All storage bags
are not made equal. Although some bags are still manufactured using a single
thick layer of plastic, today’s industry standard
is the three-layer, co-extruded polyethylene tube, and
the norm is one that is 9 ft. (2.70 meters) in diameter
and 200 ft. (60 meters) in length, capable of holding
about 200 tons of grain (some 8,000 bushels of corn)
or more. It is important to lay emphasis on the fact
that these bags are specifically designed to hold grain,
not chopped forage. Although they may look similar,
a grain bag must conform to more demanding standards,
basically because grain’s higher specific weight
and the fact that it flows freely impose a far heavier
load on a bag’s sidewalls and underside than forage
does.
The outer layer of a grain bag is a bright off-white
color to reflect infrared radiation (i.e., heat from
the sun) back into the atmosphere, while its inner layer
is black in order to help maintain a lower than ambient
temperature inside the bag by acting as a sunlight (i.e.,
visible light) barrier.
Even though polyethylene is the basic material of all
grainbags, manufacturers have developed proprietary resin
formulations to withstand the rigors that bags are subject
to. In a top quality bag the plastic sheet should possess
several attributes: |