Phenolic Resin

Modified phenolic resin overcome the shortcomings of phenolic resin, such as poor heat resistance and low mechanical strength. They offer excellent mechanical properties, strong heat resistance, strong bonding, and chemical stability. They are widely used in compression molding powders, coatings, glues, fibers, anti-corrosion, and thermal insulation applications.   1. Applications of Modified Phenolic Resins in Compression Molding Powders Compression molding powders are essential for the production of molded products. They are primarily made from modified phenolic resins. In manufacturing, a common method involves using both roller compaction and twin-screw extrusion. Wood is used as a filler to impregnate the resin, and other reagents are then added and mixed thoroughly. The powder is then pulverized to produce compression molding powder. Materials such as quartz can be added to produce compression molding powders with enhanced insulation and heat resistance. Compression molding powders are a raw material for various plastic products, which can be manufactured industrially through injection molding or compression molding. Figure 2 shows the application of modified phenolic resin in compression molding powders. Compression molding powders are primarily used in electrical components such as switches and plugs for household items.   2. Application of Modified Phenolic Resins in Coatings For 70 years, coatings have used phenolic resins. Rosin-modified phenolic resins or 4-tert-Butylphenol formaldehyde resin are the main ones in phenolic coatings. These resins make coatings better at resisting acid and heat, so they're common in lots of engineering projects. Still, because they give things a yellow color, you can't use them if you want a light-colored finish. Besides being mixed with tung oil, they can also be blended with other resins. To increase a coating's alkali resistance and air-dried hardness, alkyd resins can be added to improve the coating's alkali resistance and hardness. For coatings requiring acid and alkali resistance and good adhesion, epoxy resins can be added to enhance the coating's performance. Figure 3 illustrates the application of modified phenolic resins in coatings.   3. Application of Modified Phenolic Resins in Phenolic Adhesives Phenolic adhesives are mainly made from modified thermosetting phenolic resins. If phenolic resin is used to create adhesives, its viscosity can be a problem, restricting it to plywood bonding. But, modifying phenolic resin with polymers can improve its heat resistance and adhesion. Phenolic-nitrile adhesives can even have good mechanical strength and toughness, especially when it comes to impact resistance.   4. Application of Modified Phenolic Resins in Fibers Phenolic resins also have a wide range of applications in the fiber industry. Phenolic resin is melted and drawn into fibers, which are then treated in polyoxymethylene. After a period of time, the filaments solidify, resulting in a fiber with a solid structure. To further enhance the fiber's strength and modulus, the modified phenolic resin can be mixed with molten low-concentration polyamide and drawn into fibers, as shown in Figure 4. The spun fibers are typically yellow and possess high strength. They will not melt or burn even at temperatures of 8,000°C. It will also self-extinguish in these harsh environments, preventing fires from occurring at the source. At room temperature, polyamide-modified phenolic resin fibers are highly resistant to concentrated hydrochloric and hydrofluoric acids, but less resistant to strong acids and bases such as sulfuric acid and nitric acid. These products are primarily used in factory protective clothing and interior decoration, minimizing employee injuries and fatalities in the event of a fire. They are also commonly used as insulation and thermal insulation materials in engineering projects.   5. Application of Modified Phenolic Resins in Anti-Corrosion Materials Phenolic resins are used to make anti-corrosion stuff, but the modified versions are more common. You'll often see these as phenolic resin mastics, phenolic-epoxy composite fiberglass, or phenolic-epoxy coatings. A good example is phenolic-epoxy coatings, which mix the acid resistance of phenolic resins with the alkali resistance and stickiness of epoxy resins. This mix makes them great for protecting pipelines and vehicles from corrosion.   6. Application of Modified Phenolic Resin in Thermal Insulating Materials Because modified phenolic resin offers superior heat resistance compared to pure phenolic resin, modified phenolic resin foams occupy a prominent position in the thermal insulation market, as shown in Figure 5. Modified phenolic resin foams also offer thermal insulation, are lightweight, and are difficult to spontaneously ignite. Furthermore, when exposed to flames, they do not drip, effectively preventing the spread of fire. Consequently, they are widely used in thermal insulation color-coated steel sheets, room insulation, central air conditioning, and pipes requiring low temperatures. Currently, polystyrene foam is the most widely used insulation material on the market, but its performance is far inferior to that of modified phenolic resin foam. Modified phenolic resin foam, due to its low thermal conductivity and excellent thermal insulation, has earned it the title of "King of Insulation" in the insulation industry.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com

1. Introduction to Phenolic Resins     Phenoic formaldehyde resin are primarily formed by the polycondensation of phenol and formaldehyde. Phenolic resins were first accidentally created by the German scientist Bayer in the 1780s. He mixed phenol and formaldehyde and processed them to produce a fluid product. However, Bayer did not further research or discuss this product. It was not until the 19th century that Bloomer, building on the work of the German chemist Bayer, successfully produced phenolic resin using tartaric acid as a catalyst. However, due to complex operation and high costs, industrialization was not achieved. It was not until the 1820s that the American scientist Buckland ushered in the era of phenolic resins. He noticed this chemical product and, through systematic research and discussion, ultimately proposed the "pressure and heat" curing method for phenolic resins. This laid the foundation for the future development of phenolic resins, and the subsequent rapid development of this type of resin.   2. Research on Modified Phenolic Resins However, with technological advancements, scientists have discovered that traditional phenolic resins are increasingly unable to meet the needs of emerging industries. Therefore, the concept of modified phenolic resins has been proposed. This involves using phenolic resin as a matrix and adding a reinforcing phase to enhance the performance of the phenolic resin through the properties of the reinforcing phase. While traditional phenolic resins possess remarkable heat resistance and oxidation resistance due to the introduction of rigid groups such as benzene rings into the matrix, they also have numerous drawbacks. During preparation, phenolic hydroxyl groups are easily oxidized and do not participate in the reaction, resulting in a high concentration of phenolic hydroxyl groups in the finished product, leading to impurities. Furthermore, phenolic hydroxyl groups are highly polar and readily attract water, which can lead to low strength and poor electrical conductivity in phenolic resin products. Prolonged exposure to sunlight can also severely alter the phenolic resin, causing discoloration and increased brittleness. These drawbacks significantly limit the application of phenolic resins, making modification of phenolic resins essential to address these shortcomings. Currently, the main types of modified phenolic resins include polyvinyl acetal resin, epoxy-modified phenolic resin, and silicone-modified phenolic resin.   2.1 Polyvinyl Acetal Resin Polyvinyl acetal resin is currently modified by introducing other components. The principle is to condense polyvinyl alcohol (PVA) and aldehyde under acidic conditions to form polyvinyl acetal. This is primarily because polyvinyl alcohol is water-soluble and the aldehyde condensation prevents it from dissolving in water. This aldehyde is then mixed with a phenolic resin under certain conditions, allowing the hydroxyl groups in the phenolic resin to combine with those in the polyvinyl acetal, undergoing polycondensation and removing a molecule of water to form a graft copolymer. Due to the introduction of flexible groups, the added polyvinyl acetal enhances the toughness of the phenolic resin and reduces its setting speed, thereby reducing the molding pressure of polyvinyl acetal products. However, the only drawback is that the heat resistance of the polyvinyl acetal products is reduced. Therefore, this modified phenolic resin is often used in applications such as injection molding.   2.2 Epoxy-modified phenolic resin Epoxy-modified phenolic resin is typically prepared using bisphenol A epoxy resin as the reinforcing phase and phenolic resin as the matrix. This reaction primarily involves an etherification reaction between the phenolic hydroxyl groups in the phenolic resin and the hydroxyl groups in the bisphenol A epoxy resin, resulting in the bonding of the hydroxyl groups in the phenolic resin and the hydroxyl groups in the bisphenol A epoxy resin, removing a molecule of water and forming an ether bond. Subsequently, the hydroxymethyl groups in the phenolic resin and the terminal epoxy groups in the bisphenol A epoxy resin undergo a ring-opening reaction, forming a three-dimensional structure. In other words, the curing action of the bisphenol A epoxy resin is stimulated by the phenolic resin, leading to further structural changes. Due to its complex structure, this modified resin exhibits excellent adhesion and toughness. Furthermore, the modified product also possesses the heat resistance of bisphenol A epoxy resin, meaning the two materials can be considered to complement and improve each other. Therefore, this material is primarily used in molding, adhesives, coatings, and other fields.   2.3 Silicone-Modified Phenolic Resin Silicone-modified phenolic resin uses silicone as a reinforcing phase. Due to the presence of silicon-oxygen bonds in silicone, silicone possesses excellent heat resistance, significantly higher than that of typical polymer materials. However, silicone has relatively poor adhesion. Therefore, silicone can be introduced to enhance the heat resistance of phenolic resin. The principle is that silicone monomers react with the phenolic hydroxyl groups in the phenolic resin to form a cross-linked structure. This unique cross-linked structure results in a modified composite material with excellent heat resistance and toughness. Tests show this material holds up well under high heat for a long time. That's why it's often used in rockets and missiles that need to withstand extreme temperatures.   Phenolic resins are usually modified using the methods above. You can make modified resins like epoxy-modified, silicone-modified, and polyvinyl acetal resins by starting with phenolic resin. Another way is to turn aldehydes or phenols into other stuff, and then react that with phenols or aldehydes to make modified resins like phenolic novolac resin and xylene-modified phenolic resin. Alternatively, reactions without phenol can produce a first-stage phenolic resin, which then reacts to produce a second-stage phenolic resin, such as diphenyl ether formaldehyde resin.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com

Carbon foam, a functional carbonaceous material with a honeycomb structure, not only boasts excellent properties such as low density, high strength, oxidation resistance, and adjustable thermal conductivity, but also boasts excellent processability. Therefore, it can be used as a thermal conductor, insulator, catalyst carrier, biosolidifier, and absorber. It holds broad application prospects in military applications, energy-saving building insulation, chemical catalysis, biological wastewater treatment, and energy. Carbon foam can be sorted into two kinds—one that lets heat pass through easily (thermally conductive) and another that stops heat from passing through (thermally insulating). The difference lies in how much the original carbon material has been turned into graphite. Mesophase pitch and phenolic resin are two typical carbonaceous precursors for producing high- and low-thermal-conductivity carbon foams, respectively. Currently, both thermosetting and thermoplastic phenolic resins are high-quality carbonaceous precursors for producing low-thermal-conductivity carbon foam. Using phenolic resin as the raw material, a phenolic resin foam can be produced by adding a blowing agent and a curing agent and foaming at normal pressure. Carbon foam is then produced by high-temperature carbonization. The compressive strength of this carbon foam is below 0.5 MPa, which restricts how it can be used.   When Phenolic Resin 2402 is used as the raw material, the pores of the carbon foam produced at different foaming pressures are all nearly spherical (Figure 6). Since no foaming agent is added, the foaming process follows a self-foaming mechanism, whereby the matrix material undergoes a cracking reaction at a certain temperature, generating corresponding small molecular gases. As gases form, they gather and grow into pores. The viscosity, structure, volume, shape, and gas production rate of the base material change as cracking gas is produced. This means the structure of pores in carbon foam depends on the base material's viscosity, gas production rate, volume, how quickly its viscosity changes, and outside pressure within the foaming temperature range. At foaming temperatures between 300 and 425°C, 2402 phenolic resin makes lots of cracking gas (Figure 3(a)) and has low viscosity (<2×104Pa·s, Figure 4(d)). Because of this, surface tension causes the pores to be round. When the foaming pressure is 1.0 MPa, the low outside pressure causes bubbles to merge and grow, leading to larger pore sizes (500-800 μm). Also, the larger pores mean the carbon foam has thinner connections and many pores are close to becoming open cells (Figure 6(a)).   When the foaming pressure goes up to 3.5 MPa, the pore size of the carbon foam goes down (300-500 μm), the connections get thicker, and the pore structure is more consistent (Figure 6(b)). If the foaming pressure keeps increasing to 5.0 MPa, the pore size keeps going down, but the consistency of the pore structure starts to get worse (Figure 6(c)). At a foaming pressure of 6.5 MPa, the pore structure of the carbon foam keeps getting worse, but the pore density goes up (Figure 6(d)).   When the foaming temperature goes above 425°C, the viscosity of the 2402 phenolic resin quickly goes up. The foaming pressure clearly has an important impact on how consistent the pore structure is and how dense the carbon foam is. If the foaming pressure is less than the pressure inside the bubble, the cracking gas produced later can still overcome the base material's viscosity and keep gathering and growing in the already formed bubble. This results in a fairly consistent pore structure in the bubble, but no new bubbles will form. But, if the foaming pressure is high enough, the cracking gas produced later can only form new, smaller bubbles at the connections of the already formed bubbles or in the base material, which makes the pore structure of the foamed carbon worse and increases the pore density.   Conclusion (1) The way thermoplastic phenolic resin (resin for refractory) foams is based on its own reaction. How well it foams depends on the conditions (pressure, temperature, and time). It's also influenced by how the molecules interact, considering their size, distribution, how they lose weight when heated, and how their viscosity changes with temperature. Viscosity and temperature are key. (2) When heated to 300-420°C, 2402 Phenoic formaldehyde resin breaks down fast, making a lot of gas. If the material's viscosity is below 2×104 Pa·s at this point, the resulting foamed carbon has good bubbles that are round and evenly spaced. (3) Lower pressures when foaming help make foamed carbon with consistent pores. Higher pressures stop the gas from clumping together and getting bigger, which causes more bubbles to form. This makes the pore structure uneven and increases how many bubbles there are.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com

Phenoic formaldehyde resin (PF) are a varied group of synthetic resins produced through the reaction of phenolic compounds and aldehydes. These resins were first noted in the 1870s, with Bayer creating the first synthesis. Later, through continued study, L.H. Baekeland, an American scientist, created a useful phenolic resin system in 1909. He then started the Bakelite Company, which began the industrial production of phenolic resins. These resins are now common in molding compounds, styling products, insulation, coatings, encapsulation materials, and refractory materials.     1.Synthesis of Phenolic Resins   Phenolic resins are made from a variety of raw materials, resulting in varying types and properties. Phenol-formaldehyde resin is the industrial resin people use most. It is created from phenol and formaldehyde using a two-step process involving addition and polycondensation. Depending on the specific material requirements, the reaction process and rate of the addition and polycondensation reactions can be controlled by varying the synthesis process conditions of phenolic resins to produce resins with varying molecular structures, viscosities, solids contents, and residual carbon content.   2. Classification of Phenolic Resins   The molecular structure of phenolic resins can be changed by controlling the synthesis settings. These settings affect the addition and polycondensation reactions. Based on these molecular structures, phenolic resins can be classified as thermoplastic phenolic resins and thermosetting phenolic resins. 2.1 Thermoplastic Phenolic Resin ( Novolac )   Thermoplastic Phenolic Resin (such as Phenolic Resin 2402) are linear phenolic resins characterized by their straight-chain molecular arrangement.They are primarily produced by reacting excess phenol (P) with formaldehyde (F) under acidic conditions. Thermoplastic Phenolic Resin are created through a two-stage reaction: first, an addition reaction, then a polycondensation reaction. Because the reaction takes place in an acidic environment, the addition mostly results in monomethylol groups forming at the ortho and para locations on the benzene ring (see Figure 2). The second stage, polycondensation, mainly involves the dehydration of the produced monomethylolphenol with the phenol monomer. Furthermore, under acidic conditions, the rate of the polycondensation reaction is much faster than the addition reaction. Furthermore, the presence of phenol in the reaction system is greater than that of formaldehyde. This causes the hydroxymethyl groups generated during the addition process to rapidly react with the excess phenol in the system to form linear macromolecules, resulting in the absence of active hydroxymethyl functional groups in the reaction product molecules. The structural formula is shown in Figure 4. 2.2 Thermosetting Phenolic Resin ( Resole )   Thermosetting phenolic resin (such as Phenolic resin for electronic materials) is a relatively reactive intermediate product synthesized by reacting for a certain period of time under the action of an alkaline catalyst and heat at a molar ratio of formaldehyde to phenol greater than 1. Therefore, if the synthesis process is not controlled, it can easily react violently, leading to gelation and even cross-linking reactions, ultimately forming insoluble and infusible macromolecules.   The synthesis process of thermosetting phenolic resin is also divided into two steps. The initial stage involves an addition reaction where hydroxymethyl groups are formed on the benzene ring, specifically at the ortho and para positions, leading to the creation of monomethylolphenol. Because the reaction activity of the active hydrogen atoms at the ortho and para positions on the benzene ring is much greater than that of the hydroxyl group on the hydroxymethyl group under alkaline conditions, the resulting hydroxymethyl group is not easily polycondensed.The active hydrogen atoms on the benzene ring can react with more hydroxymethyl groups, leading to the creation of dimethylol and trimethylolphenol. Figure 5 shows this addition reaction. Next, a polycondensation reaction occurs where the polymethylol groups react with active hydrogen atoms on the phenol monomer. This creates a methine bridge, or the hydroxymethyl groups dehydrate to form an ether bond. As this polycondensation keeps happening, it makes a branched resol phenolic resin.   The curing mechanism of thermosetting phenolic resins is quite complex. Currently, the most widely accepted theory is based on the active hydroxymethyl groups present in the molecular structure of thermosetting phenolic resins. During heating, these hydroxymethyl groups react in two ways: with active hydrogen atoms on the benzene ring to form methylene bonds, or with other hydroxymethyl groups to form ether bonds.   3.The Bonding Mechanism of Phenolic Resins as Binders   Four main ideas exist to explain how polymer adhesives stick things together: mechanical interlocking, diffusion, electronic attraction, and adsorption. For phenolic resin systems, mechanical interlocking is key.   The sticking process for phenolic resins occurs in two steps. At the start, the resin goes into all the small holes and uneven areas on the surface of what it's bonding to. For this to happen, the resin needs to be able to wet the surface well. Next, the phenolic resin hardens. During this process, molecules join together to form a network. This lets the resin molecules get stuck in the holes and uneven spots, creating a strong grip that holds the resin and the surface together tightly.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com