Anti microbial additives for polymers

1. Antimicrobial Additives
Vinay Ghosalkar
Mathias Mayer

2. Table of contents
 Definition of Antimicrobial Additives
 Why do we need them ?
 Classification of Antimicrobial Additives
 Mode of Action
 Commonly used Antimicrobial Additives in plastics
I. Silver ion
II. Zinc
III. Copper
 How to create an Antimicrobial Additive ?
 Tests methods to validate the additive
 Application of Antimicrobial Additives
 Important Regulations
 Future trends

3. What is an antimicrobial additive ?
• An antimicrobial additive is an active agent that when included in the
processing of a material will inhibit the life or growth of microbes. These
microbes can include a variety of organisms such as bacteria, mold, fungi,
algae, and even viruses.

4. Why do we need Antimicrobial
Additives ?
 The result of using antimicrobial additives can mean the
production of intrinsically cleaner, more robust, and longer
lasting products by means of:
 Reducing illness and infection causing bacteria
 Resisting the growth of unpleasant mold and mildew
 Minimizing stain and odor causing bacteria
 Inhibiting physical degradation from bacteria and fungi,
which feed on plastics and their additives
https://www.youtube.com/watch?v=Sb2-wSaC9Tw&ab_channel=PlasticsColor

5. The main effects caused by microbials
The results of microbial attack on plastic materials are manifold. The main effects caused
by microbial activities are:
Staining
This discoloration can be a result of intracellular pigments (e.g., by pigmented molds such as Penicillium and Aspergillus species)
or extracellular dyestuffs (i.e., microorganisms release colored metabolites from the cell).
Effect on electrical properties
Changes in electrical properties, especially insulating power, may be a result of microbial attack. This phenomena is often
caused just by the migration of microbes on the plastic surface, without any deterioration of the material. The deterioration of
electrical proper ties can be exacerbated if the microbes produce polymeric materials such as exo-poly saccharides.
Deterioration of mechanical properties
This is the most serious consequence of microbiological degradation. Metabolization of the plasticizers by bacteria and/or fungi
may result in brittleness. Shrinkage. and finally. loss of tensile strength and integrity. The breakdown of plasticizers into smaller
molecules also enables microorganisms that are not capable of metabolizing the intact plasticizer to grow.

6. Classification of Antimicrobial
Additives
Based on Mode of
Action
Microbicidal
One That kill the
Microbes
completely
Micro biostatic
One that inhibit
the growth of
microbes
Based on Type of
Active Ingredient
Organic Inorganic

7. How Does a Antimicrobial Additive Work?
Controlled Release Mechanism
•The efficacy of most antimicrobial active
ingredients in plastic can be described as
controlled release mechanism.
•The active ingredients in the antimicrobial is
slowly released from the polymer matrix and
migrate to the surface.
•Under Ideal condition matrix can serve as a
reservoir of antimicrobial.
Regeneration Method
• The active ingredients in the antimicrobial can be
regenerated by treatment with bleaching agent
during laundering or by UV light during drying.
•It has gained importance in recent times for
synthetic textile fibre.

8. Active Ingredients Used to Make Antimicrobial additives in Plastics ?
• Historically, the plastic industry - most notably the vinyl and polyurethane foam industries - viewed 10,10'-
oxybisphenox-arsine or "OBPA" as the golden standard in antimicrobial protection. This arsenic-based biocide
was preferred due to low cost and antimicrobial effectiveness.
• Today, OBPA cannot be used in Europe since it is not BPR listed and goods imported into the EU are not
allowed to contain this biocide. In addition, OBPA is currently under review by the US Environmental Protection
Agency.
• As a result, a generation of newer, greener and equally effective antimicrobial options have been developed to
replace OBPA.
• The most common additives used to manufacture antimicrobial plastics include various isothiazolinone
treatments, zinc pyrithione, thiabendazole, and silver antimicrobial products. Each active ingredient has its
strengths and weaknesses.
• For example; zinc and silver have strong antibacterial activity at low concentrations, but high levels are needed
to achieve adequate antifungal properties. Others, such as isothiazolinones and thiabendazole, have robust
antifungal profiles but are not as effective against bacterial attack.

9. Commonly used Antimicrobial Additives in
plastics
• Antimicrobial technology typically contains one of three inorganic active ingredients:
• Silver ion antimicrobials: suitable for a wide range of materials and applications, including medical
coatings, plastics and food-contact products.
• Zinc antimicrobials: a broad spectrum antimicrobial that is commonly favored for it's antifungal
properties.
• Copper antimicrobials: often used as a preservative and popular for medical products and surfaces.
• Antimicrobial technologies can also consist of organic active ingredients such as Quaternary
Ammonium Compounds (QUATs).

10. How Does a Antimicrobial Additive Work?
https://www.youtube.com/watch?v=NYDOZzpH99E&ab_channel=BioCladLtd

11. On which factors activity of anti-microbials depends
I. Molecular weight
II. Counter ion
III. length of Alkyl chain
IV. pH Effect
V. Tolerance of the bacteria
VI. Mode of activity of antimicrobial
VII. Surface tension and texture of the plastic surface
Requirements of Anti-microbials ingredients
I. Low toxicity to humans, animals & environment
II. Easy to apply
III. Compatibility with other processing aids § additives
IV. storage stability
V. The polymer should not decompose during use, or emit toxic residues.
VI. Antimicrobial activity should be able to be regenerated upon loss of activity.
VII. Antimicrobial polymers should be biocidal to a broad range of pathogenic microorganisms in brief times of contact

12. How to create an Antimicrobial Additive ?
• Antimicrobial additives for polymers can be applied by direct addition, or as an antimicrobial
masterbatch, during the manufacturing process.
• An antimicrobial masterbatch can be supplied in carriers suitable for most polymers including
PVC, PE, HDPE, PP, polyamide, polyester, ABS, polycarbonate, and styrene.
• Antimicrobial additives for plastics are also used to treat elastomeric polymers and rubbers
such as TPEs and TPVs.

13. Tests methods to validate the additive efficacy
• When looking at a newly manufactured polymer, antimicrobial additives are not noticeable. Antimicrobial additives for plastic
don't emit an odor. They should not cause a difference in color and they can't be seen or felt on the surface. In fact,
antimicrobial plastics look exactly the same as untreated ones. So how does antimicrobial plastic work and how can it be
tested?
• Many test methods developed by organizations such as the American Association of Textile Chemists and Colorists (AATCC);
American Society for Testing and Materials (ASTM); International Organization for Standardization (ISO); and Japanese
Industrial Standard (JIS) are available to evaluate the performance of antimicrobial polymer additives.
• Such standardized test methods are often developed for specific types of materials, end-uses, or antimicrobial agents;
therefore, choosing the correct test method is crucial.
• Common test methods used to assess antifungal polymers include the ASTM G21 and AATCC Method 30, whereas
antibacterial plastic is often tested using the ISO 22196 or the JIS Z 2801.
• Polymer materials destined for marine or outdoor applications are often also assessed for susceptibility to pink staining using
the ASTM E1428

14. Tests methods to validate the additive efficacy
• There are various tests developed by ASTM (American Society for Testing and
Materials) & AATCC (American Association of Textile Chemists and Colorists) to
investigate antimicrobial activities in plastics.
• For general assessment of an antimicrobial substance, a term called as MIC is used.
 MIC stands for Minimum Inhibition Concentration of the substance against microorganisms.
 It is defined as lowest concentration in ppm (parts per million).
 It gives information on micro-biostatic activity of a substance.

15. Tests methods to validate the additive efficacy
Agar-based tests
 Agar-based tests are the most common. These tests evaluate not only the efficacy of the material in
inhibiting or killing microorganisms but also evaluate the area surrounding the material (zone of
inhibition). A large zone of inhibition surrounding the test sample indicates strong antimicrobial
activity. Typically, a small sample of the test material is placed onto the appropriate agar that has
been inoculated with a cocktail of microorganisms. After incubation (to grow the microorganisms),
the substrate and agar are examined for microbial growth and the zone of inhibition. A schematic
representation of an agar test is shown in Fig.
 Some biocides give very large zones of inhibition in agar tests with the implication of superior
performance. However, this also could mean that a large zone of inhibition can be indicative of the
fact that the antimicrobial dissolved into the agar and leached out of the plastic test material,
providing a large zone of inhibition, but made the plastic itself susceptible to microorganism growth
• ASTM G21-90/ISO 846 Part A—a fungicidal test evaluating the ability of the antimicrobial to kill microorganisms;
• JIS Z 2911/ISO 846 Part B—a fungistatic test evaluating the ability of the antimicrobial to inhibit microorganism growth;
• ASTM G22/ISO 846 Part C—an antibacterial agar test;

16. Agar plate test with HDPE samples containing no antimicrobial
(A) and 0.25% of an antimicrobial
(B) (test organism: staphylococcus aureus ATCC 9144)
Bacteriostatic and bactericidal activity of antimicrobial LDPE against staphylococcus aureus.
A: LDPE without biocide;
B: LDPE with bacteriostatic agent
C: LDPE with bactericidal agent

17. 3. In-use tests
Antimicrobial material is subjected to realistic condition
Plastic is buried 90 days to investigate the resistance to rotting.
In modified test methods physio-chemical parameters like tensile strength and integrity are
investigated along with microbial contamination.
Field Tests for 1+ years are carried out for outdoor panel exposure studies.

18. Tests methods to validate the additive efficacy
Nutrient
agar plate
Discs containing
antimicrobial
agents are placed
on surface
Inoculate plate
with a liquid
culture of a test
organism
Incubate for 24–48 h
Test organism shows
susceptibility to some
agents, indicated by
inhibition of bacterial
growth around discs
(zones of inhibition)
 Other Standard Test Methods-
1. ASTM-G21-90
 Standard practise for determining resistance of synthetic polymeric materials to fungi
 Material is placed on nutrient-free( mineral salt agar without carbon source), sterile agar is inoculated
on its surface with fungal spore suspension.
 Plates are incubated for 21 days with humidity more than 85% and temperature 28-30℃
 After 21 days incubation specimen can be used to evaluate effects of fungi on mechanical, optical
and electrical properties.
2. EN ISO846
 It is combination of agar plate test ( fungi and bacterial growth on plastic material in nutrient free and
nutrient containing agar medium) and soil burial test (determination of plastic’s resistance to attack
by soil microorganism for outdoor use)
 In addition to microbiological parameters like growth on materials, inhibition zones, etc. physical
parameters like weight change, tensile strength, electrical properties, change in colour, etc are
studied.

19. Regulations
• Regulations vary by country and require testing and registration.
United States of America Europe
• All biocides must be registered by the Environmental
Protection Agency (EPA) for intended use in plastics.
• Under Federal Insecticide, Fungicide and Rodenticide
Act (FIFRA) companies cannot sell any plastic product
unless product is approved by EPA.
• Antimicrobials used in plastic in contact with food must
be registered as indirect food additives by US Food &
Drug Administration (FDA)
• So far antimicrobial agent in non-food application have
not been regulated in European Community by any
specific directives, although few countries have national
regulations for antimicrobials in plastics like
Netherlands, Belgium, UK.
• The Biocidal Product Directive (BPD), regulates the use
of antimicrobials in plastics.
• It aims to introduce a harmonized European system for
biocidal products and provide greater protection for
both the human population and the environment.

20. Future trends
• Increased demand for plastic products with antimicrobial efficacy beyond preservation is expected.
Antimicrobials with a favorable toxicity profile that can specifically attack target microorganisms
and are present at very low concentrations on the surface of plastic (such as triclosan, which is
already approved for skin care products and recently obtained an Indirect Food Additive approval of
the EC) are very likely to increase their market share over agents that cannot make similar claims.
• Other promising approaches might be insoluble antimicrobials that exhibit negligible leaching rat5
and can be regenerated, such as the polymeric phosphonium materials, halogenated poly (styrene-
divinyl benzene) sulfonamides, and the polymeric N-halamines
• For plastics in food contact applications in particular, research on natural substances or enzymes
(e.g., peroxidase) are under investigation. In some cases, these natural substances are combined
with immobilization techniques to enhance fixation and reduce migration of the biocide.

21. References
• https://www.ultra-fresh.com/antimicrobial-applications/antimicrobial-
plastic#:~:text=The%20most%20common%20additives%20used,has%20its%20strengths
• file:///C:/Users/Dell/Desktop/DOM%20ppt/Antimicrobials.pdf%20and%20weaknesses.
• https://www.google.com/imgres?imgurl=https%3A%2F%2Fwww.intechopen.com%2Fmedia%2Fchapter%2F45091%2Fmedia%2Fimage6_w.jpg&i
mgrefurl=https%3A%2F%2Fwww.intechopen.com%2Fchapters%2F45091&tbnid=DFjPNGNpoB8BGM&vet=12ahUKEwj64dvpw737AhWn34UKHQ
MdDO8QMygQegUIARDSAQ..i&docid=dSIWIlpNlaqt5M&w=800&h=279&q=agar%20test%20for%20antimicrobial%20additives&ved=2ahUKEwj6
4dvpw737AhWn34UKHQMdDO8QMygQegUIARDSAQ
• https://pubs.rsc.org/en/content/chapterhtml/2019/bk9781788011884-00001?isbn=978-1-78801-188-4#cit181
• chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://madisongroup.com/wp-
content/uploads/2022/09/Antimicrobial_Additives_TMG_Article.pdf
• https://en.wikipedia.org/wiki/Antimicrobial_polymer#Classes_of_Antimicrobial_Polymers
• https://www.youtube.com/watch?v=BGELx7vaYAk&ab_channel=SherrySmith
• file:///C:/Users/Dell/Desktop/DOM%20ppt/Antimicrobials.pdf

22. Thank you
• Any Questions?