Sterilization effect on structure, thermal and time-dependent properties of polyamides

Abstract

This article studies the effect of different sterilization techniques on structure, thermal and time-dependent mechanical properties of polyamide 6 materials. We used two different types of polyamide 6 material: conventional polyamide 6 with monomodal molecular mass distribution and modified with bimodal one. Samples were prepared and properly shaped in order to observe the mentioned features before and after sterilization with three different techniques, namely sterilization with autoclave, ethylene oxide, and hydrogen peroxide plasma. Optical microscopy, differential scanning calorimetry and torsional creep testing were used for the properties investigation. As a main criterion to evaluate the effect of sterilization durability of materials was used. There was observed significant difference between monomodal and bimodal PA6 materials regarding their morphology and consequently thermal and mechanical properties: bimodal material exhibits more complex structure than chemically identical monomodal one. The results of analysis did not show considerable influence on both materials structure and thermal properties. However, there was observed strong effect on creep behavior. The most significant effect is detected for monomodal material sterilized by ethylene oxide, while creep compliance of the bimodal material did not change much due to any of applied sterilization techniques. Thus, modification the complexity of the material inherent structure improves sensitivity to sterilization.