Abstract:
Many diseases arise from biofilm formation, thus there is keen interest in antimicrobial plastics to prevent these infectious diseases before they break out. There are several inorganic antimicrobial agents which are used to date such as silver or metal oxides. They are very efficient in preventing the build-up of bacteria. However, these agents are susceptible to leaching which increases the chances of exposure to humans and the environment. This research is focused on using 3-(trimethoxysilyl)-propyldimethyloctadecyammonium chloride (SPODA) and synthesising modified guanidine with a triethoxysilane group to replace current antimicrobial agents in plastics. A major advantage of SPODA is that it is very effective against gram-positive bacteria and can be bonded to surfaces making it less leachable. On the other hand guanidine has proven to be effective against both gram-positive and gram-negative bacteria such as E.coli and S.aureus. Both antimicrobial agents were bound respectively onto fumed silica through anhydrous deposition. These modified silica substrates were then charactised using FTIR to acknowledge the successful deposition. The aim of the research is to incorporate the silica into polymers such as low density polyethylene (LDPE), where the modified antimicrobial functionalised silica acts as an antiblock additive for plastics packaging films. The Silica and antimicrobial agent were refluxed to allow the anhydrous reaction of the silane groups on both antimicrobial agents with the OH groups on the surface of silica respectively. Characterisation methods of the synthesised compounds and resins involved FTIR, TGA, DSC, and 1D NMR. The products were then incorporated into LDPE films and tested for antimicrobial activity against E.coli and S.aureus. Experimental results were promising for SILICA/SPODA against gram-positive S.aureus whereas the SILICA/GUANIDINE powder showed efficacy against both E.coli and S.aureus. However, upon incorporation into LDPE, the SILICA/SPODA composite still showed promising results against S.aureus, whereas the SILICA/GUANIDINE composite did not show any antimicrobial activity as a film at all and was shown to be less effective against both strains of bacteria.