E Effect of Pressure on Mechanical Properties of Polymers Alexandra Aulova, Alen Oseli, Marko Bek, Ted Prodan, and Igor Emri Faculty of Mechanical Engineering, University of Ljubljana, Ljubljana, Slovenia Synonyms Effect of pressure on material properties of polymers Definitions Polymer is a substance consisting of macro- molecules of different lengths, which have a long sequence of one or more groups of monomeric units (shorter molecules) linked together with a primary or covalent chemical bond. Time-dependent mechanical property is the characteristic of a polymer (or any other viscoelastic material) that interrelates the cause in the form of stress or strain and the time- dependent response (in the form of increasing strain or decaying stress). Time-pressure superposition principle claims that material function can be generated by shift- ing isobaric segments of time-dependent mechan- ical properties measured at different pressures along the logarithmic time scale in respect to the segment selected at reference pressure. Compressibility is a measure of relative change of the volume of polymer exposed to the pressure change. Introduction To fully comprehend the content of the following chapter, the reader should be familiar with: • Polymers and their molecular structure • Polymers’ time-dependent mechanical proper- ties, creep, and relaxation • Time-temperature superposition principle This information can be found in the chapter ⊲ “Effect of Temperature on Mechanical Proper- ties of Polymers”. Polymeric materials are used in various appli- cations and are therefore subjected to different boundary conditions, such as temperature, pres- sure, humidity, UV radiation, etc. This chapter focuses on hydrostatic pressure, which can have a significant effect on the behavior of polymeric materials and should therefore be taken into account when designing parts from polymeric materials. Applications, where pressure plays a significant role in material behavior, are, for example, sealing of pipes, insulation of deepwater pipes, deepwater cabling, etc. Another important area where pressure effects need to be © Springer-Verlag GmbH Germany, part of Springer Nature 2018 H. Altenbach, A. Öchsner (eds.), Encyclopedia of Continuum Mechanics, https://doi.org/10.1007/978-3-662-53605-6_270-1