Silver ion release from antimicrobial polyamide/silver composites

Silver ion (Ag+) the versatile antimicrobial species was released in a steady and prolonged manner from a silver-filled polyamide composite system. Metallic silver powder having varying specific surface area (SSA) has been used as a resource of biocide in polyamide. Strong evidences are found showing the release of the antimicrobial species from the resulting composite upon soaking it in water due to the interaction of the diffused water molecules with the dispersed silver powder within the matrix. The Ag+ release was observed as increasing with time and concentration of the silver powder and is found to be influenced by the SSA of the silver powder, changes in the physical state of the composite specimen as a result of the water diffusion and the composite morphology. It is observed that the Ag+ release increases initially which is followed by a marginal increase between day 4 and 6. Composites containing higher amounts of silver (4 and 8 wt%) exhibit a further rise in Ag+ release from the sixth day of storage in water. Composite containing silver particles with the lowest specific surface area (0.78 m2/g) showed highest Ag+ release. SEM shows a finer dispersion of the silver powder (4 wt%) having lowest SSA. However particles with higher (1.16 and 2.5 m2/g) SSA possess an agglomerated morphology leading to lower Ag+ release. The composites are found to release Ag+ at a concentration level capable of rendering an antimicrobial efficacy.