Plastic Foam Plugs

There are two simple alternatives to vapour cooled baffles which have been tested, namely plastic foam plugs and floating ball blankets, but both are not so effective. 

Sterilization After a suitable culture medium is selected for the cultivation of a specific microorganism, it is poured into a culture vessel. If you use test tubes or flasks as your culture vessel, the ends of test tubes or flasks should be covered with a suitable closure to allow for the exchange of gases with the atmosphere, yet to keep foreign organisms out of the media. Various types of closures are used in the modern laboratory including cotton plugs, plastic foam, screw caps, metal caps, and aluminum foil. 

Air samples were taken in a central location of the crawl space, the kitchen, and a bedroom with personal-type air samplers (10). Polyurethane foam plugs (2 cm od. by 3 cm) contained in a glass holder were attached to the sampler. A 2-h sample was taken at a flow rate of 2.8 L of alr/mln. The holder and foam were removed, placed in plastic bags, and stored at -20C until analyzed. 

New and unique methods have also been developed to produce a superior plug, machined with an outer seamless shell of high-density plastic foam, which is strong but light for easy handling, and evenly absorbs heat generated in the mold-making process. 

Forming—Syntactic Foam Plugs. Plastic Trends, p. 19, Nov.-Dee. 1989. 

Figure 3.S.IS Attenuation characteristics of different hearing protectors (A ear-muffs B plastic foam ear-plugs C acoustic wool eat plugs)...

Use metallic radiation shields instead of plastic foam neck plugs in small containers. 

In other words, when the low thermal conductivity, high molecular weight, foam gas wifliin the plastic foam is replaced by diffusion by high thermal conductivity, low molecular weight methane gas, the foam plug becomes ineffective, behaving as a thermal short circuit in the vapour space. 

With a moisture sensitive product, moisture pick by this means can be quite rapid. Alternative materials to wool are either plastic shapes or plugs of expanded polystyrene, polyethylene or polyurethane foams. Closures can also be obtained which incorporate spring extensions. Such closures may have chambers which hold desiccants. Transit tests (vibration/drops) would be advised to check whether space fillers are necessary. 

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