Experimental and theoretical investigation of stress corrosion crack (SCC) growth of polyethylene pipes

Byoung-Ho Choi, Alexander Chudnovsky, Rajesh Paradkar, William Michie, Zhenwen Zhou, Pak Meng Cham

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

Degradation of polymers is usually manifested in a reduction of molecular weight, increase of crystallinity in semicrystalline polymers, increase of material density, a subtle increase in yield strength, and a dramatic reduction in toughness. Stress corrosion cracking (SCC) results from strongly coupled thermo-mechano-chemical processes, and is sensitive to material composition and morphology. The individual crack propagation stage is critical in determining the lifetime of pipe. Based on author's previous works, crack layer (CL) theory model is adopted in this study to describe the individual stress corrosion (SC) crack propagation kinetics and the time interval from crack initiation to instability and break through. The effect of localized chemical degradation at the crack tip on SC crack growth kinetics is addressed. Typical SC crack growth is presented and discussed as a step-wise manner based on the proposed model. In addition, scanning electron microscopy (SEM) observation and Fourier transform Infrared spectroscopy (FTIR) analysis of failed samples obtained by accelerated SCC tests are applied to validate the proposed model. SEM is useful to identify the change of fracture mechanisms from chemically driven crack to mechanically driven crack by the formation of visible striations. FTIR analysis enables tracking of the accumulation of chemical degradation by detecting the amount of carbonyls on the crack surface. Carbonyl index is defined to compare the amount of chemical degradation quantitatively. The purpose of this paper is to continue to develop the technical theory and understanding behind SCC phenomena to facilitate all polymer pipe industries and in particular the polyethylene pipe industry to design better resins and piping systems.

Original languageEnglish
Pages (from-to)859-867
Number of pages9
JournalPolymer Degradation and Stability
Volume94
Issue number5
DOIs
Publication statusPublished - 2009 May 1

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Keywords

  • Crack layer theory
  • Crack propagation
  • Fracture initiation
  • FTIR
  • SEM
  • Stress corrosion crack

ASJC Scopus subject areas

  • Polymers and Plastics
  • Materials Chemistry
  • Mechanics of Materials
  • Condensed Matter Physics

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