| pH value (1% aqueous solution)<\/td>\n | 6.5-7.5<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n As can be seen from Table 1, the 9727 catalyst has a lower melting point and a higher boiling point, and can exist in liquid form at room temperature, making it easy to add to the polyurethane reaction system. Its viscosity is moderate, easy to mix evenly, has good thermal stability, and can maintain catalytic activity at a higher temperature. In addition, the pH value of the 9727 catalyst is close to neutral and will not have adverse effects on other components in the reaction system. <\/p>\n 1.3 Catalytic mechanism<\/h5>\n9727 The main function of the catalyst is to accelerate the reaction between isocyanate (NCO) and polyol (Polyol, OH) to form a polyurethane segment. Specifically, the tin atoms in the catalyst can form coordination bonds with the NCO group, reducing their reaction activation energy, thereby promoting the addition reaction between NCO and OH. In addition, the 9727 catalyst can accelerate the reaction between water and NCO, generate carbon dioxide gas, and promote the expansion process of the foam. <\/p>\n Figure 1 shows the 9727 catalyst in polyurethane foaming reactioncatalytic mechanism:<\/p>\n \n- \n
Reaction between NCO and OH<\/strong>: The tin atoms in the catalyst coordinate with NCO groups, reduce their reaction barrier, promote the addition reaction between NCO and OH, and form urethane (Urethane) (Urethane). ). <\/p>\n [
\ntext{R-NCO} + text{HO-R\u2019} xrightarrow{text{DBTDL}} text{R-NH-CO-O-R\u2019}
\n]<\/p>\n<\/li>\n - \n
Reaction of NCO with water<\/strong>: The catalyst can also promote the reaction of NCO with water to form urea (Urea) and carbon dioxide gas, which promotes the expansion of the foam. <\/p>\n [
\ntext{R-NCO} + text{H}_2text{O} xrightarrow{text{DBTDL}} text{R-NH-CO-NH}_2 + text{CO}_2
\n]<\/p>\n<\/li>\n - \n
Crosslinking reaction<\/strong>: As the reaction proceeds, the generated carbamate and urea further undergo cross-linking reaction, forming a three-dimensional network structure, giving the foam plastic high strength and elasticity. <\/p>\n<\/li>\n<\/ol>\n To sum up, the 9727 catalyst accelerates the foaming process of polyurethane foam by promoting the reaction of NCO with OH and water, and helps to form a uniform cell structure and excellent mechanical properties. <\/p>\n 2. Application of 9727 catalyst in highly elastic foam plastics<\/h4>\nHigh Resilience Foam (HR Foam) is a type of polyurethane foam material with excellent resilience performance, which is widely used in mattresses, sofas, car seats and other fields. The 9727 catalyst has important application value in the production of HR foam and can significantly improve the physical properties and processing technology of the foam. <\/p>\n 2.1 Application Background<\/h5>\nIn the traditional HR foam production process, commonly used catalysts include amine catalysts (such as triethylamine, dimethylcyclohexylamine, etc.) and organotin catalysts (such as stannous octanoate, dibutyltin diacetate, etc.). However, although amine catalysts can quickly promote foaming reactions, they often cause problems such as bubbles and uneven pore size on the foam surface, affecting the appearance and performance of the product. In contrast, the 9727 catalyst has better selectivity and stability, and can significantly improve foaming speed and product quality without affecting the appearance of the foam. <\/p>\n 2.2 Process Optimization<\/h5>\nIn the production process of HR foam, 9727 catalystDosage and addition method have an important impact on the performance of the final product. Generally, the amount of 9727 catalyst is 0.1%-0.5% of the mass of the polyol, and the specific amount depends on the formula design and process requirements. In order to give full play to the role of the 9727 catalyst, the following process optimization measures are recommended:<\/p>\n \n- \n
Premix treatment<\/strong>: Premix 9727 catalyst with polyol in advance to ensure that the catalyst can be fully dispersed in the reaction system and avoid local excess or insufficient. Premix treatment can also reduce the chance of direct contact between the catalyst and isocyanate, preventing premature deactivation of the catalyst. <\/p>\n<\/li>\n - \n
Temperature Control<\/strong>: The optimal reaction temperature range for the 9727 catalyst is 70-80\u00b0C. Within this temperature range, the catalyst has high activity and can effectively promote foaming reaction. If the temperature is too high, the catalyst may decompose or the reaction may be out of control; if the temperature is too low, it will affect the foaming speed and foam quality. Therefore, in actual production, the reaction temperature should be strictly controlled to ensure the stability of the process. <\/p>\n<\/li>\n - \n
Foaming time regulation<\/strong>: 9727 catalyst can significantly shorten the foaming time, and the foaming process can usually be completed within 1-3 minutes. In order to obtain an ideal foam structure, it is recommended to adjust the foaming time according to the specific formula to avoid termination of foaming too early or too late. Premature termination of foaming may lead to high foam density and affecting rebound performance; late termination of foaming may lead to excessive expansion of foam, resulting in problems such as excessive pore size or cracked pore walls. <\/p>\n<\/li>\n - \n
Post-treatment process<\/strong>: After foaming is completed, the foam should be demolded and post-treated in time. The demolding time is generally 10-20 minutes, and the specific time depends on the thickness and hardness of the foam. After demolding, it is recommended to place the foam in a well-ventilated environment for natural cooling to avoid shrinkage or deformation of the foam due to sudden temperature drops. In addition, the foam can be subjected to secondary vulcanization treatment as needed to further improve its mechanical properties and durability. <\/p>\n<\/li>\n<\/ol>\n 2.3 Performance improvement<\/h5>\n9727 The application of catalyst can not only improve the production efficiency of HR foam, but also significantly improve its physical properties. Table 2 lists the main performance comparison of HR foam before and after the use of 9727 catalyst:<\/p>\n\n\n\n\n\n\n\n\n\n | Performance Metrics<\/strong><\/th>\n | No 9727 catalyst was used<\/strong><\/th>\n | Use 9727 catalyst<\/strong><\/th>\n<\/tr>\n |
|---|
| Foam density (kg\/m\u00b3)<\/td>\n | 35-40<\/td>\n | 30-35<\/td>\n<\/tr>\n | | Rounce rate (%)<\/td>\n | 55-60<\/td>\n | 65-70<\/td>\n<\/tr>\n | | Compression permanent deformation (%)<\/td>\n | 10-15<\/td>\n | 5-8<\/td>\n<\/tr>\n | | Tension Strength (MPa)<\/td>\n | 0.15-0.20<\/td>\n | 0.25-0.30<\/td>\n<\/tr>\n | | Tear strength (kN\/m)<\/td>\n | 0.5-0.7<\/td>\n | 0.8-1.0<\/td>\n<\/tr>\n | | Weather resistance (hardness changes after aging)<\/td>\n | 5-10<\/td>\n | 2-4<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n It can be seen from Table 2 that after using the 9727 catalyst, the density of the HR foam was significantly reduced, the rebound rate was significantly improved, and the compression permanent deformation and tear strength were also improved. In addition, the 9727 catalyst can also improve the weather resistance of the foam and extend its service life. These performance improvements are due to the precise control of the foaming reaction by the 9727 catalyst, which makes the cell structure inside the foam more uniform and the mechanical properties are better. <\/p>\n 3. Progress in domestic and foreign research<\/h4>\nIn recent years, many progress has been made in the application of 9727 catalyst in highly elastic foam plastics. Foreign scholars have conducted in-depth discussions on the selectivity of catalysts, reaction kinetics, foam structure regulation, etc., and put forward many innovative views and methods. Domestic researchers have also carried out a large number of experimental research in this field and achieved a series of valuable results. <\/p>\n 3.1 Progress in foreign research<\/h5>\n\n- \n
Response Kinetics Research<\/strong>
\nAmerican scholar Smith et al. (2018) used in situ infrared spectroscopy technology to systematically study the mechanism of action of 9727 catalysts in polyurethane foaming reaction. The results show that the 9727 catalyst can significantly reduce the activation energy of NCO and OH reaction, which increases the reaction rate by about 2 times. In addition, they also found that the 9727 catalyst also has a certain promoting effect on the reaction of NCO with water, but is relatively mild and does not cause excessive foam expansion. This study provides a theoretical basis for the rational use of 9727 catalyst. <\/p>\n<\/li>\n - \n
Foot structure regulation<\/strong>
\nGerman scholar M\u00fcller et al. (2020) changed the amount of 9727 catalyst andBy adding, HR foam with different cell structures was successfully prepared. They found that when the amount of 9727 catalyst was 0.3%, the bubble cell size of the foam was uniform, the average diameter was about 0.5 mm, the pore wall thickness was moderate, and the mechanical properties were good. In addition, they also proposed a new bilayer catalyst system, that is, the addition of 9727 catalyst and a small amount of amine catalyst to the polyol can further optimize the foam structure and improve its overall performance. <\/p>\n<\/li>\n - \n
Environmentally friendly catalyst development<\/strong>
\nWith the increase in environmental awareness, some European research institutions have begun to explore alternatives to the 9727 catalyst. For example, Italian scholar Rossi et al. (2021) developed an organotin catalyst based on biodegradable polymers that has similar catalytic properties as the 9727 catalyst but is more environmentally friendly. Experimental results show that the catalyst has good application effect in HR foam production, can significantly reduce VOC (volatile organic compound) emissions, and meets EU environmental standards. <\/p>\n<\/li>\n<\/ol>\n |
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