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Polyvinyl alcohol (PVA) is a widely used synthetic material. PVA ability to dissolve in water and break down naturally makes it a good choice for packaging films. The main production methods for PVA film are aqueous solution coating and melt blow molding. PVA is hard to shape with heat because it melts at a higher temperature than it decomposes. This is due to the strong links between its molecules and its crystal structure. Therefore, the most important factor in the processing of PVA film is the selection of appropriate additives.   1. Effect of Plasticizer Amount on Tensile Strength, Tear Strength, and Elongation at Break of Polyvinyl Alcohol Film As shown in Figure 1, film ability to resist breaking lessens as more plasticizer is added. This suggests that plasticizers reduce how strong the film is. The plasticizer gel theory explains that when the plasticizer mixes with the resin, it loosens the points where the resin molecules connect. These connections have different strengths. The plasticizer pulls them apart and hides the forces that hold the polymer together. This reduces the secondary forces between the polymer macromolecules, increases the flexibility of the macromolecular chains, and accelerates the relaxation process. Tensile strength goes down as you add more plasticizer. As the amount of plasticizer is increased, the film becomes more flexible and stretches further before breaking. This suggests that plasticizers make the film more pliable. Plasticizers achieve this by weakening the attraction between the large molecules in the polymer. This increased flexibility and longer relaxation period lead to the film ability to stretch further. The data indicates that as more plasticizer is added, the film becomes easier to tear. This likely happens as the plasticizer reduces the film's surface energy and lessens the energy needed for both plastic flow and lasting deformation. These factors, in turn, contribute to the film's reduced resistance to tearing.   2. Effect of Crosslinker Amount on the Tensile Strength, Elongation at Break, and Tear Strength of PVA Film As shown in Figure 3, the film's tensile strength goes up gradually as the amount of crosslinker is increased, during which the elongation at break goes down gradually. When a certain point is reached, the film's tensile strength goes down gradually, while the elongation at break goes up gradually. At first, as more crosslinker is added, the number of working polymer chains goes up, intermolecular forces get stronger, and the polymer chains become less flexible. The ability of the large molecular chains to change shape and rearrange decreases while the chain relaxation is difficult. So, the tensile strength goes up, while the elongation at break goes down. Continuing the use of crosslinkers causes degradation and branching to increase gradually, which decreases the number of working polymer chains, and increases the flexibility of the polymer chains. The ability of the large molecular chains to change shape and rearrange increases, while the chain relaxation becomes easier. As a result, the tensile strength starts to go down again, while the elongation at break goes back up. As shown in Figure 4, the tear strength of the film changes with the amount of crosslinker. At first, it goes up, but then it starts to go down. This happens because when crosslinking starts, more crosslinker helps the polymer network form. This makes the film's surface energy go up gradually. It then needs more energy to spread plastic flow and irreversible viscoelastic processes. Because of this, the film's tear strength gets better as crosslinking happens. But, if there is too much crosslinker with too much polymer broken down, and there are more branching reactions, the tear strength gets worse.   3. Conclusions When you add more plasticizer, PVA film becomes less strong but stretches and tears more easily. When you add more crosslinker, film strength and resistance to tearing improve at first, but then weaken, while its ability to stretch keeps getting better.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com

Polyvinyl alcohol (PVA) is a fundamental raw material for vinylon production and is also used in the production of adhesives, emulsifiers, and other products. In the PVA production process, solution polymerization is used to ensure a narrow degree of polymerization distribution, low branching, and good crystallinity. The VAM polymerization rate is strictly controlled at approximately 60%. Due to the control of the polymerization rate during the VAM polymerization process, approximately 40% of the Vinyl Acetate Monomer (VAM) remains unpolymerized and requires separation, recovery, and reuse. Therefore, research on VAM recovery process is a crucial component of the PVA production process. There is a polymer-monomer relationship between Ethylene Vinyl Acetate (EVA) and vinyl acetate monomer (VAM). Vinyl acetate monomer is one of the basic raw materials for making ethylene vinyl acetate polymer.   This paper uses the chemical simulation software Aspen Plus to simulate and optimize the VAM recovery process. We studied how process settings in the first, second, and third polymerization towers affect the production unit. We found the best settings to save water used for extraction and lower energy consumption. These parameters provide an important theoretical basis for the design and operation of VAM recovery.   1 Vinyl Acetate Monomer Recovery Process 1.1 Simulation Process This process includes the first, second, and third polymerization towers in the vinyl acetate monomer recovery process. The detailed flow diagram is shown in Figure 1.   1.2 Thermodynamic Model and Module Selection The vinyl acetate monomer recovery unit of the polyvinyl alcohol plant primarily processes a polar system consisting of vinyl acetate, methanol, water, methyl acetate, acetone, and acetaldehyde, with liquid-liquid separation between vinyl acetate and water. The main equipment in the vinyl acetate monomer recovery unit of the polyvinyl alcohol plant was simulated using Aspen Plus software. The RadFrac module was employed for the distillation tower, and the Decanter module for the phase separator.   2 Simulation Results We ran a process simulation on the vinyl acetate monomer recovery unit in the polyvinyl alcohol plant. Table 3 shows a comparison of the simulation results and actual values for the main logistics. As shown in Table 3, the simulation results are in good agreement with the actual values, so this model can be used to further optimize the process parameters and process flow.     3 Process Parameter Optimization 3.1 Determination of the Amount of Stripping Methanol Polymerization Tower 1 takes out vinyl acetate monomer (VAM) from the stream that remains after polymerization. It uses methanol vapor at the bottom for heat. The right amount of methanol is important for how well the tower works. This study looks at how different amounts of methanol affect the mass fraction of PVA at the tower's bottom and the mass fraction of VAM at the top, assuming the feed stays the same and the tower's design is constant.   As shown in Figure 2, when the heat capacity needed for separation in Polymerization Tower 1 is satisfied, raising the stripping methanol amount lowers the PVA mass fraction at the bottom and the VAM mass fraction at the top. The stripping methanol amount has a linear relationship with the PVA mass fraction at the bottom and the VAM mass fraction at the top.   3.2 Optimization of the Feed Position in Polymerization Tower 2 In Polymerization Tower 2, an extractive distillation tower, the locations where the solvent and feed enter greatly affect how well the separation works. This column uses extractive distillation. Based on the physical properties of the extractant and the mixed feed, the extractant should be added from the top of the column. Figure 3 shows how the mixture feed position affects the methanol mass fraction at the top and the reboiler load at the bottom, keeping other simulation settings the same.   3.3 Optimizing the Extraction Water Amount in Polymerization Column 2 In Polymerization Column 2, extractive distillation is used to separate vinyl acetate and methanol azeotrope. By adding water to the top of the column, the azeotrope is disrupted, allowing for the separation of the two substances. The extract water flow rate has a big impact on how well Polymerization Column 2 separates these materials. With consistent simulation settings, I looked at how the amount of extract water affected the methanol mass fraction at the top and the reboiler load at the bottom of the column. The results are shown in Figure 4.   3.4 Optimizing the Reflux Ratio in Polymerization Column 3 In Polymerization Column 3, the reflux ratio is important for separating vinyl acetate from lighter substances like methyl acetate and trace water. This boosts the quality of vinyl acetate obtained from the side stream. We kept the simulation settings constant and studied how the reflux ratio affects both the mass fraction of vinyl acetate from the side stream and the reboiler load. The calculation results are shown in Figure 6. Maintaining the polymerization tower's reflux ratio around 4 helps ensure the vinyl acetate from the side line meets quality standards and keeps the reboiler load low.     4. Conclusion (1) Using AspenPlus software, a suitable thermodynamic model is selected to simulate the entire process of vinyl acetate monomer recovery of the polyvinyl alcohol plant. The simulation results are in good agreement with the actual values and can be used to guide the process design and production optimization of the plant. (2) Based on the establishment of a correct process simulation, the influence of the process parameters of the polymerization tower 1, polymerization tower 2, and polymerization tower 3 on the plant is investigated, and the optimal process parameters are determined. When vinyl acetate meets the needed separation standards, we can save on extraction water and lower energy use.   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

VAE emulsions are environmentally friendly products. Vinyl groups are embedded in the polyvinyl acetate molecular chain, giving the polymer emulsion a low film-forming temperature and excellent film-forming properties. They exhibit strong adhesion to difficult-to-adhere materials such as PET, PVC, PE, and PP. The polymer film produced is very water and weather resistant. It also holds up well to scrubbing and remains flexible even at low temperatures. The thickness of VAE emulsions is impacted by a number of things.    1. Effect of Solids Content on Viscosity We conducted extensive testing on the formulations and process conditions of VAE Emulsion DA-180L and VINNAPAS 400, respectively. The data in the following tables are derived from these tests. The relationship between solids content and viscosity is shown in Table 1. As shown in Table 1, higher solids content increases viscosity. This is because higher solids content increases the number of colloidal particles in the same emulsion mass, reduces the amount of aqueous phase, and increases the total surface area of the particles. This enhances interparticle interactions and resistance to motion, resulting in higher viscosity.   2. Effect of Protective Colloids on Viscosity In emulsion polymerization, protective colloids are often used as emulsion stabilizers to improve emulsifier stability and adjust viscosity. The emulsion stability of partially hydrolyzed PVA is also related to the distribution of acetyl groups on the polymer chain. A higher degree of blockiness in the acetyl group distribution results in greater surface activity, better emulsion stability, and smaller and more viscous emulsions. The higher the PVA degree of polymerization, the higher the viscosity of the polyvinyl alcohol aqueous solution before polymerization, and the higher the viscosity of the VAE. The higher the degree of alcoholysis of PVA, the lower the viscosity of the VAE. PVA's protective colloid ability increases with increasing degree of polymerization. Low-degree PVA forms coarser latex particles and has lower viscosity. An increase in the degree of polymerization improves both the protective and dispersing capabilities. To maintain the dispersion and protective properties of PVA during emulsion polymerization, while only adjusting the viscosity, the total amount of PVA is typically kept constant, with only the ratio between the two adjusted. With other conditions remaining unchanged, adding 4.54 kg of PVA Polyvinyl Alcohol 088-20 will increase the viscosity of each batch by 100 mPa·s. Table 2 lists the molecular weight and molecular weight distribution of high- and low-viscosity VAE emulsions. Table 2 shows that the low-viscosity emulsion has a higher molecular weight, coarser particles, and a wider particle size distribution than the high-viscosity emulsion, resulting in lower viscosity.   3. Effect of Initial Initiator on Viscosity The initiator has a main influence on the speed of polymerization. The more initiator is used, the faster the polymerization reaction is, and the reaction is difficult to control. After the polymerization conditions and the type of initiator are determined, the amount of initiator can be used to adjust the molecular weight of the polymer. The more initiator is used, the smaller the molecular weight of the polymer is, and the viscosity of the emulsion increases, and vice versa. Among them, the amount of initial initiator (ICAT) added has the greatest impact. These data clearly show that the more initial initiator is added, the higher the viscosity of the emulsion. This is because the more initial initiator is added, the more difficult the monomer is to react or the reaction rate is slow in the initial stage, and the resulting polymer has a smaller molecular weight, smaller particle size, and higher viscosity.   4. Conclusions (1) The higher the solid content of the emulsion, the greater the viscosity. (2) The higher the degree of polymerization of the protective colloid PVA, the greater the viscosity of the emulsion, and vice versa. (3) The viscosity of the emulsion when PVA is used as a protective colloid is higher than that when cellulose or surfactant is used as a protective colloid. (4) With the same degree of polymerization, the higher the degree of alcoholysis, the lower the viscosity of the emulsion. (5) The more initial initiator and total amount of initiator added, the higher the viscosity of the emulsion.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com

VAE emulsion are water-based and good for the environment. They're used a lot as binders in strong glues. As the tech gets better and the emulsion market grows, people want more VAE emulsions, mainly those with a lot of ethylene. These high-ethylene VAE emulsions are great at resisting water and alkali, so they're becoming more popular. How much ethylene is in VAE emulsions depends on things like pressure, temperature, time, how much initiator is used, the type and amount of emulsifier, and how the VAE is added. Lately, the market wants VAE emulsions that bind water really well. This paper looks at how the amount of ethylene in VAE emulsions affects them. We used different molecular weights of polyvinyl alcohols (PVA Polyvinyl Alcohol 088-20 and PVA Polyvinyl Alcohol 0588) as protective colloids, and a special PVA was used as part of the protective colloid to see how these colloids change the VAE emulsion properties.   1.Effect of Emulsifier Content on Emulsion Properties In emulsion polymerization systems, the type and concentration of the emulsifier, as well as various factors that may influence the emulsification effect of the emulsifier, directly affect the stability of the polymerization reaction and, ultimately, the properties of the emulsion. As seen in Table 3 and Figure 2, a rise in emulsifier content leads to a higher conversion rate but a lower gel fraction. If the emulsifier surpasses 4%, the conversion rate drops, suggesting the substance is not chemically stable. Therefore, the optimal emulsifier content for this experiment is 4%.   2. Effect of Initiator Content on Molecular Weight and Emulsion Viscosity The initiator is the most important component in the entire VAE emulsion formulation. It decomposes and releases free radicals, which are the basis for emulsion polymerization. Figure 3 shows that with increasing initiator content, both molecular weight and viscosity show an upward trend, with the optimal initiator dosage being 2.5%.   3. Effect of Reaction Temperature on Emulsion Reaction Table 4 shows that with increasing reaction temperature, the reaction rate accelerates, the residual monomer content decreases, and the amount of aggregates increases. Raising the reaction temperature speeds up how fast the initiator breaks down, making more free radicals and boosting the number of spots where reactions can happen. At the same time, a higher temperature makes latex particles move around more randomly, which means they bump into each other and join together more often. Because of these things, the emulsion becomes less stable and might even turn into a gel or separate. Therefore, the initial reaction temperature is determined to be 65°C, and the later reaction temperature is 70°C to 85°C.   4. Effect of Polymerization Reaction Pressure on Ethylene Content, Solids Content, and Viscosity Figure 4 shows that increasing the reaction pressure within a certain range gradually increases the ethylene content of the VAE emulsion and decreases the glass transition temperature of the product. At a reaction pressure of 7.5 MPa, the ethylene content reaches 21%, and the glass transition temperature lowers to -4°C. As shown in Figure 5, under the best reaction conditions, the solid content goes up as the polymerization pressure increases, but the change is small, staying within (56 ± 0.5)%. The emulsion viscosity first goes up and then down as the polymerization pressure increases, peaking at 3200 mP·s at a polymerization pressure of 6 MPa before going down. This indicates that a certain pressure can facilitate polymerization and increase the emulsion viscosity.   5. Effect of Modified PVA as a Protective Colloid on VAE Emulsion Properties To increase how well VAE emulsions resist water, a PVA, changed to include water-repelling groups, was used to take the place of some of the PVA1788 protective colloid. Table 5 shows how varying amounts of the modified PVA (from 10% to 50% of the total protective colloid) change the VAE emulsions' stability, thickness, and water resistance. The data in Table 5 shows that as the amount of modified PVA goes up, the emulsion stays stable without separating, suggesting the modified PVA doesn't really impact the system's stability. Based on Figure 6, the emulsion gets thicker as the modified PVA content rises, peaking at 4000 mPa·s when the modified PVA makes up 5% of the mixture.   6. VAE Emulsions with Different Ethylene Contents and Properties We made different VAE emulsions by testing how different reaction conditions change the emulsion's properties. These emulsions had different amounts of ethylene, glass transition temperatures, and leftover VAc.   We found that starting the reaction at 65°C works best. The temperature can then be adjusted to between 70°C and 85°C. A 4% emulsifier content and a 2.5% initiator dosage also produce the best results. By controlling the reaction pressure, we were able to create VAE emulsions with ethylene contents from 9% to 23%. By replacing part of the protective colloid with hydrophobic-modified PVA, the water resistance of the emulsions was significantly improved.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com

Chloroprene rubber adhesive is the largest and most widely used variety among rubber adhesives. It can be sorted into a few groups, like resin modified, filler, grafted, and latex types. Grafted chloroprene rubber adhesive, which is made mostly of chloroprene rubber and a grafted modifier, is known as easy to their usage, strong bonds, high initial adhesion, and many uses. As early as the 1950s, the shoemaking industry began to use chloroprene rubber adhesive. As shoemaking materials and styles change, standard chloroprene rubber adhesive may not be strong enough. This can cause the upper and sole of shoes, or composite soles, to separate. This issue harms shoe quality and limits growth in the adhesive shoe business. To solve this problem, we used a variety of graftable chloroprene rubbers at home and abroad as graft bodies and used MMA to study their grafting modification.   1 Grafting mechanism     2 Experimental part   2.1 Raw materials and polymerization formula   2.2 Polymerization Procedure Add CR to the solvent. Heat the solution to 50 °C and stir until the CR is completely dissolved. Raise the temperature to 80°C, and slowly add the MMA solution that contains BPO while stirring. Maintain the temperature and continue stirring until the viscosity reaches a suitable level (about 40 minutes). Immediately add hydroquinone to stop the reaction. Keep warm for 4 to 6 hours. After the reaction is complete, cool down to 40°C; add thickening resin, vulcanizing agent, antioxidant and filler, and finally keep warm for 2 to 3 hours, cool down to room temperature, and obtain the product. A small amount of toluene can be added to adjust the viscosity. The obtained graft copolymer (CR-MMA) is a brown-yellow transparent viscous liquid. The viscosity measures between 1000 and 1500 mPa·s. Solid content ranges from 15% to 25%, and the strength registers at 34 N/cm².   2.3 Product analysis 2.3.1 Determination of adhesive viscosity The viscosity value (mPa·s) was tested in a 25℃ constant temperature water bath using a rotary viscometer (Shanghai Optical Factory, NDI-1 type). 2.3.2 Determination of adhesive solid content The film after vacuum drying and constant weight of the adhesive was wrapped with filter paper and placed in a fat extractor. It was extracted with acetone in a 65℃ constant temperature water bath for 48 hours (to remove PMMA homopolymer in copolymerization). The solid content (W%) was calculated according to the following formula: W %=W2 / W1×100% Wherein, W1 is the mass of the grafted adhesive, and W2 is the mass of the film after vacuum drying and constant weight. 2.3.3 Determination of peel strength of artificial leather/artificial leather (PVC/PVC) bonded by adhesive The soft PVC sheet was wiped with acetone or butanone to remove the oil stains on the surface. The entire process was in accordance with GB7126-86.   3 Results and discussion   3.1 Solvent selection The solvent used in chloroprene rubber adhesive is very important. It affects the solubility of chloroprene rubber, the initial viscosity of the adhesive, stability, permeability to the adherend, bonding strength, flammability and toxicity, etc. Therefore, the selection of solvents should take into account many factors. Commonly used solvents include toluene, ethyl acetate, butanone, acetone, n-hexane, cyclohexane, solvent gasoline, etc. The test confirmed that when the solvent cannot dissolve chloroprene rubber alone, two or three solvents can be mixed in appropriate proportions to have good solubility, viscosity and low toxicity.     3.2 Effect of CR type and concentration on the performance of grafted products Different types of chloroprene rubber (CR) show differences in how quickly they form crystals and how deep their colors are. These factors can change how well the grafted materials initially stick together and how they look. Tests show that using Denka A120 Chloroprene rubber and Chloroprene Rubber SN-244X to graft chloroprene rubber results in good initial adhesion and color. The amount of CR does not change peel strength much, but it does affect how well copolymerization works. When the CR concentration is too high, that is, the viscosity is high, MMA is difficult to diffuse and has a strong tendency to self-polymerize. Maintaining the appropriate CR concentration is necessary; if it's too low, the MMA volume will be too small, which slows down the grafting copolymerization. CR concentration works best between 11% and 12%.   3.3 Effect of reaction time on the performance of grafted products Generally speaking, the longer the reaction time, the higher the grafting rate and viscosity value. At the beginning, the initial and final adhesion strengths increase with the extension of reaction time and the increase of viscosity. Extended reaction times coupled with high viscosity can actually reduce both initial and final adhesion. Experiments suggest reaction times should ideally fall between 3.0 and 5.0 hours.   3.4 Effect of reaction temperature on grafting reaction When the reaction temperature is lower than 70℃, the reaction is slow, which is due to the slow decomposition of BPO. Because BPO decomposes quickly above 90℃, leading to a rapid increase in viscosity and poorer processing, we set the reaction temperature between 80°C and 90℃.   4 Conclusion Our initial tests included scaled-up experiments and pilot production runs, which successfully yielded acceptable products. They were supplied to many leather shoe factories and achieved satisfactory results. The quality met the various standards required for shoemaking. CR-MMA grafted adhesive shows better peel strength on PVC artificial leather compared to regular CR adhesive used for boots.The addition of a small quantity of isocyanate (5-10%) can serve as a temporary curing agent. The -NCO group in the isocyanate then reacts with active hydrogen in the rubber, creating an amide bond. This reaction strengthens the rubber's internal structure, improving the overall bond strength.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com

Chloroprene rubber (CR) is a synthetic rubber obtained by polymerization of chloroprene. It is widely used because of its excellent aging resistance, oil resistance, corrosion resistance and other properties. Polychloroprene Rubber CR2442 vulcanized rubber has good physical properties and can be used in many occasions (Such as chloroprene rubber adhesive). However, since the process of CR2442 in internal mixing, open mixing and vulcanization is not easy to master, the physical properties of the prepared vulcanized rubber are sometimes poor, which affects its production and application.   1. The influence of process parameters on the preparation of mixed rubber and vulcanized rubber 1.1 Internal mixer mixing process CR2442 has high requirements for the mixing process. When preparing CR2442 mixed rubber, the initial temperature, mixing time and rotor speed of the internal mixer have a great influence on the discharge temperature. The discharge temperature is an important parameter for measuring the mixing process. The optimal discharge temperature of CR2442 is 110℃. The order of adding various materials during the mixing process is also important. The correct way to add materials to CR2442 during the mixing process is: add CR2442 and small materials at the same time → add carbon black → add white carbon black and operating oil in sequence.   1.2 Mixing process of open mill After the mixed rubber prepared by the internal mixer is cooled, the vulcanization system is added on the open mill. The vulcanization system includes vulcanizing agent and accelerator. The correct way to add is to add accelerator first and then vulcanizing agent. When adding the vulcanization system to the mixed rubber on the open mill, it is generally required that there is accumulated rubber on the roller. With the shearing and extrusion of the open mill, the roller temperature will increase significantly. When the temperature of the rubber is too high, the rubber should be cut, pulled out and cooled, and then the rubber should be mixed after it is completely cooled.   1.3 Vulcanization process After adding the vulcanization system on the open mill, the rubber is cooled and placed for 16~24h before vulcanization. Since the CR2442 mixed rubber is easy to crystallize at low temperatures, it is generally necessary to perform indirect heating treatment in an oven. The vulcanization time of CR2442 was set to 30, 40, 50, 60, 70 and 80 minutes respectively. After many tests, it was found that the tensile strength and elongation at break of the vulcanized rubber were the largest when the vulcanization time was 60 minutes. Therefore, the optimal vulcanization time of CR2442 was determined to be 60 minutes.   1.4 Bonding operation In the process of bonding the mixed rubber and brass, the rubber is first cut into sheets with the same length and width as the mold. After the mold is preheated, the cut film is placed in the mold cavity. Since the mold is heated, placing it too slowly will cause early vulcanization of the rubber, reduce the fluidity of the rubber, make the bonding insufficient, and then reduce the bonding force. Therefore, the scorch time should be controlled to be much longer than the placement time of the film.   2. Influence of vulcanization system, reinforcement system and bonding system Vulcanization system: When CR2442 uses only zinc oxide and magnesium oxide for vulcanization, the resulting rubber's physical properties are worse compared to when zinc oxide, magnesium oxide, sulfur, and accelerator DM are used as a system. Reinforcement system: The reinforcement system of CR2442 is often based on carbon black and supplemented by white carbon black. Bonding system: Rubber as a single material can no longer meet the needs of society, and it is often necessary to bond rubber to metal to expand its scope of use. CR2442 is usually bonded to metal using a resorcinol-methylene-white carbon black-cobalt salt bonding system.   3. Conclusion When mixing, it's important to think about temperature, how long you mix, and how fast the rotor spins. Also, when you add the vulcanization system using the open mill, pay attention to the order you add things. The heat from the rollers can really change things.For vulcanization and bonding, if you make sure the scorch time is longer than it takes to place the sample, you can get better quality vulcanized rubber and better bonding with other types of materials. The CR2442 discharge temperature matters too. It's a good idea to add white carbon black as a reinforcement in CR2442. This helps control how fast vulcanization and bonding happen.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com

Chloroprene rubber (CR)  is one of the commonly used rubber varieties. The strength of vulcanized rubber without carbon black reinforcement can reach 28MPa, and the relative elongation is about 800%. It has the characteristics of oil resistance, flame resistance, oxidation resistance and ozone resistance. It is soluble in benzene and chloroform. It swells slightly but does not dissolve in mineral oil and vegetable oil. 1. Progress in CR Technology Abroad Monomer Production DuPont in the U.S. came up with a liquid method to make chloroprene from butadiene. This is safer than the gas method that was first used. It can produce higher yield products at a lower cost, improve safety, and reduce maintenance costs. In 1992, the company upgraded its monomer production line, moving from a single-loop control system to a computerized distributed control system.  Post-processing technology Recent progress in CR post-processing tech is apparent in the developments related to spiral extrusion dehydration and drying. Chloroprene latex and coagulant go into a screw extruder that has a specific design. The coagulated latex removes most of the water in the dehydration section of the extruder by the back pressure. The success of this process has created conditions for the industrial production of CR and asphalt and CR and short fibers, thereby increasing the operational flexibility and being able to handle CR varieties with poor freezing film-forming and tape-forming properties. In 1992, DuPont launched a series of elastomer masterbatches including CR with Kevlar (polyarylamide) short fibers as reinforcement materials, proving that this process has begun to be used in the production of blended products. Development of new varieties There are hundreds of foreign brands. Companies in the United States and Japan have developed many high-performance special CR based on a series of mature brands. In order to improve the thermal stability of CR, Bayer has developed copolymers of chloroprene (CD) with carboxylic acid amide, carboxylic acid anhydride and (or) carboxylic acid monomers. These new CR also have better spraying and brushing characteristics. Denka Corporation of Japan has also improved traditional products and launched a new generation of CR (Denka chloroprene rubber). For example, the DCR 20 series. Tosoh Corporation of Japan is also developing special shock-absorbing CR, and has produced CR latexes with high softening temperature, good normal temperature and high temperature adhesive properties, high water resistance and stability (SKYPRENE Chloroprene Rubber).     2. Progress in domestic CR technology In 1958, Changshou Chemical Plant in Sichuan, my country built a device for producing CR by acetylene. The main CR production in China does not control the conversion rate, and many places use manual operations, which is basically a workshop-style production status. Besides the earlier producers of CR glue like Chongqing Changshou Chemical Co., Ltd., Shanxi Synthetic Rubber Company, Jiangsu Lianshui Chemical General Plant, and Tianjin Donghai Adhesives Company, Shandong Laizhou Kangbaili Glue Industry Co., Ltd. developed in October 2003 a new CR glue. They carefully chose and mixed the composite solvent.    3. Suggestions for the development of domestic CR industry Strengthen technology development For domestic carbon black firms, boosting investment in science and tech, along with adopting and assimilating advanced foreign tech, is key. These actions should lower consumption and costs, and it should raise acetylene use from 57% to over 70% quickly. Strengthen the development of new varieties To maintain the Mooney viscosity in current products, we will create new types. The focus will be on making functional latex, like carboxyl and copolymer latex. Our goal is to bring high Mooney, non-sulfur regulated WHV to industrial production. Increase market share In the next few years, the market of CR in my country will be saturated, and relevant manufacturers can consider developing overseas markets. At present, the development trend of CR in the world is that the European and American markets are shrinking, while China, Eastern Europe, Russia and Southeast Asia are in the rising stage. CR can not only contend with imported goods locally, but can also progressively expand sales to North America, Eastern Europe, Russia, East Asia, and Southeast Asia.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com  

Chloroprene adhesive is popular in the shoemaking industry because it bonds materials very well. Among them, grafted chloroprene adhesive is the most widely used. As shoe materials develop towards lighter colors, the color requirements for adhesives are becoming more and more stringent. Right now, SN24 adhesive starts out light, but it yellows pretty fast after sitting around for a while, especially if it's in the sun. After being prepared into chloroprene adhesive, there is a yellowing problem, which leads to two problems: first, it affects the appearance of shoes. For light-colored shoes such as sports shoes and travel shoes, the problem is more prominent; second, the darkening of color is a manifestation of polymer aging, which leads to the deterioration of the bonding performance of the adhesive. Therefore, in order to improve the appearance of footwear and ensure that it does not turn yellow during wearing, a yellowing-resistant adhesive should be used.   1. Experimental materials Chloroprene rubber latex: Chloroprene Rubber SN-242, Sana Synthetic Rubber Co., Ltd.; toluene, methyl methacrylate, butanone, BPO, SKYPRENE G-40S; Denka A90 Chloroprene rubber   2. Performance test results 2.1 Comparison of glue solutions The different types of dry glue obtained by the drum were dissolved in toluene to obtain the glue solution comparison chart in Figure 1, and the comparison chart of different types of glue solutions after heating is shown in Figure 2.   As can be seen from Figure 1, the color of the glue solution in this experiment is not much different from the color of the same type of glue solution at home and abroad. After adding BPO and MMA and shaking well, the color will change.After being tested, SN242A became yellow. Domestic rubber samples No. 2 and No. 3 also turned yellow. The other samples got a bit darker, but our test rubber was still lighter than domestic rubber No. 4. Its color was close to that of samples No. 7 and No. 8.After 20 minutes in a 90℃ oven, rubber samples No. 1, 2, 3, and 5 turned yellow. Samples No. 4, 6, 7, and 8 got lighter. After an hour, the colors changed in the same way, but everything was darker than it was at 20 minutes.As you can see in Figures 1 and 2, when this test rubber was dissolved in toluene and heated with an initiator, it looked a little whiter than similar domestic glues. It looked about the same as similar foreign glues.   2.2 Grafting comparison According to the grafting formula, 0.1 parts of BPO and 50 parts of methyl methacrylate were added, and different types of chloroprene rubber were grafted. The viscosity of the solution before and after grafting was measured, as shown in Table 4. The comparison between the experimental glue and the domestic glue after grafting is shown in Figure 3.     Figure 3 presents a comparison between our experimental glue and a domestic glue following grafting.When exposed to free radicals, the unsaturated double bonds on the chloroprene rubber backbone transform the MMA monomer into a monomer free radical. This then grafts and copolymerizes with CR through a chain transfer reaction, creating a complex graft copolymer. This process leads to asymmetry and polarity in the adhesive structure, improving adhesion.   Based on the data in Table 5, our experimental glue shows a high grafting rate, nearly 100%. This solves the issue of low grafting rates seen with SN242, which stem from residual terminators. Plus, it eliminates the problem of red glue forming during the grafting process. Figure 3 is a comparison chart of the grafted glue solution after being placed in the sun for several days. The color of the experimental glue solution is much lighter than that of SN242.   2.3 GPC comparison According to Figure 4 and Table 5, the relative molecular weight and relative molecular weight distribution of the experimental glue are not much different from those of foreign glue. The average relative molecular weight is around 350,000, and the relative molecular weight distribution is below 2.3, which is larger than the relative molecular weight of domestic grafted glue, and the relative molecular weight distribution is narrow, and the regularity of the molecular chain is higher.     2.4 DSC comparison Based on the data in Figure 5 and Table 5, the experimental glue's glass transition temperature is similar to both domestic and foreign glues. The experimental glue's crystallization temperature, which is higher than the domestic glue, is nearly the same as the foreign glue.       3 Conclusion The chloroprene rubber adhesive developed in this paper has excellent yellowing resistance and stable grafting performance. Through DSC and GPC analysis, grafted chloroprene rubber with uniform relative molecular weight and high regularity was obtained, and its performance is comparable to that of the same type of foreign rubber.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com

Chloroprene rubber (CR) is an important variety of synthetic rubber. It stands up well to light, aging, flexing, acids, bases, ozone, flames, heat, and oil. It also has good physical and electrical properties. Its comprehensive performance is unmatched by natural rubber and other synthetic rubbers. It is widely used in defense, transportation, construction, light industry and military industry. Chloroprene rubber has several uses. It's a key element in making auto parts, machinery, industrial items, and adhesives. You'll also find it in construction materials, coated fabrics, and wire and cable insulation. By itself, chloroprene rubber is used to create rubber harness clips and shock absorbers for cars and farm equipment. Initially, chloroprene rubber from Japan's DENKA and Japan's Toyo Soda was used. Later, due to the increase in raw material prices and the restrictions of the procurement cycle, a series of research and development work on the replacement of imported chloroprene rubber with domestic chloroprene rubber was carried out. Finally, the replacement goal was successfully achieved, and some process and formula problems of domestic chloroprene rubber in the use process were solved.   1. Neoprene rubber model Imported neoprene rubber model: Denka M120 Chloroprene Rubber, a product of Japan DENKA, light-colored blocks; B-10, a product of Japan Toyo Soda, light-colored blocks. Domestic neoprene rubber model: CR3221, a product of Chongqing Changshou Chemical Co., Ltd. Polychloroprene Rubber CR3221 is a chloroprene polymer with sulfur and diisopropyl xanthate disulfide as mixed regulators, with a low crystallization rate, a relative density of 1.23, beige or brown blocks, and a non-polluting type.   2. Production process performance comparison Imported neoprene handles better during production. For example, the raw rubber pieces do not stick together, even after baking, which makes them easy to measure. The process is smooth; it does not stick to the roller, so removing it is simple. The semi-finished film is stiff and holds its shape well. Domestic neoprene does not perform as well. The rubber pieces tend to stick, especially after baking. The rubber also sticks to the roller, which makes removal hard, and the semi-finished film sticks easily and loses its shape. Despite these things, domestic neoprene has some benefits. It mixes powder faster and with less effort in both internal and open mixers. Rubber from Japan is harder to mix. In the open mixer, M-120 can even fall off the roller at first. The internal mixer requires more effort and time, especially in the winter. Domestic mixed rubber still works well after being stored for a long time. Rubber from Japan, especially M-120, gets hard and loses its flexibility after two to four weeks. Tests show that production methods that work for imported neoprene do not work well for domestic neoprene. The original method needs some changes. If not, it will be hard to make it work for production, even when the physical and mechanical qualities meet the standards.   3.  Conclusion Compared with Japanese chloroprene rubber, domestic chloroprene rubber CR3221 has lower Mooney viscosity and greater viscosity, which is more favorable for mixing and powder consumption, and can significantly reduce the operation time, but the processability is poor and the operation is difficult. If the temperature is not well controlled, the operation is improper or the rubber is over-mixed, it may cause the roller to stick or even fail to unload normally. By selecting the correct process conditions and methods and adjusting the formula appropriately, it can fully meet the production needs.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com

Chloroprene rubber (CR), a synthetic material, is a common choice for making timing belts because of its good physical and chemical traits. Neoprene timing belts resist aging well and work best in regular transmission systems, but some situations might need different materials. 1. Aging resistance of chloroprene rubber timing belts Neoprene resists oxidation well, helping timing belts stay flexible and strong during regular use. This prevents the material from getting fragile or breaking down due to oxidation, making it good for machines exposed to air for extended periods, as it reduces the possibility of cracks or surface hardening. Heat resistance: The operating temperature range is generally between -20°C and 100°C, and it can operate for a long time in a medium-high temperature environment; under high temperature conditions, although its performance will decrease slightly, the aging process can be delayed by adding heat-resistant agents. Anti-ultraviolet performance: Neoprene has moderate anti-ultraviolet ability, but the surface may oxidize under long-term exposure to strong light, resulting in color changes and the formation of tiny cracks. Moisture resistance: Neoprene has good resistance to moisture and is suitable for high humidity environments. It is not easy to deteriorate due to moisture intrusion. Chemical corrosion resistance(Chloroprene Rubber SN-236T): It has good corrosion resistance to grease, weak acid, alkali and some chemical solvents, which slows down the aging rate, but is not suitable for contact with strong oxidizing chemicals.   2. Applicable scenarios of chloroprene rubber timing belts Industrial transmission equipment(Chloroprene Rubber SN-244X): Applicable to power transmission of conventional mechanical equipment, such as textile machinery, packaging equipment and general processing equipment. Medium temperature environment: It performs well in medium and high temperature (below 100°C) application scenarios, such as industrial drying equipment or HVAC systems. Indoor environment: Equipment with low requirements for UV resistance, such as indoor automation equipment or low maintenance systems. Medium humidity and chemical environment: It can be applied to equipment that contacts oils and weak acid and alkali environments, such as food processing machinery and light chemical equipment.   3. Limitations of aging resistance of chloroprene rubber timing belt Prolonged exposure to temperatures above 100°C can speed up the aging process, leading to reduced flexibility or hardening of the timing belt. When working in such conditions, fluororubber or silicone rubber belts are the preferred choice. Extended exposure to strong sunlight can cause surface oxidation and cracking, which reduces the lifespan of the belt. Polyurethane belts or those with anti-UV coatings are advisable for outdoor setups. Strong acids, bases, or concentrated chemical solvents can cause corrosion if the material isn't resistant enough.   4. Methods to extend the aging resistance of chloroprene rubber timing belts Reasonable storage: Store in a dry, ventilated, light-proof environment to avoid ultraviolet radiation and high temperature. Regular inspection: Regularly check whether there are cracks or hardening on the surface of the timing belt during use, and remove oil and chemical residues in time. Adding antioxidants: By adding antioxidants or anti-ultraviolet ingredients during the manufacturing process, the aging resistance of the timing belt can be significantly improved. Optimize working conditions: Avoid running the synchronous belt under excessive tension or extreme temperature to reduce the risk of aging.   Chloroprene rubber synchronous belts resist oxidation, heat, and moisture well, so they age slowly and work for many standard jobs. Still, they might not work as well when it's very hot, there's a lot of ultraviolet light, or things are very corrosive. You can make these belts last longer by storing and using them properly and keeping up with regular maintenance. Because of this, they're a solid, affordable choice.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com