International Journal of Plastics Technology

, Volume 21, Issue 2, pp 404–426 | Cite as

Effect of injection molding parameters on crystallinity and mechanical properties of isotactic polypropylene

Research Article


The effects of injection molding parameters namely mold temperature, melt temperature and injection speed on crystallization and mechanical properties of isotactic polypropylene were studied. The specimens were molded as per the Taguchi design of experiment and analyzed for signal to noise ratio and for analysis of variance test. The crystallinity and crystal sizes were determined by wide angle X-ray diffraction data. The specimens were tested for tensile, impact, flexural, stress relaxation and dynamic mechanical properties. It was observed that mold temperature was the most influential injection molding parameter governing the crystallinity and other mechanical properties. It was observed that increase in crystallinity is favorable from tensile and flexural strength point of view but impact properties deteriorate with increase in crystallinity. At high injection speed β-phase changes to α-phase due to shear induced orientation of polymer chains. It is interesting to notice that stress relaxation occurred in elastic as well as in plastic regions has the similar trends and can be modeled by the same decay model proposed in this paper.


Taguchi design of experiment ANOVA α-PP β-PP Stress relaxation Wide angle X-ray diffraction 



The author is thankful and acknowledge the extension of testing and characterization facilities by Prof. Alim Hussain Naqvi, Prof. Ameer Azam and Dr. Wasi A. Khan, Center of Excellence in Nanotechnology, Department of Applied Physics, Aligarh Muslim University, Aligarh, for this experimental study.


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Copyright information

© Central Institute of Plastics Engineering & Technology 2017

Authors and Affiliations

  1. 1.Department of Petroleum Studies, Faculty of Engineering and TechnologyA.M.U.AligarhIndia

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