Higher crystallinity generally leads to increases in which property(s)?

• A. Ductility
• B. Optical transparency
• C. Melt viscosity
• D. Density, stiffness, strength, heat resistance, and chemical resistance

Answer: (D)

Higher crystallinity means more ordered, tightly packed regions in the material. That dense packing raises density and makes the material stiffer and stronger because crystal domains resist deformation and failure more effectively. The orderly structure also requires more energy to disrupt, which boosts heat resistance, and it presents a tougher barrier to chemical diffusion, improving chemical resistance.

Ductility tends to decrease with more crystallinity because the rigid crystal regions restrict plastic deformation. Optical transparency often drops because crystal domains scatter light. Melt viscosity isn’t typically increased by crystallinity, since the melt is the disordered, liquid state; crystalline order only develops upon solidification.