Enhancing the Longevity of Biomedical Polyurethanes with Antioxidants and UV Stabilizers

Biomedical polyurethanes (PUs) are crucial in various applications, but their longevity and performance are often compromised by photooxidative degradation and tackiness. Recent studies have highlighted the significant role of additives like UV stabilizers and antioxidants in extending the lifespan of these materials. A notable example is the incorporation of Tinuvin 315 or Sanduvor EPU stabilizers, which doubled the photo UV life-aging of certain PU systems from 72 to 144 hours.

Further research by Chu and Fischer demonstrated that combining Tinuvin 328 with Irganox 1010 successfully extended the time before tackiness appeared from 120 hours to 226 hours. Although UV stabilizers like Tinuvin 328 improve UV resistance, challenges remain—particularly the persistence of tackiness. The observed improvement in color stability may be attributed to the reduced formation of color-contributing species rather than solely to the effectiveness of the stabilizers.

Interestingly, the effectiveness of UV stabilizers can vary significantly among different PU formulations. For instance, while Tinuvin 120 delayed tackiness in aliphatic polyether urethane (PEU) systems for up to 250 hours, it failed to prevent melting in Calthane ND 2300 after 192 hours of UV exposure. This variability underscores the complex interactions between the chemical nature of the PU formulation and the stabilizer's performance.

In addition to UV stabilizers, the use of antioxidants like Irganox 1010 has shown promise in enhancing thermal stabilization of the soft segments in these materials. Studies indicate that the presence of antioxidants can significantly improve the mechanical properties of PUs under photooxidative conditions, although tensile strength may still decrease with prolonged UV exposure.

Research by Zhao et al. further emphasized the importance of combining multiple additives. Their findings revealed that formulations with Santowhite, Tinuvin 328, and Cyasorb UV 3346 not only improved UV stability but also enhanced the fatigue lifetime of PUs exposed to environmental factors like papain. The stabilized systems exhibited superior performance, demonstrating how thoughtful incorporation of additives can mitigate degradation issues.

In summary, the integration of antioxidants and UV stabilizers in biomedical polyurethanes is a critical factor in enhancing their durability and performance. As ongoing research continues to refine these formulations, the potential for more resilient biomedical applications remains promising.