ACIDS Parker manufactures several compounds which satisfy FDA standards for rubber parts used in contact with foods and beverages. To be deemed acceptable by FDA regulations, the finished products must also pass extraction tests. The Parker compounds which fulfill the FDA rulings are:
After a long period of immersion in water, many O-ring compounds will swell significantly. In a static seal, this may not pose any problem at all. The static seal will not leak, of course, and in operations where the O-ring is to be replaced before it has swelled more than a few percent, the increased size may not even be noticed. But. as a long term dynamic seal, the compound's swelling can cause a slow but significant increase in friction. For water and steam application sin temperatures up to 300°F.. E540-80 is strongly recommended. Parker has developed compound E962-90 ethylene propylene for even greater steam resistance. This compound has been tested in steam at temperatures as high as 600°F RESISTANCE TO FUNGUSThe ability of a material to resist degradation by fungus has become increasingly important under the extreme environmental conditions experienced by the military and in space exploration. A number of Parker compounds have been tested for resistance to fungus and results show many Parker compounds are non-nutrient to fungus as defined by MIL-STD-810B. Method 508. RESISTANCE TO RADIATION Based on radiation tests conducted on Parker compounds in 1972 and 73. including effects on modulus, tear strength, low temperature properties (TRIO) and compression set. plus hardness, tensile strength and elongation, the results show that the majority of elastomers can be expected to maintain a seal after exposure to 10' rads of gamma radiation. However, no rubber material is likely to maintain a reliable seal as the exposure level nears 10» rads. The Parker compounds below are listed in accordance with their resistance to gamma radiation as reflected in its effect on compression set. The effect is least seen on the first compound listed. S604-70 Silicone E740-75 Ethylene Propylene S455-70 Silicone E515-80 Ethylene Propylene P642-70 Polyurethane V747-75 Fluorocarbon ELECTRICAL CONDUCTIVITYIt is often essential to shield electronic devices from electromagnetic interference, or to prevent electromagnetic energy from escaping. Parker's PARSHIELD conductive elastomers were developed to provide this shielding, plus hermetic sealing and grounding. These Parker PARSHIELD materials can be fabricated into O-rings, molded shapes, sheet stock and die-cuts. The filler materials, which make these PARSHIELD compounds conductive, are as follows:
RESISTANCE TO EXTREME TEMPERATURES When air or other gases are to be contained at temperatures below 65°F., (the recommended low temperature limit for some silicones). Parker compound S383-70 can be used in temperatures as low as 175°F If the permeability of silicone is expected to be a disadvantage, it is important to remember that permeability decreases with lowered temperatures. |
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