The continuous push to move American made product to low-cost countries has been a common practice in most markets for many years including the seal industry. Due to this trend, the North American-manufactured rubber compound N674-70 originated a generic designation titled NBR-70 or N70 material that comes from various Pacific Rim rubber manufacturers with a generic ASTM specification. Our initial investigation uncovered large discrepancies in the actual performance and material characteristics of the same type of NBR-70 or N70 O-ring compounds, even when used in equal applications.
These variances are due, in part, to the instability of physical and chemical properties caused by inconsistent compounding and processing. Some of the tested materials had little or no batch-to-batch mixing or ingredient controls; some switched vulcanization processes; some did hand-trim, tear-trim, and/or slurry finishing; and almost no one used cryogenic de-flashing due to the cost of nitrogen. All of the above contribute to an inconsistent manufacturing process that negatively impacts the seal performance.
In 2002, when Zatkoff Seals & Packings was first tasked to respond to the market demand for an inexpensive material, the company took the approach to standardize its offering with the lower-cost Nitrile compound N1470-70 that maintains the standards our customers expect. An additional step to our Pacific Rim supply process is to check that all incoming materials not only meet compound characteristic specifications, but also show consistency in testing methodologies such as modulus, tensile, elongation, and more. Furthermore, we implemented an incoming FTIR scan procedure for the finished rubber materials to internally verify that the compound material did not change from batch to batch.