1. The possibility of intermediate products from the perspective of the curing reaction mechanism
The curing reaction of pulse aldehyde resin curing agent and aldehyde resin is a complex chemical process. In most aldehyde resin curing reactions, cross-linking and curing are achieved based on the reaction between aldehyde groups (-CHO) and other active groups. When pulse aldehyde resin curing agent participates in the reaction, intermediate products are likely to be generated.
Taking urea-formaldehyde resin (UF) as an example, when urea-formaldehyde resin reacts with pulse aldehyde resin curing agent, the curing agent may first react with the free aldehyde groups in urea-formaldehyde resin. In this reaction process, an unstable addition compound may be formed as an intermediate product. This is because in the synthesis of urea-formaldehyde resin, the reaction between formaldehyde and urea is incomplete, and free aldehyde groups exist. When the active ingredients in the curing agent react with aldehyde groups, it may not directly form the final cross-linked structure in one step, but first form an intermediate substance with a specific chemical structure.
2. Phased changes in the chemical reaction process
In the early stages of the curing reaction, some components in the pulse aldehyde resin curing agent may undergo nucleophilic addition reactions with the active groups in the aldehyde resin. For example, if the curing agent contains an amino group, it may react with the aldehyde group to form an intermediate product containing a hydroxyl group (-OH) and an amino group (-NH₂). The chemical properties of this intermediate product are relatively unstable, and it continues to react in the reaction system.
As the reaction proceeds, further condensation reactions will occur between the intermediate products or between the intermediate products and the unreacted aldehyde resin molecules. In this process, the active groups such as hydroxyl and amino groups interact with each other, remove small molecules (such as water molecules), and gradually form a more complex cross-linked structure. In the process of transforming from a relatively simple intermediate product to the final cured structure, there may be other intermediate products in the transition state. These intermediate products may exist for a short time, but they play a key role in connecting the previous and the next in the process of the entire curing reaction.
3. The influence of intermediate products on curing performance
If intermediate products are generated, they have an important influence on the performance of the final cured product. The structure and properties of the intermediate products determine the direction and rate of subsequent reactions. For example, if unstable intermediate products cannot be converted into final products in time, they may affect the hardness and strength of the cured product. Because the presence of intermediate products may hinder the complete formation of the cross-linked network, resulting in incomplete curing. In addition, the chemical composition of the intermediate product may also affect the water resistance, heat resistance and other properties of the cured product. If the intermediate product contains more hydrophilic groups, the water resistance of the cured product may be reduced. Therefore, studying whether the pulse aldehyde resin curing agent generates intermediate products during the curing reaction and the properties of these intermediate products is of great significance for optimizing the curing reaction conditions and improving the performance of the cured product.
