Project background 1. Analysis of the current situation of cage culture. Our country's cage culture industry has experienced more than 30 years of development, from small traditional breeding cages near the coast to the current intensive and large-scale deep-sea storm-resistant cages, and through the unremitting efforts of governments and scientific and technological workers at all levels, it has developed into an emerging industry of aquaculture, with considerable scale in coastal provinces. Cage culture: A production method in which boxes made of nets are placed in a certain water area for fish farming. Cage cages are mostly set up in lakes, rivers, reservoirs and other waters with certain water flow, fresh water quality, and high dissolved oxygen. High-density intensive breeding can be implemented, mainly raising carp, non-crucian carp, rainbow trout, etc. In China, silver carp, bighead carp, grass carp, amblycephala, etc. After the cage is put into the water for a period of time, the mesh is blocked due to the attachment of organisms and organic matter, which affects the exchange of water bodies and is not conducive to the elimination of feces and residual bait in the box and the replenishment of natural bait and dissolved oxygen. 2. The formation and harm of algae attachments in net boxes. Since a large number of my country's marine culture cages are concentrated in harbors and near the coast, in some bays, there is no stream injecting new water or the injection amount is small. When the water level in the reservoir area is stable for a long time, the water body in the bay flows weakly and is almost static, and the renewal is slow. At this time, if there are many breeding cages in the bay and are fixed in a certain water area for a long time, with the inflow of a large amount of organic matter such as bait residue and fish excrement generated during breeding, causing eutrophication of the water body. Under the nourishment of the eutrophic water body, various algae in the water body grow and reproduce in large quantities. During the cage culture process, due to poor water exchange and lack of safe and effective anti-attachment measures for cage nets. However, the net is immersed in the relatively static water of the Bay for a long time. Filamelike floating species such as Spirogyra, Double Star algae, and Rotaria in the water attach to and grow on the net. Large amounts of fine particulate suspended matter in the water are deposited and occupied at the same time. If the mesh of the box is not cleaned in time, the growth of algae and suspended matter will be adsorbed and deposited together, forming massive algae mud sheets attached to the net. As the algae mud sheets increase, the mesh will eventually cause clogging. It not only hinders the smooth flow of water and the exchange of water bodies, but also increases the weight of the net box, affects the buoyancy balance of the cage system, and forms a dangerous factor that cannot be ignored. However, the residue, bait, and fish excreta generated during the production process are not discharged in time and are deposited at the bottom of the box for fermentation, decomposition, and oxygen consumption, resulting in deterioration of the water quality and lack of oxygen in the water body in the box, seriously affecting the healthy growth of fish. Algae, residual bait, and fish excreta attached to the net box are an ideal place and source of nutrition for fish pathogenic organisms to inhabit, reproduce and reproduce. As the number of pathogenic organisms increases and the virulence of pathogens increases, it is harmful to the health of cultured fish. It poses a great threat and ultimately leads to disease and death in fish. During the breeding and feeding process, undigested nutrients such as cultured fish, sea cucumbers, abalone, and shellfish accumulate in the cage and accelerate the growth of polluting organisms. The existence of fish feces and residual bait provides sufficient nutrients for algae and bacteria and microorganisms, and also accelerates the growth of seaweed attached to the net of the cage. Nets that have been immersed in water for a long time will quickly plug the mesh due to the rapid growth of a large number of filamentous algae and other attachments. This results in reduced water filtering performance of the cage, reduced dissolved oxygen in the water in the cage, and greatly fluctuated. The cultured organisms in the cage grow poorly due to lack of oxygen or failure to filter and feed plankton, which affects the normal growth rate of the cultured organisms., feed efficiency, survival rate and yield, especially with the cultivation of famous, special and excellent aquatic products in cages,(such as sea cucumbers, abalone, eel, carp, etc.) and the development of juvenile fish and fish species needed for supporting cultivation and breeding, small-mesh cages are increasingly widely used, and their mesh pollution and blocking problems are more serious. In addition, the intensification of net attachments will also increase the overall weight of the cage, increase the resistance of the cage, seriously affect the safety and service life of the cage, and greatly affect the economic benefits of cage culture. 3. Traditional treatment methods for algae attached to cage culture boxes At present, the algae and plankton attached to floating cages are mainly cleaned with high-pressure water or moved to the shore at the right time to use sun exposure and chemical cleaning. The summer temperature is high. If it is traditional nets, seaweed and other attachments grow wildly, the nets must be picked up and cleaned every other week, and washed every 2-3 weeks in spring and autumn. It is troublesome and laborious, which is not conducive to the growth of aquatic products. At present, various methods are used to clean breeding cages at home and abroad, mainly divided into the following: (1) Manual cleaning method (2) Mechanical cleaning method (3) Replacement of new cages (4) Pharmaceutical cleaning method Currently, net water-based anti-pollution coatings are also used on the market. Their role is to prevent the attachment of aquatic organisms. This kind of coating can prevent the attachment of several types of aquatic organisms to a certain extent, but it cannot prevent the attachment of all organisms 100% and has many defects. In addition, the action time of this coating is limited, which greatly increases the cost of aquaculture. The copper alloy mesh cage technology, born in 1975, uses the natural antibacterial properties and corrosion resistance of copper to prevent marine biological attachments from growing in the breeding net, thereby creating cleaner and healthier conditions for fish breeding. At the same time, this technology greatly reduces the number of times fishing nets need to be cleaned and replaced, and reduces losses caused by predators catching or fish escaping. Although the industry pays high attention to copper alloy netting, for now, high prices are still its weakness. For the same specification of netting, copper alloy is five times higher than traditional netting, which is still difficult for ordinary farmers to accept for a while. Preliminary results of this project 1. Research and development of new antibacterial guanidine salt polymer antifouling materials 1. Organic guanidine salt antibacterial agents and their germicidal mechanism (1) Organic guanidine salt antibacterial agent guanide (guā) exists in natural products such as protein, nucleic acid, and streptomycin. In many plants such as sugar beets, rice, mushrooms and beans, humans and animals also contain trace amounts of guanidine. However, free guanidine is very unstable and easily absorbs carbon dioxide in the air to produce guanidine carbonate. Therefore, guanidine is usually stable in the form of guanidine salt. Guanidine salts are an important part of guanidine-based compounds and can be derived into a wide variety of guanidine-based derivatives, which have good antibacterial properties. Guanidine antibacterial agents refer to antibacterial compounds containing guanidine groups in their structure. As a non-toxic, efficient and broad-spectrum antibacterial agent, people have gradually attracted people's attention. In recent years, with the deepening of research on this type of compounds, their uses have become increasingly widespread. (2) Sterilization mechanism of organic guanidine salts antibacterial bacteria consist of cell wall, cell membrane, cytoplasm and cell nucleus. The cell wall and cell membrane are composed of phospholipid bilayer and have negative charges. The best conditions for cell survival and reproduction are neutral or weakly alkaline environments. When bacteria come into contact with a substance treated with a cationic compound, the negatively charged bacteria will be attracted by the cations on the substance, thereby constraining the bacteria's freedom of activity and suppressing its respiratory function, that is,"contact death" occurs. In addition, under the gravity of the electric field, bacteria are deformed by uneven distribution of negative charges on the cell wall and cell membrane, causing physical rupture, causing the internal organs of the cells such as water and proteins to exude out of the body, causing "cell lysis" phenomenon and death. The guanidine compound is a basic, monobasic organic base equivalent to sodium hydroxide. Guanidine ions combine with acid radical ions to form guanidinium salts. Organic guanidine compounds are most widely used as fungicides. Their effects on fungi are multi-faceted, usually by affecting the growth and division of bacteria, germination of spores and causing inhibition of respiration, cell expansion, disintegration of cytoplasmic bodies and cell walls. Damage and other abnormal phenomena, thereby achieving the purpose of suppressing or killing organisms. 2. New antibacterial guanidine salt polymer antifouling materials The research and development of new antibacterial guanidine salt polymer antifouling materials is mainly aimed at improving the antibacterial efficiency of antibacterial agents. Grafting organic guanidine salt antibacterial agents into polymer materials can achieve a safer and long-term antibacterial effect. New antibacterial guanidine salt polymer antifouling materials refer to polymers with antibacterial and bactericidal functions. Antibacterial polymers can be obtained from polymers with antibacterial active tubular monomers, or antibacterial groups can be fixed on polymers through coordination bonds or covalent bonds, or antibacterial groups can also be introduced into natural polymers. Compared with small molecule antibacterial agents, antibacterial polymers containing antibacterial groups have significant antibacterial effects, good heat resistance, good stability and low toxicity. This project adopts a new generation of molecular assembly antibacterial technology, mainly by assembling selected antibacterial functional groups on the molecular chain of the matrix resin through chemical grafting methods. It utilizes the positive electricity of the antibacterial functional groups and the opposite attraction principle of negatively charged proteins of bacteria to adsorb microbial cells and affect the normal respiratory and metabolic functions of the cells, causing the rupture of the cells (walls) to achieve antibacterial purposes, thereby making the product achieve lasting antibacterial in the true sense. The safety and long-term effectiveness of the antibacterial effect of the finished product are greatly improved and ensured. Application of new antibacterial guanidinium salt polymer antifouling materials in aquaculture cage nets. Traditional nets are generally made of polyethylene or nylon. To develop antifouling cage nets in this project, the first thing is to study and select environmentally friendly, safe and long-term antibacterial materials. The antibacterial guanidinium salt polymer is used to modify polymer materials such as polyethylene to make antifouling cage nets. Due to its antibacterial property, it can replace the currently used traditional nets and effectively avoid the growth of seaweed and other appendages. Reduce the workload of cleaning nets, so that aquaculture can grow healthily in an ecological environment close to nature. Launch trial and evaluation In May 2018, the launch trial was conducted at the cage culture base in the South China Sea in Shenzhen. Judging from the trial effect, there is basically no growth of seaweed and other appendages on the culture cage nets made of the new antibacterial guanidinium salt polymer antifouling material. There is no need to clean the nets, and the fish grow healthily. 1. In May 201800, comparison of antibacterial guanidinium salt polymer cages and traditional cages: 2. In June 201800, at the beginning and end of the month, the comparison of antibacterial guanidinium salt polymer cages and traditional cages: 3. 2018.07.01 Comparison of antibacterial guanidinium salt polymer cages and traditional cages: Test and evaluation of mechanical properties of new antibacterial guanidinium salt polymer antifouling materials 1. The test method used INSTRON-4466 universal testing machine (Instron, USA, tensile mode). The monofilament was tested at room temperature according to SC/T5005-2014 standard. The fiber nip distance was 500mm and the tensile speed was 300mm/min. Samples were tested and averaged to obtain fiber breaking strength, nodule strength and elongation at break. The knot strength is the tensile strength of the monofilament after being knotted and is an important evaluation feature of fishing monofilament. The network cable is tested at room temperature according to SC/T5007-2011 standard, with a tensile speed of 300mm/min and a rupture time of about 20 seconds. The mesh is tested at room temperature according to GB/T21292-2007 standard, and the tensile speed is 200mm/min. Use a length gauge and balance to measure the monofilament and net wire and then calculate the linear density. 2. Mechanical properties of antifouling monofilament Figure 1 shows the load and tensile strain curve of antifouling monofilament, and the corresponding results are listed in Table 1. The damage of fishing nets is generally caused by net nodules, and the nodule strength is the tensile strength after knot tying, lower than the breaking strength. It can be seen from Table 1 that compared with ordinary synthetic fibers, antifouling monofilament has significant nodule strength advantages. The nodule strength of antifouling monofilament is 19.2% higher than that of ordinary PE fiber and 7.3% higher than that of ordinary PA monofilament. In addition, the elongation of antifouling monofilament is less than that of ordinary synthetic fiber, and the elongation at break of antifouling monofilament is 18.6%, which is 7.0% lower than that of ordinary PE fiber and 15.4% lower than that of ordinary PA monofilament. 3. Mechanical properties of anti-fouling network cable A 10×3 anti-fouling network cable was prepared using anti-fouling monofilament as the matrix fiber. Its tensile mechanical properties test results are shown in Figure 2, and its comparison results with PE network cable of the same diameter (qualified product) are shown in Table 2. It can be seen from Table 2 that the breaking strength of the antifouling network cable meets the requirements of SC/T 5007 standard, and its nodule strength is 30.7% higher than that of the SC/T 5007 standard PE network cable qualified product index. 4. Mechanical properties of anti-fouling net A knot net with a mesh length of 50mm was prepared with 10×3 anti-fouling net. The test results of its mesh breaking mechanical properties are shown in Figure 3, and the comparison results with PE net (qualified product) are shown in Table 3. The mesh breaking strength of the antifouling mesh meets the GB/T 18673 standard qualified product indicators, and is 17.9% higher than that of ordinary PE mesh qualified products. Preliminary economic analysis of the industrialization of this project 1. Cost analysis of anti-pollution cage nets Traditional deep-water cages use polyethylene fishing nets or polyamide (commonly known as nylon) fishing nets. The unit price of ordinary polyethylene cage raw materials is only 13 yuan/kg. At present, copper alloy net cages promoted in the industry have a high one-time investment, and the unit price of raw materials is 68 yuan/kg. The cost of raw materials for this project is expected to increase by only 30%-50% on the original basis. If the market sales unit price is between the above two, or the price of existing market products increases by 80%-100%, the price is more affordable but still It is the best choice for breeding cage nets. It can not only meet user needs, but also achieve better economic benefits. 2. The market scale is large enough. China is a big country in cage culture. After years of development, the number of offshore cages in the country has reached more than 1.2 million, and the total number of deepwater cages has reached more than 6000. The annual market size of pure net clothes exceeds 10 billion. According to the 2-3 year replacement cycle of cage nets, there is a large domestic demand space. After this project is further promoted, the number will become very large around the world. The cooperation area is based on the antibacterial guanidinium salt polymer technology platform. Our research group will conduct in-depth research on new antibacterial guanidinium salt polymer antifouling materials in a wide range of fields such as water purification pipes, household appliances, water purifier materials, and antibacterial packaging materials.