Company: Liaoyang Xinyu Chemical Co., Ltd.
Address: No. 29 Vanward two road, Hongwei District, Liaoyang, Liaoning, China.
The main factors affecting the synthesis of epoxy resin include the molar ratio of phenolic resin, reaction temperature and time, the composition of brominated epoxy resin phenol and the molar ratio of epichlorohydrin, alkali, catalyst to phenolic resin. Because the length of discussion is too large, the qualitative description is only here. Crystalline epoxy resin brominated epoxy resin
In the synthesis of phenolic resin, the softening point of the resin increases with the increase of the ratio of bisphenol to phenol, and the hardness and temperature resistance of the film are improved. However, too high softening point will make the powder processing difficult, and the appropriate ratio is 1/2-1/4. With the increase of molar ratio of aldehyde to phenol, the softening point of the resin increases, the amount of aldehyde is too small, the reaction rate of phenol is too low, the softening point of the resin is too low, and the resin is easy to agglomerate. On the contrary, the softening point of the resin is too high and it is not suitable for processing, and the solubility of the resin decreases, which brings difficulties in epoxidation. At 3/4-4/5. The condensation reaction temperature of phenolic resin is generally 85-95 C, the time is 4-6 hours, too short, inadequate reaction, too long, has little effect on the reaction rate.
In epoxidation of phenolic resin, the epoxy value and softening point of the resin increase with the increase of the amount of epichlorohydrin, and the influence of epoxy value, cross-linking density, hardness and temperature resistance of the film is reflected in the high epoxy value, high hardness and high temperature resistance, but brittleness also increases, taking into account the comprehensive performance of the film and the processing performance of powder, resin ring. The oxygen value is controlled at 0.11-0.13eq/100g, and the corresponding epichlorohydrin dosage is 1/1.0-1/1.2 (mol/mol hydroxyl), and the alkali dosage is generally controlled at the same mole or slightly excessive with epichlorohydrin. Too little can make the closed loop not enough and too much, which can lead to alkaline hydrolysis of epoxy.
The most important factor affecting the properties of curing agent is the ratio of hydroxyl-terminated polymer compound to anionic catalyst, followed by the molecular weight of hydroxyl-terminated polymer compound and the molar ratio of phenolic aldehyde to polyether. In this compound curing agent, the curing mechanism of hydroxyl-terminated polymer compounds is different from that of anionic catalysts. Hydroxyl-terminated polymer compounds are mainly additionally polymerized by hydroxyl-terminated and epoxy groups, resulting in the gradual increase of the molecular chain. When the molecular weight reaches a certain degree, the end group is encapsulated due to the curling of the molecular chain. The reaction activity decreases and the reaction rate slows down. The anionic catalytic curing agent reacts with the epoxy group to open the ring and form a new anion, which reacts with the new epoxy group to form a chain growth.
This chain reaction is characterized by the rapid growth of molecular chains as soon as they are initiated, and the reaction speed is fast, but there are many factors that may lead to chain termination, and the degree of polymerization is difficult to grasp. In addition, because the polymerization speed is fast and the heat release is intense, it is easy to form internal stress and make the film crisp. There are also great differences in the ratio of the two, the former is based on functional group addition polymerization, the ratio should be close to the same molar ratio; and the latter is mainly initiated, the amount of its use is not proportional to the functional group, the amount is very small.
The molecular weight of linear polyether and phenolic resin mainly depends on the ratio of raw materials. The closer the ratio of phenolic aldehyde (epoxide/alcohol, phenol) is, the higher the molecular weight is, the better the toughness is, and the higher the softening point is. Compared with polyether resin, phenolic resin has high aromatic density, good temperature and chemical resistance, and fast curing speed, but because of its high aromatic density, the film is easy to be brittle.