His presentation provided a comprehensive overview of challenges facing the industry and practical approaches to prevent plastic failures, with a focus on environmental stress cracking (ESC) as it applies to plastics used in medical devices. McDonald noted that ESC typically begins with a solvent or chemical being absorbed into a polymer, weakening the material locally and increasing tensile stresses that can propagate into material failures.
“ESC accounts for about 25% of failures in all plastics1, and that’s mostly involves amorphous polymers,” said McDonald. “Brittle failure is the ultimate, but when we’re discussing medical devices, even failures like crazing, whitening or cracking are still a cosmetic defect and a concern.”
ESC is a complex subject to navigate even within the medical industry, as there are a variety of factors that can contribute to chemical interactions, such as service life, sterilization, manufacturing process, polymer compounds, storage and more.
McDonald stressed the importance of evaluating material choices rather than relying on tradition. He noted that medical device manufacturers often default to polycarbonate (PC) because it has historically been used, but that does not mean it is always the best option. “Each polymer has its own strengths and weaknesses — there’s no perfect one,” said McDonald. “You need to ask, ‘Will this work for our application?’”
To improve ESC resistance, McDonald urged companies to start by clearly defining performance requirements to address their specific challenges. From there, they can collaborate with material partners to fine-tune solutions—such as blending polymers, introducing new comonomers, building predictive models, and conducting chemical resistance testing—to achieve the desired performance.
Trinseo is a specialty material solutions provider that brings ideas to life in a variety of industries. The Company’s high-performance, medical-grade polymers address the materials challenges of their customers and include a portfolio of solutions: CALIBRE™ and CALIBRE™ MEGARAD™ PC Resins, MAGNUM™ Acrylonitrile Butadiene Styrene (ABS) Resins and PLEXIGLAS® Acrylic Resins.
For medical device engineers grappling with material selection and chemical compatibility challenges, McDonald's presentation offered practical guidance on testing methodologies and the importance of application-specific evaluation. His insights reinforce Trinseo's position as a technical partner capable of supporting customers through complex material science challenges.
1. Jeffrey A. Jansen (2004), ASM Handbook, Volume 11B: Characterization and Failure Analysis of Plastics, https://madisongroup.com/wp-content/uploads/2022/09/Janse_ASM_ESC_TMG2011.pdf
