Foam peanut
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Foam peanuts, also known as packing peanuts, are a common loose-fill packing material which is also used to prevent damage to fragile objects during shipping. They were introduced circa 1965 by Dow Chemical. They are roughly the size and shape of a peanut (in its shell) and usually made of polystyrene. They are shaped to interlock when compressed and free flow when not compressed. Originally made from 100% virgin polystyrene resin, peanuts made from 100% recycled polystyrene have been commercially available since the mid-90s. In the loosefill world, the color and shape tell what it is made of and who made it. Green is 70% or more recycled polystyrene, white is 70% or more virgin resin and pink means anti-stat has been applied; although there are some variations. For example, few green peanuts have pink applied even though they may be sprayed with anti-stat, just as there are expanders who make 100% recycled white peanuts. The most common shapes are the "S" for the STOROpack PelaSpan peanut and the "W" for the RAPAC WingPac peanut. The Figure 8 peanut shown in the photo attached to this article is made of extruded polyurethane manufactured by Free Flow. The advantage of polystyrene loosefill as a void-fill for shipping is that it is very light (usually 0.17 to 0.2 lb per cu ft) and easy to use. The biggest negative is that it can develop a static charge and that heavy objects tend to migrate to the bottom of the box during shipping, reducing the protection offered.
Polystyrene peanuts may be used and reused many times with little or no loss in protection for the product shipped. They may be recycled at virtually any packing and shipping store.
In the early-1990s, a more environmentally friendly starch-based alternative was developed. One of the first brands of biodegradable peanuts, Biofoam, is made from the grain sorghum; other brands are made from corn starch. Biodegradable foam peanuts have no electrostatic charge, another benefit over polystyrene. Being biodegradable and nontoxic, they are also edible. Their main drawbacks are a lesser resilience, higher weight relative to polystyrene (0.4 to 0.8 lb per cu ft), dusting and they are more expensive. In addition, since they are edible, starch-based peanuts do tend to attract rodents and bugs.
Starch-based peanuts are soluble in water, and polystyrene peanuts are soluble in acetone, but not vice versa. Because polystyrene peanuts are non-soluble in water, they are also used as a light-weight aggregate in hydroponics.
