What is crystallinity in the context of polymeric material? What effect does crystallinityhave on elongation, tensile strength, density and melting temperature? Briefly explain why

Crystallinity in the context of polymeric materials refers to the degree of structural order in a polymer. It is a measure of how closely the polymer chains are packed together in a regular and repeating pattern.

1. Elongation: Crystalline polymers tend to have lower elongation than amorphous polymers. This is because the tightly packed chains in crystalline polymers have less freedom to move and stretch.

2. Tensile Strength: Crystalline polymers generally have higher tensile strength than amorphous polymers. The strong intermolecular forces and close packing of chains in crystalline polymers make them more resistant to breaking under tension.

3. Density: Crystalline polymers have higher density than amorphous polymers. The close packing of chains in crystalline polymers means they have more mass per unit volume.

4. Melting Temperature: Crystalline polymers have a sharp melting point, while amorphous polymers soften over a range of temperatures. This is because the ordered structure of crystalline polymers breaks down at a specific temperature, while the random structure of amorphous polymers can break down over a range of temperatures.

The reason for these effects is that in a crystalline polymer, the chains are packed together in a regular, ordered way. This gives them less freedom to move, making them more rigid and resistant to deformation, but also less able to stretch. The strong intermolecular forces between the chains also make them more resistant to breaking under tension. The close packing of the chains also means that crystalline polymers have more mass per unit volume, giving them a higher density. Finally, the ordered structure of crystalline polymers means that they have a specific temperature at which they melt, unlike amorphous polymers which can soften over a range of temperatures.