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Since many of the terms used in the composite industry are confusing; We try to clarify everything in a few lines.
"Composite" is an engineering material that consists of two or more different components. These components are usually classified into two categories: matrix and amplifier. The matrix can be made of plastic or polymer, metal or ceramic, and the reinforcement can be particles or fibers. Metal and ceramic matrix composites are commonly referred to as MMCs or CMCs. But in reality, most composites are polymer-based and fiber-reinforced, which we call FRP (Fiber Reinforced Plastics). In the fiber section, glass, carbon, aramid, etc. can be used, and in the plastics section, usually A thermal resin such as polyester, vinyl ester or epoxy is used. If the reinforcing fiber is glass, this composite is called "GFRP" or "GRP". Although the terms "composite" and "FRP" are generally synonymous, it means that both of them are synonymous. They mean reinforced polyethylene fiber or polymer, but the term "composite" is commonly used for carbon fiber reinforcing fibers in expensive industries such as aerospace, and the term "FRP" is commonly used in the materials engineering industries. "GRP", on the other hand, is a term commonly used in industry for low-value applications such as swimming pools, shower cabins, roofs, enclosures, and so on. Finally, although these words are almost synonymous, they are different. In fact, GRP is a type of FRP and FRP is a type of composite.
Epoxy resins
Vinyl ester resins
Polyester resins
Unsaturated polyester resins are divided into two general categories based on the type of phthalic acid used
Iso phthalic polyester resins
And ortho-phthalic polyunsaturated resins.
If the phthalic acid used is ortho-type, it is called orthophthalic unsaturated polyester resin, and if ISO phthalic acid is used, it is called isophthalic unsaturated polyester resin. A high percentage of unsaturated polyester resins used in the composite industry are orthophthalic unsaturated polyester resins. In products that need to be used against chemicals and corrosives and in gel layers (gel coat) of Isophthalic unsaturated polyester resins are used. Orthophtalic resins are used in general applications, while isophthalic unsaturated polyester resins have special applications. The advantage of orthophthalic unsaturated polyester resins has Low price, good flexural and tensile strength and high hardness. The advantages of isophthalic unsaturated polyester resins, high tensile and flexural strength, good resistance to water and chemicals.
The top layer of composite surfaces, which looks like a glossy coating, is called a gelcoat.
In addition to playing a beautiful role for the part, Zelkut is responsible for protecting the surface of composite parts from abrasion, corrosion, chemicals, weather and ultraviolet rays of sunlight.
In other words, gelcoat is the most vital part of a composite part. Although gelcoat has the lowest consumption of composite parts compared to other raw materials, the life of composite parts and their proper performance depends on the correct choice of gelcoat and method of application. it has.
The main material used to produce gelkot is resin, which determines the physical and chemical properties of gelkot according to its chemical composition. Gelcoats are often made from unsaturated polyester, vinyl ester and epoxy resins, which are selected and produced according to the application required by the final part.
Knowing the properties of different resins used in the production of gelcoats, helps a lot in choosing the right one and thus achieving the desired quality in the manufacture of composite parts, especially when the final part must have special resistances such as water resistance, sunlight, mechanical strength. And دهد offer.
Today, anti-moss paints are very common and widely used in the marine industry. These anti-moss paints are used to apply to different parts of the ship that are in contact with water, and cause the mossing process in the hull of ships to be disrupted through mechanisms. . To know about anti-moss dyes, we must first know about mosses. Increase of surface roughness, increase of friction force between seawater and moving ship, increase of cost related to fuel consumption, destruction of hull cover and its repair, increase of corrosion and damages and increase of stopping time in the place for repair of hull for all surfaces Creates a fixed and moving sea. After about 48 hours, the barnacles hardly adhere to the hull. These creatures do not need sunlight to survive, so they can live in all parts of a ship that is in contact with seawater. Another factor in the growth of moss is the speed of the ships. If the ship is stopped for a longer period of time, the growth of these mosses will increase.
Moss control has been around for a long time. In the past, bitumen was used for anti-moss coating in wooden boats, but with the development of marine industry and the spread of science, arsenic and tin compounds were used as anti-moss marine paints. Among the tin compounds, the following can be mentioned:
Tributyltin oxide (TBTO)
Tricobutyltin fluoride (TBTF)
• Triphenyltin fluoride (TPTF)
Tricobutyl acrylate (TBTA)
Tributyltin methyl methacrylate (TBTMMA)
The use of anti-moss marine paints containing tin compounds was banned by environmental laws passed by the International Maritime Organization in 2008.
Copper compounds such as copper oxide (II), copper thiocyanate and copper sulfide are also used as anti-moss. Of course, the use of these compounds is limited, but they have far less environmental hazards than tin compounds.
These products are a range of coatings that have a great variety of shades and beauty. Polyurethane surface paints have high tolerance to sunlight. Alkyd paints are also a good option for staining and application in limited areas due to their one-component and ease of application. Shelf life of these paints, if applied correctly on the hull of vessels, can last up to 5 years, and if standard marine paints with high polishing and gloss are used, after each year by applying special marine scrub and wax, the paint shines again and Will find its novelty.