Author：Baby & Adult Diaper Materials FROM：Diaper Materials Manufacturer TIME：2023-03-02
Generally, when the polymer is operated in an environment above 170 °C, bond breakage or bond phenomenon will occur. A good quality elastic adhesive must still have excellent thermal stability against aging and cracking when it is supplied to the application manufacturer. Those with poor thermal stability will rapidly carbonize during the high temperature operation of the gluing system and adhere to the melt tank wall, inside the die or on the gluing roller. These coking glues will affect the heat conduction of the heat medium or the electric heating system, so that the working temperature must be continuously increased to melt them during gluing, which further accelerates their deterioration. Elastic adhesive with good thermal stability should meet the following basic conditions.
When the thermoplastic polymer is operated under high temperature and high shear force, various free radicals (R, RO, OH) that are extremely active and can cause a chain reaction of cracking will be generated due to chain scission. Adding an appropriate and appropriate amount of antioxidants can be used to stop the elastic adhesive cracking chain reaction.
Usually, hot melt adhesive systems with good compatibility are clear and transparent, and can be stored in the glue tank for a long time without phase separation and carbonization; systems with poor compatibility are translucent foggy or even completely opaque. When this kind of glue is operated in a high temperature glue tank for a long time, the phase separation between the components will gradually occur and the phenomenon of accelerated coking will occur.
Oxygen is one of the main elements that cause the oxidation of hot melt adhesives. In order to prevent it from being oxidized in contact with oxygen during the manufacturing process, it is a necessary processing procedure to fill nitrogen in the glue tank to block oxygen or vacuumize the production during the mixing process.
The impurities in the elastic adhesive may be foreign objects carried in some raw materials or accidentally introduced during feeding, such as paper scraps, textiles, dust or metal, or carbonized rubber peeled off from the groove wall or the molecular weight is too high. melted polymer. Without proper filtration procedures, impurities will be carried into the downstream melt operation system, causing filter clogging or further deterioration of the glue. If the melting operation system does not have filtering equipment, impurities or coke will be brought to the surface of the coated object. In addition to causing contamination of the coating surface and scratches, impurities may also wear the die head or the sizing wheel and scraper, causing serious losses.
As one of the raw materials, elastic adhesive has been paid more and more attention in manufacturing. To ensure good thermal stability of rubber rubber, the above basic conditions must be met.
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