Open Cell Foam has interconnected air chambers throughout the
material, which produces an extremely soft and highly compressible
foam. Open Cell Foam is used in the construction of many high quality
self-inflating camping mattresses. Whilst Open Cell Foam is very
comfortable, self-inflating air mattress have a layer of air that
provides support and insulation properties, and is highly compressible
once the air is released. Open Cell Foam is not very good as a solitary
padding material for backpacks. The high compressibility of the
Open Cell Foam can cause shoulder straps and hip belts to over compress
under load, providing minimum of comfort. While the padded straps
may look great and feel wonderfully soft at the time of purchase,
this will not be the case when the backpack is under full load.
Determining whether the padded straps are Open Cell Foam is easy
enough, simply squeeze with you hand, and if the straps compress
to less than one half of the original size it is Open Cell Foam.
Closed Cell Foam has open air chambers surrounded by foam that
are not interconnected. The completely encapsulated air cells in
the Closed Foam do not compress easily yet provides good padding.
Closed Cell Foam is used in the production of Closed Cell Foam mats
and its construction prevents full compressibility.. Since the Closed
Cell Foam is a rubber based material and has completely encapsulated
air chambers, it provides excellent insulation and absorbs very
little water. For many years, better backpack designers cut and
sewed the Closed Cell Foam into fabric sleeves providing the main
source of shoulder and hip belt padding. The foam is dense, impervious
to perspiration, and very comfortable. Closed Cell Foam is the main
material used in backpack padding today, and it is a perfectly good
material for backpack straps and hip belts. Determining whether
the padded straps are Closed Cell Foam is easy enough, simply squeeze
with your hand, and if the straps compress very little, then it
is Closed Cell Foam.
Concluding that Open Cell foam is more comfortable next to the
body (more compressible, therefore softer) and Closed Cell foam
is better next to the load (less compressible, therefore firmer),
several manufacturers use Dual Density Foam in padding their backpacks.
Backpacks with Dual Density Foam capitalize on the advantages of
both foams, placing the Open Cell Foam against the body and the
Closed Cell Foam against the load. This combination is more comfortable
than either Closed Cell Foam or Open Cell Foam, supporting the load
well and providing comfort for body.
One manufacturing drawback to Closed Cell Foams concerns the
manner of its fabrication. The material is typically poured into
a frame and cooked into flat sheets that are cut to size, then cut
to create a desired shape. The cost of cutting and shaping foam
is highly labour intensive and results in significant material wastage.
Because of these reasons another process was developed for the shaping,
forming and customization of the next generation of foam, Compression
Compression Moulded Foam originally appeared in European backpacks
in the late 1980's and used a different manufacturing technique.
The outer nylon material is adhered to a block of polyethylene foam
using a heat sensitive adhesive, and then the entire assembly is
heated so that the foam and adhesive soften. At this point, the
assembly is compressed into a shaped mould to provide the final
product. The shaped hip belt, shoulder strap, or lumbar pad is then
cooled to re-solidify the foam and adhesive. The final product is
a pad shaped into a customized form.
Compression Moulded Foam is Closed Cell Foam, although slightly
lighter in weight and shaped to the body without cut edges. An added
benefit is the cavities formed inside the moulded foam pads, and
different densities of foam can be included to provide flexibility
to the final shape.