News
Working Principle and Feeding Ratio of Epoxy Resin 650 Polyamide Curing Agent in Composite Material Impregnating Compounds
2025/08/25
The following explanation is divided into two aspects:
1. Principle of Use
650 polyamide curing agent is a low-molecular-weight polyamide produced by the reaction of fatty acid dimers with polyamines. Its molecular structure contains a large number of primary amino groups (-NH?) and secondary amino groups (-NH-), and these reactive amino groups can undergo a ring-opening addition reaction with the epoxy groups (-C-O-C-) in epoxy resins:
- Primary amino groups first react with epoxy groups, opening the ring to form hydroxyl groups (-OH) and secondary amine structures;
- The generated secondary amino groups further react with other epoxy groups, continuing the ring-opening process and forming a cross-linked structure;
- Finally, through three-dimensional network crosslinking, the epoxy resin is transformed from a liquid state to a solid state, and at the same time, it is tightly combined with reinforcements (such as fibers, fabrics) in composite materials, endowing the materials with mechanical strength, chemical resistance and other properties.
2. Feeding Ratio
The ratio is mainly calculated based on the epoxy equivalent weight (EEW) of the epoxy resin (millimoles of epoxy groups per gram of resin) and the active hydrogen equivalent weight (AHEW) of 650 polyamide (millimoles of active hydrogen per gram of curing agent). In practical applications, the mass ratio is often used for simplification:
- For commonly used bisphenol A epoxy resins (e.g., E-44 with an epoxy equivalent weight of approximately 210-240; E-51 with an epoxy equivalent weight of approximately 180-200), the addition amount of 650 polyamide curing agent is usually 20%-40% (relative to the mass of epoxy resin).
- Example: 100 parts of E-51 epoxy resin mixed with 30-40 parts of 650 polyamide can cure at room temperature (curing time is about 24-72 hours), and the product has good flexibility;
- If it is necessary to accelerate the curing speed, a small amount of accelerator (e.g., DMP-30, with an addition amount of 1%-3% of the resin mass) can be added. In this case, the dosage of 650 polyamide can be appropriately reduced to 20-30 parts.
The specific ratio needs to be adjusted according to the composite material’s requirements for curing speed, hardness and flexibility. It is recommended to verify through experiments to match the actual process needs.
Yueyang Zhongzhan Technology produces 650 polyamide curing agent and DMP-30 epoxy accelerator, with stable quality that has been recognized by customers for many years. Welcome to inquire. Contact: 13975090964.
