HNBR and NBR gasket rubbers for plate heat exchangers: Thermo‐oxidative aging and service lifetime prediction

Abstract

Among several available rubbers used in gaskets for plate heat exchangers, the selection of the appropriate material for each operation window is crucial. This work evaluated nitrile butadiene rubber (NBR) and hydrogenated butadiene rubber (HNBR) gaskets aged at high temperatures for up to 60 days. The properties assessed of compression set (CS), hardness, and cross‐link density demonstrated superior degradation rates for the NBR specimens. Fourier transform infrared analysis showed that the hydrogenation process predominantly affected CC double bonds. Compress stress relaxation highlighted the impact of aging on the counterforce of rubber over time. Furthermore, indentation modulus profile analysis showed heterogeneous degradation for both materials at 140°C for NBR and 170°C for HNBR. The end‐of‐life criteria of 79% CS for both materials were determined through sealing tests of the aged samples. The service lifetime prediction, using the time–temperature superposition and Arrhenius methods through the CS evolution curves, demonstrated a higher degradation resistance of HNBR gaskets, that have a superior service lifetime of at least 3.5 times at 80°C concerning those of NBR, proving a superior behavior for the hydrogenated elastomer. In addition, the evaluation of the lifetime prediction enables the verification of which rubber gasket is recommended for each operational condition in terms of material cost, service lifetime, and maintenance costs.