Industries and Applications for AGXX
Heraeus' AGXX particles can be incorporated into a wide variety of materials, making them ideal suited for a wide range of applications. AGXX can already be successfully incorporated into polymers, textiles, filters, and paints and coatings without significantly affecting their desired properties.
Polymers
Polymers are used in a wide variety of applications. Due to the large number of applications, the polymers must also have a wide variety of capabilities to function properly in the respective applications. For example, antimicrobial efficacy is also elementary in many areas to protect the material from microorganisms. Polymer applications that benefit greatly from antimicrobial capabilities include food conveyor belts, wound dressings, mattresses, films and many more.
AGXX represents the optimal technology for polymer applications, as the antimicrobial technology provides the material with sustainable antimicrobial properties.
Due to its innovative mechanism of action, AGXX shows excellent efficacy in water-absorbent polymers such as polyamide 6 types and polyurethanes. Its efficacy has been proven by tests conducted by Heraeus' partners.
Tests with different AGXX concentrations were carried out in PA6 and PA6/66. AGXX was incorporated into PA6 and PA6/66 granules using a screw extruder, which was then injection molded into sheets. Microbiological tests were performed with these sheets according to standardized ISO 22196 tests. The antimicrobial activity of the equipped material was tested against E.coli and S.aureus strains. All tested AGXX concentrations showed excellent antimicrobial activity, thus in all plates the bacterial concentration of E.coli and S.aureus strains was reduced by more than 99.9%. In addition to the excellent antimicrobial efficacy of the equipped PA6 and PA6/66 plates, good processability was observed for the AGXX-additivated plastics during extrusion and injection molding. Since no changes in processing parameters occurred compared to the AGXX-free reference, it can be assumed that the AGXX additive does not affect the manufacturing processes.
In addition to polyamides, AGXX was incorporated into PU flexible foam at different concentrations. After incorporation, antimicrobial efficacy tests and material tests were conducted with the equipped flexible foams. The antimicrobial particles can be easily incorporated into the foam and distributed homogeneously without affecting the foam structure of the polyurethane. To investigate the antimicrobial activity of the material, standardized ASTM E2149 tests were carried out, whereby the foam bodies were incubated in bacterial suspensions for 24 hours and the germ reduction was determined hourly. Here, testing was performed against E. coli and S. aureus strains.
The result of the ASTM test: All AGXX concentrations showed a significant germ reduction in contrast to the AGXX-free reference. In addition to investigating the antimicrobial efficacy of the equipped PU foams, material tests were also carried out. For this purpose, the compressive stress of the additivated PU foams was measured in compression tests directly after production and after one week of storage. The AGXX-additivated foams showed a slightly increased strength compared to the AGXX-free reference but behaved analogously to the reference after one week of storage.
Textiles
Microorganisms feel very comfortable on textiles. Everyone knows the unpleasant smell of laundry after sports. The trigger for this odor is not the sweat itself, but bacteria that decompose the sweat. While odor triggered by microorganisms causes discomfort for the wearer and those around him, the presence of microorganisms on textiles is also a huge social problem. Because most hospital infections are transmitted via textiles, so microorganisms on textiles pose an enormous threat to people's health. AGXX makes it possible to provide textiles with long-term antimicrobial properties, even after multiple washing cycles. Thus, AGXX can help to reduce the number of hospital infections and save human lives.
In addition to this advantage, AGXX can also provide a remedy against unpleasant odors in the private sphere and thus ensure that users simply feel more comfortable in their clothing.
Various tests have shown that AGXX can be used to provide textiles with antimicrobial properties without any problems. AGXX can already be successfully incorporated into textile coatings and textile fibers.
In the field of textile coatings, AGXX particles were incorporated into hydrophilic as well as slightly hydrophobic PU-based systems. After incorporation, all samples were subjected to several washing cycles and subsequently tested for their antimicrobial efficiency. Standardized ISO 22196 tests for antimicrobial efficacy were performed.
As a result, both AGXX-containing samples showed excellent antimicrobial efficiency against the S.aureus bacteria used (germ reduction >99.9%), compared to the AGXX-free references.
The processability of the AGXX-additivated finishes was smooth and the AGXX had no influence on the properties of the coatings, such as dirt and scuff resistance.
The tests shown were carried out at the German Institute for Textile & Fiber Research (DITF) and were part of a feasibility study. Based on the successful results, the application of AGXX in textiles is being developed and investigated together with the DITF in a project publicly funded by the German Federal Ministry of Economics and Climate Protection. So that further textile finishes, coatings and incorporation into synthetic textile fibers will be investigated as part of the funded joint project. Initial tests on the incorporation of AGXX particles into nylon fibers on a laboratory scale have already shown promising results in terms of processability. Earlier trials by technology partner Largentec also demonstrated flawless antimicrobial efficacy of AGXX-additivated nylon fibers in ISO 20743 tests. Heraeus is continuously working on particle optimization to enable optimal incorporation into textile fibers. In addition to investigating the antibacterial and antiviral effect and processability of AGXX, the joint project with the DITF is also addressing questions relating to reprocessing processes, functionality, and the influence of various sterilization methods.
Paints and Lacquers
Paints and lacquers usually contain biocides to ensure pot and film preservation. Pot preservatives are used to ensure that paints or lacquers do not mold in the pot. While pot preservatives are used to control microorganisms in the unprocessed state, film preservatives are used to prevent fouling of the material after application. Film preservatives play a central role, particularly in facade paints and antifouling paints, to protect surfaces from algae growth.
A key problem with conventional biocides in such systems is that they leach out after some time and pollute the environment. As a result of leaching, antimicrobial efficacy is lost and fouling of the surface begins.
Since AGXX's mechanism of action is based on a catalytic redox reaction, AGXX can provide pot and film preservation to paints and coatings without any leaching of environmentally harmful substances.
This is illustrated by tests conducted with AGXX by independent laboratories. Tests were carried out in accordance with IBRG-P16 to verify pot preservation. In the tests, AGXX-equipped paint samples were inoculated with test strains so that a CFU of approximately 1x103/ml was present. Subsequently, the samples were tested weekly for germs at the end of each week for ten weeks. The interior paints equipped with AGXX showed excellent antimicrobial activity, so that no microbial growth was detectable on the paints. On the biocide-free reference, microbial growth could be detected after only 3 weeks.
The tests were performed with AGXX concentrations of 0.01 wt%, but further reduction of AGXX in paints is conceivable. The sufficient AGXX concentration depends on the material properties of the respective paint or coating.
To demonstrate the functionality of AGXX as a film preservative, tests were carried out according to ISO 22196 against S.aureus and E.Coli strains. For this purpose, AGXX was incorporated into a biocide-free interior paint and into a biocide-free polyurethane lacquer. In the interior paint, AGXX showed excellent antimicrobial efficacy against both bacterial strains, while in the polyurethane lacquer, the antimicrobial technology showed excellent efficacy against the S.aureus strains and slight antimicrobial efficacy against the E.coli strains.
The efficacy is related to the material properties of the system, especially the water absorption capacity of the material.
In addition to the antimicrobial efficacy of a preservative, it is fundamental that the added additive does not distort the color fastness even over a longer period. To demonstrate the preservation of color fastness despite AGXX, accelerated weathering tests (QUV tests according to ISO 16474-3) were carried out. For this purpose, the AGXX-containing samples were stored in a weathering facility for 500 hours and subjected to weekly color evaluation in comparison with the AGXX-free reference. With the result that hardly any visual differences could be detected between the antimicrobial color and the reference.
Filtration
Water and air filters are a good breeding ground for microorganisms. Microorganisms like to accumulate on filter surfaces, multiply there and can get into drinking water or the ambient air where they can cause diseases as well as unpleasant odors.
By using the AGXX technology in filter systems, the growth of microorganisms in the filters can be prevented. This has been demonstrated by testing AGXX impregnated activated carbon (AGXX-Carbon) according to ASTM E2149. AGXX-Carbon shows excellent antimicrobial efficacy in all forms (powder, granules, and pellets), keeping filter systems germ-free.
Activated carbon used in filters can be impregnated with AGXX and then inserted directly into the filter system after impregnation, so AGXX-Carbon promises easy handling.
In addition to the antimicrobial efficacy, the BET-surface of the activated carbon pellets and granules were also tested. The results show no or only slightly reduced BET-surface for AGXX-Carbon products compared to untreated activated carbon, both for granules and pellets. These data indicate that the functional properties of the activated carbons are not affected by AGXX.
In addition to protecting the filter itself, AGXX has already been tested in a laboratory-scale test setup for water filtration applications. For this purpose, two laboratory columns with a length of 200 mm and a diameter of 3.8 mm were filled with activated carbon granules with an average particle size of approximately 350 μm. The first column contained only AGXX-free activated carbon granules. The second column was filled with a mixture of 99 % AGXX-free granules and 1 % AGXX-coated activated carbon granules of the same type. Both columns were connected to a pump that simultaneously passed 150ml of E.coli suspension containing 0.4 ∙ 106 colony forming units (CFU) through both columns at a flow rate of 1ml/min. After every 15 ml, 1 ml of the filtrate was taken, plated on agar, and analyzed for the number of CFU. The analysis showed that the number of bacteria in the filtrate of the AGXX-free column increased continuously. In contrast, the filtrate passed through the column with 1 % AGXX-coated granules was completely germ-free throughout the filtration experiment. This experiment demonstrates the high antimicrobial efficacy of AGXX in water filtration.
