Summary of the development characteristics of the

Summary of the development characteristics of marine antifouling coatings

summary of the development characteristics of marine antifouling coatings

January 5, 2021

marine antifouling coating is a special coating, which is mainly used to prevent the fouling of marine organisms through the gradual seepage of antifouling agents (toxic materials) in the paint film. However, the previous antifouling coatings not only inhibit the attachment of marine organisms, but also cause secondary pollution to the marine environment. Therefore, the development of efficient and lasting green marine antifouling coatings has become a research hotspot, and considerable progress has been made

the shells below the waterline of ships and wharves have long-term contact with seawater and are corroded by seawater; The attachment of marine organisms has reduced the speed of the ship, accelerated the corrosion of the hull, destroyed the underwater platform facilities, and blocked the cooling water pipes of the power plant. The above problems can be prevented by coating it with various marine antifouling coatings

classification:

test standard:

Project

Technical Standard

antifouling paint sample signed immersion test method

gb/t5370-2007

determination of copper ion real sea exudation rate of antifouling paint on the bottom of ships

gb/t6824-2008

determination of organic tin monomer real sea exudation rate of antifouling paint on the bottom of ships

gb/t6825-2008

gb/t7789-2007

cathodic resistance of antifouling paints Peel test method

gb/t7790-2008

dynamic test method for drag reduction performance of self polishing antifouling paint disc torque method

gb/t7791-87

main factors affecting the effect of marine antifouling paint:

antifouling effect of paint is mainly manifested in two aspects: broad spectrum and long-term effect. An ideal marine antifouling coating should have antifouling effect on plants and animal marine attached organisms, and have a long antifouling period. Nowadays, the effectiveness of marine antifouling coatings is generally 1 ~ 5 years. The factors that determine the antifouling effect mainly include the following aspects:

1) the content of antifouling agent generally speaking, the higher the content of antifouling agent, the longer the validity period

2) the surface free energy of the antifouling coating is low. The coating with low surface free energy is not easy to adhere, and even if it is present, it will not adhere firmly, and it is easy to remove or be washed away by the flowing seawater

3) elastic modulus of coating the work required for fouling biological stripping is surface tension（ γ) The 1/2 power of the product of the elastic modulus (E), i.e. w=（ γ· E) ½。 On the coating with low elastic modulus, marine organisms can be stripped off under small external force

4) smoothness of coating the smoother the coating surface is, the smaller the friction resistance is, and the more difficult it is for marine organisms to adhere. Therefore, the smoothness of the coating can also prolong the service life and cleaning of the coating, which can help business users and consumer groups in the process of purchase and use

5) hydrophobic coating hydrophobic marine antifouling coating has obvious antifouling effect. At present, research has applied superhydrophobic surface (the contact angle between surface and water is greater than 150 °) to marine antifouling

6) coating pH the greater the difference between the pH value of the surface seawater and the normal seawater, the less likely it is for marine organisms to attach

main varieties: the advanced antifouling coating technology mainly comes from Europe, America and Japan. It is mainly copied from foreign countries at home, and it is relatively in the research stage. Commercial antifouling coatings are mainly divided into two categories: one is antifouling coatings containing pesticides; The second is antifouling paint without pesticides (or low surface energy antifouling paint, or stain release antifouling paint FRC)

1. Antifouling coatings containing pesticides

antifouling coatings containing pesticides are the most commonly used in the current market, accounting for 90% - 95% of the market. This kind of antifouling paint is divided into the following three kinds

1) hydrated self polishing antifouling paint

polishes through physical action (dissolved by water flow), without the effect of self smoothing the surface of the coating. The antifouling coating is mainly thinned evenly. At the same time, the formation of porous saponification layer adds a small amount of roughness and increases the friction during navigation, which will reduce the ship's speed and gradually increase fuel consumption

2) hydrolytic self polishing antifouling coating

hydrolytic self polishing antifouling coating achieves the purpose of coating polishing through chemical reaction (ion exchange type and pure hydrolytic type) in seawater, and has a good effect of self smoothing the coating surface. Not only effectively reduce the original roughness caused by coating technology. For the antifouling coating that can carry out pure hydrolysis reaction (such as hydrolysis antifouling coating based on silane copolymer of acrylic acid or silane copolymer of methacrylic acid), the hull surface will become smoother during shipping, which can reduce the friction of navigation, and then reduce the fuel consumption, so as to achieve the purpose of energy conservation and emission reduction

at present, hydrolytic self polishing antifouling coatings on the market mainly include the following types: zinc acrylate resin; Acrylic ketone resin; Silylated acrylic resin; Zinc carboxylate resin

the main mechanism of the above technologies is the hydrolysis of reverse esterification or chemical decomposition by ion exchange. The polymer itself is hydrophobic because it is bound to functional groups through an ester bond. When the polymer is immersed in seawater, the ester bond breaks, leaving carboxylate to improve the hydrophilicity of the polymer

a) copper acrylate copolymer self polishing antifouling coating (ion exchange type)

b) zinc acrylate copolymer self polishing antifouling coating (ion exchange type)

c) silylated acrylic copolymer self polishing antifouling coating

3) hybrid self polishing antifouling coating (hybrid)

hydration and hydrolysis antifouling coating technology and combination provide limited self smoothing effect. The main film-forming material of the coating is hydrolyzed (ion-exchange) polymer resin, such as copper acrylate, zinc acrylate, etc. + hydrophilic rosin. The characteristics of mixed antifouling coatings are as follows:

A) due to the existence of rosin, its solid content is higher than that of hydrolytic (ion exchange) antifouling coatings

b) why does antifouling Jiangsu Jinfa technology grow at a high speed against the market? "The company adheres to the business mechanism of 'taking the market as the leader and the order as the center'. The mechanism is to release pesticides through the dual effects of hydrolysis and dissolution.

c) the hydrolysis (ion exchange) antifouling coating of saponification layer is as high as 60" μ M or so

d) self leveling performance cannot be compared with high-performance hydrolytic (ion exchange) antifouling coatings

2 Antifouling paint without pesticides - antifouling paint with ground surface energy

1) organosilicon low surface energy antifouling paint

organosilicon refers to organopolysiloxane, which can be divided into silicone oil, silicone resin and silicone rubber according to its molar mass and structure

a) antifouling coating for ground surface based on silicone rubber. Silicone resin is generally obtained by hydrolysis and polycondensation of silicone monomers. It has the advantages of both inorganic and inorganic materials, and is a very good low surface energy material

b) low surface energy antifouling coating based on silicone resin. Silicone resin is generally obtained by hydrolysis and polycondensation of silicone monomer, which has the advantages of both inorganic and inorganic materials. It is a very good low surface energy material and can be cured at a relatively low temperature

features:

a) it has a linear, highly elastic and fluid skeleton (which is not conducive to microbial attachment)

b) have the elastic modulus as much as possible, so as to facilitate the shedding of attached organisms

c) in the marine environment, its chemical properties are relatively stable, it has sufficient resistance to hydrolysis, and the film strength can prevent the surface structure from being washed and destroyed by seawater

d) a sufficiently thick coating can ensure that marine organisms fall off by peeling with lower energy rather than shearing with higher energy

e) the coating surface is smooth at the molecular level

f) no pesticides

disadvantages of existing organosilicon antifouling coatings:

a) the curing of the coating depends on the ambient temperature and humidity

b) paint mist will pollute other ships. The cost of protection during construction is very high

c) the coating is soft, not durable and easy to be damaged by machinery, especially in the dry wet alternating parts

d) the existing technology cannot avoid the growth of bacterial and algal marine organisms, whose diameter can reach 1000 μ m。 In order to reduce the surface roughness of the hull, the coating surface must be cleaned underwater regularly. Otherwise, it will increase drag and fuel consumption. Frequent underwater surface cleaning will cause damage to the coating surface and increase the roughness

2) organic fluorine low surface energy antifouling coating

polytetrafluoroethylene has very low surface energy (contact angle with water is 114 °), which should theoretically have excellent antifouling property. However, many experts have conducted special research on the antifouling property of organic fluorine resin, and the basic theory is as follows:

A) the coating is a hot-melt film, and the compactness of the film is poor. Marine microorganisms go deep into the film and firmly adhere to the micropores of the film

b) most of the resin, especially the film surface, is CF2 group, and its stain resistance is significantly poor compared with CF3 group

c) when marine microorganisms contact the coating surface, they induce the rearrangement of polymer molecules on the surface, which is the reason for the improvement of the coating surface energy

3) silicone fluororesin low surface energy antifouling coating

people found in the research process that a great reason for the poor antifouling performance of surface energy antifouling coating is that a large number of components in the coating are not afraid of the existence of ground surface energy properties. In order to reduce the proportion of these components in the resin, the combination of organosilicon and organofluorine is worthy of a new low surface energy antifouling coating, which uses fluorine instead of polysiloxane as the base material

basic principle: take the silica chain as the main chain, and introduce a certain concentration of CF3 group into the side chain. This group will be strictly oriented to the surface due to its great surface activity. The whole macromolecule not only maintains the high elasticity and high fluidity of linear polysiloxane, but also absorbs the ultra-low surface energy characteristics of CF3 group

the performance of this kind of coating is higher than that of organosilicon antifouling coating to a certain extent, especially the mechanical strength. At the same time, the adhesion to bacteria and algae marine organisms is reduced, but it cannot be completely eliminated. This kind of coating also needs to be cleaned under water regularly

4) other resin low surface energy antifouling coatings

it is reported that Brunel enviromarine has developed a solvent-free epoxy low surface energy antifouling coating. This kind of antifouling coating has also been applied in cases to provide solutions for the increasingly complex global supply chain. Its characteristics are as follows:

a) the only solid is 100% low surface energy antifouling paint

b) it does not contain toxins and pesticides, and does not contain harmful substances that affect health

c) its antifouling mechanism: the coating surface has no solvent pores conducive to the attachment of marine microorganisms in the harbor; High gloss and low surface energy

d) two component, fixed mixing ratio, using conventional spraying equipment

e) antirust primer is not required, and the dry film thickness of the whole system is 2 × one hundred and fifty μ m。

f) its practical application is very limited, and its performance needs to be verified

coating method:

construction method: airless spraying, brush coating, roller coating

spray hole: 0.5mm

pressure: 250kg/cm2

drying time (surface drying): 7 hours (20 ℃)

launching: minimum 12 hours (20 ℃) maximum 3 months

film thickness: wet film 150 μ m； Dry film 75 μ M

recoating interval: minimum 10 hours (20 ℃); Maximum 60 days

surface treatment: paint on the matching primer, and you can directly paint it as long as the primer is dry. For other construction surfaces, it is required to be clean and dry, free of grease, dust and other pollutants, and the cleaning method can be manual, mechanical or high-pressure water washing

construction