Co-Extruded
Gasket Stops Corrosion on
Outdoor Telecom Enclosure
.....A
pole-mounted, aluminum telecom enclosure presented serious challenges
for controlling EMI and keeping out the elements. The enclosure
needed a conductive gasket capable of at least 80 dB shielding
effectiveness in the high megahertz to low gigahertz range.
A separate environmental seal was needed to protect against
rain and moisture.
.....An
early gasketing approach used a non-conductive hollow silicone
strip with a pure-silver-filled silicone extruded onto its surface.
But, in contact with the aluminum housing, and exposed to coastal
salt fog and driving rain, severe corrosion of the housing flanges
occurred.
.....To
meet these shielding and environmental requirements, Chomerics
produced a co-extruded EMI gasket. This was a CHO-SEALā conductive
elastomer extruded in parallel with a non-conductive elastomer.
The gasket's conductive side is a nickel-plated-graphite filled
silicone. The filler particles can bite through thin surface
oxides and chemical treatments on aluminum housings. The vulcanized
seam between the elastomers provides long-term integrity.
.....The
conductive side of this gasket was positioned inboard, with
the non-conductive silicone outboard. The non-conductive side
of the cross section was designed with an additional sealing
tab to fill an existing sump area in the seam where rain and
moisture collected.
.....The
co-extruded gasket allowed use of the existing flange design.
It avoided the cost for separate shielding and weather sealing
gaskets, and converting to a double-groove design. This is an
example of how Chomerics' co-extrusions offer performance and
logistical advantages at attractive prices.
