Meaning
Physical properties of a polymer shift when small, highly mobile molecules dissolve into the polymer matrix and increase the free volume between chain segments. The plasticization effect results in a lower glass transition temperature, decreased tensile strength, and increased ductility of the material. This phenomenon occurs when polymers absorb solvents, moisture, or specialized chemical additives.
Mechanical Shift
The polymer chains slide past one another with less resistance, making the plastic more flexible and easier to deform. This plasticization effect is often observed when polymers are exposed to high humidity or when recycled resins retain traces of oils and fats from their first life. This change in mechanical behavior can lead to part deflection under load.
Processing Action
Molders must adjust their processing parameters to account for the modified flow behavior. In the extruder, the plasticization effect lowers the melt viscosity, which reduces the required screw torque and injection pressure. This allows for processing at lower temperatures but can also lead to mold flashing if the pressure is not controlled.
Material Boundary
Excessive absorption of plasticizing agents can lead to permanent structural degradation or stress cracking. This limits the use of certain polymers in environments where they come into contact with aggressive organic solvents.
