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Fractography of Polycarbonate Chemical Induced Failure

I completed a failure analysis on a polycarbonate medical component that had been in contact with heptane as part of the manufacturing process. The heptane was used as a lubricant to facilitate assembly with a mating component. Cracking had been identified within a significant number of parts on the assembly line.

Through the fractographic examination, features associated with chemical effects, including crazing and severe solvation, were identified. The examination also identified that the chemical interaction was located exclusively proximal to a significant cavity void within the part. The heptane was trapped within the cavity void, which allowed chemical interaction over an extended period of time. The cavity allowed the heptane to remain in contact with the polycarbonate for an extended period of time. Without the cavity, the contact time would be relatively short, and no significant solvent effect would have taken place.

Another example of how fractography is a critical component of a failure analysis to determine how and why the failure occurred. The proper identification is critical to be able to take the next steps to correct the issue. The void problem was ultimately resolved by altering the injection molding process. The process changes in this case were made without molding simulation, although I believe that the corrections could have been made faster if simulation had been used.

Polycarbonate fracture surface chemical attack solvation

To see more fracture surfaces associated with polycarbonate failure, see this ANTEC Paper, Fractographic Characterization of Polycarbonate Failure Modes

Jeffrey A. Jansen

Jeffrey A. Jansen is the Engineering Manager and a Partner at The Madison Group. He was elected as a Fellow of the Society by the Society of Plastics Engineers. Jeff is a proven plastic professional with more than 30 years of experience solving problems and addressing opportunities related to polymeric materials. He specializes in failure analysis, material identification and selection, as well as compatibility, aging, and lifetime prediction studies for thermoplastic materials. Jeff has performed over 5,000 investigations, both for industrial clients and as a part of litigation. He regularly presents seminars and webinars, covering a wide range of topics related to plastics failure, material performance, testing, and polymer technology. Jeff is a graduate of Carroll College and the Milwaukee School of Engineering.