Environmental Degradation of Nylon, Poly(ethylene terephthalate) (PET), and Poly(vinylidene fluoride) (PVDF) Fishing Line Fibers

Ghost fishing, caused by lost fishing lines and nets,has becomea severe problem in marine environments. To eliminate ghost fishingin the ocean, the environmental degradation behavior of fishing linesmust be understood. In this study, the environmental degradation ofbiodegradable nylon 4 fishing lines and commercial nylon 6, poly-(ethyleneterephthalate) (PET), and poly-(vinylidene fluoride) (PVDF) fishinglines was simulated in the laboratory using an artificial weatheringtesterand biodegradation test in extracted seawater. To understand the degradationmechanism, the chemical and structural changes induced by photo-oxidationand biodegradation were investigated using tensile test, scanningelectron microscopy, differential scanning calorimetry, gel permeationchromatography, infrared spectroscopy, and wide- and small-angle X-rayscattering. The results indicated that photo-oxidation occurred inthe amorphous phase of the nylon 4, nylon 6, and PET fishing linesduring ultraviolet (UV) exposure. The nylon 4 fishing lines exhibitedexcellent biodegradability, whereas the nylon 6, PET, and PVDF fishinglines could not be degraded by microorganisms in the extracted seawater.Both processes, i.e., photo-oxidation and biodegradation, were confinedto the amorphous regions of nylon 4. Note that the PVDF fishing linescould not be degraded by UV exposure and biodegradation and, hence,should be recycled after use.