Aqueous phenolic resin dispersion

Due to the low molecular weight and stability of water-soluble phenolic adhesive, the concentration range of the resin is usually 55% - 70%. Therefore, most of these resins have some application problems. One of the main disadvantages of water-soluble phenolic resin is the poor environmental resistance of its film. Before crosslinking and curing, the film will be re solvated after soaking in water. The gel coat made from water-soluble phenolic resin is basically washed off. In addition, some phenolic resins modified by ionic groups are often low molecular weight, low reactivity, and difficult to obtain high cross-linking density, so the corrosion resistance of their films (especially those with high ionic groups) is very limited. In addition, some water-soluble phenolic resins need to increase the amount of formaldehyde for curing, and the emission of formaldehyde is becoming more and more strict. ***Recently, many disadvantages of water-soluble phenolic resin can be overcome by using aqueous phenolic resin dispersion.


Even though the dispersion is still a one-step resin, they are much more stable than water-soluble phenolic resin. Their appearance, viscosity and water dilution remained unchanged during aging. For water-soluble resol phenolic resin, its miscibility with water decreases rapidly at any time, but this problem does not occur in phenolic dispersion. Instead, dispersions can be diluted with water in any proportion, even after they have entered the second resin. The obvious change is that the gel time gradually shortens, which indicates that the molecular weight of the resin increases slowly.


However, when the temperature is below 5 ℃, the retention period of the dispersion developed earlier is 6 months. The stability of the dispersion depends on the control of sedimentation and flocculation rate. These variables have been adjusted and carefully controlled in some phenolic dispersion products (such as the products of United carbon company), which are obtained by selecting the appropriate interfacial agent. When silane coupling agent is added before the fiber is used, the adhesive can be achieved in wet condition. The measurement results of smoke density and air pollution during the manufacture of thermal insulator show that the emission of volatile pollutants caused by phenolic dispersion is much smaller than that of water-soluble resin, which is equivalent to powder binder.


These dispersions can be mixed with many other thermoplastic latex to form polymer alloy glue. According to their composition, they have both the advantages of thermoplastic part and thermosetting part. With this technology, the properties of the final composite can be changed in a wide range. It is expected that such materials can be used to bond synthetic fibers.