Effects of crosslinking densities on mechanical properties of nitrile rubber composites in thermal oxidative aging environment

Abstract

The effects of crosslinking densities on mechanical properties of nitrile rubber (NBR) composites before and after thermal oxidative aging are investigated. Tensile strengths of NBR composites are enhanced slightly at the initial aging stage, attributing to moderate increment of crosslinking densities. Continuous decrease with further aging is followed, resulting from over‐crosslinking and uneven distribution of crosslinking densities. The digital image correlation method is explored for large‐strain deformation measurement by displacement accumulation and establishing strain model, being promising in practical age detection and measurement of mechanical properties in complex environments. Compression sets are gradually increased with aging because of the destruction of the original crosslinking structures. The molecular chains fracture inhibits elastic recoveries of compressive NBR composites and results in residual deformation in thermo‐oxidative and compressive environment after unloading. This study provides new ideas for exploring mechanical properties of rubber‐based composites before and after thermal oxidative aging.

Dispersion and vulcanization characteristics of nitrile rubber reinforced with N,N‐dimethylacetamide/lithium chloride treated silica

“…Mechanical properties of vulcanizates reinforced with untreated silica, DMAc/LiCl treated silica without TESPT and in combination with TESPT are given in Table 6 for both grades of nitrile rubber. Interactions between rubber and silica could be more in high nitrile rubber than that of medium nitrile rubber, which results in reduction of agglomeration and improved mechanical properties 40–42 . Vulcanizates containing DMAC/LiCl treated silica, in the absence of TESPT, have not shown major change in their hardness, tensile and tear strengths, especially with high nitrile NBR.…”

“…Interactions between rubber and silica could be more in high nitrile rubber than that of medium nitrile rubber, which results in reduction of agglomeration and improved mechanical properties. [40][41][42] Vulcanizates containing DMAC/LiCl treated silica, in the absence of TESPT, have not shown major change in their hardness, tensile and tear strengths, especially with high nitrile NBR. However, modulus values at 100% and 300% elongation have increased noticeably with an associated drop in elongation at break with DMAc/LiCl treatment of silica.…”

Service lifetime prediction of nitrile butadiene rubber gaskets used in plate heat exchangers

“…Accelerated aging of NBR elastomer up to 110°C promotes predominant crosslinking oxidation reactions, 3 and presents a linear correlation to the compression set (CS) 4 . At higher temperatures (125–150°C) crosslinking reactions between rubber chains were also observed 5 . Souza et al 6 studied the oxidation mechanisms for NBR and EPDM gaskets based on chemical, surface, and mechanical analysis.…”

Molecule Dynamics Simulation of the Effect of Oxidative Aging on Properties of Nitrile Rubber

“…Nitrile rubber (NBR) has been widely used as seals in sealing structures of hydraulic systems [1], due to its excellent oil resistance and mechanical properties. However, under practical service conditions, the rubber seals are often subjected to thermal cycles, oxygen, chemical media and mechanical stress leading inevitably to deterioration in chemical structures and mechanical properties [2][3][4][5]. With increasing service time, the rubber seals gradually lose elasticity which can lead to sealing failures and consequent leakage of gases and liquid [6][7][8][9].…”