predictions for injection molded products. Int Polym Process 13:99–104.  https://doi.org/10.3139/217.980099 CrossRefGoogle Scholar
  25. 25.
    Jansen KMB, Pantani R, Titomanlio G (1998) As-molded shrinkage measurements on polystyrene injection molded products. Polym Eng Sci 38:254–264.  https://doi.org/10.1002/pen.10186 CrossRefGoogle Scholar
  26. 26.
    Krebelj K, Mole N, Štok B (2017) Three-dimensional modeling of the stress evolution in injection molded parts based on a known melt pressure field. Int J Adv Manuf Technol 90:2363–2376.  https://doi.org/10.1007/s00170-016-9533-0 CrossRefGoogle Scholar
  27. 27.
    Williams ML, Landel RF, Ferry JD (1955) The temperature dependence of relaxation mechanisms in amorphous polymers and other glass-forming liquids. J Am Chem Soc 77:3701–3707.  https://doi.org/10.1021/ja01619a008 CrossRefGoogle Scholar
  28. 28.
    Weller HG, Tabor G, Jasak H, Fureby C (1998) A tensorial approach to computational continuum mechanics using object-oriented techniques. Comput Phys 12:620.  https://doi.org/10.1063/1.168744 CrossRefGoogle Scholar
  29. 29.
    Zoetelief WF, Douven LFA, Housz AJI (1996) Residual thermal stresses in injection molded products. Polym Eng Sci 36:1886–1896.  https://doi.org/10.1002/pen.10585 CrossRefGoogle Scholar
  30. 30.
    Dawson A, Rides M, Nottay J (2006) The effect of pressure on the thermal conductivity of polymer melts. Polym Test 25:268–275.  https://doi.org/10.1016/j.polymertesting.2005.10.001 CrossRefGoogle Scholar
  31. 31.
    Schawe JEK (2014) Vitrification in a wide cooling rate range: the relations between cooling rate, relaxation time, transition width, and fragility. J Chem Phys 141:184905.  https://doi.org/10.1063/1.4900961 CrossRefGoogle Scholar
  32. 32.
    Jansen K (1994) Residual stresses in quenched and injection moulded products. Int Polym Process 9:82–89CrossRefGoogle Scholar
  33. 33.
    Bushko WC, Stokes VK (1995) Solidification of thermoviscoelastic melts. Part I: formulation of model problem. Polym Eng Sci 35:351–364.  https://doi.org/10.1002/pen.760350409 CrossRefGoogle Scholar
  34. 34.
    Greener J (2006) Precision injection molding: process, materials, and applications. HanserGoogle Scholar

Copyright information

© Springer-Verlag London Ltd., part of Springer Nature 2019

Authors and Affiliations

  • Kristjan Krebelj
    • 1
  • Miroslav Halilovič
    • 1
  • Nikolaj Mole
    • 1
    Email author
  1. 1.Faculty of Mechanical EngineeringUniversity of LjubljanaLjubljanaSlovenia

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