Plastification

Plastification is the process by which a material becomes plastic, or turns into a material that can undergo permanent deformation under stress rather than returning to its original shape when the stress is removed. In polymer science, plastification most often refers to plasticization, the deliberate introduction of plasticizers to a polymer to increase its flexibility and processability. The term can also describe the general tendency of a substance to exhibit plastic behavior under certain conditions, such as elevated temperature or humidity, where the material softens and flows more easily.

Mechanisms: Plasticizers are typically low-molecular-weight compounds that are compatible with the polymer. They insert between polymer chains, reducing intermolecular forces, increasing free volume, and lowering the glass transition temperature (Tg). As Tg decreases, the polymer becomes more ductile at a given temperature. Plastification can be achieved by blending with compatible polymers, absorption of solvents, or thermal softening.

Common materials and examples: PVC is a notable example where plasticizers like phthalates are used to produce flexible films. Other plastics such as polyvinyl acetate, polyurethanes, and some biopolymers can be plastified. In some contexts, plastification occurs unintentionally during processing when solvents migrate out or plasticizers migrate away or vaporize.

Limitations and considerations: Plasticizers can migrate over time, leading to loss of softness or blooming. They may affect mechanical properties, barrier properties, and color. Environmental and health concerns have led to regulation and the search for alternative plasticizers and non-plasticized polymers. In addition, excessive plastification can reduce strength and increase creep.