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Plastic Failure Analysis

Coating Failure on a PVC Substrate
Coating failure on a PVC window frame
Environmental cracking of an EPDM air intake elbow
Environmental cracking of an EPDM rubber air intake tube

Plastics, Synthetic Rubbers, and other Polymeric Materials are becoming more prevalent in our society. From their widespread use initiating in the 1960’s, they are still relatively new as compared to the different metals which have made our products for 100’s of years.  Plastics can be low cost materials, which can have service lives measured in years, not decades.

Polymers have impacted materials science and engineering greatly due to their ability to be formed.  They have a short but distinct existence of only 125 years. Four major areas of consideration applied to the manufacture of plastics are material, design, processing and service conditions.

Failures in modern polymeric materials are caused by factors such as:

  • material defects,
  • loss of plasticizer,
  • poor thermal stability,
  • overload failures,
  • creep,
  • impact,
  • flammability,
  • environmental incompatibilities

Unique challenges with polymeric materials includes environmental degradation (embrittlement and cracking as the result of UV or chemical exposure), their inherent high degree of elasticity.

Another unique aspect of plastics failure analysis is that residual stresses as a result of processing can be sufficient to initiate environmental stress-cracking, or stresses as a result of ‘snap-fit’ assemblies can be sufficient to initiate impact fracture at the time of manufacture.