A Correlation between Reinforcing Effect and Antibacterial Performance of Carbon Black and Silica Filled Natural Rubber Vulcanizates Containing Hpqm-Based Neusilin

Abstract

This work pursued, for the first time, a correlation between antibacterial performance and mechanical properties of natural rubber (NR) compounds reinforced with commercial fillers, i.e. precipitated silica (PSi) and carbon black (CB), using 2-hydroxypropyl-3-piperazinyl-quinoline carboxylic acid methacrylate (HPQM)-based Neusilin as an antibacterial agent against Escherichia coli (E. coli) ATCC 25922 and Staphylococcus aureus (S. aureus) ATCC 25923. Antibacterial efficacy was determined by the inhibition zone from a halo test and by the percentage reduction of bacteria using the plate count agar (PCA) method. The results suggested that the optimum loadings of PSi and CB in NR compounds were 20 and 40 phr, respectively. HPQM-based Neusilin could be used simultaneously as a co-activator and antibacterial agent in the NR compounds. The overall mechanical properties of the NR vulcanizates were not affected by the addition of HPQM-based Neusilin, which was more effective for killing E. coli. It could be concluded that the antibacterial efficacy was conversely associated with the reinforcement level of the NR vulcanizates by the PSi and CB fillers: the higher the reinforcement level, the poorer the antibacterial efficacy. At the optimum loadings of PSi and CB fillers, the antibacterial efficacy of PSi-filled vulcanizates was better than that of CB-filled vulcanizates.