In addition to unsaturated polyester resins, epoxy resins, and phenolic resins, the following thermosetting resins are mainly available.
First, melamine formaldehyde resin Melamine formaldehyde resin is a thermosetting resin made from polycondensation of melamine and formaldehyde. Glass fiber-reinforced melamine formaldehyde laminates have high mechanical properties, excellent heat resistance, electrical insulation, and self-extinguishing properties.
Second, furan resin from furfural or furfuryl alcohol homopolymerization or condensation polymerization with other monomers obtained by the polycondensation product, customarily known as furan resin. There are many types of such resins, of which furfural phenol resin, furfural ** resin and furfuryl alcohol resin are more important.
(1) Furfural phenol resin. Furfural can be polycondensed with phenol to form a second-order thermosetting resin. The polycondensation reaction generally uses a basic catalyst. Commonly used basic catalysts are sodium hydroxide, potassium carbonate or alkali earth metal hydroxides. The main feature of the furfural phenol resin is its long flow time at a given cure speed, which makes it suitable for use as a molding compound. Compressed powders made from furfural phenol resins are particularly suitable for pressing articles that are more complex or larger in shape. The heat resistance of molded products is better than that of phenolic resins, and the use temperature can be increased by 10 to 20°C. The dimensional stability and electrical properties are also good.
(2) Furfural ** resin. The condensation reaction of furfural and ** under alkaline conditions to form fluorenone monomer can be further polycondensed with formaldehyde under acidic conditions, so that the fluorene ketone monomer molecules are connected by methine bonds to form furfural ** resin.
(3) Furfuryl alcohol resin. Sterols can be easily condensed into resins under acidic conditions. It is generally believed that in the polycondensation process, the hydroxymethyl group in the sterol molecule may be condensed with the alpha hydrogen atom in the other molecule to form a methine bond, and the condensation formed product still has a hydroxymethyl group, and the polycondensation reaction may continue. A linear polycondensation product furfuryl alcohol resin is formed.
Furan Resin Properties and Applications—Uncured furan resins are well-mixed with many thermoplastic and thermosetting resins and can therefore be modified by mixing with epoxy or phenolic resins. The cured furan resin is resistant to strong acids (except strong oxidizing ** and **), strong alkali and organic solvents, and is stable at high temperatures. Furan resin is mainly used as a material resistant to chemical corrosion and high turbidity.
(1) Chemically resistant materials Furan resins can be used to prepare corrosion resistant cements used as linings for chemical equipment or other corrosion resistant materials.
(2) Heat-resistant materials Furan glass fiber reinforced composites have higher heat resistance than ordinary phenolic glass fiber reinforced composites and can usually be used at about 150°C for a long period of time.
(3) Modification by mixing with epoxy resin or phenolic resin The use of furan resin with epoxy resin or phenolic resin can improve the mechanical properties of the furan glass fiber reinforced composites and the process performance during preparation. Such composite materials have been widely used to prepare chemical reactors such as stirring devices, storage tanks, and pipelines.
Third, polybutadiene resin Polybutadiene resin is a low molecular weight liquid, macromolecular main chain contains mainly 1,2-structure, also known as 1,2-polybutadiene resin. This resin has many vinyl side chains on the macromolecular chain, so that in the presence of a free radical initiator, it can further crosslink into a bulk polymer of a three-way network structure.
1,2-polybutadiene resin can be synthesized by anionic polymerization process from butadiene initiated by alkyl lithium, alkali metal (usually ***) or soluble alkali metal complex (such as sodium-naphthalene system) initiator. . The macromolecular chain of the 1,2-polybutadiene resin is entirely composed of hydrocarbons, so the cured resin has excellent electrical properties, good bending strength, and excellent water resistance.
4. Organic silicone resins In organic silicone polymers, polymers that have practical value and are widely used are mainly composed of organosilicon monomers (such as organohalosilanes) that are hydrolyzed and polycondensed and whose main chain structure is a silicon-oxygen bond. Silicon compounds. This main chain is composed of a silicon-oxygen bond, and a polymer whose side chain is linked to an organic group through a silicon atom is called a polyorganosiloxane.
Silicone resin is a kind of thermosetting resin with low molecular weight in polyorganosiloxane. Glass fiber reinforced composites made of these resins can maintain excellent electrical properties even after being used continuously for a long time (200-250°C) in a high temperature range. At the same time, they also have good arc resistance and good hand resistance. Water moisture resistance. The performance of the silicone resin is as follows:
(1) Thermal stability. The Si-O bond of the silicone resin has a relatively high bond energy (363 kJ/mol), so it is relatively stable and has high heat resistance and high temperature resistance. Generally speaking, its thermal stability can reach 200-250°C, and special types of resins can be higher.
(2) Mechanical properties. The mechanical properties of the silicone resin after curing are not high. If the chlorophenyl group is introduced on the macromolecular backbone, the mechanical properties can be improved. The silicone resin fiberglass laminates have poor interlayer adhesive strength, and their bending strength is greatly reduced when heated. When phenylene is introduced into the main chain, rigidity, strength, and use temperature can be increased.
(3) Electrical properties. Silicone resin has excellent electrical insulation properties, its breakdown strength, high voltage arc and electric spark performance are superior. Under the effect of arc and electric spark, even if the resin is cracked to remove organic groups, the remaining silica on the surface also has good dielectric properties.
(4) Water repellency. The water absorption of the silicone resin is very low, and the water droplets can only roll on the surface and cannot wet. Therefore, the silicone resin glass fiber reinforced composite material can still maintain its excellent performance under humid environment conditions.
(5) Corrosion resistance. The silicone resin glass fiber reinforced composite material can have a concentration (mass) of 10% to 30%**, 10%**, 10% to 15% of sodium hydroxide, 2% of sodium carbonate, and 3% of hydrogen peroxide. Alcohols, aliphatic hydrocarbons, and lubricating oils have less of an effect on it, but they have poorer resistance to solvents and certain solvents (such as carbon tetrachloride, carbon monoxide, and silver).
First, melamine formaldehyde resin Melamine formaldehyde resin is a thermosetting resin made from polycondensation of melamine and formaldehyde. Glass fiber-reinforced melamine formaldehyde laminates have high mechanical properties, excellent heat resistance, electrical insulation, and self-extinguishing properties.
Second, furan resin from furfural or furfuryl alcohol homopolymerization or condensation polymerization with other monomers obtained by the polycondensation product, customarily known as furan resin. There are many types of such resins, of which furfural phenol resin, furfural ** resin and furfuryl alcohol resin are more important.
(1) Furfural phenol resin. Furfural can be polycondensed with phenol to form a second-order thermosetting resin. The polycondensation reaction generally uses a basic catalyst. Commonly used basic catalysts are sodium hydroxide, potassium carbonate or alkali earth metal hydroxides. The main feature of the furfural phenol resin is its long flow time at a given cure speed, which makes it suitable for use as a molding compound. Compressed powders made from furfural phenol resins are particularly suitable for pressing articles that are more complex or larger in shape. The heat resistance of molded products is better than that of phenolic resins, and the use temperature can be increased by 10 to 20°C. The dimensional stability and electrical properties are also good.
(2) Furfural ** resin. The condensation reaction of furfural and ** under alkaline conditions to form fluorenone monomer can be further polycondensed with formaldehyde under acidic conditions, so that the fluorene ketone monomer molecules are connected by methine bonds to form furfural ** resin.
(3) Furfuryl alcohol resin. Sterols can be easily condensed into resins under acidic conditions. It is generally believed that in the polycondensation process, the hydroxymethyl group in the sterol molecule may be condensed with the alpha hydrogen atom in the other molecule to form a methine bond, and the condensation formed product still has a hydroxymethyl group, and the polycondensation reaction may continue. A linear polycondensation product furfuryl alcohol resin is formed.
Furan Resin Properties and Applications—Uncured furan resins are well-mixed with many thermoplastic and thermosetting resins and can therefore be modified by mixing with epoxy or phenolic resins. The cured furan resin is resistant to strong acids (except strong oxidizing ** and **), strong alkali and organic solvents, and is stable at high temperatures. Furan resin is mainly used as a material resistant to chemical corrosion and high turbidity.
(1) Chemically resistant materials Furan resins can be used to prepare corrosion resistant cements used as linings for chemical equipment or other corrosion resistant materials.
(2) Heat-resistant materials Furan glass fiber reinforced composites have higher heat resistance than ordinary phenolic glass fiber reinforced composites and can usually be used at about 150°C for a long period of time.
(3) Modification by mixing with epoxy resin or phenolic resin The use of furan resin with epoxy resin or phenolic resin can improve the mechanical properties of the furan glass fiber reinforced composites and the process performance during preparation. Such composite materials have been widely used to prepare chemical reactors such as stirring devices, storage tanks, and pipelines.
Third, polybutadiene resin Polybutadiene resin is a low molecular weight liquid, macromolecular main chain contains mainly 1,2-structure, also known as 1,2-polybutadiene resin. This resin has many vinyl side chains on the macromolecular chain, so that in the presence of a free radical initiator, it can further crosslink into a bulk polymer of a three-way network structure.
1,2-polybutadiene resin can be synthesized by anionic polymerization process from butadiene initiated by alkyl lithium, alkali metal (usually ***) or soluble alkali metal complex (such as sodium-naphthalene system) initiator. . The macromolecular chain of the 1,2-polybutadiene resin is entirely composed of hydrocarbons, so the cured resin has excellent electrical properties, good bending strength, and excellent water resistance.
4. Organic silicone resins In organic silicone polymers, polymers that have practical value and are widely used are mainly composed of organosilicon monomers (such as organohalosilanes) that are hydrolyzed and polycondensed and whose main chain structure is a silicon-oxygen bond. Silicon compounds. This main chain is composed of a silicon-oxygen bond, and a polymer whose side chain is linked to an organic group through a silicon atom is called a polyorganosiloxane.
Silicone resin is a kind of thermosetting resin with low molecular weight in polyorganosiloxane. Glass fiber reinforced composites made of these resins can maintain excellent electrical properties even after being used continuously for a long time (200-250°C) in a high temperature range. At the same time, they also have good arc resistance and good hand resistance. Water moisture resistance. The performance of the silicone resin is as follows:
(1) Thermal stability. The Si-O bond of the silicone resin has a relatively high bond energy (363 kJ/mol), so it is relatively stable and has high heat resistance and high temperature resistance. Generally speaking, its thermal stability can reach 200-250°C, and special types of resins can be higher.
(2) Mechanical properties. The mechanical properties of the silicone resin after curing are not high. If the chlorophenyl group is introduced on the macromolecular backbone, the mechanical properties can be improved. The silicone resin fiberglass laminates have poor interlayer adhesive strength, and their bending strength is greatly reduced when heated. When phenylene is introduced into the main chain, rigidity, strength, and use temperature can be increased.
(3) Electrical properties. Silicone resin has excellent electrical insulation properties, its breakdown strength, high voltage arc and electric spark performance are superior. Under the effect of arc and electric spark, even if the resin is cracked to remove organic groups, the remaining silica on the surface also has good dielectric properties.
(4) Water repellency. The water absorption of the silicone resin is very low, and the water droplets can only roll on the surface and cannot wet. Therefore, the silicone resin glass fiber reinforced composite material can still maintain its excellent performance under humid environment conditions.
(5) Corrosion resistance. The silicone resin glass fiber reinforced composite material can have a concentration (mass) of 10% to 30%**, 10%**, 10% to 15% of sodium hydroxide, 2% of sodium carbonate, and 3% of hydrogen peroxide. Alcohols, aliphatic hydrocarbons, and lubricating oils have less of an effect on it, but they have poorer resistance to solvents and certain solvents (such as carbon tetrachloride, carbon monoxide, and silver).
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