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POLA®, manufactured by Parker Chomerics, is made up of silicone and orientated wires; both of which can be altered to suit the purpose of the application. POLA® not only provides excellent shielding performance against EMI but its cost-effectiveness and ability to be incorporated simply into assembly applications, offers an easy transition away from a non-EMI solution. POLA® is available in strip or sheet form, with Monel or aluminium wires embedded in either solid or sponge silicone.
The variations are explained in detail, within these PDF's, here:
Essentially POLASHEET® contains individual wires embedded within silicone whereas POLASTRIP® is composed of a knitted wire mesh which is embedded. The wires within POLASHEET® must be orientated perpendicularly to the mating flange surface in order to provide EMI shielding and the wires themselves are crimped for strain relief; allowing flexibility within the sheet. In comparison, POLASTRIP® has a knitted wire mesh structure which provides the EMI shielding and resilience for functionality and unhindered performance. Both materials come with a non-conductive pressure sensitive adhesive backing - due to the wire "bite-through” during gasket deflection - allowing a greater bond to be achieved.
POLASHEET® is provided in sheet form offering the ability to cut to specifications with low-cost dies. Sheets are available at standard lengths of 3 feet and widths up to 9 inches; two or more widths can be bonded together allowing wider sheets to be supplied, POLASTRIP® is provided in strip form or alternatively as custom gaskets produced from the strip material; . Strips are supplied at standard lengths of 11 feet and widths, with standard intervals, from 0.93 to 1.00 inch. POLASTRIP® can also be supplied in a twin-strip version, where only a portion of the total width contains wires leaving the rest unoccupied, providing greater sealing performance and corrosion resistance. It is recommended that die-cut sheets, rather than spliced strips, be used for gaskets with overall dimensions less than 4.5 inches.
Whether sponge or solid silicone should be used depends upon the pressure sealing and gasket load requirement. POLA® SPONGE's recommended closure force is 10 to 40 PSI with a compression of 10 to 30% and POLA® SOLID's recommended closure force is 25 to 100 PSI with 10 to 30% compression. It should also be noted that once compressed, then released from said compression, neither material should be used once again; as it will not return to its original shape completely after being deformed by the compression force. A solid material such as POLA® SOLID will provide increased durability and sealing performance compared to POLA® SPONGE. But less force is required to obtain an EMI shielding and weatherproof seal with POLA® SPONGE due to its low-hardness.
Where both materials coincide is their cost-effectiveness; both offer multiple wire alloys for galvanic compatibility, reducing the risk of corrosion between the gasketing and mating surfaces, decreasing rework costs. Though this function POLA® SOLID can potentially reduce the total cost of ownership savings over 50% and POLA® SPONGE - alongside its weight, material and labour savings - reduces the total cost of ownership over 75%.
If you would like further information on our orientated wire in silicone materials, please contact HITEK Electronic Materials Ltd. Contact Us.
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