Micromechanical Property Study of Nylon 11 and Organoclay Systems for Offshore Flexible Pipe

• Published in: Fibers and polymers 2021, 22(11), , pp.3172-3182
• Main Authors: da Costa Rodrigues, Aline, Bastos, Ivan Napoleão, Kappel, Marco André Abud, Nascimento, Christine Rabello, Ferreira, Luciana Spinelli, da Silva, Ana Lúcia N.
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Contact pressure; Creep (materials); Crystal structure; Flexible pipes; Hardness tests; Hybrid systems; Internal pressure; Modulus of elasticity; Montmorillonite; Morphology; Nanoindentation; Nylon 11; Ocean floor; Offshore platforms; Optimization; Photomicrographs; Polyamide resins; Polymer Sciences; Sea level; Sheaths; Wellheads; 섬유공학
• ISSN: 1229-9197; 1875-0052
• DOI: 10.1007/s12221-021-0391-5

Flexible pipe structures are made up of bounded or unbounded concentric cylindrical polymeric and metallic layers, which connect seafloor wellheads to sea-level oil platforms. The inner thermoplastic sheath, called pressure barrier, has the function of sealing, preventing the contact of the oil with the metallic layers. Polyamide 11 (PA11) is a commercial polymer used as an internal pressure sheath. A hybrid system based on PA11 was developed for offshore umbilicals, with 3.5 and 5.0 wt% of nanoclay grade montmorillonite (MMT) by melting processing. The compatibility test of PA11 with crude oil was performed for aging times were up to 28 days. The instrumented nanoindentation was used to investigate the micromechanical properties of aged material. The indentation test stages, loading, creep, and unloading, were fitted with hybrid optimization methods, and the complete load-displacement profile was obtained. The addition of MMT in the PA11 matrix led to an exfoliated morphology and more ordered crystal structures. SEM/EDS micrographs depicted a well-dispersion of the nanoclay particles in the PA11 matrix. The modeling of the indentation analysis presented an excellent adherence of the simulated data to the experimental curves. The mechanical results showed that MMT’s addition to the PA11 matrix improved the elastic modulus and the hardness properties. PA11/MMT compositions exhibited a similar creep tendency but presented lower creep values regarding neat PA11. The indentation test was useful to assess the micromechanical properties caused by the aging exposure of nylon 11 and organoclay in contact with oil.