Fracture of a Dyed Medical Instrument

The Challenge

One effect that can be difficult to anticipate in polymer products is the influence of colorants and fillers on the final properties of a plastic component. This was precisely the case for a manufacturer with a failed medical instrument of a specific color while other instruments appeared to be performing as expected. The manufacturer colored raw material, combined with using a dry blending technique, prior to a molding process. The client, faced with a growing number of back orders and frustrated customers, needed answers fast and turned to Lucideon’s team of Polymer experts to diagnose the issue.

What We Delivered

Samples were sent to Lucideon for testing which included an unused reference component, a failed component, and a sample of raw polymer material and colorant. Lucideon proposed the exploration of the chemical composition, thermal properties and crystal structure of the failed instrument using mass spectrometry (MS), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques, respectively. Optical microscopy was also utilized to investigate the fracture surface and surrounding material. DSC and XRD indicated an increase in crystallinity and growth of large crystals. Subsequently, large spherulites were observed when viewed between the cross polarizers of the optical microscope. Through this analysis, Lucideon’s polymer experts were able to verify that uneven mixing during the dry mixing process encouraged the nucleation of crystallites in the polymer matrix which acted as stress raisers, ultimately leading to brittle anisotropic properties.

Value to The Client

Through a combination of expert consultancy and identification of the specific colorant, Lucideon not only provided the client with a more suitable colorant, but they were also able to advise of alternative techniques that result in better mixing, such as compounding and the use of master batches. The client now has piece of mind to confidently produce high quality instruments without the cost of periodic failures or concern for reliability in their end use application.

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