Investigation of the Impact of Surface Blending and Ultraviolet Radiation Exposure on Elastomer Seal Leak Rate Performance for Space Seal Applications

Abstract

Surface blending is a typical step in the manufacturing process of molded elastomer seals used to remove surface imperfections. Using O-rings molded from S0383-70 silicone elastomer oriented in a face seal configuration, this study screened for negative effects of docking seal surface blending. The study was separated into two distinct phases. Phase I used twenty-seven different surface treatments applied to a sample set of 130 O-ring specimens to examine the individual and combined effects of surface blending and ultraviolet radiation exposure on air leak rate. Combinations of blend surface area, blend location, and ultraviolet radiation exposure level were screened to determine the most influential factors and to narrow the variables investigated in Phase II. The second phase employed an enhanced leak rate test system and a test sample set comprised of both Phase I specimens and supplementary O-rings to quantitatively examine the impact of blending and ultraviolet radiation exposure on measured leak rate. Statistical analysis of leak rate test data indicated that blending alone did not significantly affect the leak rate of specimens not exposed to ultraviolet radiation. In the absence of surface blending, ultraviolet radiation exposure was shown to increase sample leak rate at statistically significant levels. The largest leak rate increases, however, occurred when O-ring sealing surface blending was coupled with subsequent ultraviolet radiation exposure. In those instances, the ability of the O-rings to create an effective seal was significantly compromised.