PETROMAKS2-Stort program petroleum

Low temperatures are known to pose a major threat for elastomeric materials; many are prone to excessive stiffness or even brittleness. Although the use of elastomers in the oil and gas industry is relatively low compared to other materials, the role of these materials is quite essential: they are used as seals and gaskets and in many applications are the primary barrier against leakage. Building a better understanding of how elastomer seals perform at low temperatures has been the focus of this research. The mechanical properties of elastomers are viscoelastic which means that they respond differently to mechanical loading at different temperatures and different loading rates. This also affects how they behave when loaded under constant stress, as in sealing applications. Few studies are dedicated to these phenomena at low temperatures, and therefore, there was a strong need for research in this area. In this project, several experimental elastomer compounds were developed with different strategies to give better sealing at the low temperatures. Some of these elastomer compounds are completely new and represent the state of the art in this field of research. This research work has resulted in two PhD theses and several peer-reviewed papers in the following areas: Elastic recovery after compression: Elastic recovery is one of the key indicators of elastomer performance in sealing applications, such as O-rings in flange joints. The compression set at ambient and sub-ambient temperatures has been investigated and a viscoelastic material model describing the time-temperature variation of the compression set has been developed and verified experimentally [1]. Low temperature viscoelasticity: Material models which describe the viscoelastic behaviour of a typical material at low temperature have been applied to finite element analyses (FEA) of simple geometries, to demonstrate how the compressive stress relaxation may be modelled. In addition, the effect of different fillers on the mechanical properties, compression set and coefficient of thermal expansion have also been investigated [2-4]. Static seal function: The mechanisms of adhesion of elastomer surfaces to neighbouring metal surfaces contributes to the function of the seal. The effect of surface roughness on the low temperature leaking of elastomer seals has also been investigated [5,6]. Adhesion has also been analysed as this also influences seal performance [7,8]. Dynamic seal function: Friction and adhesion between the elastomer and the surrounding metal components also play a significant role [9,10] in dynamic seals. The effect of the direction of movement has been investigated, since the elastomer surface after use has been reported to be asymmetric [11]. In conclusion, the new materials developed in this project, and the experimental methods and numerical models built for assessing the low temperature performance of elastomers are highly valuable to the oil and gas industry, and other industries which rely on elastomers at low temperatures. The research on elastomer friction, adhesion and sealing is also very relevant to applications outside the oil and gas industry, such as car tyres, wiper blades and syringe seals. Since these new materials can be used to reduce oil leakage in the arctic, the implementation of these technologies would be expected to have a highly positive effect on protecting the delicate arctic environment. References: [1] Compression Stress Relaxation in Carbon Black Reinforced HNBR at Low Temperatures. doi.org/10.1016/j.polymertesting.2017.08.023 [2] Elastic Recovery after Compression in HNBR at Low and Moderate Temperatures: Experiment and Modelling. doi.org/10.1016/j.polymertesting.2017.05.003 [3] Thermomechanical properties of zirconium tungstate/hydrogenated nitrile butadiene rubber (HNBR) composites for low-temperature applications. dx.doi.org/10.1007/s10853-016-0236-6 [4] Elastomer composites based on filler with negative coefficient of thermal expansion: Experiments and numerical simulations of stress-strain behaviour. www.ipme.ru/e-journals/MPM/no_33217/MPM332_07_shubin.pdf [5] The Effect of Surface Roughness and Viscoelasticity on Rubber Adhesion. doi.org/10.1039/C7SM00177K [6] Interfacial leakage of elastomer seals at low temperatures. doi.org/10.1016/j.ijpvp.2017.11.014 [7] Role of Preload in Adhesion of Rough Surfaces. doi.org/10.1103/PhysRevLett.118.238001 [8] Rubber adhesion below the glass transition temperature: Role of frozen-in elastic deformation. doi.org/10.1209/0295-5075/120/36002 [9] Rubber contact mechanics: adhesion, friction and leakage of seals. doi.org/10.1039/C7SM02038D [10] The effect of surface roughness and viscoelasticity on rubber adhesion. doi.org/10.1039/C7SM00177K [11] Rubber Friction Directional Asymmetry. doi.org/10.1209/0295-5075/116/66002