Meaning
Thermal treatment applied to semi-crystalline polymer parts after the initial molding cycle to promote structural stability and relieve internal stresses. Implementation of post crystallization annealing allows for the completion of crystal growth that was suppressed by rapid cooling in the mold. This process typically occurs in an oven at a temperature above the glass transition point but below the melting point.
Molecular Alignment
Chains within the amorphous regions of the polymer gain enough mobility to reorganize into ordered structures. Effective post crystallization annealing leads to a more uniform crystalline morphology throughout the part thickness. This uniformity reduces the likelihood of future dimensional changes during the product life.
Stress Relief
Molding often leaves high levels of residual strain near the gates or in areas of varied wall thickness. Use of post crystallization annealing permits these frozen-in stresses to dissipate through molecular relaxation. Reduced internal tension lowers the risk of environmental stress cracking when the part encounters chemical agents.
Mechanical Enhancement
Finished parts exhibit increased hardness and improved heat deflection temperatures following the heat treatment. While post crystallization annealing might slightly reduce ductility, it ensures the part remains stable under load. Manufacturers use this step for high-precision gears or connectors where zero movement is acceptable.
