The best curing conditions of epoxy curing agent

Actual use is different and the nature requirements are also different. The optimal amount of HDT given to the highest value does not necessarily result in the highest values ​​for other properties. For example, the requirements for thermal shock strength are as follows: the amount of epoxy resin curing agent is reduced from the optimal amount, and the crosslink density is reduced, resulting in a drop in HDT, but the thermal shock strength is increased. The complete curing conditions for the curing reaction are the optimum curing conditions.

What is an incomplete curing reaction? Under non-optimal curing conditions (such as room temperature), when the complex is in a vitrified state, the microscopic Brownian motion of the segment is suppressed, the reaction rate stays low, and the degree of reaction is very low. This is an incomplete curing reaction. When the liquid bisphenol A epoxy resin is cured with DETA, the degree of reaction does not exceed 65%; when cured with a low molecular weight polyamide resin, it does not exceed 40%. Since such a low reaction rate provides practicality, the change in the addition amount within a certain range has little effect on the properties of the cured product (especially when cured with a low molecular weight polyamide). This is the reason why the optimum dosage range is relatively wide.

In order to achieve a fully cured state, post-cure is necessary at a higher temperature than the system Tg. For example, a cured product of an aromatic polyamine has a high crosslinking density and a high Tg, and must be postcured at a high temperature in order to be completely cured.

Under the condition that the curing is not complete, various properties of the cured product will not be fully exerted, and the general cured product performance data are mostly various data measured after being completely cured by means of post-curing.