Effect of molecular weight and hydration on the tensile properties of polyamide 12

Abstract

Polyamide 12 (PA12) has found significant applications in the medical device industry, including its common use as an outer jacket layer in catheters. Like all polymers, PA12 can undergo degradation reactions, which compromise the mechanical and physical properties of the material. In this paper FTIR/ATR, 1H NMR, kinematic viscosity, GPC, DMA and DSC were used to characterize several PA12 catheter jackets. The results showed a decrease in elasticity when the PA12 molecular weight dropped below a critical value. Additionally, stress/strain measurements of dry and hydrated PA12 samples were used to investigate the plasticization effect of water on the properties of the material. An increase in elasticity was observed as the hydration of the samples increased, although the PA12 samples quickly dried back out to their initial stiff state. The PA12 extrusion conditions were also examined to determine how the selection of draw down ratio and air gap can affect the elastic properties of the final part.