How is polyamide 6 produced?

Production Process of Polyamide 6 (Nylon 6)

1. Raw Material Preparation

Core Monomer: Caprolactam (a transparent crystal), produced from benzene extracted from petroleum through a multi-step reaction.
Additives: A small amount of water (to initiate the reaction) and stabilizers (to control molecular weight) are added.

2. Polymerization Reaction

Ring-Opening Reaction: Caprolactam reacts with water under high temperature and pressure, "opening" the molecular ring to form an active chain.
Chain Growth: Active molecules continue to connect, forming a long-chain polymer (i.e., polyamide 6).

3. Post-Processing

Slicing and Granulation: The molten polymer is extruded into strips and cut into nylon slices (approximately the size of rice grains).
Extraction and Purification: Unreacted caprolactam in the slices is washed away with hot water (for recycling).
Drying and Dehydration: The slices are dried with hot air to ensure a moisture content <0.1% (to prevent air bubbles from forming in subsequent processing).

4. Modification Processing (Optional)

Reinforcement Modification: Glass fiber (to increase strength), flame retardants (for fire resistance), etc., are incorporated into the melted slices.
Injection Molding: Modified particles are injected into a mold to create finished products such as gears and housings.

5. Key Quality Control Points

Molecular Weight Testing: Ensures uniform chain length (affects material toughness).
Impurity Control: Filters out metal residues (prevents high-temperature degradation).
Viscosity Testing: Monitors melt flowability (determines injection molding difficulty).