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Experimental Research Paper | Material Science and Engineering | Volume 15 Issue 5, May 2026 | Pages: 1611 - 1620 | India
Comprehensive Evaluation of White Patch Formation in Polypropylene (PP) Carboys Manufactured by Extrusion Blow Molding
Abstract: Background: Surface stress whitening was observed on the lower regions of extrusion blow molded polypropylene (PP) carboys during routine quality inspections. Although stress whitening is commonly regarded as a cosmetic phenomenon. Objective: This study aimed to characterize the morphology, origin, and performance impact of stress induced whitening observed in PP carboys and to assess whether the phenomenon poses any risk to mechanical integrity, containment performance, or sterilization compatibility. Methods: Carboys exhibiting visible white patches were subjected to a comprehensive evaluation including visual and tactile inspection, wall thickness analysis, mechanical impact testing, Chemical impact testing, hydrostatic leak testing, vacuum integrity testing, thermal, and gamma sterilization. Morphological and risk based assessments were supported by failure mode and effects analysis (FMEA). Results: Stress whitening was confirmed to be superficial and localized, with no evidence of crack initiation, polymer degradation, or material embrittlement. Mechanical performance, structural stability, leak integrity, and sterilization resistance were unaffected. Whitening did not progress following thermal or irradiation exposure. Conclusion: A comprehensive evaluation of polypropylene (PP) carboys exhibiting visible white patches confirmed that the observed condition is surface-level stress whitening only, caused by handling-related surface stress. It is cosmetic in nature and does not indicate material degradation or structural weakness. Highlights: 1) Whitening confirmed superficial; no cracks or embrittlement 2) Impact, leak, and vacuum tests showed no product failures 4) Wall thickness remained within specification across samples after tested with chemical 5) Autoclave (121?C) and gamma did not worsen whitening 6) FMEA confirmed cosmetic defect with low integrity risk.
Keywords: Stress whitening, Polypropylene carboys, Extrusion blow molding, Surface morphology, Environmental stress cracking, Thermal cycling, Mechanical integrity, Leak integrity
How to Cite?: Thomas Foxx Taylor, S. R. Rizvi, Rupendra Singh, "Comprehensive Evaluation of White Patch Formation in Polypropylene (PP) Carboys Manufactured by Extrusion Blow Molding", Volume 15 Issue 5, May 2026, International Journal of Science and Research (IJSR), Pages: 1611-1620, https://www.ijsr.net/getabstract.php?paperid=SR26519123955, DOI: https://dx.dx.doi.org/10.21275/SR26519123955