Nylon monofilament fishing nets are widely used in marine fisheries due to their high strength, wear resistance, and aging resistance. However, prolonged immersion in seawater makes the net surface susceptible to biofouling and corrosion, leading to mesh blockage, increased weight, and shortened lifespan. To enhance their resistance to biofouling and corrosion, surface coating technology has become a key technical approach, achieving comprehensive protection through multiple mechanisms including physical barriers, chemical inhibition, and material modification.
The core of antifouling coatings lies in preventing marine organisms from adhering to and growing on the fishing net surface. Traditional coatings often use antifouling agents containing heavy metals such as copper and tin, which slowly release metal ions to kill larvae or spores. With increasing environmental protection requirements, low-toxicity or non-toxic biomimetic coatings are gradually becoming mainstream. For example, low surface energy coatings based on the microstructure of marine organism epidermis, by mimicking the nanoscale "valley" structure of dolphin skin, reduce surface wettability, making it difficult for biological slime to adhere. Furthermore, enzyme-based antifouling coatings utilize chitinases, proteases, etc., to decompose biofouling substances or achieve active defense by affecting biofouling ability, combining high efficiency and eco-friendliness.
Anti-corrosion coatings focus on blocking the chemical reaction between seawater and the nylon substrate. While nylon monofilaments are resistant to chemical corrosion, prolonged immersion in seawater can still lead to molecular chain breakage. Environmentally friendly coating technologies effectively isolate corrosive media such as chloride ions and dissolved oxygen by forming a dense protective layer on the nylon surface. For example, copolymer-modified nylon materials, by introducing polar functional groups, increase surface energy and optimize crystallinity, significantly enhancing the adhesion between the coating and the substrate. Simultaneously, coatings with added antioxidants and light stabilizers can resist UV aging, extending the lifespan of fishing nets in outdoor environments.
Optimizing coating processes requires balancing functionality and durability. Multilayer composite coating technology achieves a synergistic effect of anti-biofouling and corrosion protection by alternately depositing different functional layers. For example, an epoxy resin base layer enhances adhesion, an antifouling agent is added to the middle layer, and a low surface energy material is applied to the surface, forming a gradient protective structure. Furthermore, nanotechnology is widely used in coating modification; by embedding nanoparticles such as titanium dioxide and zinc oxide, the coating is endowed with self-cleaning and photocatalytic bactericidal capabilities, further reducing the risk of biofouling.
The development of environmentally friendly coatings is a crucial direction for the industry. Traditional heavy metal coatings are gradually being phased out due to toxicity issues, replaced by antifouling agents based on natural products, such as sideroxylonal A extracted from eucalyptus leaves, or those utilizing polysaccharides and proteins from bacterial metabolites to inhibit biofouling. These bio-based coatings are not only non-toxic but also biodegradable, meeting sustainable development requirements. Simultaneously, the application of water-based and powder coatings reduces the use of organic solvents, lowering the risk of pollution to marine ecosystems.
The combination of coating processes and fishing net weaving techniques enhances overall performance. For example, knotless weaving reduces water flow resistance by minimizing knots in the net surface, while also ensuring a more uniform coating distribution. High-density weaving processes, by reducing mesh size, prevent microbial intrusion, creating a double layer of protection in conjunction with the coating. Furthermore, modular design allows users to customize coating types and thicknesses according to operational needs; for example, thicker anti-corrosion coatings are used in deep-sea aquaculture, while near-shore operations prioritize antifouling performance.
In practical applications, coated fishing nets must undergo rigorous environmental adaptability testing. Simulated seawater immersion, UV aging, and mechanical tensile tests were conducted to verify the stability of the coating in complex environments. For example, after a marine ranch project adopted customized coated fishing nets, the stocking density increased, the yield per unit area increased, and the net maintenance cycle was extended, resulting in significantly improved economic benefits. Furthermore, the coated fishing nets also performed well in bird protection and anti-pecking applications in farmland, expanding their application scope.
In the future, the coating process for nylon monofilament fishing nets will develop towards intelligence and multi-functionality. Real-time monitoring of the net's condition using IoT technology, combined with self-healing coatings to automatically repair damaged areas, can significantly reduce maintenance costs. Simultaneously, intelligent fishing nets with integrated sensing functions will be able to detect environmental changes, providing data support for fisheries production. With advancements in materials science, new environmentally friendly coatings will further balance performance and ecological impact, driving the fishing net industry towards a green and sustainable transformation.
