POLASHEET®/ POLASTRIP® Gasketing POLASHEET and POLASTRIP gasketing are composite EMI shielding and weather sealing materials. Either solid or sponge silicone may be specified as the weather seal. In POLASHEET gasketing, individual monel or aluminum wires embedded in the silicone and oriented perpendicular to mating flange surfaces provide the EMI shielding. Wires are crimped for resiliency. Solid silicone POLASHEET gasketing is available with high-tack pressure-sensitive adhesive backing. In POLASTRIP gasketing, EMI shielding is provided by monel or aluminum knitted wire mesh embedded in silicone. POLASHEET and POLASTRIP gasketing with solid silicone weather seal are recommended for sealing under high pressure conditions. The silicone seal is rated for use at temperatures from -70&176;F (-56.7&176;C) to 500&176;F (260&176;C). Sponge silicone is used only for pressures below 5 psi (0.03 MPa) and for rain, drip, dust and ventilating air seals. For particularly severe pressuresealing requirements, up to 250 psi (1.72 MPa), COMBOPOLASTRIP® gasketing is available. In this configuration, the conductive paths are molded into only 0.250 in. (6.35 mm) of the width of the gasket. POLASHEET materials are supplied in sheet form, from which custom gaskets can be readily cut.
Even intricate gaskets can be cut with inexpensive rule dies, and custom gaskets can be factory-fabricated to customer specifications. POLASTRIP gaskets are supplied in strip form or as finished custom gaskets fabricated from strips. For gaskets with overall dimensions less than 4.5 in. (114 mm), die-cut sheets are recommended rather than spliced strips. Solid silicone sheets available in 9.0 in. (229 mm) widths with no bonds.3.0 in. (76 mm) width is formed by bonding 1.0 in. (25.4 mm) wide strips. Each sheet has 2 bonds. For wider sheets without bonds, inquire– substantial minimum order requirements apply.
Mounting Flange EMI Gaskets CHO-SEAL die-cut gaskets provide EMI shielding and environmental sealing when inserted between a connector flange and a mounting bulkhead. The EMI gaskets described in this section are designed for use with MIL-C-83723, MIL-C-5015, MIL-C-26482, MIL-C-38999 and MIL-C-81511 connectors.They are interchangeable with non-conductive gaskets. Standard mounting flange gaskets are available in CHO-SEAL 1212 material, for continuous-use temperatures to 125°C, and CHO-SEAL 1285 and 1224 materials, for temperatures to 200°C. Because CHO-SEAL 1224 material is filled with pure silver particles, prices are substantially higher than for CHO-SEAL 1212 or 1285 gaskets. In addition to the standard sizes and configurations listed here, connector gaskets and ground planes can be custom designed. Connector gaskets should be used in conjunction with conductive interfacial EMI seals.
Custom Extruded Gaskets These custom extruded gaskets produced in special configurations, ranges from unusual sizes in standard shapes to highly complex designs that meet specialized shielding and environmental sealing requirements.
Custom Co-Extruded Gaskets Extruded in parallel, dual conductive/non-conductive co-extruded gaskets provide optimum EMI shielding and corrosion protection in a single, cost-effective design.
POLA-H Composite Gasketing POLA-H is a composite EMI shielding and weather seal gasket strip designed for low frequency H (magnetic) field shielding, but providing outstanding E (electric) field and plain wave shielding as well. The material consists of continuous solid copper conductive paths (ASTM-B-545) in a solid silicone pressure seal. Protruding tips of copper are plated with tin alloy (ASTM-D-152) for low contact resistance (high contact conductivity) at mating surfaces, a primary factor in achieving effective H field shielding. POLA-H gasketing is normally supplied in strip form in 3 ft. (99.44cm) lengths (for longer applications 3ft. lengths can be bonded together), in widths from 0125′′ (3.18mm) to 0.625′′ (15.88mm), and in seven standard heights from 0.125′′ (3.18mm) to 0.500′′ (12.7mm). Custom fabricated gaskets also can be supplied to customer specifications.
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