2. Experimental materials and techniques

2.1 Description of subsea pipelines

Today's commercial pipelines are made of steel pipe (X65 steel) with outside diameters of between 150 and 500 mm and thicknesses of between 15.0 and 40.0 mm. They are covered with a layer of porous polypropylene, also known as "syntactic polypropylene", typically 90.0 mm thick, which serves as thermal insulation (Figure 5 ). This insulator consists of conventional polypropylene ((C ₃ H ₆ ) _n density 0.9 g/cm ³ ), the pores of which are filled with quartz microbeads (SiO _...