Formation of craze-like pattern in polypropylene UV-induced surface cracking

Author(s)

De Freitas, Amanda De S. M. ; Rodrigues, Jessica S. ; Botaro, Vagner R. ; Lemes, Ana Paula ; Cruz, Sandra Andrea ; Waldman, Walter R.

• Document type: Journal article
• Source: JOURNAL OF POLYMER RESEARCH; v. 29, n. 12, p. 8-pg., 2022-12-01.

Abstract

Polypropylene (PP) samples were exposed to accelerated aging with UV-C light and showed a morphology inside the crackings like that of thermoplastic polymers under stress, known as craze. Herein we used the well-established photodegradation of polypropylene to build the relationship between the phenomenon of fibrillation inside the crackings and the microvoid formation during the evolution of the craze process. The basis of our proposition is the similarity of the processes but the stress source: whereas an external tensile stress load drives the craze, in photodegradation the stress comes from the changes caused by the crystallization, which reduces volume, creating tensions and forming cracks. We followed the polypropylene photodegradation using Scanning Electron Microscopy (SEM), tensile tests, Dynamic Mechanical Thermal Analysis (DMTA), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffractometry (XRD) to prove the correlation between the cracking evolution and the craze mechanism. From this similarity, we paved the way to applying the current knowledge about the craze phenomenon to understand better the cracking evolution on polypropylene surfaces. (AU)

• FAPESP's process: 16/24936-3 - Development of thin films deposited by plasma for polymeric materials photoprotection
• Grantee: Walter Ruggeri Waldman
• Support Opportunities: Regular Research Grants
• FAPESP's process: 19/15976-0 - Biodegradation as treatment proposal and recovery of carbon nanotubes arising from residues of biodegradable polymeric nanocomposites
• Grantee: Ana Paula Lemes
• Support Opportunities: Regular Research Grants
• FAPESP's process: 19/19401-1 - Deconstruction of plant tissues: possibilities for obtaining higher added-value materials
• Grantee: Vagner Roberto Botaro
• Support Opportunities: Regular Research Grants