The utilisation of synthetic mooring ropes for marine renewable energy (MRE) devices is a recent occurrence. Despite current use in the offshore industry, MRE mooring components are typically subjected to highly dynamic loads, necessitating the detailed characterisation of operational and long-term component performance for lifecycle analysis and operations management. To address the uncertainties associated with synthetic mooring components in this application, tension experiments have been conducted on nylon 6 parallel-stranded rope samples at IFREMER, France and the University of Exeter, UK under the consortium MERiFIC (Marine Energy in Far Peripheral and Island Communities). Measurements are reported from harmonic loading tests with different initial bedding-in levels used to investigate the influence of load history on the immediate dynamic properties of the rope. Two irregular load regimes were also applied based on mooring tensions recorded by the South West Mooring Test Facility (SWMTF). Datasets are provided to facilitate the development of rope modelling tools. For the load regimes studied it was found that the operational performance of the rope is strongly influenced by the instantaneous load-strain characteristic. This study provides unique insight into the stiffness and damping properties of synthetic rope in the context of loading regimes relevant to MRE devices.