Company: Liaoyang Xinyu Chemical Co., Ltd.
Address: No. 29 Vanward two road, Hongwei District, Liaoyang, Liaoning, China.
The main methods to realize the flexibility of epoxy resin system are physical addition method and chemical modification method, or the combination of the two. Physical addition is mainly to add toughening agent or plasticizer. Chemical modification can be used to modify both curing agent and epoxy resin, and the latter has better effect. Crystalline epoxy resin
1. adding toughening agents or plasticizers
The advantage of adding tougheners or plasticizers is that they are cheap and have been used in many previous formulations of coatings, adhesives and castables. The most widely used plasticizer is ortho two carboxylic acid ester. These plasticizers can increase toughness, but because they do not participate in the curing reaction, they are easy to precipitate and migrate and can be dissolved by solvent. The existence of small molecules will affect the electrical and chemical properties of products. In addition, because the plasticizer is not involved in the formation of macromolecular network, the impact strength of the cured products is not significantly improved, but the thermal deformation temperature is greatly reduced.
Another kind of long fatty chain toughening agents with hydroxyl and ether bonds can play a better role because of their high molecular weight. Its hydroxyl group can be involved in curing reaction, also known as active toughening agent. However, the reaction activity of hydroxyl group with epoxy group of the active toughener is much lower than that of amine curing agent, so it is difficult to play an active toughening role in amine curing agent system, but is basically a physical mixture. Under the condition of high temperature curing in anhydride system, the active toughening agent can react with epoxy group or anhydride. Therefore, the suitable amount of curing agent should be paid attention to in order to achieve the best effect.
2. use flexible curing agent.
Flexible anhydrides mainly consist of long fatty chain anhydrides, such as polysebacic anhydride, azelaic anhydride, maleic anhydride, dodecyl succinic anhydride and their modifiers, such as Tung oleic anhydride. This kind of flexible anhydride curing agent has good cold and heat shock resistance, but the curing temperature is low, and the curing reaction rate is slower than the general anhydride curing agent. This kind of curing agent can be used alone or mixed with other anhydride. Properties of commonly used flexible anhydride and properties of solidified materials are shown in Table 1.
The representative variety of flexible amine curing agent is polyether amine curing agent. Its structure is as follows:
This kind of polyether amine curing agent has light color and low viscosity; it can be cured at room temperature, but the curing speed is slow; its curing material also has good flexibility at low temperature, good cold and heat shock resistance, good surface luster, good color retention, the main properties and curing properties as Table 2.