BOOK_CONTENT
From Practical Guide to Polyvinyl Chloride

3.9 Microbiocides

PVC-P materials, such as flooring and roofing material, can be prone to microbiological attack in humid or damp conditions. This can be due to micro-organisms, such as algae, bacteria, and fungi, using the plasticiser at the surface of the article as a nutrient carbon food source. This can lead to partial discoloration (pink colour or black specks) which can further cause a tacky surface where dirt can accumulate. Unpleasant odours may also be a consequence.

Biocides function by becoming active on the surface of the material to destroy micro-organisms. Constant microbiocide transfer to the surface is necessary at a rate sufficient to maintain an effective concentration at the surface. This is achieved by the process of diffusion of the plasticiser within the material, the organism also acting as a leaching solvent. Addition levels of the active ingredient are at the 400 2000 ppm level and the active biocide is normally supplied dispersed in a plasticiser or ESBO carrier.

Based on their thermal stability, compatibility, permanence, and broad-spectrum performance against different fungi, the most common microbiocides are 10,10 ?-oxybisphenoxyarsine (OBPA), 2- n-octylisothiazolin-3-one (OIT), and 4,5-dichloro-2- n-octylisothiazolin-3-one (DCOIT).

Various laboratory and accelerated outdoor test methods are available to determine the effectiveness of microbiocides in simulated performance situations covering weathering, water leaching, and resistance to soil burial. These are the areas where performance can be negatively influenced.

Some of the microbiocides mentioned previously also have some limited bacteriocidal activity but specific antibacterial additives may also be necessary to provide...

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