Influence of natural ageing on mechanical, thermal and antimicrobial properties of thermoplastic elastomers containing silver nanoparticles and titanium dioxide

Abstract

The current spread of pathogenic bacteria has brought about an increase in the research for products with antimicrobial properties. Thermoplastic elastomer (TPE) compounds are widely used for personal care objects and sporting goods manufacture and may be produced with the incorporation of antimicrobial additives. TPE compounds (based on styrene–ethylene/butylene–styrene, polypropylene and mineral oil) containing silver nanoparticles (AgNp, 0.05%) and titanium dioxide (TiO2, 4.0%) was exposed to natural ageing; a compound with no antimicrobial additive (Standard) was also tested. Antibacterial activity, mechanical and thermal characteristics of TPE samples was determined after 3, 6 and 9 months of exposure. After 9 months, both Standard and AgNp-loaded samples had a loss of mechanical properties, while the TiO2 sample was more resistant to the action of natural ageing. The infrared and thermal analysis suggested that not only the chain scission, but also the segregation of components that integrate the polymer matrix were one of the causes for mechanical properties loss. Both metal-loaded samples showed a decay of antibacterial efficiency after 9 months of exposure. The decay in antibacterial action can be assigned to the presence of dirt that provides a substrate to microbial proliferation and also avoid contact between the metal-containing surfaces and microorganisms cells.