Curing agent is another major component of electronic sealing adhesive and epoxy resin sealing material. By selecting different curing agents, epoxy potting materials with different properties can be obtained. Amines and anhydride are two commonly used curing agents in the formulation system of potting materials.
1. Amine curing agent is a commonly used curing agent for room temperature curing potting materials. Although a general fatty amine curing agent can cure epoxy resin at room temperature, it is highly irritating, has a small dosage, a short shelf life, a high exothermic peak, and is prone to react with carbon dioxide in the air, making it difficult to obtain a bright and flat surface curing substance. It is usually rarely used. In most cases, their modifiers are used, such as 593, 793 curing agents, etc. Compared with fatty amines, modified amine curing agents have significantly reduced irritation, increased dosage, reduced exothermic peaks, extended trial period, and improved surface condition of cured products.
2. Although aromatic amine curing agents have good curing properties, they are often solid and require heating for curing, making their use inconvenient. Not commonly used in potting materials. The modified aniline formaldehyde condensate developed in recent years is a low viscosity liquid that can cure epoxy resin at room temperature. It has a large dosage, low exothermic peak, and a smooth and bright surface of the cured product. It is a good liquid aromatic amine curing agent. The disadvantage is that it has a darker color and is often used for black epoxy potting materials.
3. Anhydride curing agent is the most important curing agent for two-component heating cured epoxy potting materials. Commonly used varieties include liquid methyltetrahydrophthalic anhydride, liquid methylhexahydrophthalic anhydride, etc. These curing agents have low viscosity and large dosage, and can play a dual role in curing and diluting in potting material formulas. After adding tertiary amine accelerators, they can cure at 80-120 ℃ and have a trial period of more than 4 hours at operating temperature (30-40 ℃). Mild heat release during curing, and good comprehensive performance of the cured product!