Analysis of the feasibility of the reuse of polyamide 11 rejected in the manufacturing process of thermoplastic hoses of umbilicals

Thermoplastic hoses are composed of thermoplastic liner, synthetic fiber reinforcement, and thermoplastic sheath. Pilot liner batches, generally polyamide 11 (PA 11), are produced for checking the extruder calibration. Pilot batches out of specification are discarded and considered production waste. The objective of this work was to study the possibility of reusing this rejected material, in the sheath manufactured of PA 11 with carbon black (PA 11 Black). Initially, a comparative analysis was performed using FT-IR (infrared spectroscopy with Fourier transformed), TGA (thermogravimetry analysis) and DSC (differential exploratory calorimetry) characterization techniques between the rejected material and PA 11 in pellets, in order to verify possible degradation during the extrusion process and the similarity of materials. The characterization showed that the rejected PA 11 is similar to pellet. Thus, specimens with different percentages of PA 11 and PA 11 Black were manufactured to analyze the effects that the decrease in carbon black concentration would cause on materials when subjected to ultra violet (UV) aging. PA 11, PA 11 Black, and their blends were aged by UV for 720 h and then thermal, spectroscopic, and mechanical tensile tests were performed. All the mixtures showed similar thermal behavior of PA 11 Black. The FT-IR analysis showed a tendency for the appearance of bonds representative of degradation in the blends with higher percentage of PA 11. The tensile test showed that PA 11 Black as well as all blends became more brittle after aging by UV due to the appearance of unsaturation along the chain. There is no evidence that the insertion of PA 11 impacted the mechanical properties.