Effects of injection molding conditions on the mechanical performance of plastic parts
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The quality of parts manufactured by thermoplastics injection molding can be evaluated based on product weight, appearance, and presence of defects. Furthermore, the conditions of the injection process can significantly influence the mechanical performance of the molded parts. Residual stresses generated during plastic processing may contribute to the formation of cracks or premature failures when the product is subjected to external loads or forces. This study aims to evaluate the effects of the injection process on an injected part and how they affect its mechanical performance. For this purpose, specimens were injected under different process conditions and, subsequently, employed in a. Some parts were also subjected to annealing (a thermal treatment) to induce molecular relaxation, which helps to reduce internal or residual stresses generated during the injection process. Additionally, a qualitative evaluation of the distribution of residual stresses in the injected parts was conducted using the s technique to complement and validate the results of the mechanical tests. The results of the specimens injected at a mold temperature of 50°C showed a greater release of residual stresses, as indicated in photoelasticity images analyzed here, and a noticeable increase in flexural strength if the heat treatment had been applied. This suggests that more residual stresses are produced at 50°C than at the recommended mold temperature of 80°C. The heat treatment significantly improved the mechanical performance of all the parts injected in this study under different processing conditions.
Maxwell a. S, Turnbull a. Measurement of residual stress in engineering plastics using the hole-drilling technique. Polym Test. 2003 Apr;22(2):231-3.
https://doi.org/10.1016/S0142-9418(02)00087-9 DOI: https://doi.org/10.1016/S0142-9418(02)00087-9
Turnbull A, Maxwell AS, Pillai S. Residual stress in polymers-evaluation of measurement techniques. J Mater Sci. 1999 Feb;34(3):451-9.
https://doi.org/10.1023/A:1004574024319 DOI: https://doi.org/10.1023/A:1004574024319
Chang H jui, Mao Z fa, Su Z ming, Zhang G yi. applied sciences Using Recognizable Fuzzy Analysis for Non-Destructive Detection of Residual Stress in White Light Elements. 2021;
https://doi.org/10.3390/app11041550 DOI: https://doi.org/10.3390/app11041550
Shrivastava A. 3 - Plastic Properties and Testing. In: Shrivastava A, editor. Introduction to Plastics Engineering. William Andrew Publishing; 2018. p. 49-110. (Plastics Design Library).
https://doi.org/10.1016/B978-0-323-39500-7.00003-4 DOI: https://doi.org/10.1016/B978-0-323-39500-7.00003-4
Xu Y, Lu H, Gao T, Zhang W. Predicting the low-velocity impact behavior of polycarbonate: Influence of thermal history during injection molding. Int J Impact Eng. 2015 Dec;86:265-73.
https://doi.org/10.1016/j.ijimpeng.2015.08.013
Engels T, Govaert L, Meijer H. The Influence of Molecular Orientation on the Yield and Post‐Yield Response of Injection‐Molded Polycarbonate. Macromol Mater Eng. 2009 Nov;294:821-8.
https://doi.org/10.1002/mame.200900050
Kim B, Min J. Residual stress distributions and their influence on post-manufacturing deformation of injection-molded plastic parts. J Mater Process Technol. 2017;245:215-26.
https://doi.org/10.1016/j.jmatprotec.2017.02.015 DOI: https://doi.org/10.1016/j.jmatprotec.2017.02.015
Sudsawat S, Sriseubsai W. Warpage reduction through optimized process parameters and annealed process of injection-molded plastic parts. Journal of Mechanical Science and Technology. 2018;32(10):4787-99.
https://doi.org/10.1007/s12206-018-0926-x DOI: https://doi.org/10.1007/s12206-018-0926-x
Gu F, Hall P, Miles NJ, Ding Q, Wu T. Improvement of mechanical properties of recycled plastic blends via optimizing processing parameters using the Taguchi method and principal component analysis. Mater Des. 2014;62:189-98.
https://doi.org/10.1016/j.matdes.2014.05.013
Katmer S, Bilgileri K. THE EFFECTS OF MOLDING CONDITIONS ON THE RESIDUAL STRESSES IN INJECTION MOLDED POLYSTYRENE FLAT PARTS. Journal of the Faculty of Engineering and Architecture of Gazi University. 2012;27(3).
Ovsik M, Hylova L, Fiala T. The Influence of Process Parameters of Injection on Nano-mechanical Properties of Polypropylene. IOP Conf Ser Mater Sci Eng. 2018;448(1).
https://doi.org/10.1088/1757-899X/448/1/012015 DOI: https://doi.org/10.1088/1757-899X/448/1/012015
Wang G, Zhao G, Wang X. Effects of cavity surface temperature on mechanical properties of specimens with and without a weld line in rapid heat cycle molding. Mater Des. 2013;46:457-72.
https://doi.org/10.1016/j.matdes.2012.10.054 DOI: https://doi.org/10.1016/j.matdes.2012.10.054
Zhang W, Xu Y. Mechanical properties of polycarbonate: Experiment and modeling for aeronautical and aerospace applications. Mechanical Properties of Polycarbonate: Experiment and Modeling for Aeronautical and Aerospace Applications. 2019. 1-184 p.
Xu Y, Lu H, Gao T, Zhang W. Processing-induced inhomogeneity of yield stress in polycarbonate product and its influence on the impact behavior. Polymers (Basel). 2016;8(3).
https://doi.org/10.3390/polym8030072 DOI: https://doi.org/10.3390/polym8030072
Macías C, Meza O, Pérez E. Relaxation of residual stresses in plastic cover lenses with applications in the injection molding process. Eng Fail Anal. 2015;57:490-8.
https://doi.org/10.1016/j.engfailanal.2015.07.026 DOI: https://doi.org/10.1016/j.engfailanal.2015.07.026
Tsai YP, Wei JJ, Hsu RQ. The research of reduce residual stress of polycarbonate products by heat treatment. In: Annual Technical Conference - ANTEC, Conference Proceedings. 2009. p. 2051-5.
Guevara-Morales A, Figueroa-López U. Residual stresses in injection molded products. J Mater Sci [Internet]. 2014 Mar 28 [cited 2014 Jun 9];49(13):4399-415. Available from: http://www.scopus.com/inward/record.url?eid=2-s2.0-84899624113&partnerID=tZOtx3y1
https://doi.org/10.1007/s10853-014-8170-y DOI: https://doi.org/10.1007/s10853-014-8170-y
Liang JZ, Ness JN. The calculation of cooling time in injection moulding. J Mater Process Technol. 1996;57(1-2):62-4.
https://doi.org/10.1016/0924-0136(95)02044-6 DOI: https://doi.org/10.1016/0924-0136(95)02044-6
BASF Plastics. Estimating cooling times in injection moulding. 2023 [cited 2023 Apr 2]. Estimating cooling times in injection moulding. Available from: https://pmtools-na.basf.com/quickcost/cooling_time_est.pdf
Materials: Annealing Tips for Amorphous Polymers, Part 2 | Plastics Technology [Internet]. [cited 2024 Jan 18]. Available from: https://www.ptonline.com/blog/post/materials-annealing-tips-for-amorphous-polymers-part-2
Annealing Guidelines for Plastic Stock Shapes | Boedeker [Internet]. [cited 2024 Jan 18]. Available from: https://www.boedeker.com/Technical-Resources/Technical-Library/Plastic-Annealing-Guidelines
Covestro. Annealing of Molded Makrolon® Polycarbonate Parts [Internet]. Pittsburgh; 2019. Available from: https://solutions.covestro.com/-/media/covestro/solution-center/brochures/pdf/cov-211_annealing-of-molded-makrolon.pdf?rev=6334dd40fb2b4fb8902c03a654a6e3e5
ASTM INTERNATIONAL. D790. Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials. Annual Book of ASTM Standards. 2002.
Xu Y, Lu H, Gao T, Zhang W. Predicting the low-velocity impact behavior of polycarbonate: Influence of thermal history during injection molding. Int J Impact Eng. 2015 Dec;86:265-73.
https://doi.org/10.1016/j.ijimpeng.2015.08.013 DOI: https://doi.org/10.1016/j.ijimpeng.2015.08.013
Wang J, Hopmann C, Kahve C, Hohlweck T, Alms J. Measurement of specific volume of polymers under simulated injection molding processes. Mater Des. 2020;196:109136.
https://doi.org/10.1016/j.matdes.2020.109136 DOI: https://doi.org/10.1016/j.matdes.2020.109136
Dar UA, Xu YJ, Zakir SM, Saeed MU. The effect of injection molding process parameters on mechanical and fracture behavior of polycarbonate polymer. J Appl Polym Sci. 2017;134(7):1-9.
https://doi.org/10.1002/app.44474 DOI: https://doi.org/10.1002/app.44474
Gu F, Hall P, Miles NJ, Ding Q, Wu T. Improvement of mechanical properties of recycled plastic blends via optimizing processing parameters using the Taguchi method and principal component analysis. Mater Des. 2014;62:189-98.
https://doi.org/10.1016/j.matdes.2014.05.013 DOI: https://doi.org/10.1016/j.matdes.2014.05.013
Katmer S, Bilgileri K. THE EFFECTS OF MOLDING CONDITIONS ON THE RESIDUAL STRESSES IN INJECTION MOLDED POLYSTYRENE FLAT PARTS. Journal of the Faculty of Engineering and Architecture of Gazi University. 2012;27(3).
Brzęk P, Sterzyński T. Stress whitening as an observation method of residual stress in mabs polymer material through the example of holding pressure in an injection molding process. Polymers (Basel). 2020;12(12):1-12.
https://doi.org/10.3390/polym12122871 DOI: https://doi.org/10.3390/polym12122871
Engels T, Govaert L, Meijer H. The Influence of Molecular Orientation on the Yield and Post‐Yield Response of Injection‐Molded Polycarbonate. Macromol Mater Eng. 2009 Nov;294:821-8.
https://doi.org/10.1002/mame.200900050 DOI: https://doi.org/10.1002/mame.200900050
Vargas-isaza C, Posada-correa J, León JB de. Analysis of the Stress Field in Photoelasticity Used to Evaluate the Residual Stresses of a Plastic Injection-Molded Part. Polymers (Basel). 2023;15(16):1-14.
https://doi.org/10.3390/polym15163377 DOI: https://doi.org/10.3390/polym15163377
Accepted 2024-02-14
Published 2024-02-26
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