The mitigation of the ghost nets threat by recycling of polypropylene: Blends, their ageing tests and spectral characterization

Abstract

Lost or abandoned fishing gears threaten the natural environment and its inhabitants through an entanglement of animals, by-catch, and potential release of microplastics. One of the efficient methods to tackle this issue is to propose recycling strategies to limit ghost netting. Although the complex composition of the fishing gear, with numerous blended polymers, added compounds, and supporting elements (like floats or metal weights), is challenging, polypropylene (PP) is still one of the most frequently encountered materials. Thus, within this research, we propose the method of recycling the PP from the naturally weathered ghost net (left back on shore by the storm wind and waves), with the minimal use of added chemicals (water purification only). The first step consisted of detailed spectral studies of the net and its components using both Raman spectroscopy and FTIR (Fourier-Transform Infrared Spectroscopy). Obtained signals allow the identification of the polymer, estimation of its ageing and crystallinity level, or ratio PE: PP, as some traces of a polyethene (PE) are common. After the separation, two types of fibres were cut and mixed with the pristine PP nurdles (in the following ratio 5, 10, 15, 20, 30: 100) and integrated via extrusion into the composite material, forming a blend. Materials were spectrally characterized, including ATR-FTIR (Attenuated Total Reflectance FTIR) and Raman spectroscopy measurements. Finally, the obtained specimens were laboratory-aged in the artificial seawater according to the standard protocol ASTM D1141–98 using the ageing chamber and characterized from the mechanical point of view. All obtained materials preserved their properties during ageing, exhibiting a performance comparable to that of pristine material and allowing conclusions about their potential usefulness in numerous applications.