What process can increase the rigidity of polymers?

The process of crystallization is key in enhancing the rigidity of polymers. When a polymer undergoes crystallization, its molecular chains become more ordered and aligned, which increases the intermolecular forces acting between the chains. This ordered structure contributes to a higher modulus of elasticity and, consequently, greater rigidity.

Crystallization allows the material to resist deformation more effectively, providing it with better mechanical properties, including strength and stiffness. Many semi-crystalline polymers exhibit significant increases in rigidity compared to their amorphous counterparts due to this process.

In contrast, furnace melting, normalizing, and shot peening do not apply in the context of modifying polymer rigidity. Furnace melting typically relates to thermoplastic processing rather than structural improvement, normalizing is a heat treatment used primarily for metals, and shot peening involves impacting a surface to improve fatigue resistance, which is not directly aimed at enhancing the rigidity of polymers. Thus, crystallization emerges as the most effective method for increasing the rigidity of polymer materials.