Deformation and fracture behaviour of extruded CPVC sheet and pipe after exposure to chemical solvents

  • Author / Creator
  • The work described in this thesis concerns the influence of chemical solvents (acetone and primer) on the strength and ductility of extruded chlorinated polyvinyl chloride (CPVC) sheet with a nominal thickness of 1/32-inch, and of pipe that is 2-inch in diameter. The work also includes finite element (FE) simulations of tensile tests of CPVC dog-bone specimens with and without immersion in acetone or primer.
    Dog-bone specimens from CPVC sheet and ring specimens from CPVC pipe were prepared for mechanical testing. Test results revealed opposite trends of change in ductility for these two types of specimens after exposure to chemical liquids. The ductility of dog-bone specimens increased after immersion in chemical liquids, whereas the ring specimens showed a ductility decrease under similar conditions.
    Upon local exposure of the inner surface of ring specimens to chemical liquids, ductility of the specimens also decreases. Post-test examination on specimens with local exposure on the inner surface showed cracks around the area that had been exposed to chemical liquids, suggesting that such exposure encourages crack initiation, resulting in early fracture. Based on experimental observation, ductility reduction is caused by early formation of cracks in the surface region that was exposed to chemical liquids, which introduces stress concentration leading to premature fracture.
    FE simulation of the mechanical behavior of CPVC dog-bone specimens in tension was used to establish the constitutive equations for linear and nonlinear deformation, neck initiation and strain hardening. FE models based on a one-quarter size specimen used in experimental testing were built using ABAQUS 6.12, with material input based on a table of more than 1500 points, to closely mimic the experimentally determined force versus stroke curves.
    This thesis concludes that exposure to acetone and primer weakened the mechanical properties of extruded CPVC sheet and pipe, but generated a different effect on ductility, i.e., causing a ductility increase for sheet specimens, but a permanent ductility loss for pipe specimens. It is believed that early fracture of CPVC pipe was caused by contact with acetone and primer on the inner surface, which led to early yielding in the solvent-affected-zone (SAZ) and resulted in stress concentration and crack generation. Therefore, solvents or detergent-based liquids should be carefully handled to avoid unnecessary contact with CPVC surfaces. Finally, it is suggested that the influence of chemical liquids on the ductility of CPVC material, especially in pipe forms, should be carefully characterized to ensure the reliability of the material in long-term service.

  • Subjects / Keywords
  • Graduation date
    Spring 2021
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.