Page 336 - Handbook of Plastics Technologies

PLASTICS ADDITIVES

5.16 CHAPTER 5

Testing usually begins by placing plastics samples in Petri dishes, injecting microor-
ganisms, and observing whether they grow. Further testing may include humidity, soil
burial, and other natural exposures. A major problem is that species of microorganisms
vary from one geographic region to another, so it is hard to design reliable broad-spectrum
laboratory tests and to recommend successful additives from one region to another.
The greatest problem is differential toxicity. Any chemical that is toxic to microorgan-
isms will probably be toxic to macroorganisms such as ourselves. Thus, it is necessary to
distinguish those additives that offer maximum toxicity toward microorganisms along
with minimum toxicity toward macroorganisms, and to define the critical balance for dif-
ferent plastic products.
5.1.5.1 10,10´-oxy-bis(phenoxarsine) (OBPA). This (Fig. 5.4-I) is the leading commer-
cial antimicrobial. It is very efficient, so it can be used at very low concentration (0.04 per-
cent) and can be synergized by bis(trichloromethyl) sulfone.

FIGURE 5.4 Biostabilizers.

5.1.5.2 2-n-octyl-4-isothiazoline-3-one. This (Fig. 5.4–II) is a newer antimicrobial that
is nontoxic to humans and is used at 3 percent in vinyls and paints.
5.1.5.3 Trichloromethyl Thio Phthalimide. This (Fig. 5.4–III) is harmless to humans
and is useful at 0.25 to 0.50 percent to control actinomycetes, which cause pink staining of
plasticized vinyls.
5.1.5.4 Diphenyl Antimony 2-Ethylhexoate. This (Fig. 5.4–IV) is approved for use in
vinyl shower curtains, wallpaper, upholstery, and rug underlay.
5.1.5.5 Copper Quinolinolate. This (Fig. 5.4–V) is relatively harmless to humans. Used
at 0.5 percent, it controls mildew. Because of its deep yellow-green color, it is used mainly
for military purposes.

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