Biocides are additives able to kill and stop bacteria or fungi proliferation, to prevent degradation of polymer’s physical and sensorial properties, both within the material and at its surface. They act as a complementary technique for cleaning, which is also simplified and less costly. The growth of micro-organisms can lead to unpleasant odors, surface and bulk degradations. Biocides can be mineral such as silver compounds or organic with a multitude of molecules containing halogens, aromatic rings, arsenic, sulphur, nitrogen etc. Considering their chemical structure and their bio-activity, they are concerned by several regulations differing according to the countries and uses.
Traditional biocides are being replaced by more persistent grades and by more environment-friendly biocides also more expensive. Silver based biocides benefit from those trends but other tracks are exciting, for example nano-titanium oxide or nano-silver, modified silicone oligomers and, of course, direct grafting or molecular modification of polymers themselves.
Completely new ways are under investigation or development, using totally new solutions based on physical routes such as NIMBUS antimicrobial polymers having high charge density and high molecular weight. They physically disrupt the cell wall of bacteria, working very quickly because of their high charge density. In addition, bacteria cannot develop resistance. Following chemical routes, completely new chemical entities are emerging such as polyalkanals jointly developed by Chemeq and Arkema.
Carbon nanotubes are reported to be antimicrobial agents and CNT coatings may offer a solution to detrimental biofilm formation.
As for other polymers and additives, a lot of work and research concern natural sourced biocides. Inorganic Cu+, Ag+, Zn++ and Ba++ salts boost antimicrobial activity of PA66 when organic concentrate produced from citrus extracts control or retard the growth of bacteria, fungus and algae in plastic molded parts. Other plant derivatives such as Hinokitiol and Propolis have antiseptic, antibiotic, anti-fungal, and even antiviral properties.