The difference between urea-formaldehyde and urea-formaldehyde resin used in compound fertilizers

I just started paying attention to urea-formaldehyde. In some information I found online, I couldn’t find any explanations for this issue. Some information has been found, such as: \"Urea and a 37% aqueous formalin solution can be polycondensed under the catalysis of acids or bases to yield linear urea-formaldehyde oligomers. Industrially, a base is used as the catalyst, the reaction takes place at around 95°C, and the molar ratio of formalin to urea is 1.5–2.0 in order to ensure that the resin can cure.\" In the first step of the reaction, 1 and 2-hydroxymethylurea is formed; subsequently, the hydroxymethyl groups undergo further condensation with amino groups to yield a soluble resin. If acid is used as a catalyst, gelation can occur easily. The product must be stored under neutral conditions. ”It is unclear whether there are significant differences in the production process of urea formaldehyde between the two usage methods.

Furthermore, in some sources, the description of the production process of urea-formaldehyde compound fertilizer varies as well. Some state that: \"Urea-formaldehyde compound fertilizer is produced by reacting urea with methanol at high temperatures to generate two types of polymers, 1-methylenedioxyurea and 2-methylenedioxyurea; these are then combined with monoammonium phosphate and potassium fertilizers to form granules, thereby creating the compound fertilizer.\"”； Some say, “Urea-formaldehyde oligomers, primarily composed of monohydroxymethylurea and dihydroxymethylurea, are formed through the reaction of urea and formaldehyde under certain conditions.” Which statement is correct?

Why is no one paying attention to me? Where are all the experts? Looking forward to your arrival with great anticipation! :'(

This post was last edited and replied to by Xiao Shoudong on 2012-1-6 at 12:11. Reply 4# lily_72q: Introduction to urea formaldehyde – A polymer obtained from the reaction of urea and formaldehyde. Also known as urea-formaldehyde resin. English abbreviation UF. 　　Urea formaldehyde, also known as urea-formaldehyde fertilizer, was first produced by BASF in 1955; it was the first commercially available slow-release nitrogen fertilizer. It is formed by the condensation of urea and formaldehyde, and appears as a white, odorless powder or granules. Depending on the molar ratio of urea to formaldehyde, urea-formaldehyde fertilizers with different degrees of condensation (release rates) can be produced. 　　Release mechanism: It provides slow-release nitrogen within a polymer linked to carbon; it has a low salt index, and the nitrogen is slowly decomposed by water over 12 to 16 weeks. Healthy soil requires a high proportion of microorganisms. Urea-formaldehyde-based slow-release nitrogen can be consumed by microorganisms as nutrients and energy. A very small proportion of nitrogen can be immediately supplied to plants through its solubility in water, while the remaining nitrogen is released gradually as microorganisms absorb and decompose it. This combination of reliability and safety makes urea-formaldehyde-based slow-release nitrogen an ideal product for maintaining golf courses and other professional lawns. 　　Fertilizer characteristics: 1. Controllable: Based on the fertilizer requirements of crops, slow-release fertilizers with varying release periods can be designed and produced by adjusting the amount of additives used. 　　2. Efficient: Nutrients can be released according to the needs of the crops, in the amount required, **reducing nutrient loss and improving fertilizer efficiency. 　　3. Environmental protection: Few nutrients are released into the environment, and the coating is completely biodegradable, making it environmentally friendly. 　　4. Safety: Low salt index, preventing seedling burn and root damage. 　　5. Economy: It can be applied once, providing fertilizer benefits throughout the entire growing period; at the same time, it reduces the amount of fertilizer needed compared to conventional methods, thus saving fertilizer and labor costs. During production and processing, cross-linking occurs, resulting in a thermosetting resin that is neither soluble nor fusible. The color of the cured urea-formaldehyde resin is lighter than that of the phenol-formaldehyde resin; it is semi-transparent. It is resistant to weak acids and weak bases, has good insulating properties and excellent wear resistance. It is inexpensive, but it decomposes easily when exposed to strong acids and strong bases, and its weather resistance is poor. Trade name: Beetle. 　　Urea and a 37% aqueous formalin solution can be polycondensed under the catalysis of acid or base to yield linear urea-formaldehyde oligomers. Industrially, a base is used as the catalyst, the reaction takes place at around 95°C, and the molar ratio of formalin to urea is 1.5–2.0 to ensure that the resin can cure. In the first step of the reaction, 1 and 2-hydroxymethylurea is formed; subsequently, the hydroxymethyl groups undergo further condensation with amino groups to yield a soluble resin. If acid is used as a catalyst, gelation can occur easily. The product must be stored under neutral conditions. 　　Linear urea-formaldehyde resin can cure at room temperature when ammonium chloride is used as a curing agent. The molding powder is heated and cured at 130–160°C, with accelerators such as zinc sulfate, trimethyl phosphate, and diethyl oxalate used to speed up the curing process. Urea-formaldehyde resin is mainly used in the production of molded plastics, as well as in manufacturing household items and electrical components. It can also be used as an adhesive for sheets, in pastes for paper and fabrics, for veneers, and in construction decorative panels. Due to its light color and ease of coloring, the products often have rich and vibrant colors. Use: Urea-formaldehyde compound fertilizer. Urea-formaldehyde compound fertilizer is produced by the reaction of urea and methanol at high temperatures to yield two types of polymers: 1-methylenediurea and 2-methylenediurea; these are then combined with monoammonium phosphate and potassium fertilizers to form granules. This type of compound fertilizer belongs to the high-end category of fertilizers, offering high efficiency and long-lasting effects, as well as slow-release and controlled-release properties. It is mainly used in golf course lawns, and it is currently the only compound fertilizer that can be used in drip irrigation systems. Classification: 1. Built-in urea-formaldehyde compound fertilizer refers to the addition of powdered urea-formaldehyde resin to the raw materials used in the production of compound fertilizers; the resulting compound fertilizers can also provide slow- and controlled-release effects. 　　2. Urea-formaldehyde resin-coated compound fertilizer refers to a type of compound fertilizer whose surface is coated with a layer of urea-formaldehyde resin, thereby providing slow and controlled release effects. 　　Compound fertilizer is a polymer formed from urine and formaldehyde at certain temperatures; it is a type of controlled-release fertilizer. Reaction principle: After being applied to the soil, urea-formaldehyde compound fertilizer rapidly melts into a colloid that is tightly adsorbed and integrated by the soil, thereby ensuring that nutrients are not lost over time. Urea can be converted, through microbial decomposition, into inorganic nitrogen that can be directly absorbed by crops within a short period of time; this enables rapid release of nutrients and forms the quickly available component in urea-formaldehyde fertilizers (within 10 to 40 days) ； 1-methylethyl-2-urea must be decomposed by microorganisms over a certain period of time in order to be converted into inorganic nitrogen that can be directly absorbed by crops; thus, it becomes the medium-acting component in urea-formaldehyde fertilizers (with an action period of 40 to 80 days) ； 2-Methylene-3-urea must undergo prolonged and repeated decomposition by microorganisms in order to be converted into inorganic nitrogen that can be absorbed by crops; this is what constitutes the long-acting component in urea-formaldehyde fertilizers (with an action period of 80 to 120 days). Principles for applying urea-formaldehyde fertilizers Nitrogen form and properties of urea-formaldehyde fertilizers Urea-formaldehyde is produced through a condensation reaction between urea and formaldehyde in factories. The product is not a single compound, but rather a mixture of methyl ureas with varying chain lengths and molecular weights, including polymers in the series from monomethyldihydrazone to pentamethyldihydrazone. Its total nitrogen (N) content is about 38%. 　　What is the solubility of urea formaldehyde? This is a fundamental trait that determines the release rate and effectiveness of a fertilizer. Now, a comparison is made between the three components in urea-formaldehyde and urea in terms of their water solubility: at a room temperature of 20°C, 100 grams of water can dissolve 108 grams of urea ； Only 2.18 grams of methylenediurea (MDU) can be dissolved ； Dissolve 0.14 grams of dimethylenetriurea (DMTU) ； Dissolve 0.018 grams of trimethylenetetramine (DMTU). This indicates that the solubility of the three components of urea-formaldehyde in water is much lower than that of urea, and urea-formaldehyde is a slow-release nitrogen fertilizer. 　　A further comparison of the solubilities of several components of urea-formaldehyde showed that 3-methyl-4-urea had the fastest release rate, making it the most suitable component among the urea-formaldehyde condensates. Because overly short chain segments decompose too rapidly, while longer chain segments are highly resistant to decomposition. However, it is very difficult to produce pure 3-methyl-4-urea on an industrial scale. Urea-formaldehyde condensation fertilizers contain both shorter and longer chains; as the length of the polymer chains increases, the solubility of the fertilizer decreases, and correspondingly, its slow-release period becomes longer. 　　Nitrogen slow-release performance in urea-formaldehyde fertilizers and its characterization: To evaluate the quality of urea-formaldehyde fertilizers, the following 5 parameters need to be tested: total nitrogen content, nitrogen soluble in cold water, nitrogen insoluble in cold water, and nitrogen insoluble in hot water. The nitrogen activity index is determined by calculating these parameters. The release characteristics of urea-formaldehyde fertilizers are expressed by the “nitrogen activity index”. The direct meaning expressed by this index is the percentage of nitrogen in the fertilizer that is soluble in hot water, relative to the nitrogen that is insoluble in cold water. The formula is as follows: Nitrogen activity index = (Nitrogen insoluble in cold water – Nitrogen insoluble in hot water) × 100% / Nitrogen insoluble in cold water. Among the various parameters, nitrogen soluble in cold water and residual urea nitrogen represent the readily available nitrogen ； Hot water-soluble nitrogen is slowly-release nitrogen ； Hot-water insoluble nitrogen is urea-formaldehyde with a higher degree of condensation, and its release period is very long, sometimes even reaching several years. In agriculture, it is generally required that at least 40% of nitrogen be insoluble in cold water but soluble in hot water, with the standard nitrogen activity value ranging from 50% to 70%. 　　Understanding the performance of urea-formaldehyde products: According to the relevant standards in force, urea-formaldehyde fertilizer products must have on their packaging the values for total nitrogen content, urea nitrogen content, nitrogen insoluble in cold water, and nitrogen insoluble in hot water. When the product is packaged in tons, it is sufficient to indicate the type of urea-formaldehyde compound, total nitrogen content, urea nitrogen content, nitrogen insoluble in cold water, nitrogen insoluble in hot water, net weight, as well as the name and address of the manufacturing company. 　　When purchasing urea-formaldehyde fertilizer products, farmers should read the information carefully or consult relevant experts to understand their properties, in order to avoid making mistakes. In particular, many advertisements on the market currently make empty and exaggerated claims, and there are also cases of using new types of fertilizers to deceive and mislead consumers. 　　Principles for applying urea-formaldehyde fertilizers. Common types of urea-formaldehyde fertilizers include urea-formaldehyde slow-release nitrogen fertilizers, urea-formaldehyde slow-release compound fertilizers, and some urea-formaldehyde slow-release blended fertilizers. These fertilizers are available in both granular and powder form, and liquid forms can also be prepared for application. 　　The production and use of urea-formaldehyde fertilizers abroad have a long history; they are not new types of fertilizers. It is mainly used for golf courses, vegetables, and gardens; in Japan, urea-formaldehyde fertilizers are used in paddy fields. 　　The main advantage of urea-formaldehyde slow-release nitrogen fertilizers is their slow release in the soil, which helps to reduce nitrogen volatilization, leaching, and fixation ； In intensive agricultural production, large amounts of fertilizer can be applied at once without causing seedling burn, and nitrogen loss does not occur even in sandy soils and rainy areas, ensuring a lasting effect. 　　Urea-formaldehyde slow-release nitrogen fertilizers are only suitable for use as base fertilizers. Apart from lawns and gardens, when applied to field crops such as rice, wheat, and cotton, they should be combined with readily available water-soluble nitrogen fertilizers to ensure optimal fertilizer efficacy. If quick-acting nitrogen fertilizers are not used, there is often a shortage of nitrogen supply during the early stages of crop growth, making it difficult to achieve high yields while also resulting in unnecessary increases in fertilizer costs. In some cases, sulfuric acid and urea should be applied as appropriate. Of course, in any case, the proper combination of phosphorus and potassium fertilizers, such as single superphosphate and potassium chloride, cannot be ignored. 　　Since solubility is directly related to the rate at which nutrients are released and the duration for which fertilizers remain effective, a comparison of the solubility of different types of fertilizers is presented here: For example, with a total nitrogen content of 38%, 28% of that is soluble in cold water ； The activity index is about 50. 　　When urea-formaldehyde with a nitrogen activity index of 49 is used, it provides the best fertilization effect for crops grown in the current season. The increase in crop yield and nitrogen uptake during the growing season are lower compared to the use of urea and ammonium sulfate, but the long-term effects are better. 　　Due to its excellent physical properties, it can be used to manufacture products and processed into mixed fertilizers or granulated fertilizers. 　　After urea-formaldehyde is applied to the soil, some chemical decomposition occurs, but it is primarily released through microbial breakdown, making it less likely to be lost due to leaching. It can be broken down into formaldehyde and urea; urea is then hydrolyzed into carbon dioxide and ammonia, which are absorbed by plants for use. Formaldehyde, on the other hand, remains in the soil, and it has adverse effects on crops and microorganisms until it volatilizes or decomposes. 　　Since urea-formaldehyde contains less water-soluble nitrogen, it must be applied to annual crops in combination with some quick-acting nitrogen fertilizers, to prevent poor growth of the crops in the early stages due to insufficient nitrogen supply.

Hello, moderator. Thank you for taking the time and effort to answer my questions. There’s one more thing: urea-formaldehyde is itself a slow-release nitrogen fertilizer, but there is also a type of fertilizer known as urea-formaldehyde compound fertilizer. The production process for this compound fertilizer involves reacting urea and methanol at high temperatures, followed by mixing it with phosphorus and potassium fertilizers in a granulator to form granules. However, some other sources indicate that urea formaldehyde is produced by the reaction of urea and formaldehyde. In short, I’m not quite sure about these two.

This post was last edited and replied to by Chemical Gas Purification on 2012-1-9 at 09:18. Reply 6# lily_72q: Urea formaldehyde and urea formaldehyde-based fertilizers are not the same concept; urea formaldehyde contains nitrogen at most and cannot be considered a compound fertilizer. Moreover, pure urea formaldehyde cannot be used directly as a fertilizer – it is rather a type of gel with coating properties. The main nutrient in fertilizers is nitrogen, so they cannot be called compound fertilizers. Urea-formaldehyde compound fertilizer, on the other hand, is a compound fertilizer that contains various elements such as nitrogen, phosphorus, and potassium; the role of urea-formaldehyde is to act as a coating, providing a slow-release effect.

In addition to coating, the existing forms of urea-formaldehyde compound fertilizers also include those with internal granulation