Meaning
Intense hydrostatic forces applied to a polymer blend or copolymer during cooling trigger the formation of shared crystalline structures. Pressure induced co crystallization is a material science phenomenon where different polymer chains or additives crystallize together under the influence of intense pressure. This process changes the morphology of the plastic compared to what would occur at atmospheric pressure.
The resulting structure can improve the barrier properties or the stiffness of the material.
The Molecular Alignment
Chain movement becomes more efficient when external pressure overcomes the steric hindrance of the polymer branches. This forcing of molecules into a denser lattice creates a material with higher thermal stability. Co-crystallization often involves the interaction between a polymer matrix and a nucleating agent.
Under pressure, these components form a more cohesive and uniform grain structure.
Injection Hold Times
Machines that maintain high hold pressures for extended periods are more likely to exhibit this effect in the final part. The cooling rate must be carefully managed to ensure the crystals have time to form before the material reaches its glass transition temperature. Failure to control the pressure during the critical cooling window results in an amorphous or weakly structured part.
This lack of crystalline order reduces the chemical resistance of the component.
High Pressure
Loading lowers the mobility of the chains but increases the nucleation rate.
