Drug Delivery Device Using Polymers With Improved Tribology

significant plasticizing effect on the polymer. This is highly dependent on the part in question, tooling and machine. Waxes provide modest improvement in tribological performance at low cost, while PTFE provides further improvement but with a significant running-in period to achieve full effect. Higher levels of PTFE reduce the running-in period at the cost of reduced mechanical performance, increased cost and some risk of mold deposit.

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Celanese has added an MT® POM formulation to their friction and wear portfolio. This was done in hopes of meeting the increasing demands of tribological performance and to provide more design freedom in complex devices. These grades enable low friction in POM-on-POM pairings with a range of other counterparts (Figure 8), without sacrificing mechanical performance. The tribological performance is comparable to external lubrication of POM. Celanese Hostaform® MT® SlideX® grades exhibit low coefficients of friction versus unmodified Hostaform® POM such as Hostaform® MT® 8U01 POM, and with a similar stick-slip performance as direct lubrication of MT8U01 with silicone oil (Figure 7).

Figure 7: Performance of Hostaform® MT® SlideX® 1203 vs. unmodified Hostaform® (MT®8U01 POM) in comparison to external lubrication

The two Hostaform® MT® SlideX® grades are distinguished by their viscosities. Hostaform® MT® SlideX® 1203 POM is a standard flow injection molding grade. It is accompanied by a high flow version, Hostaform® MT® SlideX® 2404 POM, for thin walled complex part designs. The Hostaform® MT® SlideX® grades are the best performing medical POM grades with tribological modification and medical compliance.

Figure 8: Coefficient of friction of Celanese Hostaform® MT® SlideX® 1203 POM vs. other thermoplastics/metals