Coating thickness and silver addivtive dosage effect the antimicrobial performance

Dry film thickness of coatings

Silver additive is necessary to expose appropriately on the top surface of the coated components for better antibacterial performance. Migration of antibacterial agent to the surface of the coatings is most important to achieve the best antibacterial protection. However this migration depends on number of factors such as thickness of the coatings, binder content, recipe of formulation, dosage level of antibacterial agent, degree of cross linking, cross reaction of antibacterial agent with other ingredients(i.e. disturbance caused by other ingredients present in the formulation) etc.

In general lower dry film thickness is preferred to achieve good antibacterial performance. Migration of silver additive is easier at low thickness and as per our experiments we suggest 40-55 micron thickness for better antibacterial performance. However better migration of antibacterial agent can also be achieved by selecting appropriate particle size of silver additive, recipe of formulation etc. Extrudable grade version of antibacterial powder coating shows good performance even at higher thickness.

Dosage level of silver additive

Higher dosage level of silver additive improves the performance of coatings. However it has some adverse effect on the other properties of the coatings. So optimum dosage level to be decided based on the results of experiments and the optimum dosage level also depends on the recipe of formulation. Clear powder coating requires less dosage whereas highly pigmented versions may need higher dose of additives.

• Higher dose of silver additive leads to gloss reduction. Clarity of the coatings (DOI) is less at higher concentration level of silver additive. Haze would be severe if the particle size of the additive is coarser and its proportion in the formulation is high.
• Speckle type appearance can be noticed at higher dosage level. This effect would be severe if the particles size of silver additive is coarser and its proportion is very high in the formulation. Entrapment of moisture in the silver additive can also lead to speckle type appearance.
• Higher dose of silver additive can lead to discoloration.

Optimum dosage level of silver additive depends on various parameters such as type of silver additive, recipe of formulation etc. it is necessary to conduct thorough experiments to decide about optimum dosage level.